Linking Alkali Content to Admittance and Impedance Signatures in CIGS Solar Cells through 2D Device Simulations

E. Lichocki^a, A. Urbaniak^a, R. Wuerz^b

^a Faculty of Physics, Warsaw University of Technology, Koszykowa 75, PL 00-662, Warsaw, Poland

^b Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Meitnerstr. 1, 70563, Stuttgart, Germany

Admittance spectroscopy (AS) is a widely used technique for probing defect states and charge-carrier transport in thin-film photovoltaic materials. However, despite its experimental simplicity, the interpretation of AS data remains difficult. Capacitance steps observed in AS spectra and the extracted activation energies (E_a) may originate from fundamentally different physical mechanisms, such as deep bulk defects, electrically active grain boundaries, or potential barriers at the back contact. This intrinsic ambiguity limits the reliability of AS when used as a standalone characterization method.

In this contribution, we demonstrate that impedance spectroscopy (IS), analyzed in the frequency domain, provides a complementary and highly sensitive approach for disentangling these mechanisms. Our study combines experimental investigations with advanced numerical modeling. Two-dimensional TCAD simulations of CIGS thin-film solar cells were carried out using Sentaurus, explicitly incorporating the columnar grain morphology and discrete defect states at planar grain boundaries. The simulations are based on the self-consistent solution of Poisson and carrier continuity equations. Bulk defect density, grain-boundary state density, doping concentration, and back-contact barrier height were systematically varied to generate AS and IS spectra and to analyze their temperature evolution.

Impedance spectra were evaluated using Nyquist plots and fitted with an equivalent circuit consisting of a series resistance and two parallel R–CPE branches, where constant-phase elements account for material and structural inhomogeneities. The temperature dependence of the extracted circuit parameters shows clear correlations with the material's underlying physical properties. Based on these results, we establish criteria for distinguishing between different defect-related mechanisms. In particular, we show that the appearance or deformation of a second semicircle in the Nyquist plot is a fingerprint of specific defect contributions, which cannot be resolved by conventional capacitance–frequency analysis.

The simulation results are validated against experimental data obtained from CIGS solar cells fabricated at ZSW using a one-stage process, with controlled sodium and potassium incorporation via post-deposition treatment. The combined experimental–theoretical approach enables an interpretation of defect-related spectroscopic signatures and provides deeper insight into the role of bulk and grain-boundary defects in CIGS thin-film materials.

Growing crystalline selenium (c-Se) thin-films is the most crucial step in fabricating Se solar cells. The mechanisms of this growth is however not well understood. The as-deposited Se film is usually amorphous (a-Se), but this phase is less stable and of poorer optoelectronic quality than the crystalline trigonal Se phase.

Herein we try to better understand how to form highly crystalline Se thin-films with fewer defects, large grain-size, and optimal orientation.

a-Se was deposited using thermal evaporation under high vacuum conditions. Various techniques reported in recent literature are used to obtain c-Se; thermal annealing, substrate heating, light assisted annealing, and encapsulation. Phase was confirmed by XRD; morphology by SEM.

With 100 oC substrate heating Se grows in long (~2 um) preferentially oriented crystals or nanorods. This morphology is however unsuitable for solar cells. The growth depends strongly on the substrate temperature during the deposition.
Re-evaporation of Se was prevented using encapsulation. This allowed for temperatures up to 250 oC during annealing. Encapsulation was achieved in two ways. Using two opposing substrates with a-Se in a hot-press we achieved large crystal grains up to several micrometers. The hole transport layer can also act as an encapsulant. Results suggests the possibility of avoiding de-wetting during annealing even without the standard tellurium adhesion layer.
The next step is to investigate the defect concentration of these new films.

These results show new possible synthesis ways to allow for higher quality c-Se films. Increasing the grain-size, orienting the crystals, and removing defects could lead to higher optoelectronic quality of the films and higher photovoltaic performance of Se solar cells.

The binary chalcogenide compound, antimony sulfide (Sb₂S₃), has garnered considerable interest as a promising candidate for solar applications due to its bandgap of about 1.7 eV, alongside a range of distinctive and beneficial characteristics such as the 1D structure. Although Sb₂S₃ has fascinating promise as a material for thin-film solar cells, development has been constrained by various interface and bulk active defects. The unfavorable [hk0] orientations of Sb₂S₃ is also highlighted in the literature as a key problem although results are not yet conclusive.

The glass/FTO/TiO₂/Sb₂S₃/P3HT/Au solar cells were investigated, with a focus on identifying the origin of performance degradation after exposure to high relative humidity and to mild heat stress. Analyzing the photovoltaic output and Deep-Level Transient Spectroscopy (DLTS) results, we probed the evolution of defect states after thermal exposure and after long-term storage of Sb2S3 based devices. The DLTS analysis revealed that shallow hole traps govern the stability of the Sb₂S₃ cells. Significantly, it will be shown that this shallow defect is not related to chlorine in the absorber, indicating an intrinsic origin. In the broader context of Sb₂S₃ photovoltaics, this study underlines the paramount importance of defect engineering towards achieving more stable and efficient Sb₂S₃ solar cells.

The reproducibility along with the key technical details should be considered. The internal reference is a 5.5% PCE HTL/Sb₂S₃/ETL/FTO/glass device, the spin-coating of molecular ink being used to obtain the Sb2S3 films. The electron transport layer used is a combination of compact/mesoporous TiO₂, compact TiO₂ or CdS, while P3HT is employed as hope transport layer. All cells are measured with same equipment in controlled laboratory conditions. Correlations of photovoltaic parameters with the type of engineered ETL in the photovoltaic device, as well with absorber synthesis parameters, will be also presented in detail.

Authors acknowledge the M-ERA.NET Ligthcell project “Quasi-1D materials for advanced thin-film photovoltaics”, the UEFISCDI PN-IV-PCB-RO-MD “Engineering Sustainable Antimony Chalcogenide Alloys for Customized Power Thin Film Photovoltaics” and the COST Action Research and International Networking project “Emerging Inorganic Chalcogenides for Photovoltaics (RENEW-PV),” CA21148, supported by COST (European Cooperation in Science and Technology).

Modelling photovoltaic devices is a cornerstone of scientific progress. Through the past two decades, the wide availability of free and open modelling tools has played a key role for accelerating research and even supporting scientific training, particularly for early-career researchers, which is especially important in photovoltaics, as the field brings together researchers from diverse backgrounds who may initially struggle with the fundamental physical principles governing solar cells. Despite these advances, a significant knowledge gap remains between the different modelling approaches used across the photovoltaic development. Detailed balance models ("first principles" for devices), drift-diffusion simulations at lab scale, and empirical tools for utility-scale applications operate in full isolation from each other. This disconnect is a major limitation: detailed balance models offer limited quantitative predictive power, drift-diffusion models are often restricted to well-controlled laboratory conditions, and utility-scale tools rely heavily on empirical assumptions and necessitate extensive characterisations that limit their versatility.

To address these limitations, we have developed and recently released SOLEY, a modelling software designed to bridge the gap from device-level physics to utility-scale performance. SOLEY relies on thermodynamic equations and an extended detailed balance formalism, which enables high-throughput calculations required for large-scale simulations while retaining the quantitative accuracy needed for research applications. In this presentation, we first introduce the modelling principles on which is based our approach, with a particular emphasis on how detailed balance can be extended to incorporate realistic loss mechanisms without compromising computational efficiency. We also describe the optical model implemented in SOLEY, which accounts for advanced and realistic effects such as light scattering and light trapping, essential for quantitative modelling of thin films.

We then demonstrate how this high-throughput, physics-based framework can be applied to realistic utility scale scenarios. Case studies are presented for application where thin film technologies have distinct advantages, especially agrivoltaics, building-integrated photovoltaics, and indoor photovoltaics. These examples illustrate how our approach permits, for the first time, a direct evaluation of thin-film device performance in realistic operating conditions rather than relying on extrapolations from laboratory scale measurements. As the photovoltaic community increasingly shifts its focus towards high technology readiness levels, the ability to connect device physics to system-level performance under real operating conditions is not optional, but essential. Integrated, physics-based modelling tools such as SOLEY are therefore a prerequisite for the thin-film community to translate laboratory innovations into competitive technologies.

Antimony selenide (Sb₂Se₃) is considered a promising absorber for sustainable thin-film photovoltaics due to its earth abundance, non-toxicity, high absorption coefficient, and near-optimal bandgap. Despite rapid progress in material synthesis and interface engineering, the power conversion efficiency of Sb₂Se₃ solar cells remains significantly below the Shockley–Queisser limit, primarily because of large open-circuit voltage (V_oc) and fill-factor deficits. An in-depth understanding of these losses requires advanced studies of defect-assisted recombination. In that context, temperature-dependent electrical characterization represents a powerful tool to identify the defect nature and position (bulk, interface, ...)[1], yet overlooked up to now in the case of antimony chalcogenides.

In this work, current–voltage–temperature (JVT) measurements were performed in a broad temperature window on co-evaporated Sb₂Se₃ substrate thin-film solar cells. Dark forward-bias analysis demonstrates the applicability of the single-diode formalism and the resulting proper extraction of the diode ideality factor and saturation current at all temperatures. The dark diode activation energy extracted therefrom exhibits deviations smaller than 30 mV as compared to the 1 sun V_oc-T measurements estimate of 1.29 eV, suggesting agreement between the dark and illuminated behaviours. The observed 100 meV discrepancy with the expected absorber bandgap may originate in interface-dominated recombination associated with a cliff-like conduction band alignment at the Sb₂Se₃/CdS heterojunction. Dark reverse-bias analysis reveals a transition in the dominant transport mechanism with temperature -  carrier trapping–detrapping via shallow states governs low-temperature conductivity while thermal generation from defects becomes significant at higher temperatures - the observation of which is likely facilitated by the low ohmic leakage levels.

Overall, this study shows that the lower efficiency of the studied Sb₂Se₃ solar cells as compared to state-of-the-art devices does not translate into inapplicability of the temperature-dependent single-diode modelling, i.e. the JVT methodology. Instead, this formalism enables to highlight important features both qualitatively and quantitatively, without requiring highly sophisticated measurement setups. On the one hand, a change in the dominant reverse current mechanism between thermal generation from defects at higher temperatures and shunt leakage at lower temperatures is identified. On the other hand, the prominence of heterojunction recombination with cliff-like band misalignment is emphasized, aligning with the established need for interface-related improvements strategies regarding defect passivation and band engineering in antimony chalcogenide solar cells. This work aims at building a framework for similar investigations on higher-performance devices in the future.

[1] Scaffidi et al, Newton, 1, 8, 100198 (2025)

Heterostructure engineering is a powerful strategy for overcoming the intrinsic trade-off between spectral range and carrier transport in photodetectors.¹ Here, we demonstrate a broadband, solution-processable photodetector based on a two-dimensional MoSe₂–Ag₂Se heterostructure, which integrates the strong visible absorption and high photogain of semiconducting 2H-MoSe₂ with the narrow-bandgap, high-mobility characteristics of Ag₂Se.² Structural analysis by X-ray diffraction and transmission electron microscopy confirms intimate heterointerfacing without compromising crystallinity. The resulting type-II band alignment enables electron transfer from MoSe₂ to Ag₂Se and efficient hole confinement in MoSe₂, thereby promoting long-lived carrier populations. Photodiodes of these nano heterostructures exhibit a broad spectral response from 300 nm to 900 nm, a peak responsivity of 1.2 A W⁻¹ at -3 V bias and 600 nm, a high detectivity of 8.5 × 10¹⁰ Jones, and faster response time with rise/decay times of 150/252 ms. The synergistic combination of broadband absorption, low dark current, and efficient charge extraction highlights the MoSe₂–Ag₂Se heterostructure as a promising candidate for next-generation, low-cost, and scalable photodetection technologies.

References:

1.   Shi, Yaru, et al. "Environmental-friendly Ag2S QD-multilayer MoSe2 van Der Waals heterostructure for high-performance broadband photodetection." ACS Applied Materials &                Interfaces 16.16 (2024): 20734-20743.

2.   Chen, Huiying, et al. "High-Performance Broadband Mixed-Dimensional Phototransistors Based on the Boron Nitride Quantum Dots/MoSe2 Heterostructure with Enhanced UV              Sensitivity." ACS Applied Materials & Interfaces 17.11 (2025): 17260-17269.

   Lightweight flexible solar cells are attracting increasing attention as a promising photovoltaic technology due to their potential to expand installation locations beyond conventional rigid modules. Their flexibility and lightweight nature enable deployment on curved or non-flat surfaces. Among thin-film photovoltaic technologies, copper indium gallium selenide (CIGS) solar cells have demonstrated good long-term stability on rigid glass substrates. Laboratory-scale CIGS solar cells have achieved conversion efficiencies of up to 23.64%[1]. CIGS solar cells also exhibit favorable characteristics such as radiation tolerance, long-term operational stability, and short energy payback time. In this study, we report on the development of integrated-structure CIGS solar cells fabricated on lightweight flexible substrates. Polyimide (PI) films and titanium (Ti) foils were investigated as candidate flexible substrates. An integrated module structure with multiple serially connected sub-cells was employed to enhance output voltage. For the polyimide substrates, laser and mechanical scribing processes originally developed for glass substrates were adapted. To enable low-temperature processing that is compatible with polymer substrates, silver (Ag) doping was applied to promote high-quality CIGS absorber growth at approximately 400 °C. Furthermore, optimizing the argon background pressure (P_Ar) during molybdenum (Mo) back-contact sputtering effectively suppressed crack formation in the Mo layer[2]. Cracks in the Mo layer caused failures during mechanical scribing of the upper layers. The scribing failure was improved after the optimization of Mo sputtering conditions. On the other hand, for Ti substrates, the impact of P_Ar is less significant than for PI substrates, likely due to the higher Young’s modulus of Ti and the use of a scribe-free interconnection process.

References

[1] J. Keller et. al., Nature Energy, 9 (2024) 467.

[2] Y. Kamikawa et. al., Solar Energy, 241 (2022) 327.

Acknowledgements

This work was partly supported by the New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade, and Industry. The authors would like to thank Mr. H. Takahashi, Mr. H. Higuchi, and Mr. M. Iioka for their invaluable assistance with the experiments. The authors would like to thank Mr. T. Masuda (Toyota Motor Corporation) for valuable discussions.

CuIn₁₋ₓGaₓ(S,Se)₂ (CIGS) thin-film absorbers represent a benchmark chalcogenide material system for photovoltaic applications, combining efficiencies above 23.6% with low material consumption, long-term stability, and compatibility with monolithic tandem integration. Despite this progress, a substantial open-circuit voltage (V_oc) deficit persists relative to the Shockley-Queisser (SQ) limit, indicating that recombination mechanisms intrinsic to disordered chalcogenide thin films continue to hinder device performance.

In this work, a spectroscopic framework grounded in the SQ detailed balance theory is established to quantitatively analyze V_oc losses and recombination processes in both the bulk and interfacial regions of CIGS solar cells. Herein, photoluminescence (PL) and electroluminescence (EL) measurements are employed to correlate quasi-Fermi level splitting (QFLS) with sub-bandgap absorptivity, enabling an assessment of the radiative-limit V_oc in CIGS solar cells. PL spectra are quantitatively interpreted using the Katahara–Hillhouse model, which explicitly accounts for band-tail states arising from compositional disorder. QFLS and absorption-tail parameters are extracted simultaneously instead of simplified logarithmic analyses, providing an accurate description of radiative recombination in disordered chalcogenide absorbers.

This framework yields a more accurate and physically consistent radiative-limit Voc by explicitly incorporating tail-state energetics, allowing Voc losses among different CIGS devices to be resolved with an accuracy on the order of 20 meV. Additionally, the framework is further extended to CIGS/perovskite tandem solar cells, where consistent PL/EL-derived parameters across sub-cells are essential for identifying the origin of V_oc losses and establishing V_oc accumulation. By leveraging the intrinsic complementarity between perovskite and chalcogenide absorbers, tandem architecture provides a viable pathway beyond the efficiency limits of single-junction thin-film devices. Overall, this spectroscopic approach provides direct insight into disorder-related recombination losses and establishes practical design guidelines for chalcogenide thin-film solar cells and their tandem applications.

Reference

1. Boukortt N. E. I., Adouane M., AlHammadi R., High-performance ultrathin Cu(In, Ga)Se₂ solar cell optimized by silvaco tools. Solar Energy, 2021, 228: 282-289.

2. Rau U., Reciprocity relation between photovoltaic quantum efficiency and electroluminescent emission of solar cells. Physical Review B—Condensed Matter and Materials Physics, 2007, 76(8): 085303.

3. Katahara J. K., Hillhouse H. W., Quasi-Fermi level splitting and sub-bandgap absorptivity from semiconductor photoluminescence. Journal of Applied Physics, 2014, 116(17).

Alloy engineering has emerged as an effective strategy for tuning the optoelectronic properties of two-dimensional transition-metal dichalcogenides. To this aim, large-area bilayer MoS2(1−x)Se2x alloys are synthesized on SiO2/Si substrate using a controlled chemical vapor deposition (CVD) technique, where the influence of several growth parameters are investigated. Raman and photoluminescence spectroscopic techniques are employed to investigate the systematic changes in the structural and optical properties of MoS2(1−x)Se2x alloys. Specifically, a 5% H2-mixing with the carrier gas (Ar) has been proven to be a successful strategy to obtain large-area growth coverage and improved alloy formation. To evaluate the electronic performance of the MoS2(1−x)Se2x alloys, a field-effect transistor (FET) is fabricated by wet-transferring the CVD-grown film on photomicrographed electrodes. The FET shows n-type transfer characteristics with a high (≈103) on-off ratio. Temperature-dependent current–voltage measurements of the fabricated FET revealed activated conduction as the primary charge transport mechanism. Under white light illumination, the device exhibited an impressive three-order magnitude enhancement in the drain current, reflecting a higher degree of photo-generated charge carriers and efficient charge transport. These findings reveal that CVD-grown MoS2(1−x)Se2x is a highly versatile material with tunable optoelectronic properties, making it a promising candidate for advanced transistor and photodetector applications.

Accurate optical modelling is a requirement for optimisation of thin-film PV devices, especially for emerging absorber technologies where interface roughness, and light-trapping strategies strongly influence performance. However, commonly used approaches like transfer matrix often rely on fully coherent thin-film optics which ignore scattering effects, or on computationally intensive full wave or ray tracing methods which limit their applicability to large parameter sweeps and device level optimisation.

In this work, we present an optical modelling method that explicitly separates and couples distinct physical regimes of light matter interaction within thin film solar cells. While we still use coherent optical propagation in smooth, sub-wavelength layers using the transfer matrix method, this time roughness induced phase randomisation at subwavelength interfaces is described through Debye-Waller attenuation of coherent Fresnel coefficients combined with conserving energy through diffuse redistribution. For interfaces with super-wavelength texture, like in crystalline silicon for example, a geometric optics model is employed to describe angular redistribution and multi-pass light trapping. Because the corrections are applied after the coherent calculations and reduce the scattering problem to closed-form algebraic factors, the method retains sub-second computation times. This is the main novelty of this approach.

The regime specific constraints prevents unphysical double counting of scattering processes. Indeed, geometric light trapping is permitted only at interfaces adjacent to absorbing layers, ensuring that light is not artificially trapped within passive or transparent layers. The angular redistribution associated with geometric scattering is derived directly from surface morphology through the RMS roughness and correlation length, which links both the mean scattering angle and angular spread to surface slope statistics and naturally recovering the specular limit for smooth interfaces. Metallic layers are treated explicitly using complex fresnel reflectance to account correctly for diffuse reflection and absorption losses.

Each individual model used is well known and not new, but their integration into a regime-explicit and physically constrained method is new. It model converges in less than one second for typical thin-film device architectures, allowing efficient parameter sweeps and seamless coupling with device-level electrical models. This framework has been developed for integration into the SOLEY solar cell simulation platform, with the aim of providing a fast yet physically accurate optical engine for experimentalists and theoreticians. While the methodology is general, it is relevant for chalcogenide thin-film solar cells, where strong absorption, interface roughness, and textured back reflectors play a central role in determining optical losses and photocurrent generation. 

Thin-film semiconductors are widely studied for photoelectrocatalytic (PEC) applications, including water splitting and CO₂ reduction to value-added products. However, their practical application is often hindered by aqueous instability, low Faradaic efficiency, and poor catalytic performance. These limitations are often associated with surface reconstruction processes under operating conditions, the control of which remains a major challenge. Recently, wide bandgap Cu(In,Ga)S2 (Eg > 1.6 eV) has emerged as an efficient and stable material system for direct H2 production and CO2 reduction in non-aqueous and aqueous media. In CIGS, high densities of surface states can induce Fermi level pinning (FLP), strongly influencing interfacial band alignment and charge-transfer kinetics. While FLP is well studied in photovoltaics, its impact on PEC processes is largely unexplored. Here, we fabricated CIGS photocathodes via sulfurization of the sputtered metal stack on Mo substrate. Subsequently, we integrated Au as a catalyst on the CIGS surface via sputtering deposition. A detailed characterization was performed to analyze the surface morphology and phase via scanning electron microscopy, X-ray diffraction (XRD), and Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) was used to investigate the surface chemistry over 10 hours. Furthermore, the bandgap was determined by photoluminescence (PL) and band edges via Ultraviolet Photoelectron Spectroscopy (UPS), which showed an adequate band alignment for reduction applications. Photoelectrochemical tests were performed in 0.1 M KHCO3 electrolytes saturated with CO2 to evaluate their activity and selectivity. Bare CIGS thin films have shown photocurrents of -3.5 mA cm-2 at -0.4 V vs RHE, while CIGS-Au showed a photocurrent 2.5 times higher than bare CIGS. Surface modifications become evident after 1 h, showing In-enrichment without Cu or Ga depletion. The results showed that CO2R selectivity can be modulated on CIGS through Au engineering, offering a new dimension of control in reduction reactions.

As global population growth intensifies, the demand for sustainable, renewable energy sources becomes critical. Solar energy, being abundant and clean, offers great potential for future power generation. Yet, the efficiency of traditional crystalline silicon solar cells nears its theoretical limit¹, prompting research into novel materials that promise higher efficiencies, stability, and environmental compatibility.

Emerging alternatives like organic-inorganic halide perovskites, GaAs, CdTe, and CuInGaSe have shown significant photoconversion potential but simultaneously face challenges such as synthesis complexities, long-term stability, toxicity, and resource scarcity, hindering their large-scale application^2-4. Therefore, new classes of semiconductors are needed to overcome these limitations.

Ionic semiconductors with spinel structure, particularly lithium-based thiospinels Li₂ASn₃S₈ (A = Cu, Mn, Mg, Co or Fe), have shown to be promising candidates⁵. Structurally, the unique combination of tetrahedral and octahedral cation coordination imparts chemical stability. Predominantly ionic bonds foster defect tolerance, prolonging charge carrier lifetimes. Initial bulk studies reveal favourable optical properties, including suitable band gaps and high absorption coefficients, enabling an efficient light harvesting⁵. However, these investigations have been limited to bulk materials.

This work focuses on fabricating and characterizing Li₂ASn₃S₈ thin films via pulsed laser deposition (PLD). We searched a growth parameters to enhance film quality, the photoelectronic properties are thoroughly analysed through transmittance spectra, photoluminescence, and photocurrent measurements, shedding light on how morphology and microstructure influence electronic performance. Our findings aim to advance next-generation photovoltaic materials that combine high efficiency with environmental sustainability, contributing to the development of more effective, eco-friendly solar energy solutions.

References:

1. Andreani LC, Bozzola A, Kowalczewski P, Liscidini M, Redorici L. Silicon solar cells: Toward the efficiency limits. Adv Phys X. 2019;4(1).

2. Xu F, Zhang M, Li Z, Yang X, Zhu R. Challenges and Perspectives toward Future Wide-Bandgap Mixed-Halide Perovskite Photovoltaics. Adv Energy Mater. 2023;13(13):1–14.

3. Scarpulla MA, McCandless B, Phillips AB, Yan Y, Heben MJ, Wolden C, et al. CdTe-based thin film photovoltaics: Recent advances, current challenges and future prospects. Sol Energy Mater Sol Cells. 2023;255(March):112289. 

4. Polman A, Knight M, Garnett EC, Ehrler B, Sinke WC. Photovoltaic materials: Present efficiencies and future challenges. Science (80- ). 2016;352(6283).

5. Quintero MA, Hao S, Patel S V., Bao JK, Zhou X, Hu YY, et al. Lithium Thiostannate Spinels: Air-Stable Cubic Semiconductors. Chem Mater. 2021;33(6):2080–9.

The goal of this work is the optimization of MoOx HTL to enhance chalcogenide- based  PV device performance. The influence of MoOx layer thickness on the PV parameters of the final solar cells is evaluated by varying the time, power, pressure of oxygen during the sputtering process. The structure, morphological, and optical properties are measured by X-ray diffraction, SEM, and transmittance measurements. As a result, it is expected that the incorporation of the MoOx HTL results in an enhanced solar cell efficiency. Chalcogenide materials are promising candidates for scalable energy technologies due to their favourable electronic and optical properties, enabling efficient light absorption in thin-film architectures. However, the performance of chalcogenide-based solar cells is strongly influenced by interface quality and charge-selective contacts, which remain key challenges for device optimization. In this context, avoiding the use of CdS is particularly attractive for sustainable and scalable PV technologies. Here, improved charge selectivity is achieved using TiO₂ as the electron transport layer (ETL) and an ultrathin MoOx layer as the HTL, deposited by magnetron sputtering. This contact configuration enables favourable energy level alignment and reduced interfacial recombination losses. 

Buildings consume approximately one-third of global energy, while land availability remains a constraint for photovoltaic (PV) deployment. Current building-integrated photovoltaics (BIPV) predominantly utilize opaque facade elements, leaving large glass surfaces widely unused. These glazed areas, typically characterized by average visible transmittance (AVT) of 50–80%, represent a significant and unexploited opportunity for PV integration. One solution is semi-transparent photovoltaics (STPV), which allow for seamless implementation of PV in buildings as windows and in agriculture-integrated photovoltaics (agri-PV). Moreover, STPV offer tri-functionality by providing a physical barrier, enabling natural light illumination and generating power.

Cu(In,Ga)Se2 (CIGS) thin-film solar cells with power conversion efficiency (PCE) up to 23.6 % [1] and proven stability are a promising candidate for semi-transparent solar cells. In our work, semi-transparency is accomplished by structuring the solar cell into narrow micro-stripes separated by transparent gaps. This design strategy allows for a colour-neutral device with unobstructed view and tunable transparency. In contrast, the most common approach of thinning down the absorber typically leads to increased shunt paths and back-junction recombination. Furthermore, this approach suffers from reduced light transmittance at shorter wavelengths, leading to red-to-yellow colours.

Micro-stripped devices have already been demonstrated by Santos [2] and Jeong [3] on Mo and ITO back contacts, respectively. These methods use top-down manufacturing approaches through chemical etching and laser scribing, which leads to performance losses due to inactive areas at the edges. To mitigate this issue, we propose a bottom-up fabrication process using photolithography techniques to define the micro-pattern on photoresist and subsequently remove the excess material. The use of transparent conductive oxides (TCOs) as a back contact, compared to Mo, is preferable because it allows the device to capture albedo light, further improving energy generation.

We fabricated devices with 500 µm wide and 1 cm long micro-stripes using ITO as transparent back contact. The device showed an average active area PCE of 2.6% with a 50% aperture area ratio. Compared to the Mo devices (8-10%) this represents lower efficiency mainly due to the blocking effect on ITO [4]. To overcome this, a thin Ag or Mo interlayer can be used between the back contact and the absorber layer [3][5]. In this work, we compare the effects of both interlayers on the performance and bifaciality of the devices.

[1] Keller J et al. Nat. Energy 9 (2024) 467–478.

[2] Santos P et al. Thin Solid Films 770 (2023) 139778.

[3] Jeong A et al. Prog. Photovolt. Res. Appl. 30 (2022) 713–725.

[4] Nakada T et al. Sol. Energy 77 (2004) 739–747.

[5] Demling A et al. ACS Appl. Mater. Interfaces 17 (2025) 33027–33035.

Thin film solar cells are the most ubiquitous and reliable energy generation systems for aerospace applications. For these applications the extreme conditions in space, like radiation, low temperatures and extreme temperature swings, have to be taken into account. Thus the low temperature behavior of solar absorber materials in PV devices potentially used in space applications, are of extreme importance. 

Chalcogenides used as absorbers in thin-film PV technologies are CdTe, Cu(In,Ga)Se₂ (CIGS) and Cu₂ZnSnSe₄ (CZTSe). The corresponding thin-film solar cells reach power conversion efficiencies of 23.1%, 23.6%, 16.6%, respectively [1]. These compound semiconductors adopt a crystal structure characterized by a network of corner sharing tetrahedra. It is known, that compounds whose crystal structures are based on tetrahedrally coordinated ions show a negative thermal expansion (NTE) at low temperatures [2], which can influence the mechanical stability and the operation of the PV device at low temperatures as present in space.

Because of the negative linear thermal expansion coefficients, negative Grueneisen parameters are be expected in the low-temperature region. The presence of high-pressure induced structural phase transitions are also an indication of negative Grueneisen parameters. Interestingly CdTe (adopting the zincblende structure), CuInSe₂ (adopting the chalcopyrite structure) as well as Cu₂ZnSnS₄ (adopting the kesterite structure) transform to the rocksalt structure at high pressure [3, 4, 5]. Thus it can be expected, that tetrahedrally coordinated quaternary compounds show a NTE as well.

We studied the crystal structure of Cu₂ZnSnSe₄, Ag₂ZnSnSe₄ and (Ag,Cu)₂ZnSnSe₄ by in-situ neutron powder diffraction in a temperature range between 300 and 3K. All studied compounds crystallize in the tetragonal kesterite-type structure in the whole temperature range studied. The linear thermal expansion coefficients αa and αc are highly anisotropic. Cu₂ZnSnSe₄ shows a negative thermal expansion coefficient αL at temperatures below 30K and Ag₂ZnSnSe₄ below 125K. In the latter compound αc is negative in the whole temperature range from 300 to 3K, indicating the special behavior of the Ag-containing tetrahedrally coordinated semiconductors.

The presentation will provide a comprehensive overview of the low temperature behavior of different key chalcogenide PV materials, laying the groundwork for designing more robust and efficient energy materials capable of functioning under extreme temperature conditions, including space-based solar energy conversion.

[1] NREL Solar Cell Efficiency Chart, https://www.nrel.gov/pv/cell-efficiency

[2] T. F. Smith and G. K. White, J. Phys. C: Solid State Phys. 8 (1975) 2031

[3] D. Martinez-Garcia et al., Phys. Stat. Sol. (b) 211 (1999) 461

[4] A. Jayaraman et al., High temperatures - high pressure 9 (1977) 97

[5] I. Efthimiopoulos, et al., Appl. Phys. Let. 110 (2017) 041905

Solar photovoltaics (PV) are projected by the International Energy Agency to become the leading technology in the renewable energy sector, as forecasted by the International Energy Agency, playing a central role in the energy transition and in meeting the European Green Deal targets. Such prominence requires a sustainable use of the available material resources and expanding the PV portfolio, favouring device architectures that combine reduced material consumption with mechanical flexibility and low weight. At the laboratory scale, record-efficiency Cu(In,Ga)(S,Se₂) (CIGSSe) solar cells are primarily developed through co-evaporation [1,2], a technique that offers control over growth kinetics and depth-dependent composition. Nevertheless, magnetron sputtering presents a more viable route for large-area, high-throughput manufacturing; however, it traditionally lacks the precise elemental control required for high-efficiency absorbers [3]. This work addresses the challenges of developing all-sputtered CIGSSe cells by performing several process optimization iterations to enhance the performance of sub-micrometer flexible CIGSSe solar cells, while enabling an increased throughput. The absorber deposition temperature, composition, thickness, cooling process, and alkali doping have been systematically explored and characterized through current density-voltage and external quantum efficiency measurements, X-ray photoelectron spectroscopy, X-ray diffraction, and electron microscopy. Through these optimization steps, the light-to-power conversion efficiency was improved by approximately 3% (absolute) relative to the process baseline. An optimized all-sputtered CIGSSe solar cell with an inline process provides a pathway to expand the CIGSSe market presence, while the flexibility and sub-micrometer characteristics can broaden the technological application portfolio and meet sustainable goals.

References

[1] J. Keller et al., “High-concentration silver alloying and steep back-contact gallium grading enabling copper indium gallium selenide solar cell with 23.6% efficiency” Nat. Energy 9 (2024) 467

[2] J. Lindahl et al., “Inline Cu(In,Ga)Se₂ Co-evaporation for High-Efficiency Solar Cells and Modules” IEEE J. Photovolt. 3 (2013) 1100

[3] Chen et al., “A promising sputtering route for one-step fabrication of chalcopyrite phase Cu(In,Ga)Se₂ absorbers without extra Se supply” Sol. Energy Mater. Sol. Cells 103 (2012) 25–29

The well-known Cu₂ZnSn(S,Se)₄ (CZTSSe) thin-film solar cells have the potential to deliver high efficiency even when fabricated using vacuum-free processes.

In this work, CZTSSe absorber layers were deposited using an airbrush spray-coating technique, a simple, solution-based, and highly scalable approach suitable for large-area and roll-to-roll manufacturing. Compared to traditional spin coating, the airbrush method enables uniform precursor deposition on larger substrates without complex equipment, thus offering strong potential for industrial implementation.

Our process has undergone a comprehensive optimisation study to enhance absorber quality and device performance. The investigation focused on multiple parameters influencing the spray-coated precursor films, including solution chemistry, deposition conditions, and post-deposition annealing. Focus was devoted to the selenization process of sprayed layers, in which the selenization temperature was maintained at 550 °C, while the argon partial pressure was systematically varied from 100 to 400 mbar. The analysis of the layers by Raman, X-Ray diffraction, energy dispersive X-Ray, scanning electron microscopy show that the selenization pressure affects crystallinity, stoichiometry, grain growth, phase purity, and the optoelectronic properties of the resulting CZTSSe absorbers.

Morphological analyses revealed that low selenization pressure (100 mbar) promotes the formation of large, compact grains, leading to more homogeneous absorber layers. In contrast, higher pressure (400 mbar) results in less uniform grains and increased microstructural inhomogeneity. Structural characterisation by X-ray diffraction and Raman results confirm the formation of CZTSSe phase for all the cases, but with different stoichiometry and crystallisation.

The best-performing device at 100 mbar achieved an efficiency of 5.82%, with a fill factor of 55.14%, a short-circuit current density of 33.59 mA/cm², and an open-circuit voltage of 314 mV.  At higher selenization pressures, solar cells achieved a PCE of 3.57%, a FF of 31.64%, a JSC of 31.04 mA/cm², and a VOC of 363 mV.

Overall, the combination of airbrush spray-coating with optimised low-pressure selenization provides a robust and economical pathway for producing high-quality CZTSSe absorbers.

Heterostructures with two configurations, antimony sulfide (Sb₂S₃)/cadmium sulfide (CdS) and CdS/Sb₂S₃, were deposited on glass substrates by Chemical Bath Deposition. Sb₂S₃ films were deposited at a constant temperature of 40 °C, with deposition times of 25, 30, 35, and 40 minutes. Subsequently, CdS films were deposited onto the first layer at 70 °C, using the same deposition times. The procedure was also carried out in the reverse order to obtain CdS/Sb₂S₃ heterostructures under identical deposition parameters.

The structural, morphological, optical, and electrical properties were analyzed using X-ray diffraction, scanning electron microscopy, ultraviolet–visible spectroscopy, and photoconductivity measurements, respectively.

X-ray diffraction analysis revealed that Sb₂S₃ monolayers exhibit an amorphous structure, whereas CdS monolayers showed characteristic reflections of the cubic phase. In CdS/Sb₂S₃ heterostructures, a preferential orientation of the (111) plane of cubic CdS was observed only at the longest deposition time. In Sb₂S₃/CdS heterostructures, the same crystalline planes of CdS were identified, indicating that its crystalline structure is not affected by the presence of an amorphous Sb₂S₃ layer.

Morphological analysis by SEM was performed on both the individual monolayers and the heterostructures. Morphological analysis showed compact spherical grains for Sb₂S₃ and a granular morphology for CdS films. Optical measurements yielded band gap energy values of 2.4–3.4 eV for Sb₂S₃ and 3.8–3.9 eV for CdS, while the heterostructures exhibited intermediate values depending on the layer sequence. Photoconductivity measurements demonstrated an enhanced electrical response in the heterostructures compared to Sb₂S₃ monolayers. These results indicate that the stacking sequence plays a key role in tailoring the properties of Sb₂S₃/CdS and CdS/Sb₂S₃, heterostructures, highlighting their potential for integration into photovoltaic devices.

A current trend in Cu(In,Ga)Se2 (CIGS) technology is centred on reducing the absorber thickness to an ultrathin regime, enabling a decrease in critical raw materials consumption as well as an improvement in solar cell production throughput.[1] However, ultrathin CIGS devices’ performance is limited by incomplete light absorption and interface recombination losses. Regarding optical losses, nanoscale light-trapping scattering schemes are required to overcome short-circuit current density (JSC) losses without optoelectronic degradation.[1,2] Moreover, scattering strategies may be coupled with nanopatterned interface passivation schemes to ensure efficient charge carrier collection.[3] Nanoimprint lithography (NIL) offers a compelling solution to develop nanopatterned schemes with high resolution, low complexity, and compatibility with high-throughput processes for large-area processing. Thereafter, in this work, a full NIL process-flow, compatible with conventional glass and flexible substrates, was developed and optimised to attain high-performance solar cell substrates with a coupled light trapping and passivation scheme based on plasmonic nanopillars. The periodic array is composed of Au nanopillars with a maximum feature height of 60 nm, enabling large optical gains without electrical degradation, encapsulated within dielectric (SiOx, AlOx, and TiOx) point-contact passivation schemes. The process-flow optimisation comprised several steps starting from the development of a NIL master mould via e-beam lithography, residual resist removal, etching process for an anisotropic pattern transfer, effective encapsulation with dielectric layers, resist strip and wet etching of residual nanopillars from point-contact areas to inhibit Au diffusion into the absorber, which could lead to non-radiative recombination centres. The effectiveness and viability of the developed processes were iteratively monitored using scanning electron microscopy and atomic force microscopy measurements, and the viability of the light trapping schemes for ultrathin and bifacial CIGS devices was assessed through UV-VIS-NIR spectrophotometry. Large diffuse reflectance and transmittance gains were obtained compared to reference substrates, and optical simulations indicates JSC enhancements over 3 mA/cm2 in a full solar cell due to light scattering.

References

[1] I. Massiot, et. al., Nat Energy (2020) 5, 959–972.

[2] A. J. N. Oliveira, et. al., Adv. Photonics Res. (2022),3, 2100190.

[3] A. J. N. Oliveira, et. al., Sol. RRL. (2024), 8, 2400147.

Solution-based fabrication of Cu₂ZnSnS₄ (CZTS) thin films exhibits considerable potential for photovoltaic applications due to its high efficiency, process simplicity, and cost-effectiveness. However, the power conversion efficiency (PCE) of CZTS solar cells remains limited by poor absorber crystallinity and a high density of intrinsic defects. 

This study aims to elucidate how precursor solution concentration influences crystallization behavior, defect formation, and photovoltaic performance in solution-processed CZTS absorbers. A series of Cu-poor, Zn-rich precursor solutions covering a wide range of concentrations was prepared by dissolving copper, tin, and zinc salts with thiourea in dimethyl sulfoxide (DMSO). The precursor solutions were adjusted by maintaining constant Cu (Zn+Sn) = 0.85 and Zn/Sn = 1.2 ratios, together with a fixed sulfur-to-total-metal ratio of S/(Cu+Zn+Sn) = 2, while varying the solvent-to-precursor salt ratio in the range of 0.2–1.0 g mL⁻¹ to control the overall concentration. CZTS absorber layers were deposited via spin coating, followed by sequential hot-plate annealing, sulfurization to promote phase formation and grain growth, buffer layer deposition, and window layer fabrication.  

The effects of precursor solution concentration on CZTS film morphology, crystallinity, and elemental and defect composition were examined using Raman spectroscopy, scanning electron microscopy, and X-ray diffraction, photoluminescence spectroscopy, while device performance was evaluated by current-voltage and external quantum efficiency (EQE) measurements.

Highly concentrated, viscous precursor solutions enabled the formation of thicker CZTS absorber layers with fewer spin-coating cycles, resulting in enhanced photovoltaic performance. The best-performing devices achieved an open-circuit voltage of 641 mV, a short-circuit current density of 23 mA/cm², a fill factor of 56 %, and a PCE of 8.3 %. In contrast, diluted precursor solutions yielded thinner absorbers under identical deposition conditions, resulting in reduced device efficiencies. Nevertheless, optimized diluted formulations still exhibited competitive performance, with efficiencies approaching 7 %. To decouple the effects of precursor concentration from absorber thickness, additional experiments were conducted using CZTS layers of identical thickness. This approach enabled a systematic assessment of how precursor concentration influences absorber quality and contributes to mitigating crystallinity- and defect-related limitations. Detailed results will be presented at the conference.

Flexible Cu(In,Ga)Se₂ (CIGS) solar cells offer high efficiency and stable performance for niche applications. The integration of highly conductive metal grids helps reduce the resistive losses and increase the efficiency without affecting the structural layers^[1]. Inkjet printing emerges as a precise, low-cost, non-contact deposition process with broad tuneable deposition parameters and consequently applications^[2], being optimal for investigation purposes, with an upscaling potential. In this work, the Inkjet grid deposition process is being optimised in sub-micrometre flexible CIGS solar cells and the results are validated and compared with the metal grids deposited by Screen Printing, a large-scale industrial process used to mass produce these contacts^[3], yet leading to an increased material waste generation. Considering the versatility of the Inkjet process, different strategies can be adopted to enhance the optoelectronic performance of the cells, which was evaluated via current density - voltage (JV) characterization. The focus is on two different strategies: (1) varying metal grid annealing temperature. Overall, from a baseline of a two-cycle annealing of 120 °C for 30 min and 200 °C for 30 min, increasing the temperature to 200 °C for 30 min and 230 °C for 30 min allowed a significant Fill Factor (FF) value increase of ~5 %, which might be associated with the metal grid resistance, since higher temperatures may ease the removal of organic components. Moreover, an improvement on the solar cell open-circuit voltage (V_OC) value was additionally obtained, by approximately 40 mV, suggesting a beneficial impact on the absorber properties; and (2) varying the number of inkjet layers, and consequently, the metal grid thickness. Adding up to 5 inkjet layers translates to an expected growth in thickness, which lead to a solar cell conversion efficiency improvement, mainly due to the enhancement of the FF value by almost 10 %. Above 5 layers, the conversion efficiency value decreases which may be attributed to the increased amount of ink and consequent difficulty in drying it, as the annealing temperature and time remained the same among the different layers. Overall, with the improvements implemented in this study, the efficiencies of Inkjet-based solar cells were able to reach and even surpass conventional Screen-printed ones.

[1] Hu, C. et al., Solar Energy, 284, (2024).

[2] Singh, M. et al., Advanced Materials, 22(6), (2010).

[3] Tepner, S., & Lorenz, A., In Progress in Photovoltaics: Research and Applications, 31, (2023).

Ternary diamond-like copper chalcogenides are amongst the highest performing single-junction thin film photovoltaic materials. They exhibit lower toxicity and greater stability than CdTe and perovskite single-junction photovoltaics, while maintaining high performance at reduced film thicknesses relative to silicon. The highest performer Cu(In,Ga)Se₂ has reached a record power conversion efficiency of 23.6% at thicknesses lower than 2.0μm¹.  However, industry applications are limited due to the high cost of scarce elements and the precise synthesis required to minimize performance-reducing defects. Copper zinc tin selenide was developed in an attempt to produce a low-cost high-performance thin film material, but performance has stalled at 15.8% due to high concentrations of charge recombination centres².  As a result, developing new thin film photovoltaic materials remains an important area of research.

Cu₂GeSe₃ has been explored as a thermoelectric for many years, it contains a larger proportion of cheap, non-toxic and abundant materials than CIGS, with good thermal and chemical stability. Previous work by the Scanlon Materials Theory Group has identified the silicon analogue Cu₂SiSe₃ as a promising defect tolerant photovoltaic material with a high theoretical power conversion efficiency of 30%³. Despite its narrower optical band gap of 0.78-0.85 eV, the germanium system may offer promising properties as a bottom layer for tandem cells, dopant or alloy in photovoltaic thin films. However, little is known about the structure and properties of Cu₂GeSe₃. Once believed to be ordered, Cu₂GeSe₃ has now been shown to be more complex9. It is essential to comprehensively characterise Cu₂GeSe₃ to ensure its suitability as a photovoltaic material.

This work aims to explore the structure and properties of Cu₂GeSe₃ for use in photovoltaic alloys by employing a combined density functional theory, machine learning approach. Our approach uses machine learning interatomic potentials to calculate the vibrational free energies of a range of structures for use in cluster expansions for Monte Carlo simulation-based disorder studies.
[1] Green, M.A., Dunlop, E.D., Yoshita, M., Kopidakis, N., Bothe, K., Siefer, G., Hinken, D., Rauer, M., Hohl‐Ebinger, J. and Hao, X., 2024. Solar cell efficiency tables (Version 64). Progress in photovoltaics: research and applications, 32(7), pp.425-441.
[2] Shah, U.A., Wang, A., Irfan Ullah, M., Ishaq, M., Shah, I.A., Zeng, Y., Abbasi, M.S., Umair, M.A., Farooq, U., Liang, G.X. and Sun, K., 2024. A deep dive into Cu2ZnSnS4 (CZTS) solar cells: a review of exploring roadblocks, breakthroughs, and shaping the future. Small, 20(30), p.2310584.
[3] Nicolson, A., Kavanagh, S.R., Savory, C.N., Watson, G.W. and Scanlon, D.O., 2023. Cu 2 SiSe 3 as a promising solar absorber: harnessing cation dissimilarity to avoid killer antisites. Journal of Materials Chemistry A, 11(27), pp.14833-14839.

Bias-free photoelectrochemical (PEC) hydrogen production coupled with plastic reforming represents a sustainable strategy for simultaneous clean fuel generation and value-added utilization of organic waste under solar irradiation. Herein, we report a silver (Ag)-modified Cu₂CdSnS₄ (Ag-CCTS) photocathode designed to enhance and stabilize PEC performance through controlled cation substitution.

Partial substitution of Cu⁺ with Ag⁺ significantly improves the crystallinity and promotes grain growth while tailoring the electronic structure, leading to enhanced light absorption and charge transport properties. A series of Ag-CCTS thin films with Ag/(Ag+Cu) atomic ratios ranging from 0 to 25% were fabricated via a sol–gel method. Among them, the Ag-CCTS photocathode with 10% Ag incorporation delivered the optimal performance, achieving a photocurrent density of 18.15 mA cm^-2 at 0 V versus RHE, a positively shifted onset potential of +0.23 V compared to pristine CCTS, and stable operation over 3 h under simulated sunlight.

When integrated with a Cu₃₀Pd₇₀ alloy anode that selectively catalyzes the oxidation of ethylene glycol derived from polyethylene terephthalate (PET) waste, the tandem PEC system enables bias-free solar hydrogen production coupled with plastic reforming. This work highlights an effective defect and composition engineering strategy for CCTS-based photocathodes and demonstrates a practical PEC platform for integrating hydrogen evolution with plastic-to-chemical conversion in a single solar-driven device.

Voltage losses in monolithic tandem solar cells often originate from spatially localized recombination pathways that remain hidden in area-averaged measurements. Hyperspectral Photoluminescence (PL) imaging addresses this limitation by recording a full emission spectrum at each pixel and converting it into maps of physically meaningful voltage metrics. In particular, the quasi-Fermi level splitting (QFLS) provides a contact-independent optical analogue of the maximum attainable open-circuit voltage, while comparison to the radiative limit enables spatially resolved quantification of non-radiative voltage losses [1].

Here, we apply hyperspectral PL imaging to a monolithic two-terminal perovskite(PSK)/Cu(In,Ga)Se₂ (CIGS) tandem device and extract pixel-resolved maps of effective bandgap, radiative QFLS, QFLS under one-sun-equivalent excitation, non-radiative QFLS loss, and voltage headroom for both subcells [2]. This multi-parameter approach enables separation of voltage losses associated with local bandgap variations from those dominated by non-radiative recombination [3].

The PSK top cell exhibits relatively homogeneous QFLS under 1-sun excitation despite device-scale bandgap variations, indicating that bandgap tuning alone does not determine the local voltage outcome. In contrast, the CIGS bottom cell displays a markedly more heterogeneous voltage landscape, with extended regions of suppressed QFLS and elevated non-radiative losses showing weak correlation with local bandgap variations. This decoupling points to recombination-driven limitations rather than composition as the dominant origin of voltage loss in the bottom cell, consistent with previous reports on interface- and contact-limited losses in thin-film photovoltaics [4-6].

Notably, the spatial signatures observed in the CIGS QFLS maps are consistent with degradation mechanisms commonly associated with transparent conductive oxide (TCO) integration. Supporting ultrafast optical measurements reveal a reduced prompt optical response in processed regions compared to unprocessed layers, implying enhanced carrier quenching or modified interfacial recombination dynamics. While hyperspectral PL alone does not identify a unique microscopic mechanism, the combined spatial and temporal optical evidence indicates TCO deposition—e.g., ITO—as a likely contributor to the observed bottom-cell voltage losses.

Overall, this work demonstrates that hyperspectral PL imaging provides quantitative, spatially resolved insight into voltage-limiting mechanisms in complex tandem architectures by localizing recombination losses and separating them from bandgap-related effects.

[1] U. Würfel et al., doi: 10.1038/ncomms7951.
[2] U. Rau, doi: 10.1103/PhysRevB.76.085303.
[3] M. Jošt et al., doi: 10.1002/aenm.201904102.
[4] O. Almora et al., doi: 10.1002/aenm.202203313.
[5] M. Gloeckler et al., doi: 10.1063/1.2128054.
[6] U. Rau et al., doi: 10.1063/1.1737071.

Thin‐film chalcogenide semiconductors are key materials for next‐generation photovoltaic and optoelectronic applications due to their direct bandgaps, strong optical absorption, and compatibility with scalable processing. While device performance is strongly influenced by material quality, identical compositions can exhibit markedly different optoelectronic responses depending on the fabrication route and post‐processing history. In particular, variations in crystallinity, defect density, and substrate‐induced strain often complicate the interpretation of optical measurements, as intrinsic material properties are frequently obscured by laser‐induced thermal effects.

In this work, we present a comparative study of thin‐film chalcogenide layers prepared via three distinct fabrication routes: as‐grown (Grown, G) films directly synthesized on the substrate, transferred (Transferred, T) films relocated onto a target substrate, and mechanically exfoliated (Exfoliated, E) samples serving as a high‐crystallinity reference. These samples provide a systematic platform to elucidate process–structure–property correlations. Power‐dependent photoluminescence (PL) and Raman spectroscopy were performed under ambient, room‐temperature vacuum, and low‐temperature vacuum conditions. By suppressing thermal broadening and excitation‐induced redshifts, low‐temperature vacuum PL enables reliable isolation of intrinsic excitonic behavior.

Despite the minimized thermal contribution, pronounced differences in PL linewidths, peak energies, and excitonic features persist among the Grown, Transferred, and Exfoliated samples. This observation indicates that fabrication‐route‐dependent crystallinity and substrate‐induced strain play a dominant role in governing intrinsic optoelectronic responses. Raman spectroscopy further reveals distinct phonon signatures associated with lattice disorder and strain variations introduced by growth and transfer processes, while the mechanically exfoliated samples exhibit characteristics consistent with reduced defect density and minimal strain.

These results demonstrate that fabrication route engineering critically determines the intrinsic optical properties of thin‐film chalcogenides beyond extrinsic thermal effects. The findings highlight the importance of correlating growth and processing pathways with crystallinity and strain control to enable reliable optoelectronic characterization and optimized material quality. This work provides practical guidelines for thin‐film growth and processing strategies relevant to chalcogenide materials for photovoltaic and solar energy conversion applications.

      In-situ incorporation of alkali elements to the absorber layer and especially Na is of primary importance to increase the PV performances of Cu(In,Ga)Se2 (CIGS) solar cells, mainly by passivating defects in the absorber layer. Alternatively, an additional recrystallization step induced by the implementation of metal-halide compounds such as InBr3, InCl3, CuCl, CuCl2 or AgBr after the Cu-rich stage of a co-evaporation process could result in larger grain size and overall higher structural and compositional homogeneity of CIGS or CGS absorber layers.

      While most research has focused on comparing the passivating effects of alkali elements like Na, potassium (K), cesium (Cs), and rubidium (Rb) in fluorinated forms, the specific impact of halides remains understudied. In this work, we systematically investigated the influence of NaF and NaBr on CIGS performance, depending on their introduction stage during the three-step co-evaporation process: after the first stage, after the second stage, or as a post-deposition treatment. We also analyzed the effects of alkali incorporation and layer recrystallization on solar cell performance at two deposition temperatures (350 °C and 450 °C) and in CIGS layers with and without silver (Ag). Our results demonstrate that performance improvements differ significantly between NaF and NaBr, depending on the alkali introduction stage. Unlike NaF, which can degrade absorber properties when introduced after the second stage, NaBr proved more effective in this configuration, leading to enhanced power conversion efficiency (PCE) through improvements in open-circuit voltage (Voc) and fill factor (FF). This study underscores the potential of NaBr as a promising alternative to NaF for optimized CIGS growth. To go further, detailed insights into the impact of these treatments on the morphological properties, compositional evolution within the absorber bulk, and their influence on cell properties and performance will be discussed, utilizing characterization techniques such as SEM, GD-OES, Raman spectroscopy, XRD, and photoluminescence (PL).

The quaternary chalcogenides, such as Cu₂ZnSn(S/Se)₄ (CZTS) and CuInGa(S/Se)₂ (CIGS), have already been extensively explored as a stable alternative to the highly efficient lead halide perovskites, which degrade under ambient conditions. Here, we focus on the synthetically simpler, non-toxic ternary analogue, Cu₂SnS₃ (CTS), which is an impure phase of CZTS. This p-type low-bandgap material has a broad absorption range covering the visible to near-infrared (NIR) with a high absorption coefficient, making it a good photoabsorber material. Beyond its use in photovoltaic cells, we have studied its solar light-to-heat generation ability. We experimentally found that the as-synthesized CTS nanocrystals coated quartz substrate (2 × 2 cm²) shows a temperature rise of 8.4 ˚C compared to the bare quartz substrate within ten minutes of solar illumination (1 Sun; 100 mW/cm²).

The origin of this heat generation is not due to copper vacancies, as confirmed by the absence of the plasmonic peak in the absorption spectrum. Rather, the crystalline defects are responsible for the photothermal behavior. The crystalline defects are identified using a high-resolution transmission electron microscope, causing the trap states within the bandgap.¹ Further, the presence of trap states is validated through the transient absorption spectroscopy (TAS), which indicates that the trapped charge-carrier lifetime exceeds 7 ns. The presence of trap states and the absence of photoluminescence spectra of CTS sample suggest that the photoexcited charge carriers (electron-hole pair) recombined via a trap-assisted method ―a phenomenon known as Shockley-Read-Hall (SRH) recombination. This non-radiative relaxation is accompanied by lattice heating due to electron-phonon and phonon-phonon interactions.

The generated thermal energy is subsequently converted to electrical voltage through a commercially available thermoelectric device. The CTS solution-coated (on the solar-illuminated side) device shows an 85.7 mV higher voltage than the uncoated device, indicating an efficient use of CTS as a photothermal material to convert solar energy to electrical energy.² Our study also highlights the effect of surface passivating molecules on defect states, thereby affecting exciton recombination dynamics.

(1) Roy, A.; Chonamada, T. D.; Santra, P. K.; Defect-Induced Persistent Photocurrent in Cu₂SnS₃ Nanocrystals: Insights from High Resolution Transmission Electron Microscopic and Surface Passivation. ChemPhysChem 2025, 26, e202500420. https://doi.org/10.1002/cphc.202500420

(2) Roy, A.; Singh R.; Santra, P. K.; Sapra S.; Defect State Engineering of Cu₂SnS₃ Nanocrystals for Solar-Thermal-Electrical Conversion Application. (Under preparation)

Fourth component alloy adsorber films of CuInGaSe (CIGS) are used widely now due to high efficiency (about 23.6%), which can be obtained on CIGS solar cells. Usually, fabrication of CIGS films demands employment of enough complicated equipment, and deposition temperature is about 550°C. In this work we propose a method of the high quality CIGS absorber fabrication in magnetron sputtering equipment using granulated CIGS target and temperature of substrate not more than 300°C. The CIGS absorber layer was deposited onto both glass and Ni/Mo flexible substrates using unordinary regime of RF (13.56 MHz) magnetron sputtering technique so named “pulsating arc mode” due to the increase in discharge current significantly higher than the glow discharge current values in the magnetron sputtering system. In this case the target surface is heated to the melting temperature of the material, which in turn increases the emission currents in the discharge gap and causes a significant increase in the discharge power. This mode of the generator leads to an increase in the current load above the limit, so the system automatically reduces power to the preset values. Then the process is repeated.

SEM and EDS have shown well-formed CIGS layer granular structure with average grain sizes of 300-500 nm, while the elemental composition of material was found to be: Cu – 21.3%, In – 21.2%, Ga – 7%, Se – 50.5%, that is Ga/(Ga+In) = 25% and Cu/(Ga+In) = 76%, that indicates a slight deficiency of Ga and Cu in the film. Spectra of X-ray diffraction (XRD) in 2Ɵ regime show the major diffraction peaks corresponding to CIGS chalcopyrite phase with composition Cu(In0.70Ga0.30)Se2, where a preferred orientations are (112), (220) and (312) at 2θ = 26.9°, 44.6° and 52.9°, and narrow half-widths of the peaks are very similar to material fabricated at 550°C, which has a good crystallinity and photo response. Micro-Raman spectroscopy demonstrated that our CIGS material is Cu poor in which observed formation of Cu-poor Cu-In-Se ordered vacancy compound (OVC) phases. Presence of these phases in the surface region of the CIGS absorbers is assumed to be beneficial for the characteristics of the solar cells.

The CIGS films deposited on glass in optimal regime show electrical resistance about 1.6×102 Ohm×cm and good photoresponse in photoconductance regime (changing of photocurrent up to 150% on level of dark current about 7×10-8 A). Estimation of optical band gap from spectral dependency of photoconductivity gives us value about 1.2 eV. Thus, the fabricated CIGS films are suitable for fabrication effective solar cells.

            The work was supported partially by the Program Science for Peace and Security (NATO project SPS G5853).

In the pursuit of commercialising CZTSSe solar cells, it is widely recognised that the choice of substrate plays a crucial role, strongly influencing the final photoconversion efficiency. Despite this, the majority of studies still rely on in-house sputtered molybdenum-coated glass, which, while convenient for laboratory-scale investigations, does not fully reflect the characteristics and constraints of industrial standards.

In this work, we present a systematic comparative study focused on evaluating the differences between laboratory-sputtered molybdenum with different process parameters and commercially available Mo/glass substrates. We investigate how the efficiency of CZTSSe solar cells is affected when fabricated on sputtered molybdenum deposited at two different temperatures (200 °C and 400 °C), and on commercial molybdenum/glass substrates. Special attention is devoted to correlating substrate properties with device performance. The microstructure and morphology of both the substrates and the absorbers were analysed by X-ray diffraction and atomic force microscopy, revealing that the nature of the molybdenum back contact has a significant impact on absorber crystallisation and, consequently, on photovoltaic efficiency.

The selenization temperature was fixed at 580 °C, while the partial pressure of inert Ar gas was varied to assess its influence on absorber morphology and composition, as well as on the thickness of the interfacial MoSe₂ layer. The chemical composition and phase purity were evaluated using Raman Spectroscopy and X-ray Photoelectron Spectroscopy, whereas the depth distribution of MoSe₂ was determined by Secondary Ion Mass Spectrometry. The results clearly demonstrate that intrinsic differences in the microstructure and mechanical stability of sputtered versus commercial molybdenum back contacts strongly affect absorber crystallisation and MoSe₂ formation. Notably, the commercial Mo/glass substrates show a higher tolerance to increased selenisation partial pressures, effectively suppressing excessive MoSe₂ growth and preventing absorber delamination under conditions that lead to the failure of in-house sputtered counterparts.

In conclusion, this comparative analysis shows that the tune of molybdenum substrates enables more aggressive and extended selenisation conditions that are incompatible with laboratory-deposited molybdenum films, thereby opening pathways for further optimisation of absorber quality and device efficiency.

Today’s PV research, in addition to the development of traditional roof-mounted photovoltaic panels, also focuses on devices specifically designed for new applications, such as cells integrated into building elements, vehicles, and Internet of Things devices. Thin-film solar cells are particularly suitable for these applications, as they can be deposited on various substrates, including flexible ones, using different deposition techniques still at low production costs. Among them, Sb2Se3 has recently attracted attention for its peculiar properties, especially its quasi-one-dimensional structure, which could attenuate charge recombination through anisotropic charge transport. In slightly more than 10 years, Sb2Se3 solar cells have achieved an efficiency of 10.57 % [1]. The two main challenges with this material appear to be controlling the stoichiometry, since selenium is volatile, and the Sb2Se3 design with the ribbons’ orientation perpendicular to the substrate. It is therefore essential to understand how the deposition method and its parameters influence the absorber's properties to improve solar cell efficiency.

In our laboratory, we fabricate Sb2Se3 devices in superstrate configuration. Typically, we deposit the absorber by vacuum evaporation (VE) on a CdS or CdSe buffer layer, maintaining a low substrate temperature at around 300 °C, and achieving a conversion efficiency of about 4 % [2].

Recently, we implemented a vapour-transport deposition (VTD) of Sb2Se3 using a three-zone tubular furnace, which is connected on one side to a vacuum pumping system and on the other to an argon inlet system with a flowmeter. This method, unlike the other one (VE), allows to change the pressure and the argon flux during deposition, at substrate temperatures well above 300 °C without re-evaporation, and easily adjusting the evaporation temperature.

The morphology and structure of Sb2Se3 thin films deposited from the same starting material using the two different techniques have been analysed and compared by AFM, XRD, and Raman spectroscopy. Exhibiting a much larger grain size and more compact morphology in favour of the VTD case. Also, ribbons’ orientation has shown to be affected by the fabrication process. Moreover, devices fabricated with the same structure using the differently deposited Sb2Se3 absorbers have been electrically characterized by current-voltage, capacitance-voltage and drive-level capacitance profiling measurements. This comparison of samples fabricated in the same laboratory using different Sb2Se3 deposition techniques helps to clarify the advantages and disadvantages of the deposition methods and their influence on absorber and device performance.

[1]          Y. Zhao, et. al, Energy Environ. Sci. 15 (2022). https://doi.org/10.1039/d2ee02261c.

[2]          N. Torabi, et. Al, Solar Energy 264 (2023). https://doi.org/10.1016/j.solener.2023.111990.

CdTe is not only a simple binary alloy material but especially it has an extremely simple phase diagram that allows to fabricate thin films by a large variety of methods. Now, CdTe is the thin-film technology that sees the larger industrialization, with very good stability and very promising efficiencies (over 23%).
For this reason, a very interesting application is to pair this technology with crystalline silicon solar cells which has a very high reliability and high efficiency. A tandem CdTe-Si solar cell is possible if the typical CdTe structure is redesigned, and an optimization of the band gap value is studied.
In this work we have pursued the preparation of CdTe solar cells designed for working as a upfront cell in the CdTe/Si tandem device. In particular: 1) the thickness of the cell has been brought to less than 1 micrometer by tuning the CdSeTe/CdTe junction and allowing an increased transmission of the light up to 1.5 eV; 2) a transparent back contact has been designed by depositing a simple transparent conductive oxide (namely ITO) to deliver a transparent layer in the range mentioned above and allow the light to reach the bottom cell.
Preliminary results have shown an efficiency of 12.8% (Voc=762 mV, Jsc= 24 mA/cm2 and F.F.= 69%) for an absorber thickness of 800nm. When a transparent conductive oxide is applied as back contact -but with an absorber thickness of 2 mm- the delivered conversion efficiency goes to around 10% (Voc=720 mV, Jsc= 23 mA/cm2 and F.F.= 60%), main drop is on the fill factor which reveals still a missing  optimization of the back contact at this stage of the work. The cell, in this configuration, is bifacial with an overall efficiency of 2.3% in back illumination, this is particularly limited by the absorber thickness. A finished 4T tandem device will be presented and their performance will be analysed.

Kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells are promising sustainable photovoltaics, but their PCEs are limited by intrinsic defects and cation disorder. While Ag/Ge/Cd alloying can help, these elements are costly, scarce, or environmentally undesirable. Here, we systematically compare light (Li) and heavy (K, Rb, Cs) alkali incorporation in CZTSSe absorbers made by a simple in-situ aqueous spray process. Optimized alkali addition suppresses defect-assisted recombination, improving bot VOC​ and FF. Li is effective at low concentrations, whereas heavier alkalis require higher loadings; Cs is detrimental due to SnSe₂ formation. Without Ag co-alloying, the best devices reach 11.84% PCE for K- and Rb-alloyed cells. Defect analyses show reduced trap energies (lowest for K) and defect densities (lowest for Rb), consistent with stronger PL, longer lifetimes, lower Urbach energies, and weaker potential fluctuations. On Mo/glass, performance follows K > Rb > Li > Na > Cs, reflecting the combined roles of intentional alkali doping and Na diffusion from the substrate. Notably, Na+K and Na+Rb co-alloying further boosts PCE to above 13%, which will be discussed in detail.

Solar energy harvesting is well developed and contributes greatly to the global production of green energy. However, rigid solar panels – which are by far the most used type – are typically mounted on buildings (including rooftops and facades) or in fields. Going to lightweight and flexible modules opens room for new fields of application, where weight and mechanical flexibility are more critical than high photon conversion efficiency, such as wearables, space application or different Building Integrated Photovoltaic (BIPV) applications. Thin films photovoltaics, such as chalcogenides, are very attractive for such purposes compared to other technologies.
In this work, we aim at developing high efficiency lightweight and mechanically flexible Copper Indium Gallium Sulfide Selenide (CIGSSe) photovoltaic mini-modules of at least 50 cm² active area. In addition, optimization of the absorber growth conditions on a new kind of substrate is required. Using AVANCIS’ standard growth method – stacked elemental precursors followed by Rapid Thermal Processing (RTP) – various bendable substrates were investigated, specifically stainless-steel foils (40 to 100 μm thick) and Titanium foils (10 to 250 μm thick). Keeping the same precursors composition, the temperature of the RTP was reduced by 30% compared to AVANCIS’ standard CIGSSe process.
On all but one substrate type, closed and continuous CIGSSe films of reasonable quality – assessed via Raman spectroscopy – could be obtained. It has been demonstrated that films grown on flexible metallic substrates, using such reduced RTP temperatures, can achieve similar elemental distribution profiles (measured by Glow Discharge Optical Emission Spectroscopy – GDOES) as films grown applying the standard process on 2.1 mm thick rigid glass. Nevertheless, strong reaction of the substrate itself – especially stainless steel – may occur during the RTP performed in a S-rich atmosphere, leading to substrate’s back side corrosion and/or (partial) delamination of the film.
Promising efficiencies were achieved at low RTP temperatures with 1.8 cm² cells: 9.7% and 7.4% on stainless steel foil and titanium foil, respectively. Moreover, the samples remain bendable after processing and don’t show significant performance losses after bending. We showed that the use of flexible substrates to form CIGS can significantly reduce the thermal budget cost while at the same time increasing the specific power (per weight (W/g) compared to similar absorbers grown on standard thick glass. In the best case, the RTP power consumption per process is reduced by one third, and the specific power is 10 times larger. These first results prove the potential of metallic foils as substrate for the development of high efficiency, flexible and lightweight CIGSSe modules.

   Selenium has reemerged as a promising absorber material for a range of energy harvesting applications due to its elemental simplicity, unique structural features, and exceptional optoelectronic properties. With a wide direct bandgap of 1.8-2.0 eV, selenium is an ideal candidate for indoor solar cells and as the top cell in tandem photovoltaic devices^[1]. Furthermore, research activity on selenium is accelerating, as evidenced by the rapidly increasing device efficiencies being reported^[2]. However, despite this renewed focus, the carrier properties of selenium remain poorly understood, limiting the realization of its full potential as a high-efficiency photovoltaic material.

   Here, we build on our fundamental understanding of both the majority and minority carriers by simultaneously mapping their properties using a high-sensitivity, variable-temperature photo-Hall system^[3]. The results are compared and integrated with those from other advanced characterization tools, including transient THz spectroscopy, capacitance-based techniques, and voltage-dependent quantum efficiency measurements. To systematically resolve the identified discrepancies, we construct semiconductor physics models that account for non-idealities at interfaces and surfaces, perform device simulations, and accurately reproduce experimental JV-curves and EQE-spectra. By providing a holistic view of carrier dynamics and non-idealities in state-of-the-art selenium thin films, we identify key performance limitations and delineate clear strategies for enhancing the efficiency of selenium solar cells.

[1] R. Nielsen, A. Crovetto, A. Assar, O. Hansen, I. Chorkendorff, P. C. K. Vesborg, Monolithic Selenium/Silicon Tandem Solar Cells, PRX Energy 3 (1), 013013 (2024)
[2] W. Lu, M. Feng, Z. Li, B. Yan, S. Wang, X. Wen, Z. An, S. Liu, J. Hu, D. Xue, Ordering one-dimensional chains enables efficient selenium photovoltaics, Joule 8 (5), 1430-1442 (2024)
[3] R. S. Nielsen, O. Gunawan, T. Todorov, C. B. Møller, O. Hansen, P. C. K. Vesborg, Variable Temperature and Carrier-Resolved Photo-Hall Measurements of High-Performance Selenium Thin-Film Solar Cells, Phys. Rev. B 111, 165202 (2025)

The application of transparent back contacts (TBCs) in Copper Indium Gallium Selenide (CIGSe) solar cells is essential for the development of bifacial and tandem photovoltaic devices. However, replacing the conventional Molybdenum contact with Indium Tin Oxide (ITO) introduces complex morphologic and electronic modifications. A primary concern is the absence of an impassable barrier for majority carrier transport in experimental current-voltage (J−V) measurements. Contrary to theoretical expectations, no secondary, parasitic pn⁺-junction at the rear ITO/CIGSe interface is formed and holes in the CIGSe valence band are able to enter the ITO conduction band.

Additionally, elemental depth profiles of samples, applying substrate temperatures ≥550°C during CIGSe deposition reveal significant accumulation of gallium and oxygen at the back contact in Glow Discharge Optical Emission Spectroscopy. This suggests the potential formation of a gallium oxide interlayer, which has been reported in the literature by conducting microstructural analysis of the rear ITO/CIGSe interface. This layer is acting as an additional barrier for injection of majority charge carriers from the CIGSe into the ITO and vice versa.

Experimentally, admittance spectroscopy is our primary method to investigate transport processes at the back contact. For most of our CIGSe solar cells with an ITO back contact, a capacitance step – called W – is observed that exhibits only a weak temperature dependence of the characteristic frequency. Systematic variation of the thickness of intentionally incorporated gallium oxide or aluminum oxide interlayers between the CIGSe and ITO reveals a reduction in the characteristic frequency of this step with increasing insulating layer thickness.

In this work, we present a numerical simulation model, developed to resolve the transport phenomena at the rear interface. The model focuses on the extraction of holes from the CIGSe valence band via tunneling. To enables charge carriers to tunnel between the CIGSe valence band and the ITO conduction band (band-to-band or interband tunneling) requires an increased p-type doping density of 10¹⁹ cm^-3 in CIGSe near the gallium oxide interface. So, charge carriers are also effectively traversing gallium oxide layers with thicknesses of 1-5 nm. This approach allows the modelling of the weak temperature dependent of the W-step, found in our experimental admittance spectroscopy results.

Looking forward, our model facilitates a deeper understanding of transport processes between CIGSe and TBC. It further enables the identification of optimal parameters, such as rear-side doping profiles and gallium oxide thicknesses. These insights are crucial for enhancing carrier transport and increasing the efficiency of CIGSe solar cells with TBC.

The relentless pace of technological advancement, rapid population growth, climate change, and current geopolitical dynamics have driven an exponential increase in global energy demand in recent years. Thin‐film Cu(In,Ga)Se2 (CIGS) solar cells are among the key technologies capable of addressing these energetic and environmental challenges, particularly in the context of building‐integrated photovoltaics. Moreover, reducing the absorber thickness to the ultra‐thin regime can lower manufacturing time and cost, increase throughput, and minimize the consumption of critical raw materials.[1] However, the absorber thickness reduction leads to optical and electrical losses due to incomplete light absorption and enhanced rear‐interface recombination. Rear‐interface recombination has been mitigated through the implementation of Ga gradients and/or passivation layers, either in patterned architectures, where localized openings allow direct contact between the absorber and rear contact, or via full‐coverage layers, such as tunnel oxides used in c‐Si TOPCon technologies.[1,2] In CIGS based devices, rear passivation materials are typically dielectric and insulating, making the development of effective full‐coverage passivation layers particularly challenging, even considering an ultra‐thin tunnel oxide layer. In the latter case, charge transport is generally assumed to occur through tunnelling mechanisms or via pinholes and porous regions. [4] In this work, the implementation of a deliberately porous full SiOₓ rear passivation layer in ultra‐thin (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells was investigated and compared with that of patterned passivation layers (≈70% passivated area) and a non-passivated reference. With a complete and intact passivation layer after deposition of a 700 nm ACIGS absorber, the full‐coverage passivated device achieved the highest conversion efficiency, with a 2% absolute increase reaching 16.4%. Patterned passivation devices also improved performance, albeit to a lower extent. A detailed analysis based on the one‐diode model reveals an increase in shunt resistance for all passivated samples, most notably for the full‐coverage passivation device. While patterned passivation also led to an increase in series resistance, the full‐coverage passivation resulted in a reduction. STEM‐EDS and SEM top‐view analyses after peel‐off indicate a uniform Se distribution beneath the full 8 nm SiOx passivation layer which is an indication of the formation of MoSe2, likely enabled by Na and/or Se interdiffusion through the porous passivation layer. In conclusion, the near‐complete rear passivation significantly reduced harmful interface defect density that coupled with the randomly distributed MoSe2 layer at the Mo interface forming an ohmic-type contact, is believed to be responsible for the superior device performance.

Thin-film tin monosulfide (SnS) is a promising, low-cost binary chalcogenide material for solar cell applications. Its suitability as an absorber material stems from its earth-abundant constituent elements (Sn, S), an ideal direct bandgap (~1.3 eV) and a high absorption coefficient (>10⁴ cm⁻¹). In this study, we utilize zinc tin oxide (ZTO) and molybdenum oxide (MoOₓ) as the electron transport layer (ETL) and hole transport layer (HTL), respectively, within a heterostructure where SnS serves as the absorber. Zinc Tin Oxide (ZTO) thin films were deposited via spin coating on glass substrates at room temperature. Optical characterization revealed high transparency (>80%) in the visible spectral range, with an optical bandgap varying between 3.3 and 3.7 eV. Depending on the material composition, the ZTO work function ranged from 4.3 to 5.0 eV. Molybdenum Oxide (MoOx) was deposited using RF reactive magnetron sputtering from a MoO₃ target, exhibiting an optical bandgap of 2.6–2.9 eV and a work function between 5.32 and 5.67 eV, sensitive to deposition conditions. The fabricated heterostructure followed an ITO/ZTO/SnS/MoOx/Ag architecture. Photovoltaic performance was evaluated through current-voltage (J-V) measurements, yielding an open-circuit voltage (Voc) exceeding 280 mV at standard illumination.

Sb₂Se₃-based thin-film solar cells are currently at an early stage of technological development, where many fundamental material properties and device-related phenomena remain poorly understood. At this stage, as with any emerging photovoltaic technology, identifying the nature of electrically active defects, determining their parameters, and understanding their impact on device performance are crucial.

In this work, defect states in polycrystalline Sb₂Se₃ thin-film solar cells are investigated using admittance spectroscopy, deep-level transient spectroscopy (DLTS), and drive-level capacitance profiling (DLCP). Complementary measurements were also performed on single-crystalline Sb₂Se₃ samples to assess and minimize the influence of grain boundaries. The objective of the study is to identify dominant defect levels, determine their activation energies and associated charge carriers, estimate their concentrations, and distinguish between bulk- and interface-related defects.

Admittance spectroscopy and DLTS measurements reveal three distinct defect-related signals with activation energies in the range of 0.25 - 0.4 eV. Analysis of the DLTS signal polarity indicates the presence of two minority-carrier traps (holes in the investigated devices) and one majority-carrier trap (electrons). DLCP measurements were performed to determine the doping levels in the investigated samples. The extracted doping profiles are non-uniform and vary between devices; however, the overall doping concentration is estimated to be on the order of 10¹⁷ cm⁻³. Based on this information, defect concentrations were estimated from the DLTS peak amplitudes and found to be approximately 10¹⁵ cm⁻³ for the dominant acceptor-like defect and in the range of (1-5) × 10¹⁴ cm⁻³ for the remaining two defect signals. In the investigated samples, one defect signal is clearly dominant, with an amplitude several times larger than that of the remaining two. This defect corresponds to a minority-carrier trap observable at and above room temperature. Its emission time constants and activation energy show a pronounced dependence on the applied bias, suggesting a non-bulk origin, likely associated with an interface or extended defects such as grain boundaries. A second minority-carrier trap exhibits a well-defined activation energy of approximately 270 meV that remains independent of bias, consistent with a bulk acceptor-type defect. The third signal, related to majority carriers, appears to be a superposition of two overlapping traps, complicating its interpretation.

These results provide insight into the defect landscape and doping levels in Sb₂Se₃ thin-film solar cells and contribute to understanding defect-related limitations in this emerging photovoltaic technology.

Thin-film tandem solar cells have emerged as a primary focus of photovoltaic research due to their potential to surpass the Shockley-Queisser limit associated with conventional single-junction devices. Currently, wide-bandgap perovskite solar cells are the preferred choice for top-cell applications, while crystalline Si or Cu(In,Ga)Se₂ (CIGSe) typically serve as the bottom-cell absorbers. CIGSe is of particular interest because its bandgap can be tuned to ≈1.00 eV, aligning with the theoretical optimum for tandem configurations with a top cell with a bandgap of 1.60 eV.

High-performance CIGSe absorbers are conventionally synthesized via high-temperature processes (530–600 °C) on soda-lime glass to ensure the formation of a high-quality chalcopyrite crystal structure. However, reducing the deposition temperature is critical for the integration of low-melting-point flexible substrates. To facilitate efficient low-temperature growth, Ag is incorporated into the lattice to form ((Ag,Cu)(In,Ga)Se_2​) ACIGSe.

Furthermore, the optoelectronic properties of state-of-the-art CIGSe devices are typically optimized via alkali post-deposition treatments (PDT). These treatments enhance the V_OC​ and FF through improved grain boundary passivation and carrier dynamics.

This study evaluates the impact of reduced substrate temperatures on the growth of low-bandgap CIGSe absorbers utilizing a thin Ag precursor layer within a three-stage co-evaporation process. Additionally, the effects of RbF-PDT on these absorbers were examined.

The experimental results demonstrate that, Ag incorporation improves the grain morphology of the CIGSe absorbers. Additionally, an enhanced diffusion and intermixing of In and Ga led to a widening of the optical bandgap. Furthermore, lowering the deposition temperature induced compositional segregation within the absorber layer. This inhomogeneity resulted in the formation of electronic transport barriers, significantly degrading device performance. However, the application of RbF-PDT to the low-temperature grown absorbers yielded a substantial recovery in device performance.

These findings confirm that alkali treatments, specifically RbF-PDT, are compatible with Ag-alloyed CIGSe and are essential for mitigating the electronic defects associated with low-temperature processing. This provides a viable pathway for high-efficiency flexible tandem photovoltaics.

Kesterite-type (Cu,Ag)₂ZnSnS₄ thin films were synthesized by aqueous electrodeposition followed by post-deposition sulfurization, with the aim of developing low-cost and earth-abundant chalcogenide absorber layers for thin-film solar cell applications. Electrodeposition was performed in a three-electrode configuration using an aqueous electrolyte containing Zn and Sn precursors and appropriate complexing agents, while the relative Cu and Ag contents were controlled by adjusting the Cu/Ag ratio in the deposition bath. The Ag substitution levels were set to 0, 25, 50, and 100%, corresponding to compositions ranging from CZTS to AZTS. All depositions were performed at a fixed cathodic potential of −1.15 V vs Ag/AgCl on FTO-coated glass substrates. Post-deposition sulfurization was carried out at 550 °C in a tubular furnace using elemental sulfur placed inside a graphite box. The influence of Ag substitution on film composition, morphology, and phase formation was investigated using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). XRD and Raman analyses confirmed the formation of the kesterite phase, with a progressive shift of the main diffraction and vibrational peaks from CZTS toward AZTS, indicating partial to full substitution of Cu by Ag. SEM observations revealed the influence of the graphite box on grain growth and film crystallinity. EDS analysis showed consistent elemental compositions across the samples, with systematic variations in the Ag/Cu ratio in agreement with the intended substitution levels. These results demonstrate the feasibility of Ag alloying in electrodeposited kesterite absorbers and highlight the critical importance of electrolyte design and process control in achieving homogeneous (Cu,Ag)₂ZnSnS₄ thin films suitable for photovoltaic applications.

The binary chalcogenide material antimony sulfide (Sb₂S₃) has attracted significant attention as a promising absorber for thin-film photovoltaics. In this study, FTO/TiO₂/Sb₂S₃/P3HT/Au heterostructure were fabricated. Sb₂S₃ thin-film were deposited using the spin-coating chemical deposition method, with the number of deposited layers varied from 1 to 3 to investigate their influence on structural and electrical performance. X-ray diffraction (XRD) analysis revealed that increasing the number of layers leads to higher peak intensities, indicating improved crystallinity. Subsequently, a seed layer was introduced to enhance film growth, and its effect was studied again with 1–3 layers. The presence of the seed layer promoted enhanced nucleation, improved surface uniformity, and sharper, more intense diffraction peaks, confirming an overall improvement in the thin-film quality. The electrical performance of the devices was studied under both dark and illuminated (light) I–V conditions. In dark measurements, the series resistance (Rs) decreased with increasing number of layers for both devices with and without a seed layer, attributed to improved film continuity and reduced defects. Conversely, under illumination, Rs increased with the number of layers, likely due to longer transport pathways and higher recombination of photo-generated carriers in thicker films. The shunt resistance (RSh) was significantly higher for seed-layer devices (up to 2.797 × 10⁷ Ω·cm²), reflecting reduced leakage pathways and improved junction quality.In terms of device efficiency, the single-layer device without a seed layer achieved the highest efficiency (~3%), while the single-layer device with a seed layer showed slightly lower efficiency (~2.01%), indicating a trade-off between enhanced junction quality and increased series resistance under illumination.

Authors acknowledge the M-ERA.NET Ligthcell project “Quasi-1D materials for advanced thin-film photovoltaics”, the UEFISCDI PN-IV-PCB-RO-MD “Engineering Sustainable Antimony Chalcogenide Alloys for Customized Power Thin Film Photovoltaics” and the COST Action Research and International Networking project “Emerging Inorganic Chalcogenides for Photovoltaics (RENEW-PV),” CA21148, supported by COST (European Cooperation in Science and Technology).

Over the years, luminescence spectroscopy has become one of the fundamental methods for analyzing the photophysical properties of a wide variety of samples, ranging from organic molecules to semiconductor materials and photovoltaic (PV) devices. It should be emphasized that detection sensitivity is a key parameter to meet today's requirements for handling weakly luminescent samples and for short measurement times in the optical evaluation of PV devices. The introduction of single-photon counting based data acquisition has proven to provide a significant increase in sensitivity and a very high dynamic range – it is the ideal method for measuring weak photoluminescence (PL).

The commonly used steady-state luminescence spectroscopy methods provide valuable insight into the photophysics of a sample. However, such results offer only a partial picture of the sample’s behavior after photoexcitation. Another piece of the puzzle is often revealed by performing time-resolved PL spectroscopy, which provides deeper insights into the photophysical processes occurring in the sample under investigation. An even more comprehensive picture is gained by incorporating spatial information. Acquiring time-resolved spectroscopic data at regions of interest (ROI) in the sample can help to infer structural-to-photophysical relationships in PV materials. Gathering such information is an important step towards optimizing the structure as well as the preparation process of such materials in order to increase the performance of PV devices.

Herein, we will demonstrate that the combination of time-resolved microscopy and PL spectroscopy provides a powerful tool for the characterization and analysis of various PV materials, providing spectral, spatial and temporal information on semiconductor samples studied by PL emission. This combination allows the mapping of a broad range of phenomena including time-resolved PL, carrier diffusion, wavelength and power dependent emission with high spatial resolution. We will also discuss the advantages of the MicroTime 100 confocal photoluminescence lifetime microscope combined with the FlexLambda software-controlled wavelength selection unit for time-resolved imaging of very weakly emitting PV materials such as perovskites up to 1000 nm.

Cu(In,Ga)S2 (CIGS) according to its high band gap (1.6 eV) is considered to be used as « top cell » absorber in tandem architecture, the « bottom cell » being the mature Si solar technology. This new monolithic two-terminal (2T) Si/CIGS tandem solar cell architecture induces a dramatic increase of the number of interfaces, which all play a crucial role. In fact, these interfaces can be a source of new losses through non-radiative recombination of electrons and holes via interface defects, or through problems of alignment of energy bands on either side of interfaces. It is therefore vital to be able to characterize these interfaces and understand their physical characteristics, so that they can be optimized to increase energy conversion efficiency.

Tin-doped indium oxide (ITO), an n-type semiconductor combining high electrical conductivity and optical transparency in the visible range [1], is widely employed as a recombination layer in 2T Si/CIGS tandem solar cell architecture. However, the high-temperature (580 °C) and long-duration (~1 h) CIGS co-evaporation process can lead to degradation of both the interlayer and the sub-cell performance. During growth, gallium diffusion from the CIGS layer may result in the formation of a gallium oxide interfacial layer [2]. Close to the back contact, gallium depletion of the absorber may induce conduction band bending, which is detrimental to device performance as it enhances recombination losses of photogenerated charge carriers.

A detailed investigation of the CIGS region near the ITO transparent back contact, as well as of the complex CIGS/GaOₓ/ITO interface, is therefore required. In this work, 700 nm-thick CuIn0.9Ga0.1S2 absorbers were grown by co-evaporation at 580 °C using a 3-stage process. The back contact used is composed of a 100nm thick DC sputtered ITO back the SOLEMS company on top of a 1.1µm thick soda lime glass substrate. X-ray photoelectron spectroscopy was employed to probe the chemical and electronic properties of the buried interface. Two complementary approaches were implemented: (i) mechanical delamination of the co-evaporated CIGS layer from the ITO substrate to directly access the interface, and (ii) ion-beam etching combined with depth-resolved XPS profiling across the CIGS/ITO stack.

These investigations aim to provide a comprehensive understanding of the chemical composition and electronic band structure of complex CIGS-based interfaces, including band alignment and interface-induced band bending. This interface investigation constitutes a key step toward the realization of high-efficiency monolithic two-terminal Si/CIGS tandem solar cells.

[1]       A.H. Sofi, M.A. Shah, K. Asokan, J. Electron. Mater. 47 (2018) 1344–1352.

[2]       T. Nakada, Thin Solid Films 480–481 (2005) 419–425.

Cu(In,Ga)Se₂ (CIGS) solar cells have been extensively studied as promising thin-film photovoltaic devices owing to their high absorption coefficient, bandgap tunability, and suitability for lightweight and flexible applications. Compared with Si solar cells, CIGS enables absorber layers only a few micrometers thick. Owing to these advantages, CIGS has become one of the most mature thin-film photovoltaic technologies.

For conventional CIGS solar cells fabricated on glass substrates, the highest conversion efficiency has been achieved at a bandgap energy (E_g) of approximately 1.15 eV [1]. However, theoretical calculations indicate that the optimum Eg for single-junction solar cells lies between 1.4 and 1.5 eV [2]. In practice, increasing the Ga content to widen the bandgap often leads to efficiency degradation, mainly due to grain refinement, which deteriorates crystallinity and enhances carrier recombination at grain boundaries. Therefore, novel crystallization processes for wide-bandgap CIGS on low-cost amorphous substrates are strongly desired.

We have previously demonstrated that large-grained polycrystalline Ge layers with grain sizes exceeding 100 µm can be formed on glass substrates via Al-induced layer exchange (ALILE) [3–5]. In this study, we focus on the close lattice match between wide-bandgap CIGS (E_g = 1.4 eV) and Ge, and investigate the growth of large-grained CIGS thin films on glass substrates using ALILE-Ge layers as epitaxial seed layers.

The ALILE-Ge seed layers were fabricated by sequential deposition of Al and amorphous Ge on soda-lime glass substrates, followed by annealing at 350 °C to induce layer-exchange crystallization. After removal of the Al layer, the resulting Ge films exhibited strong (111) orientation and grain sizes exceeding 100 µm.

Subsequently, wide-bandgap CIGS absorber layers were deposited on the ALILE-Ge seed layers using a three-stage co-evaporation process. Electron backscatter diffraction analysis revealed that the CIGS layers inherited the (111) orientation from the Ge seed layers and exhibited significantly enlarged grain sizes compared with conventional CIGS layers grown directly on glass substrates.

In this presentation, we report the fabrication and photovoltaic characterization of CIGS solar cells employing ALILE-Ge seed layers and discuss the influence of grain enlargement on carrier transport and recombination properties. This approach provides a promising pathway toward high-efficiency wide-bandgap CIGS solar cells on low-cost glass substrates.

[1] J. Keller et al., Nat. Energy 9, 467 (2024).

[2] W. Shockley, and H. J. Queisser, J. Appl. Phys. 32, 510 (1961).

[3] K. Toko et al., J. Phys. D. Appl. Phys. 53, 373002 (2020).

[4] T. Nishida et al., APL. 114, 142103 (2019).

[5] T. Nishida et al., Sci. Rep. 11, 10159 (2021).

Numerical simulation is a very important tool to realize effective thin film solar cells. This work presents an investigation on the modelled solar cell Mo/CZTS/AZTS/NZTS with SCAPS-1D software. Starting initial simulations with four CZTS samples R200, R250, PCR200 and PCR250 grown by thermal evaporation technique in vacuum from calcined and non-calcined powder and annealed in 200°C and 250°C temperatures, we have found that PCR250 (d=550 nm, Eg=1.42 eV) led to the best device performances with an efficiency η of 14.49 %. Then we tried to find the ideal thickness and band gap energy of the absorber, buffer layer and window layer CZTS, AZTS and NZTS respectively. This resulted to an overall optimised solar cell with the best photovoltaic outcome η=22,28%, a fill factor FF=70,07%, a short-current density Jsc=31,15 mA/cm2 and an open circuit voltage Voc =1,02V.

Sb₂S₃ is an earth-abundant, low-toxic new absorber with potential indoor photovoltaics (IPV) application due to a wide band gap of ≈1.7 eV better matched to indoor illumination conditions. This study focuses on the impact of growth conditions on the Sb₂S₃ absorber layer and device performance, utilising a close-space sublimation process (CSS). CSS is known for its scalability and the ability to produce high-quality thin films for photovoltaic applications. The work specifically investigates the impact of introducing a growth templating layer at the front interface as a route to improve Sb₂S₃ quality and device performance parameters. ZnO was used as a seed layer on TiO₂ electron transport layer, both being grown using the magnetron co-sputtering method. Device-level analysis, including J-V and EQE measurements, was supported by structural analysis of the grown films using XRD and SEM. The results will explain the importance of CSS growth conditions in conjunction with the templating layer to alter film quality and device performance.

Cu(In,Ga)Se₂ (CIGS) solar cells represent a mature technology among second-generation photovoltaic devices, with a record efficiency of 23.6 %. Highest performance has been achieved using CIGS films with thicknesses of 2 to 3 µm. Reducing the absorber thickness offers opportunities to lower material usage and enables the development of semi-transparent solar cells. In this study, we explored the use of a one-step deposition method to fabricate CIGS films of varying deposition time. This approach consists of simultaneously sputtering a Cu-In-Ga target and evaporating Se using an effusion cell located in the sputtering chamber. Electrical characterization of the devices showed that the efficiency and fill factor increase with thickness up to 1 µm and then decrease for larger thicknesses. The chemical composition of the films, measured by energy-dispersive X-ray spectroscopy, was found to vary with changes in CIGS thickness. In particular, lower [Cu]/([Ga]+[In]) (CGI) and [Ga]/([Ga]+[In]) (GGI) ratios were observed for thicknesses greater than 1 µm. X-ray diffractograms exhibited a broadened (112) peak for a 2.6 µm thick film. Raman spectra corroborate the EDX and XRD results, showing the formation of an ordered vacancy compound (OVC) in the 1.6 µm thick CIGS layer, with the OVC peak becoming more pronounced at 2.6 µm. The results indicate that longer processing times increase the In content in the absorber layer, leading to lower device performance.

Cadmium Sulfide (CdS) is a semiconductor with significant applications in optoelectronic devices. This study investigates the vibrational properties and Raman spectra of CdS in the hexagonal (wurtzite) phase, in both resonant and nonresonant conditions, using density functional perturbation theory (DFPT) with local density approximation (LDA) and generalized gradient approximation (GGA) functionals. Our results identify the fundamental features of resonant and nonresonant Raman vibrational modes and their intensities. We highlight the importance of symmetry group analysis in determining the Raman or IR active modes and demonstrate the ability of Raman spectra to resolve longitudinal and transversal vibrational modes in the wurtzite phase. A good agreement with experimental Raman spectra is observed, providing insights into the stability, phase identification, and potential applications. This study offers deeper insights into the stability and group symmetries of CdS, contributing to its potential use in various potential applications.

This work explores the new generation of photovoltaic cells based on chalcogenide perovskite materials. The performance of these cells depends on several factors, including the adopted architecture, the choice of material for the active layer, and the fabrication and preparation methods of the various constituent layers. The precursor used for preparing TiO2 electron transport layers (ETMs) significantly impacts the quality of the ETM and the performance of the cells. TiO2 electron transport layers are prepared using different precursors, including tetrabutyl titanate (TT) and titanium diisopropoxide bis (acetylacetonate) (TDB). TT is more suitable for producing high-quality TiO​​​​2. The presence of guanidinium (Gua) molecules at the interface between the active CuZnSnS4 layer and the molybdenum disulfide (MoS2) hole transport layer enhances the photovoltaic properties, particularly the open-circuit voltage (Voc), as well as the stability of the photovoltaic devices. An open-circuit voltage (Voc) of 1.08 V are achieved.

Semi-transparent PV allows windows to convert light energy to electricity, with greatest value coming when considering buildings that do not provide sufficient roof space to be powered using conventional PV. Cu(In,Ga)Se₂ (CIGS) based devices can be made semi-transparent by micropatterning devices to alternate between light transmitting window and energy absorbing PV on a scale that is smaller than the eye can resolve. This leads to a uniform reduction in the transmitted spectra, whilst still converting energy into electricity. Here, we compare, characterize and model the electrical performance of micropatterned CIGS devices on opaque Mo and transparent back contact (TBC) substrates, since the TBC affords a more comfortable visual appearance as compared to Mo.

Semi-transparent devices have been formed through patterning full CIGS device stacks on glass substrates (Mo/CIGS/CdS/i-ZnO/Al:ZnO) using laser ablation. The pattern consisted of thin stripes of device, separated by stripes where the device had been removed to leave just glass. Six devices were formed on Mo, all with 50 % device coverage, but with varying stripe widths from 50 to 500 micron. One additional device was fabricated with indium zirconium oxide IZrO as a TBC. Python was used to input repeated miniature solar cell circuits into LTSpice to build an equivalent circuit to model a stripe to help interpret the electrical characterization [1]. Ni/Al grid fingers were deposited through thermal evaporation on the stripes to minimize series resistance.

The performance of the micropatterned devices was lower than expected from considering the area removed by laser ablation. Gridless striped devices had active area efficiencies < 2.5% while the non-scribed reference device was at 11%. Investigations revealed that additional removal of CIGS beyond what was intended was observed at the edges of the stripes becoming significant as the widths of the stripes became smaller, reducing the active area. Structural damage was observed at the edge of the remaining absorber as shown by the broadening of Raman peaks. Simulations showed that for the 1.5 cm stripe length used, losses in short circuit current (Jsc) and fill factor (FF) were to be expected simply due to the lateral transport in the front Al:ZnO electrode.

Following the deposition of grid fingers along the length of the cell stripes the Jsc and FF increased leading to an active area efficiency of 5.3 %. The micropatterned device with IZrO back contact showed poor performance of 1 % even with a grid compared to a 3.6 % efficiency reference. Simulations showed this is due to poor lateral transport in the TBC and lower sheet resistances are required to make efficient devices. These modelling results suggest that there is need for an effective method of lateral transport in the TBC, such as series interconnects, to make this geometry feasible.

[1] Colour neutral semitransparent CIGS minimodule with micro stripes, Shital et al. WCPEC 8, Milan, 2022

Despite the stunning performance of lead-based perovskite materials as light absorbers in solar cells, the toxicity of lead is of concern warranting its replacement. The problem is exacerbated by the poor long-term stability of lead-based perovskites in ambient conditions. Thus, there is a pressing need to find lead-free, stable alternatives. Lead-free chalcogenide perovskites possess highly stable crystal structures and direct band gaps (1.5–2 eV) that are very suitable for solar cells(1). The main challenges for synthesizing chalcogenide perovskites are the complex processing routes and the high processing temperatures currently involved(2, 3). Here, we present a facile, moderate temperature, solid-state synthetic route for producing BaZrS₃ microcrystalline powders of high purity. UV–Vis spectroscopy and photoluminescence spectroscopy demonstrate the successful synthesis of the semiconducting material with a bandgap of 1.73 eV. X-Ray diffraction measurements and scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) show that a high purity product with very low oxide contamination (<5%) is obtained through this synthetic route while other routes typically have >20% unwanted oxide. Obtaining these high purities is crucial for achieving excellent optoelectronic properties suitable for their use in photovoltaic applications. On a broad note, this work opens the doors for facile synthesis of these highly versatile lead-free semiconducting materials for use in various optoelectronic applications beyond solar cells such as light emitting diodes and photodetectors(1).

References:

1.            K. V. Sopiha, C. Comparotto, J. A. Márquez, J. J. S. Scragg, Chalcogenide Perovskites: Tantalizing Prospects, Challenging Materials. Advanced Optical Materials 10, 2101704 (2021).

2.            C. Comparotto et al., Chalcogenide Perovskite BaZrS3: Thin Film Growth by Sputtering and Rapid Thermal Processing. ACS Applied Energy Materials 3, 2762-2770 (2020).

3.            S. Agarwal, J. W. Turnley, A. A. Pradhan, R. Agrawal, Moderate temperature sulfurization and selenization of highly stable metal oxides: an opportunity for chalcogenide perovskites. Journal of Materials Chemistry C 11, 15817-15823 (2023).

Cadmium Selenide (CdSe), a wide direct band gap semiconductor, is a suitable material for photovoltaic applications. Thin films containing CdSe nanoparticles are used in photosensitive multilayer structures. CdSe doped with Mg, In, La, Mn, Co, and Eu impurities demonstrates an increase in n- or p-type charge carriers concentration. An increase in fluorescence brightness and non-monotonic shift of the Fermi energy are observed in CdSe nanocrystals doped with Ag, which is associated with the material transition from n- to p-type. Cu impurity also contributes to this transition.

Сhemical synthesis of ultra-dispersed CdSe powders was carried out using three methods: hydrochemical, solvothermal and microwave. Morphology, structure and optical properties of CdSe nanopowders were investigated using X-ray diffraction and photoluminescence (PL) spectroscopy in the wavelength range from 500 nm to 750 nm. Analysis of the diffraction patterns using the Rietveld method and taking into account the scaling factor for each phase allowed a quantitative analysis of the nanopowders. The crystallite size was determined by the Williamson-Hall method modified to the Pseudo-Voight diffraction line profile function.

The minimum size of CdSe nanoparticles obtained by solvothermal method using cadmium acetate and PVA as a stabilizer is 8.7 nm for CdSe (hexagonal P63mc space group) and 6.9 nm for CdSe (cubic F-43m space group). The maximum concentration of 67.9%, of CdSe is obtained under synthesis with CdCl2 and PEG. The CdSe content in the final product increases with increasing synthesis duration. The optimal synthesis time is found to be 23-25 hours.

Optimal process parameters for preparation of nano-CdSe by solvothermal method with CdCl2, SeO2, NaOH, and PEG and doping them with transition metals (Cu, Co, Ni) and rare earth element (Er) during synthesis were established. The average size of nanocrystals in both hexagonal and cubic structural modifications is varied from 4.4 nm to 13 nm. The PL spectra at room temperature consist of broad bands in the wavelength range from 500 to 725 nm with numerous features and inflections indicating their complex structure. CdSe nanopowders doping with transition metal impurities (Cu, Co, Ni) and rare earth elements (Er) quenches PL intensity. It is found that transition metal impurities are highly effective quenchers of PL. At the same time, the PL intensity quench and its subsequent increase with increasing dopant content is observed for CdSe:Co nanoparticles.

Acknowledgement: Ministry of Education and Research of the Republic of Moldova, subprogram 011207

GaSe is a prominent representative of the class of layered AIII-BVI semiconductors with unique structural, optical, and electrical properties. GaSe crystals have been used for the preparation of optical radiation detectors in the visible and near infrared spectral regions. In this work, we report on the preparation of GaSe films with a vertically stacking wall-like structure and the study of their physical properties. GaSe thin films were prepared by CSS on mica substrates. During synthesis, the evaporator temperature was maintained at 700°C, while the substrate temperature was varied in the range of 450-600°C. X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), atomic force microscopy (AFM) and micro-Raman spectroscopy (632.8 nm laser excitation) techniques have been used for characterisation.

The wall-like structures uniformly distributed across the substrate surface with a height of 3-7 nm. The composition shows that the atomic ratio percentages of the elements present in the evaporation source material was found to be 50.87 % Ga and 49.13 % Se with Ga/Se ratio =1.035. The films prepared at a substrate temperature of 500°C exhibit stoichiometric composition. As the substrate temperature is increased to 600 °C, an increase in selenium concentration is observed.

The high-frequency (90-600 cm⁻¹) Raman spectra of GaSe single crystal contain peaks at 132.7, 208.2, 211.4, 251.1, and 306.6 cm−1 (close to known data for ε-GaSe polytype). It should be noted that the spectra of the investigated single crystals do not contain peaks characteristic of γ-GaSe and Ga₂Se₃. The spectra of the films contain a broad band at 220-280 cm⁻¹ with a pronounced doublet (243.0 and 250.0 cm⁻¹) and remain unchanged with increasing substrate temperature.

By use of AFM, the main statistical parameters characterizing the surfaces of the synthesized films, as well as their dependence on the substrate temperature, were determined. The root-mean-squared roughness, average roughness, ten point average roughness and kurtosis decrease with increasing substrate temperature, passing through a minimum at substrate temperature of 550 °С. For to study the fractal properties of the obtained GaSe films with wall-like structure the cube count method (СС), triangulation (T) method, variance (V) method, the autocorrelation function method, power spectrum density (PSD) method, height-height correlation function method were used. It should be noted that the fractal dimension values D_f, determined by different methods, differ quite significantly from one another, and their dependencies on substrate temperature sometimes even contradict each other. Thus, the D_f values calculated using the CC, T, and V methods increase with rising substrate temperature, reaching maximum values of 2.467, 2.257, and 2.377 at substrate temperature of 550°C.

Acknowledgement: Ministry of Education and Research of the Republic of Moldova, subprogram 011207

 HTI (Hemithioindigo) photochromic molecules and their derivatives exhibit reversible visible-light-induced photoisomerization between the E isomer (favored at 420nm) and the Z isomer (favored at 505nm). Functionalization of surfaces with these molecules enables controlled molecular switching and modulation of surface properties. By introducing phosphonic acid anchoring groups into HTI chromophores, stable self-assembled monolayers (HTI-SAMs) can be formed on Al₂O₃ surfaces, ensuring robust adsorption and suppressing undesired island formation. Visible-light irradiation induces reversible configurational changes in the surface-bound HTI molecules, leading to pronounced variations in dipole moment between the isomeric states and corresponding changes in surface potential. When integrated as a dielectric layer in field-effect transistors (FETs), these photo-switchable SAMs enable modulation of device capacitance in response to dipole moment changes, allowing precise and reversible control of electronic performance using visible light.

 The fundamental adsorption behavior of HTI-SAMs on Al₂O₃ surfaces was investigated using Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Reversible photo-switching at the surface was verified by surface potential measurements of the individual isomeric states using Kelvin probe force microscopy (KPFM). To overcome limitations in switching efficiency observed in pure HTI-SAM systems, binary SAMs architectures incorporating secondary molecules were developed, providing additional degrees of freedom and enhanced photo-switching performance. Detailed structural and adsorption properties of both pure and binary SAMs systems were analyzed using X-ray reflectivity (XRR), grazing-incidence X-ray diffraction (GIXD), and X-ray photoelectron spectroscopy (XPS), yielding insights into the z-profile and photoisomerization behavior of the surface-confined molecules. Finally, the optimized binary HTI-SAMs were implemented as dielectric layers in capacitors. This work demonstrates the integration of HTI-based photo-switches into optoelectronic architectures, highlighting their potential for reversible visible-light control in molecular electronics and smart surface technologies.

Thin gold film-based zero-reflection metasurfaces enable advanced optical functionalities, ranging from topologically controlled laser-like thermal emission to ultrasensitive biodetection. Although gold offers excellent optical properties and high chemical stability, its noble nature necessitates the use of an adhesion layer to ensure structural integrity. Nevertheless, mechanical stability is frequently overlooked in proof-of-concept studies, as adhesion layers are commonly avoided due to their detrimental impact on the zero-reflection condition and the associated optical response.

In this study, we investigate the impact of various adhesion layers on the plasmonic behavior of perfect absorber metasurfaces. Our experiments reveal that an optimal adhesion material should exhibit both metallic and oxide characteristics to minimize optical losses while ensuring mechanical stability. Within this framework, we identify aluminum (Al) as an ideal adhesion interface and experimentally demonstrate that an Al adhesion layer does not deteriorate the optical performance of the metasurface.

We further assess the effectiveness of the Al adhesion interface through ultrasensitive detection of protein monolayers, where the metasurfaces exhibit higher sensitivities than those employing conventional adhesion materials. In addition, the metasurfaces maintain their structural integrity under harsh operating conditions, including continuous water flow and sonication, without any observable delamination.

Overall, this work addresses a key technological limitation and provides a practical pathway for implementing zero-reflection metasurfaces in real-world applications.

Tin-based halide perovskites (THPs) have emerged as promising lead-free alternatives with suitable optoelectronic properties for p-type channels in thin-film transistors (TFTs). However, their limited crystallinity and high density of defect states often compromise conductivity and degrade device performance. Although quasi-two-dimensional (2D) perovskites offer superior environmental stability compared to their 3D counterparts, their intrinsically limited charge transport remains a critical bottleneck for high-performance electronic applications.

In this work, we report a robust surface p-doping strategy that leverages strong molecular-level interactions between a sulfur-containing polymer and quasi-2D tin (Sn) perovskites. The Sn–S interaction at the organic–inorganic interface induces efficient hole generation, thereby increasing the intrinsic carrier density and enabling significantly improved charge transport within the perovskite semiconductor channel. This interfacial doping mechanism yields a remarkable enhancement in device performance, achieving a field-effect mobility of 53.57 cm² V⁻¹ s⁻¹, representing a nearly 7.5-fold increase over the undoped control device (7.16 cm² V⁻¹ s⁻¹). Additionally, the doped devices exhibit an outstanding on/off current ratio exceeding 10⁷ and excellent operational stability. These findings demonstrate that targeted interfacial chemistry provides an effective and scalable route to overcoming transport limitations in low-dimensional perovskites, offering a promising pathway toward stable, high-mobility, and lead-free perovskite-based electronics.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention as potential materials for next-generation devices due to their atomic-scale thickness, tunable electronic characteristics, and suitability for flexible and low-power applications. Among various synthesis techniques, chemical vapor deposition (CVD) has been widely recognized as a scalable and effective method for producing large-area, uniform, and high-quality 2D TMD films. Recently, alkali metal halides have been reported to function as catalytic agents that promote the two-dimensional growth of MoS₂ during CVD processes. Na₂MoO₄ and Na₂Mo₂O₇ have been identified as important reaction intermediates, while the formation of Na₂SO₄ has been revealed as an additional reactive phase with distinct chemical behavior. In this study, the specific roles of Na₂Mo₂O₇ and Na₂SO₄ in the growth mechanism of MoS₂ are systematically investigated. The results indicate that Na₂Mo₂O₇ and Na₂SO₄ serve as the primary sources of Mo and S, respectively, and their combined presence critically influences nucleation dynamics and layer-number control. These effects, in turn, govern the lateral growth and surface coverage of MoS₂ films. This work provides deeper insight into the catalytic mechanisms underlying salt-assisted CVD and offers practical guidelines for the controlled synthesis of high-quality 2D MoS₂.

ZnO and TiO₂ are widely investigated semiconductor photocatalysts for the degradation of organic dyes in aqueous environments. Although TiO₂ is the most commonly used photocatalyst, ZnO has a comparable band gap and typically exhibits higher electron mobility and stronger light absorption, which can lead to enhanced photocatalytic activity. Furthermore, ZnO nanostructures such as nanorods provide larger specific surface areas and a higher density of active sites, thereby improving dye adsorption and reaction kinetics. However, ZnO is susceptible to photocorrosion under prolonged irradiation. To address this limitation, a novel surface modification strategy for ZnO nanorods is proposed in this study.

ZnO nanorods were synthesized on transparent conductive Al-doped ZnO (AZO) films deposited on glass substrates by radio-frequency magnetron sputtering, followed by chemical bath deposition using a mixed precursor solution of Zn(NO₃)₂·6H₂O and hexamethylenetetramine with a molar ratio of 2:1 at 95 °C for 5 h. Subsequently, anatase-phase TiO₂ and AZO thin films were individually coated onto the as-grown ZnO nanorods using the mist chemical vapor deposition (CVD) method. The photocatalytic performance was evaluated by photodegradation of methyl red aqueous solution under UV irradiation at a wavelength of 254 nm for 5 hours.

The results demonstrate that uniform anatase TiO₂ and AZO thin films were successfully coated on the ZnO nanorods. Compared with uncoated ZnO nanorods, both TiO₂- and AZO-coated ZnO nanorods exhibited enhanced photodegradation efficiency, highlighting the importance of surface modification in improving crystallinity and charge transfer behavior. In particular, TiO₂-coated ZnO nanorods with a 5-minute coating time showed the lowest absorption intensity and the most significant enhancement in photocatalytic performance.

Tantalum-based coatings are widely used in micro - and nanoelectronics due to their chemical stability, mechanical robustness, and tunable functional properties. Binary tantalum nitride (TaN) serves as a conductive diffusion barrier, while tantalum oxide (Ta2O5) provides high dielectric and optical performance. Ta2O5/TaN heterostructures combine these advantages, yet atomistic mechanisms governing oxygen diffusion across the interface remain poorly understood, particularly under thermal conditions relevant to device operation. Here, we investigate oxygen migration at an incoherent Ta2O5/TaN interface using large-scale molecular dynamics simulations with the MACE-MPA-0 machine-learning interatomic potential. A realistic slab was modeled, capturing the large lattice mismatch, interfacial disorder, and complex local bonding environments. Oxygen diffusion from Ta2O5 into TaN is simulated over 400–900 °C, and self-diffusion coefficients and activation energies are extracted from mean square displacement analysis. The results show a clear temperature dependence: increasing temperature reduces the energy barrier for oxygen atoms to detach from oxide sites, traverse the interface, and incorporate into the TaN substrate. This highlights the role of thermal activation in interfacial oxygen transport and its impact on diffusion barrier performance. Overall, the study provides molecular-level insight into oxygen migration at Ta2O5/TaN interfaces and demonstrates the effectiveness of machine-learning-driven molecular dynamics for modeling complex metal/oxide heterostructures.

 Keywords: Tantalum Nitride, Oxygen diffusion, molecular dynamics simulations, interfacial barrier energy, mean square displacement

Acknowledgements: This work is part of the FEDER Centre-Val de Loire Region project CoNuMat, "Design and digital experimentation of new resilient materials with high environmental value," funded by the European Commission.

Advanced semiconductor back‑end processes continually shrink logic device dimensions at the design level to meet the increasing demands for IC computational power and response speed. However, as logic density rises, conventional metal‑oxide‑semiconductor (MOS) technology faces significant challenges, requiring interconnect materials with lower dielectric constants (κ values) to mitigate issues such as metal diffusion. Among many candidates, amorphous boron nitride(a‑BN) exhibits an attractive dielectric constant (κ = 1.78) with excellent mechanical strength.

Currently, a‑BN growth is typically confined to high‑temperature chemical vapor deposition (CVD) processes. Yet, once device dimensions reach the 3 nm node, back‑end manufacturing must increasingly avoid high‑temperature steps because elevated temperatures cause dopant diffusion in the semiconductor and degrade interface quality, adversely affecting performance. Moreover, the dimensions demand precise control of film growth at the atomic scale.

Considering these emerging back-end film fabrication requirements, our study attempts atomic layer deposition (ALD) as the thin film growing method. Owing to its self‑limiting surface reactions, ALD enables precise control of film uniformity at the atomic level while simultaneously supporting large‑area processing. Compared with other vapor‑phase deposition techniques, ALD offers a high aspect‑ratio capability, reducing shadow‑effect issues in increasingly complex logic structures, and crucially provides superior management of the thermal budget.

Based on the aforementioned considerations, our study employed ALD on silicon substrates, utilizing borazine as the precursor with plasma activation to fabricate a‑BN at low temperature. The results show that the a‑BN derived by plasma enhanced ALD not only overcomes the critical temperature limitation, allowing the formation of a non‑crystalline BN phase at a minimum temperature of 150 °C, but also achieves an appropriate elemental stoichiometry (B/N ≈ 0.95) and yields a uniformly deposited film across 6‑inch Si wafers.

Defects in two-dimensional materials are often regarded as a limitation for many applications; however, they can confer a variety of functional properties, such as catalysis for hydrogen evolution and thermoelectricity.[1] Here, we demonstrate how spatially organised engineered defects can enhance defect-related properties and create new ones.[2] Specifically, we focus on enabling programmable charge trapping in monolayer MoS₂, establishing the first electret-like behaviour ever reported in a truly 2D system. Using Electrode-Free Local Anodic Oxidation, a particular electrochemical technique for oxidative etching in a parallel, stamp-assisted configuration, we create spatially defined sulphur-vacancy domains with sub-micrometre resolution and high reproducibility.[3] Kelvin Probe and Electric Force Microscopy reveal stable negative surface potentials confined within the patterned regions, reaching surface charge densities of up to 1 μC·cm⁻² with retention times exceeding 300 days under ambient conditions. Raman spectroscopy and XPS confirm the selective formation of sulfur vacancies that act as deep electron traps, forming an optical pattern, while steady-state and time-resolved photoluminescence demonstrate localised exciton quenching.

1.         Cavallini, M.; Gentili, D., Chempluschem 2022, 87, e202100562.

2.         Gentili, D.; Calabrese, G.; Lunedei, E.; Borgatti, F.; Mirshokraee, S. A.; Benekou, V.; Tseberlidis, G.; Mezzi, A.; Liscio, F.; Candini, A.; Ruani, G.; Palermo, V.; Maccherozzi, F.; Acciarri, M.; Berretti, E.; Santoro, C.; Lavacchi, A.; Cavallini, M., Small Methods 2025, 9, 2401486.

3.         Gentili, D.; Chini, E.; Cavallini, M., Acc. Mater. Res. 2025, 6, 1094-1104.

Flexible surface-enhanced Raman scattering (SERS) substrates have garnered considerable interest for on-site chemical analysis. Nevertheless, the fabrication of large-area substrates with a high density of electromagnetic hot spots and excellent signal uniformity remains challenging, often relying on complex and costly fabrication processes.

Herein, we present a simple yet effective strategy for fabricating transparent Ag/polydimethylsiloxane (PDMS) SERS substrates via a mechanically induced strain process. This method enables the formation of a dense and interconnected network of nanoscale gaps on the Ag surface, which play a crucial role in generating strong localized surface plasmon resonance (LSPR). The thickness of the PDMS substrate was systematically optimized to achieve an optimal balance between optical transparency and mechanical robustness, thereby facilitating a backside-excitation configuration that allows direct Raman detection through the substrate. To elucidate the electromagnetic enhancement mechanism, finite-difference time-domain (FDTD) simulations were performed, revealing a maximum enhancement factor (EF) of 6.4 × 10⁵ localized within the nanogap regions.

The practical sensing performance of the optimized SERS platform was evaluated using Rhodamine 6G (R6G) as a model analyte. The substrate exhibited excellent signal reproducibility, with a relative standard deviation (RSD) of 9.16%, demonstrating the high spatial uniformity of the generated hot spots.

By integrating a straightforward mechanical strain-based fabrication approach with high sensitivity, uniformity, and optical transparency, this work offers a promising and practical platform for reliable in-situ SERS applications.

Effect of the environmental conditions and the dielectric capping on the electrical properties of monolayer (1L) WS2 film grown by chemical vapor deposition (CVD) technique is systematically studied.  Characteristics of field effect transistors (FETs) fabricated on these films are investigated before and after capping the monolayer channels with Al2O3. 1L-WS2/SiO2/Si FETs under back-gated configuration show excellent performance with the on/off ratio reaching as high as 2 × 107, electron mobility of 26 cm2/V-s and subthreshold swings (SS) of 2.5 V/decade. Electron concentration (n) and mobility (μ) in the channel increase by several-folds after capping.  To understand the effect, annealing experiments are carried out under vacuum and controlled environments of different gases on uncapped device. The results point to the physisorption of oxygen molecules (O2) at the S-vacancy (VS) sites is the likely cause for the reduction of both n  and μ of the uncapped monolayer. Study reveals that n  and μ increase as a result of the removal of  O2 from the VS-sites upon capping. Al2O3 capped FETs are also examined using top-gate configuration. Interestingly, mobility is found to reduce by an order of magnitude when measured using top-gate as compared to the back-gate configuration. This has been attributed to the gate-bias driven filling of the Al2O3/1L-WS2 interfacial traps acting as the carrier scattering centres. Al2O3/1L-WS2 interface is found to offer higher density of traps than SiO2/1L-WS2 interface. The study highlights the need of developing a comprehensive strategy to tackle the influence of intrinsic defects, adsorption and interfacial traps induced by gate dielectric on the performance of 1L-WS2 based FETs.

Combining high hardness with thermal and chemical stability, and often also desirable electrical conductivity, transition metal nitrides (TMNs) are widely used as protective coatings. Tantalum nitride (TaN), in particular, is attractive for wear-resistant and diffusion-barrier applications due to its high melting point and chemical robustness. Further improvements in TMN performance increasingly rely on defect engineering; however, achieving this in a predictive manner requires quantitative insight into how point defects interact with other microstructural lattice imperfections, such as planar defects. This is especially important in TaN, which readily accommodates off-stoichiometric compositions (Ta- or N-substoichiometric) that have been associated with stabilization of the cubic phase.

In our work, first-principles density functional theory (DFT) calculations are used to investigate defect energetics in cubic TaN at 0 K. The energetics of representative planar defects, including stacking faults (SFs), grain boundaries (GBs), and twin boundaries (TBs), are quantified, and the impact of introduced Ta or N vacancies on the stability of these planar-defect configurations is assessed. Because these energetic quantities are challenging to determine experimentally, ab initio calculations provide a consistent framework for establishing thermodynamic trends and comparing defect stability across distinct microstructural environments.

Our results reveal consistent relative stability trends among SFs, GBs, and TBs in TaN, demonstrating that vacancies can substantially alter the energetic costs of these planar defects. In particular, Ta vacancies, which stabilize the cubic phase, shift planar defect energies from the negative values predicted for defect-free TaN to positive values, thereby suppressing spontaneous planar defect formation. The results further indicate that planar defects repel vacancies. Overall, we elucidate strong coupling between point defects and planar defects in TMN coatings, providing a mechanistic foundation for defect-informed microstructural design of hard, wear-resistant coatings.

The performance of two-dimensional materials (2DMs) is governed by how they are synthesized and by the resulting structure, from the atomic to the device scale. We combine liquid-metal catalysts (LMCats) with in situ, real-time multiscale characterization: X-ray reflectivity and grazing-incidence diffraction (XRR, GID), X-ray fluorescence and absorption (XRF/XANES), and radiation-mode optical microscopy, to establish growth–structure–property relationships.

On molten copper, we demonstrate reproducible, real-time control of graphene growth, extracting kinetic parameters and, via a curvature-aware XRR analysis, monolayer-scale metrics such as roughness and adsorption height [1,2]. Complementary machine-learning-accelerated free-energy simulations, based on moment-tensor-potential methods, resolve atomic-scale processes such as steps, carbon attachment, edge chemistry, and defect healing, revealing a regime influenced by both precursor availability and attachment reactions. Combining experimental and computational results, a microkinetic model explains the rate laws and shape transitions, demonstrating why LMCats reduce defect formation and enable self-healing more effectively than solids [3].

Building on these insights, we extend the approach to band-gap 2DMs (h-BN, GaN, SiC, Mo2C) using tailored chemical vapor deposition (CVD) on LMCats, mapping the influence of alloy composition, temperature, and gas chemistry on nucleation pathways, crystallinity, and coverage, with the goal of creating functional prototype devices for nanoelectronics. Overall, this multiscale, operando framework identifies scalable synthesis conditions and transfer-ready film qualities, accelerating the development from synthesis to structure to functional devices on emerging 2DMs.

References:

[1] M. Jankowski et al., ACS Nano 15, 9638–9648 (2021);

[2] H. Gao et al., Adv. Sci. 9, 2204684 (2022);

[3] V. Rein et al., ACS Nano 18, 12503-12511 (2024).

Titanium dioxide (TiO₂) is a material of significant importance in heterogeneous catalysis, photocatalysis and adaptable surface chemistry¹. Among its crystalline polymorphs, anatase TiO2 exhibits superior catalytic performance, largely attributed to its high surface area and undercoordinated active sites. In addition, amorphous form of TiO₂ plays a crucial role in sorption, separation, and catalytic technologies owing to its structural disorder, enhanced surface area, and electronic mobility. Conventional surface modification strategies typically rely on oxygen-based anchoring groups² such as phosphonic acids and silanes; however, organometallic functionalization provides a more direct and tunable approach to covalent surface engineering. In particular, Grignard reagents enable the formation of direct Ti–C or Ti–O–C linkages^3-4, thereby enhancing electronic coupling and facilitating interfacial charge transfer.

In this study, density functional theory calculations with a Hubbard correction (DFT+U) are employed to systematically investigate the adsorption behaviour and reactivity of methyl magnesium bromide (CH₃MgBr) on both anatase and amorphous TiO₂ surfaces. Pristine surfaces as well as intrinsically defective models⁵ which includes incorporating oxygen vacancies, titanium vacancies, and combined Ti–O vacancies—are examined to elucidate the role of defects on adsorption geometries, chemical bonding, and electronic structure. Furthermore, the influence of explicit solvent coordination, specifically tetrahydrofuran, is explored through ab initio molecular dynamics to assess its impact on the thermodynamic and kinetic aspects of surface functionalization. The results demonstrate that solvent-mediated dynamics play a critical role in stabilizing intermediates and promoting Ti–C bond formation. These findings provide fundamental mechanistic insight into solvent and defect-driven Grignard reactivity and establish design principles for the directed organometallic functionalization of TiO₂ surfaces.

¹ Chauke, N. M.; Ngqalakwezi, A.; Raphulu, M. Int. J. Environ. Sci. Technol. 2025, 22, 8521–8552.

² Gys, N.; Siemons, L.; Pawlak, B.; Wyns, K.; Baert, K.; Hauffman, T.; Adriaensens, P.; Blockhuys, F.; Michielsen, B.; Mullens, S.; Meynen, V. Appl. Surf. Sci. 2021, 566, 150625.

³ Van Heetvelde, P.; Beyers, E.; Wyns, K.; Adriaensens, P.; Maes, B. U. W.; Mullens, S.; Buekenhoudt, A.; Meynen, V. Chem. Commun. 2013, 49 (62), 6998.

⁴ Ganesan, K.; Neyts, E. C. J. Phys. Chem. C 2026, DOI: 10.1021/acs.jpcc.5c06880

⁵ Huygh, S.; Bogaerts, A.; Neyts, E. C. J. Phys. Chem. C 2016, 120 (38), 21659–21669.

Nano and micro structured materials offer unique physical and functional properties but are highly susceptible to surface degradation when exposed to ambient environments. In particular, oxidation induced by moisture and oxygen in air can severely degrade surface chemistry and long term stability. In this work, we report a surface protection technique based on low temperature atomic layer deposition of aluminum oxide thin films to improve the environmental durability of nano and micro structured materials.

Ultrathin alumina films were conformally deposited on nano and micro scale structures using a low temperature ALD process. The deposition temperature was carefully selected to avoid thermal damage while ensuring uniform coverage over complex and high aspect ratio features. The resulting coatings formed dense and continuous layers that effectively encapsulated the underlying surface structures.

Environmental stability was evaluated under ambient air exposure. The alumina coated samples showed markedly suppressed surface oxidation compared with uncoated samples, as the films effectively blocked oxygen and moisture diffusion. The original surface morphology and fine structural features were retained without observable deformation after coating and exposure.

These results demonstrate that low temperature ALD alumina films provide an efficient and reliable surface protection strategy for nano and micro structured materials. The proposed approach combines excellent conformality, precise thickness control, and compatibility with temperature sensitive substrates, making it suitable for a wide range of applications including nanoelectronics, optoelectronics, and functional nanodevices where environmental stability is critical.

Freestanding complex oxide membranes present exciting opportunities for enhancing functional properties, particularly in ferroic oxides like manganites. Modifications through external stimuli or novel heterostructures, such as straining and twisting, allow for the exploration of new physical properties. However, the growth and transfer of high-quality freestanding membranes, such as manganites (La1-x(Ca,Sr)xMnO3), remains challenging. Typically, these oxides are grown on strontium aluminate (SAO) sacrificial layers via pulsed laser deposition under conditions that differ drastically from those used for high-quality thin film growth on conventional substrates. With careful optimization of the growth process, it is possible to achieve functional properties in freestanding manganites that resemble their bulk counterparts. This work demonstrates strategies for high-quality freestanding manganite membrane growth and transfer, while also offering perspectives on future applications of these freestanding oxide membranes.

References:

[1] Brand, Eric, et al. "Epitaxial Strain Engineering of High-Quality Freestanding Single-Crystalline Complex Oxides." ACS nano 19.48 (2025): 41172-41183.

[2] Brand, Eric, et al. "Strain Engineering of Complex Oxide Membranes on Flexible Metallic Support." Advanced Physics Research 4.10 (2025): e00075.

Inorganic–organic hybrid interfaces play a crucial role in a wide range of functional materials, where their physicochemical properties are governed by molecular adsorption and the resulting modification of the electronic structure. A detailed understanding of adsorption mechanisms at oxide–organic interfaces is therefore essential for rational materials design, particularly for wide band-gap oxides combined with semiconducting organic molecules.

In this work, we investigate the adsorption and interface formation of transition metal phthalocyanines with different central metal atoms on aluminum oxide prepared by sol–gel processing, with a particular focus on the role of oxygen vacancies. Aluminum oxide represents a technologically relevant oxide material whose surface chemistry and defect structure strongly influence molecular adsorption. By varying the central metal in the phthalocyanine macrocycle, we systematically explore how metal electronegativity and electronic configuration affect molecule–substrate interactions.

The study combines Density Functional Theory (DFT) modeling with experimental spectroscopic techniques. DFT calculations are used to analyze preferred adsorption geometries, adsorption energies, charge transfer, and modifications of the electronic density of states induced by oxygen vacancies. Experimentally, the interfaces are prepared under controlled conditions, and their chemical and electronic structure is investigated using X-ray and ultraviolet photoemission spectroscopy, complemented by Raman spectroscopy to probe molecular integrity and interfacial interactions.

The combined theoretical and experimental approach provides a comprehensive picture of how defect-mediated oxide surfaces and the choice of central metal in phthalocyanines govern adsorption strength, charge redistribution, and electronic structure at the interface. These results contribute to a fundamental understanding of organic–oxide hybrid interfaces and highlight the importance of defect engineering and molecular design in tailoring interfacial properties for future functional materials.

We would like to acknowledge the National Science Center, Poland (NCN) grant no.2022/44/C/ST5/00083 and Polish high-performance computing infrastructure PLGrid (HPC Centers: ACK Cyfronet AGH) for providing computer facilities and support  within computational grants no. PLG/2024/017102 and no. PLG/2025/018210. The conference fee is covered by EU funds FSD - 10.25 Development of higher education focused on the needs of the green economy European Funds for Silesia 2021-2027: The modern methods of the monitoring of the level and isotopic composition of atmospheric CO2 (project no.FESL.10.25-IZ.01-06C9/23-00).

Two-dimensional (2D) materials possess distinctive electronic and optical properties that make them promising candidates for a variety of novel optoelectronic applications. However, their intrinsically non-magnetic nature limits their manipulation of spin degree of freedom and integration into spin-based application. The Introduction of intrinsic room-temperature ferromagnetism into 2D materials has consequently become a critical focus in the field. Among various approaches, doping with transition metals, introducing lattice defects, or applying strain have shown potential in inducing ferromagnetic behavior. In this study, we present a method to induce room-temperature ferromagnetism in the intrinsically non-magnetic layered material palladium ditelluride (PdTe2). A thin layer of chromium (Cr) was deposited onto the PdTe2 surface and subsequently annealed near the material’s phase transition temperature to facilitate Cr incorporation. XRD analysis confirms that the hexagonal structure of PdTe2 is preserved after Cr doping. A reduction in the lattice parameters along the a-axis (or c-axis) is observed, likely due to the smaller ionic size of Cr compared to Pd and Te. Magnetic measurements reveal the emergence of robust room-temperature ferromagnetism in Cr-doped PdTe2, which the magnetic response increasing with the Cr concentration. Moreover, electronic structure analysis indicates that Cr-doping significantly changes the band structure of PdTe₂, which becomes comparable to the p–d hybridized electronic configuration in 1T-CrTe₂. Detailed results and further discussions will be presented in our forthcoming reports.

The durability and corrosion resistance of stainless steel (SS) plays a vital role in applications such as biomedical implants, aerospace components, semiconductor fabrication, and industrial machinery. Plasma polymerized hexamethyldisilazane (ppHMDSZ) was prepared via plasma-enhanced chemical vapor deposition (PECVD), emerging as promising coating materials with superior barrier performance. However, fine-tuning deposition parameters remain challenging due to the complex and interconnected parameters of the PECVD process. In his study, machine learning (ML) was utilized to identify key parameters and predict optimal deposition conditions. Furthermore, the ML results were extended to investigate the long-term corrosion resistance of ppHMDSZ thin films deposited on SS (ppHMDSZ/SS). Plasma treatment was carried out in a vacuum chamber equipped with a 13.56 MHz radio-frequency generator and a vacuum pump, with deposition time varied from 2 to 30 min. The pressure of hexamethyldisilazane (HMDSZ) precursor was maintained at 75 mTorr under an applied power of 30 W.  The performance of the neural network model in predicting corrosion current density (I_corr) for organosilicon-coated metallic substrates was evaluated using input parameters including film thickness, substrate type, and elemental composition (Si, C, O, and N). The simulation results yielded a root mean square error (RMSE) of 1.69, a mean absolute error (MAE) of 1.10, and a mean absolute percentage error (MAPE) of 3.93%. In addition, the model achieved a correlation coefficient (R) of 0.96 and an R² value of 0.89, indicating the strong predictive reliability for corrosion behavior. Deposition of ppHMDSZ on SS resulted in the formation of hydrophobic surfaces, as evidenced by an increase in water contact angle (WCA) from 80.94 ± 3.11° to 104°. Film growth analyses revealed a linear increase in thickness with deposition time, from 11.35 ± 1.97 nm at 2 min to 215.5 ± 9.21 nm at 30 min, corresponding to an average deposition rate of 7.04 nm.min^-1. This result confirms that the PECVD produces a consistent linear relationship between deposition time and film thickness. Moreover, corrosion inhibition efficiency exceeding 95% was achieved for SS substrates deposited with ppHMDSZ from 10 to 30 min. Long-term immersion tests in simulated body fluid (SBF) under accelerated corrosion conditions demonstrated that the 30min-ppHMDSZ/SS samples retained an inhibition efficiency of 97% after 730 days (2 years), confirming the excellent long-term corrosion protection provided by PECVD deposited ppHMDSZ thin films on SS.

To fully exploit the potential of 2D transition metal dichalcogenides (TMDs) in next-generation electronics, achieving wafer-scale single-crystallinity is essential. While significant progress has been reported in synthesizing unidirectional monolayers via chemical vapor deposition (CVD), reliable methods to verify their quality at the wafer scale remain underdeveloped and require urgent attention. This verification gap is critical because twin domains naturally form during epitaxial growth due to the non-centrosymmetric nature of the TMD lattice. The presence of these twin boundaries acts as a primary scattering source, significantly degrading carrier transport and device uniformity.

However, assessing the global orientation alignment in fully coalesced films remains a formidable challenge. Conventional optical probes, such as polarized Raman and SHG, are inherently limited in distinguishing between inverted orientations (0° vs. 180°) due to symmetry constraints. Furthermore, while Transmission Electron Microscopy (TEM) offers atomic-scale resolution, its localized and destructive nature precludes its use for non-invasive, whole-wafer inspection. Consequently, a scalable, quantitative metric to verify single-crystallinity in continuous monolayers is currently lacking.

Low-Energy Electron Diffraction (LEED) offers a powerful solution for non-destructive, large-area surface analysis, where multiple scattering events allow for the violation of Friedel’s law (I(g)≠I(−g)). Yet, prior LEED studies have largely relied on qualitative observations of 3-fold symmetry patterns. This approach is prone to ambiguity, as apparent 3-fold symmetry can persist even in mixed-orientation films with unequal domain populations, failing to provide a rigorous proof of perfect unidirectionality.

In this study, we establish a quantitative framework to resolve this ambiguity by combining energy-dependent LEED (I−V) analysis with dynamical diffraction theory. We demonstrate that the intensity asymmetry between Friedel pairs in 2H-MoS2 is a deterministic signature of lattice non-centrosymmetry. By systematically tracking diffraction intensities from 50 to 200 eV, we successfully differentiate true single-crystalline monolayers from mixed-domain films and derive a robust method to quantify the degree of domain alignment.

Our findings clarify the direct link between atomic-scale symmetry breaking and macroscopic diffraction anomalies. This work provides the community with a standardized, surface-sensitive diagnostic tool for the rigorous quality assessment of wafer-scale 2D materials, bridging the crucial gap between advanced synthesis and reliable device fabrication.

 As the continued scaling of silicon-based electronics approaches fundmental limits, the developmen of alternative semiconductor materials has become increasingly important. Two-dimensional  (2D) semiconductors have emergedas strong candidaes for nesct-generation electronic devices due to their atomic-scale thickness, excellent electrostatic control, and high-quality interfaces. In this context, verticl field-effect transistor(VFETs) based on 2D materials offer a promising pathway toward realizing sub-nanometyer channel lengths.

Despite their potential, conventional 2D VFETs often suffer from substantial leakage currents and poor switching characteristics, primarily caused by gate-field-free regions (GFFRs) and negatively shifted threshold voltages (Vth). A negative Vth leads to incomplete channel depletion at zero gate bias, allowing unintended current flow through the GFFR and severely limiting the achievable on/off current ratio.

Here, we report high-performance MoSe₂-based VFETs achieved through a combination of defect density reduction and band alignment engineering. A vacuum pre-annealing (VPA) treatment was employed to suppress intrinsic defects and produce near-intrinsic MoSe₂, effectively reducing leakage currents in the GFFR under zero gate bias conditions. Furthermore, a high–work-function VSe₂ electrode was introduced to enhance the Schottky barrier height, thereby suppressing vertical tunneling currents.

As a result, the optimized MoSe₂ VFETs exhibit an on/off current ratio exceeding 10⁵, corresponding to an improvement of 2–3 orders of magnitude compared to previously reported MoS₂-based VFETs. These findings highlight the critical role of defect engineering and contact band alignment in enabling low-leakage, low-power VFET operation, and provide a viable route toward ultrathin CMOS technologies and future logic applications.

Hybrid heterostructures combining high-temperature superconductors and topological insulators are promising candidates for superconducting and quantum device applications. However, their practical implementation is severely limited by interfacial reactions and elemental diffusion originating from cuprate superconductors. In this study, we investigate YBa2Cu3O7 (YBCO)/Bi2Se3 heterostructures incorporating an ultrathin Al2O3 buffer layer and systematically examine the influence of buffer layer thickness on interfacial stability and device characteristics. To elucidate the thickness-dependent role of the Al2O3 buffer layer, interfaces in YBCO/Al2O3/Bi2Se3 heterostructures were systematically characterized by Raman spectroscopy, high-resolution transmission electron microscopy, and depth-resolved X-ray photoelectron spectroscopy. We find that the insertion of Al2O3 effectively suppresses Cu and Ba diffusion from YBCO, while the degree of diffusion suppression and mixed interfacial layer formation strongly depends on the buffer layer thickness. An optimized Al2O3 thickness significantly improves the structural integrity of the layered Bi2Se3 film, whereas excessively thin or thick buffers result in incomplete diffusion blocking or degraded interface quality. Electrical transport measurements demonstrate that heterostructures with an optimized Al2O3 buffer layer thickness exhibit enhanced superconducting properties and more stable device behavior compared to unbuffered or non-optimized structures. These results highlight the critical role of buffer-layer thickness in interface engineering superconductor and topological insulator heterostructures, and provide practical design guidelines for YBCO-based superconducting and quantum devices.

As the Internet of Things (IoT) grows, there is an increasing demand for energy storage systems that are high-performing, scalable, and sustainable. While Ti₃C₂T_x has shown promise as an electrode material due to high conductivity and volumetric capacitance, a full stack integration with useful functionality is yet to be demonstrated, and long-term stability is often unreported. In this work, we synthesize high-purity, delaminated Ti₃C₂T_x flakes via the in-situ HF formation route. Structural and chemical analysis confirms the successful removal of Al, revealing an expanded c-lattice parameter and surface terminations favorable for pseudocapacitance, while AFM and TEM statistics demonstrate high-quality flakes with average lengths of ~560 nm and thicknesses of ~1.3 nm.

In this work we present a fabrication approach for supercapacitors by doctor-blade deposition of these MXene electrodes onto flexible, transparent substrates using vinyl masks. The MXene films exhibit low sheet resistance (~0.6 Ω sq^-1) and strong adhesion, with symmetric interdigitated devices revealing a high areal capacitance of 10 mF cm^-2 and reliable cycling over 10,000 cycles. To meet the voltage requirements of low-power IoT devices, series supercapacitor units were stacked in various configurations, effectively increasing the operating voltage window to useful ranges of ~3.6 V. These stacked configurations demonstrate consistent performance and enhanced energy output suitable for energy-autonomous nodes. Furthermore, we employ a passivation strategy to prevent the deterioration of the MXenes into insulating TiOx and to minimize electrolyte solvent evaporation, ensuring long lifetime operation.

The goal of miniaturization in microelectronics catalyzes the evolution of field-effect transistors (FETs), transitioning from classical scaling approaches to innovative architectures like gate-all-around FETs. Among these advancements, nanowire field-effect transistors (NW-FETs) emerge as a promising solution to the limitations of traditional FET designs, offering improved electrostatic control, reduction of short-channel effects, and better overall device performance metrics. Metal oxide nanowires (NWs) provide high mobility, excellent optical transparency, mechanical flexibility, and compatibility with thin-film technology, making them ideal candidates to be the pillar of a new wave of transparent and flexible electronics with unprecedented integration levels. Here we demonstrate a direct bottom-up integration of a vertically aligned hydrothermally synthesized zinc oxide (ZnO) NW, to obtain a vertical gate-all-around NW-FET (GAANW-FET). The vertical device structure and bottom-up integration reduce process complexity, compared to conventional top-down approaches. The proposed fabrication process is compatible with both n-type and p-type semiconductor channels and can also be implemented on flexible substrates. A bottom electrical contact to the NW grown on the seed layer is provided by an underlying lattice-match ITO thin-film, with the entire structure relying on transparent metal oxides.

Two-dimensional (2D) semiconductors such as molybdenum disulfide (MoS₂) have recently attracted extensive research attention due to their promising compatibility with silicon-based electronics. However, several key challenges still limit their practical integration. Two of the critical issues are: (1) the intrinsic depletion-mode (normally-on) operation of MoS₂ field-effect transistors (FETs), and (2) the large hysteresis commonly observed in the transfer characteristics of MoS₂ FETs. Addressing them is essential for CMOS-compatible 2D-transistor technologies. In this work, we report for the first time that surface modification of the exfoliated multilayer MoS₂ FETs with PBTTT-C14 (poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene)), a p-type conjugated hydrophobic organic polymer, converts the device from depletion-mode to enhancement-mode operation while simultaneously and strongly suppressing hysteresis. Specifically, the threshold voltage (V_th) shifts from −9.6 V to +5.9 V (total shift ~15.5 V), and the hysteresis window decreases from 8.8 V to 1.3 V (~85% reduction). This originates from interfacial charge transfer at the MoS₂/PBTTT-C14 interface, enabled by favourable band alignment. Additionally, donor-like sulfur vacancy states in MoS₂ are involved in interfacial charge transfer to the p-type PBTTT-C14 layer, resulting in effectively deactivation of these donor states associated with hysteresis. Importantly, this highlights the role of electronic interaction at the interface. To further validate this charge-transfer-driven mechanism, P3HT (poly(3-hexylthiophene-2,5-diyl)) with similar energy levels to PBTTT-C14 was employed and exhibit similar enhancement-mode behaviour and hysteresis suppression. In contrast, treatment with a n-type polymer (N2200)  (poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)})  exhibits less favourable band alignment which limits interfacial charge transfer, resulted in a smaller V_th shift from −13.8 V to −8.3 V (total shift of ~5.5 V) without inducing enhancement-mode behaviour and a hysteresis reduction from 11.2 V to 5.6 V (~50%). Furthermore, treatment with the electrically inert insulating polymer polydimethylsiloxane (PDMS) leads to no observable change in V_th and hysteresis, supporting the charge-transfer-dominated origin of the observed effects. Overall, this work establishes a clear correlation between polymer energy-level alignment, interfacial charge transfer, and device performance. The results demonstrate that p-type organic polymers with suitable energy levels can simultaneously enable enhancement-mode operation and strong hysteresis suppression in MoS₂ FETs, providing a scalable and CMOS-compatible strategy for high-performance 2D electronics.

 Genetic algorithms (GAs) are population-based evolutionary optimization techniques that enable efficient exploration of global optima by simultaneously considering conflicting multi-objective performance metrics in complex design spaces. This allows inverse-design problems characterized by high-dimensional, nonlinear, and non-convex design spaces, such as aperiodic multilayer thin-film structures, to explore diverse design solutions without being trapped in local optima, thereby deriving optimal structures. The transfer matrix method (TMM) enables precise calculation of wavelength-dependent transmission and reflection characteristics based on the refractive index and thickness of each layer in a multilayer thin-film structure, and serves as a core analytical tool for evaluating the spectral response in the proposed optimization framework.

 Recently, we have developed a hybrid solar window tailored for building-integrated photovoltaic (BIPV) applications in urban environments. In such systems, precisely engineered optical filters are required to simultaneously achieve high average visible transmittance (AVT), excellent color rendering index (CRI), and high power conversion efficiency (PCE). Optical filters designed for this purpose must be optimized by simultaneously considering three inherently competing performance metrics: AVT, CRI, and PCE.

 In this work, we propose a GA–TMM–coupled framework to optimize these three competing performance metrics. By simultaneously optimizing structural design variables—including the combination of high- and low-refractive-index materials, individual layer thicknesses, and the number of stacked layers—the framework enabled inverse design of a transparent NIR-reflective filter with markedly enhanced spectral selectivity.

 Based on the proposed design strategy, an optimal filter structure that effectively balances the trade-offs among AVT, CRI, and PCE was identified. The optimized multilayer thin films were fabricated using ion beam–assisted deposition, employing TiO₂ and SiO₂ as the high- and low-refractive-index materials, respectively. The fabricated films exhibit stopband characteristics in close agreement with the target design specifications, thereby demonstrating the accuracy, robustness, and reproducibility of the proposed GA–TMM–based optimization strategy.

 Nitrogen dioxide (NO₂) has garnered increasing attention due to its detrimental effects on human health and the environment. In parallel, recent advances in wearable and flexible sensor technologies have enabled new opportunities for human-centered applications. In this study, we report a wearable NO₂ gas sensor based on a silicon nanomembrane (SiNM), which offers excellent mechanical flexibility and enables device miniaturization.

To enhance the gas sensing performance, Au thin films with varying thicknesses were deposited onto the SiNM and subsequently annealed to form Au nanoparticles with well-controlled sizes. The nanoparticle size was systematically optimized by tuning the initial Au film thickness. Gas sensing performance was evaluated at 80 °C under 50 ppm NO₂, with the gas response defined as ΔR/R₀. The pristine SiNM exhibited a response of approximately 2.3, whereas Au nanoparticle decoration significantly enhanced the response to 10.

Furthermore, a floating well-type structure was introduced into the SiNM to increase the specific surface area. This structural engineering markedly increased the number of active sites available for NO₂ adsorption, resulting in a further enhancement of the gas response up to 30. To assess the suitability for wearable applications, bending tests were conducted under various curvature conditions. The sensor maintained stable response characteristics and reliable operation even under applied mechanical deformation, demonstrating excellent mechanical robustness and sensing stability.

These results indicate that both surface functionalization with Au nanoparticles and structural engineering of SiNMs are highly effective strategies for improving NO₂ gas sensing performance. Moreover, this approach can be readily extended by incorporating other metal nanoparticles to tailor gas selectivity, highlighting its broad potential for next-generation wearable gas sensor platforms.

Keywords: Au nanoparticle, SiNM, NO₂, Well-type structure

Rare-earth-doped luminescent thin films are gaining increasing attention for next-generation optoelectronic and photonic technologies, owing to their sharp emission lines, long excited-state lifetimes, and structural tunability.

This study presents a comparative spectroscopic study of the luminescent properties of Eu3+-doped GdF3 and GdOF thin films. These materials combine the low phonon energy of fluorides, which minimizes non-radiative decay processes, with the enhanced mechanical and chemical stability provided by oxyfluorides, making them  an ideal platform for rare-earth ion doping.

The films were deposited using low-pressure Metal-Organic Chemical Vapor Deposition (MOCVD), a technique offering conformal coating on complex geometries, precise stoichiometric control, and industrial scalability. 

Using β-diketonate-based volatile precursors, uniform and conformal films were deposited on SiO2/Si and quartz substrates under optimized conditions and systematically investigated to elucidate the correlation between dopant concentration, crystal phase evolution, and photoluminescent performance.

 X-ray diffraction analysis revealed a transition from trigonal (R-3m) to monoclinic (Gd4O3F6-type) phase with increasing Eu3+ content, indicating a dopant-induced structural transformation.

Photoluminescence studies demonstrated efficient red emission arising from the intra-4f transitions of Eu3+, with the 5D0→ 7F2 electric dipole transition as the dominant feature, strongly influenced by the local asymmetry around the Eu3+ ions.  Compared to Eu3+-doped GdF3 reference films, GdOF matrices yielded enhanced emission intensity and prolonged decay lifetimes, attributed to the synergistic effects of the mixed anionic framework (F-/O2-), increased crystal field asymmetry, and improved energy transfer pathways.

The incorporation of europium, a well-known photoluminescence activator, enhances the functionality of these materials in optoelectronic devices by enabling efficient energy transfer mechanisms and potential down-conversion processes. These mechanisms allow the conversion of high-energy photons into multiple lower-energy photons, improving the efficiency of photonic devices such as solar cells and LEDs.

Overall, these results underline the effectiveness of MOCVD for the controlled growth of oxyfluoride hosts and establish Eu3+-doped GdOF films as viable candidates for integration into solid-state lighting, photonic coatings, and anti-counterfeiting technologies.

The quality of high-power impulse magnetron sputtering (HiPIMS) deposited films can often improve through the effective use of metal-ion acceleration, requiring precise measurements of time-of-flight (ToF). These measurements are commonly done using time- and energy-resolved mass spectrometry but require careful consideration of the transit time of ions inside. The transit time is typically calculated by considering the travel length in various parts of the spectrometer (e.g. from orifice to detector), but errors associated with these estimations can lead to nonphysical values in a HiPIMS process (e.g. negative ToFs). Here we report a practical approach to determine ion ToF experimentally, using a bipolar HiPIMS power supply to synchronize a gating pulse to the front-end of a HIDEN Analytical EQP-300 mass spectrometer, placed at the working distance. The ToF is measured by applying a +70 V bias to repel ions, and a 5 µs gating pulse of 0 V to accept them. To prevent interference with the HiPIMS plasma, a grounded shield is placed in front of the mass-spec head with a variable slit-opening (0.5–3 mm). The effectiveness of the shielding is verified by Langmuir probe measurements, noting negligible shifts in plasma potential for a DC sputter discharge. The gate is then synchronized to a HiPIMS pulse and data collected at 5 µs intervals by adjusting the pulse delay. Measurements of the time-of-flights of Ar+, Al+, Sc+, Y+, and W+ ions are presented; Al+ and Ar+ ions were also compared to ToF calculated using mass spectrometry flight tube equations.

Electrical control of magnetic order is a central challenge in condensed matter physics and spintronics, driven by the demand for energy-efficient, scalable, and high-density information technologies. While conventional charge-based electronics face fundamental limits in power dissipation and miniaturization, spin-based approaches offer a promising alternative by exploiting the electron’s spin degree of freedom. In this context, state-of-the-art spintronic technologies such as spin-transfer torque (STT) and spin–orbit torque (SOT) have enabled fast, non-volatile switching; however, these mechanisms operate exclusively within a ferromagnetic phase with a strong stray field and do not modify the underlying magnetic order. Electrically inducing a transition between distinct magnetic phases—particularly between ferromagnetic (FM) and antiferromagnetic (AFM) states, known as an inverse metamagnetic transition—remains an outstanding challenge.

Here, we report the experimental realization of a reversible, current-driven inverse metamagnetic transition in epitaxial Sm1-xSrxMnO₃ thin films. Above a critical current density, the system undergoes an abrupt transformation from a low-resistance ferromagnetic state to a high-resistance antiferromagnetic-like phase, accompanied by a reorientation of orbital polarization. This behaviour highlights the strong coupling between spin, charge, and orbital degrees of freedom that governs non-equilibrium magnetic reordering in correlated oxides. The magnetic origin of this transition is unambiguously confirmed by current-dependent X-ray magnetic circular dichroism (XMCD) and X-ray linear dichroism (XLD) measurements, which directly probe changes in spin and orbital configurations under applied current.

Building on this discovery, we exploit the current-induced magnetic reordering in nanoscale spin-filter tunnel junctions based on LaNiO3/Sm1-xSrxMnO₃/SrTiO₃/La₀.₇Sr₀.₃MnO₃ heterostructures. In these devices, Sm1-xSrxMnO₃ serves as an active magnetic tunnel barrier, in which electrical control of the magnetic phase directly modulates spin-dependent tunnelling. We observe robust bistable resistance switching with magnetoresistance exceeding 200%, tunable by current, temperature, and magnetic field. This mechanism is fundamentally distinct from conventional STT or SOT switching and establishes a new paradigm for electrically driven magnetic phase control in complex oxides, opening pathways toward low-power spintronic and cryogenic logic devices.

Exploring new approaches to provide a deeper understanding of nanoscale processes, like charge-carrier dynamics in energy materials, is crucial. Using NV-centers in a diamond as optically detectable quantum sensors presents a promising opportunity to gain new insights on surfaces and interfaces of materials by NMR, which have not been possible due to the low sensitivity of conventional techniques on nanoscale thin film materials.¹ In comparison to other surface-sensitive techniques, this method is capable of in-situ nanoscale measurements at room temperature, facilitated by the coupling of the NV-centers’ spins to spins and magnetic fields of the sample. Along with the investigation of magnetic fields, the method can also be used to study diffusion or hopping of ions, spins by NMR and EPR, conductivity, and even temperature changes.²
Through our joint work, we collectively design model experiments on H+ and Li+ ionic conductors, for which we investigate thin films grown by pulsed laser deposition (PLD) to learn about carrier dynamics.
i. As a representative for Li+/e- mixed solid-state conductors, we selected lithium titanate (LTO), a promising anode material for thin film solid-state batteries due to its “zero-strain” upon lithiation, structural and thermal stability.³ Thus far, first findings include the measurement of 7Li-NMR signals in a temperature dependent study and the potentially promising approach of magnetic noise spectroscopy to investigate lithium-ion and electron dynamics.⁴
ii. As a representative for solid state H+ conductors, we investigate pure ceria (CeO2-δ) and its extrinsically doped variants, with the main goal of gaining deeper insights into the proton conduction mechanism.^5-7 First experimental results include the observation of a 1H-NMR signal in CeO2 under ambient conditions. Upon doping with different mol% of gadolinia, we detect that the spin-lattice relaxation time drops significantly as a function of the amount of the dopant, as expected for the introduction of paramagnetic species.
Future research possibilities include investigations of grain boundaries, electrode-electrolyte interfaces, mapping of current flow, and nanoscale calorimetry on thin films grown by PLD, which will be pursued within the scope of our research and collaboration.

[1] Rizzato, R., et al. and Bucher, D.B., Appl. Phys. Lett. 123, 260502 (2023)
[2] Freire-Moschovitis, F.A., et al. and Bucher, D.B., ACS Nano 2023 17 (11), 10474-10485
[3] Kong, L., et al. and Rupp, J.L.M., Adv. Energy Materials, e03080 (2025)
[4] Freire-Moschovitis, F.A., et al. Bucher, D.B. and Rupp, J.L.M., to be submitted in 2025
[5] Manabe, R. et al., Solid State Communications, 2018. 270: p. 45-49.
[6] Sun, X., et al., Applied Surface Science, 2023. 611: p. 155590.
[7] Simons, P., et al. and Rupp, J.L.M., Adv. Funct. Materials, 2021. 31(31): p.2009630.

Corresponding authors: jrupp@tum.de, dominik.bucher@tum.de

In a recent study, Pliatsikas et al. suggested that defects during magnetron-sputter-deposition of thin Au films on graphene primarily emerge from energetic species generated during neutralization and backscattering of Ar+ ions at the sputtering cathode (also referred to as target) [1].

In the present work, we explore the effect of hyperthermal species—sputtered particles and backscattered argon (Ar) atoms—on defect generation during sputter-deposition of thin metal films on single-layer-graphene (SLG). We magnetron-sputter gold (Au), silver (Ag), copper (Cu), and aluminium (Al) targets at various Ar gas working pressures and grow respective 2 nm thick films on SLG supported on silicon dioxide substrates. The selected target materials: (i) have distinctly different atomic mass numbers A_target and thereby different propensities to backscatter and transfer energy to Ar+ plasma ions; and (ii) exhibit differences in their surface binding energy, the latter being the quantity that largely determines the most probable energy of the sputtered particles ejected from the target surface. Raman spectroscopy measurements show that decrease of the working (Ar gas) pressure (for a given metal/SLG system) leads to a higher defect density in SLG, while increase of A_target generally induces more damage on SLG. To understand the origin of defect generation and correlate it with the energy and flux of hyperthermal sputtered and backscattered species at the various deposition conditions, we use two complementary computational approaches: Molecular Dynamics to model the target sputtering process and Particle-in-cell Monte Carlo simulations to model the gas phase transport of species from the target to the SLG substrate. Our analysis shows that defects are primarily caused by energetic backscattered Ar species, such that targets that are less efficient in backscattering Ar+ ions along with relatively high working pressures lead to a minimization of ballistic damage on SLG. The findings presented herein pave the way for developing strategies to achieve defect-free growth of thin metal films on graphene and other van der Waals crystals and thereby enable magnetron sputtering for scalable fabrication of multifunctional metal contacts in two-dimensional-materials-based heterostructure devices.

[1] N. Pliatsikas, O. Karabinaki, M. Zarshenas, G.A. Almyras, I. Shtepliuk, R. Yakimova, J. Arvanitidis, D. Christofilos, K. Sarakinos, Energetic bombardment and defect generation during magnetron-sputter-deposition of metal layers on graphene, Appl. Surf. Sci. 566 (2021) 150661, https://doi.org/10.1016/j.apsusc.2021.150661.

Germanium telluride (GeTe) is one of phase-change materials notable for its ability to undergo reversible transformations between amorphous and crystalline states. This property has made it a widely studied phase-chance materials for non-volatile memory applications due to its high speed, low power consumption, data retention, and storage capacity [1, 2]. In search of suitable phase-change chalcogenide materials, ternary thin films with varying elemental compositions containing germanium-telluride were investigated. To this end, amorphous ternary Ge-Bi-Te and Ge-Sn-Te thin films were grown using rf magnetron co-sputtering deposition technique to investigate their growth behaviors and phase-change characteristics as a function of compositions. The elemental composition, surface morphology, structure and temperature-dependent sheet resistance were characterized via energy-dispersive X-ray spectroscopy, scanning electron microscopy, X-ray diffraction, and two-point probe measurements.  Additionally, atomic force microscopy and spectroscopic ellipsometry were employed to study the surface topography, roughness and optical properties of the deposited telluride thin films.

Acknowlegements

This research was funded, in whole or in part, by l’Agence Nationale de la Recherche (ANR), project ANR-23-CE24-0004.

References

[1] Noé, P., Vallée, C., Hippert, F. et al. Phase-change materials for non-volatile memory devices: from technological challenges to materials science issues Semicond. Sci. Technol. 33 013002 (2018) doi :10.1088/1361-6641/aa7c25

[2] Singh, K., Kumari, S., Singh, H. et al. A review on GeTe thin film-based phase-change materials. Appl Nanosci 13, 95–110 (2023). https://doi.org/10.1007/s13204-021-01911-7

Plastic waste is a global sustainability challenge. Compostable and recyclable alternatives to single-use flexible packaging exist but do not provide an adequate barrier to water-vapor and oxygen. We address this by using atmospheric-pressure spatial atomic layer deposition to apply Al₂O₃-ZnO nanolaminates on compostable polylactic acid (PLA) and recyclable polyethylene terephthalate (PET) films for flexible packaging [1]. This industrially scalable coating [2,3] is performed at 50°C, preserving film integrity while enabling nanoscale control. The nanolaminate structure is found to enhance the bending resistance, improve the coating stability, and drastically reduce the water-vapor transmission rate (WVTR) and oxygen transmission rate (OTR). An optimized 8-stack Al₂O₃-ZnO nanolaminate that is ~96 nanometers thick reduces the WVTR of PLA packaging film from ~300 g·m^-2·24hr^-1 to < 0.5 g·m^-2·24hr^-1 and its OTR from ~1000 cm³·m^-2·24hr^-1 to < 10 cm³·m^-2·24hr^-1 (both measured at 38°C and 90% relative humidity), making it ideal for packaging air-sensitive goods. When the 8-stack nanolaminate is laminated between two PET films to form a simple packaging structure and is subjected to the harshest industry-standard Gelbo flex durability testing, it retains a WVTR < 2 g·m^-2·24hr^-1. These ultrathin coatings are well-positioned to meet recyclability and compostability standards, enabling a viable path to sustainable flex packaging. 

[1] D. Vidish, S. Saha, L.-V. Delumeau, T. Grovu, K.P. Musselman, Metal-oxide nanolaminate barrier coatings to enable large-scale manufacturing of sustainable flex packaging, Mater. Today Sustain., 33: 101289 (2026).

[2] P. Poodt, D.C. Cameron, E. Dickey, S.M. George, V. Kuznetsov, G.N. Parsons, F. Roozeboom, G. Sundaram, A. Vermeer, Spatial atomic layer deposition: A route towards further industrialization of atomic layer deposition, J. Vac. Sci. Technol. A, 30: 010802 (2012).

[3] R.L.Z. Hoye, D. Muñoz-Rojas, Z. Sun, H. Asgarimoghaddam, H. Okcu, J.L. MacManus-Driscoll, K.P. Musselman, Spatial Atomic Layer Deposition for Energy and Electronic Devices, PRX Energy, 4: 017002 (2025).

Two-dimensional (2D) materials such as α-molybdenum trioxide (α-MoO₃) have attracted increasing attention for ultraviolet (UV) optoelectronic applications due to their wide bandgap, layered crystalline structure, high dielectric constant, and strong sensitivity to thermal treatments. Despite their promise, conventional integration routes often rely on costly or complex fabrication processes, which limits accessibility for low-resource laboratories. In this work, we present a low-cost and reproducible approach to synthesize, integrate, and characterize α-MoO₃ microstructures for proof-of-concept electronic devices.

α-MoO₃ microstructures were synthesized via Joule heating and subsequently mechanically exfoliated to obtain thin flakes. These flakes were transferred onto pre-patterned devices with metal contacts to enable electrical characterization. Structural and morphological analysis was performed using Raman spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), confirming the formation and transfer of α-MoO₃ flakes onto the contact region. Functional characterization included current–voltage (I–V) measurements and photoresponse evaluation under UV illumination. Additionally, thermal treatments in air and under vacuum were carried out to investigate the impact of atmospheric conditions on conductivity and device behavior.

Overall, this study establishes a practical experimental route for the preliminary integration of α-MoO₃ flakes into simple electronic structures, supporting its potential for future sensing and UV photodetection applications. Current efforts focus on baseline structural and functional characterization as a foundation for subsequent device optimization.

Plasma sprayed solid lubricant-based composite coatings are widely used in automotive, aerospace, and metal-forming industries, where liquid lubricants often tend to chemically degrade, resulting in high friction and wear rates. However, the low retention of solid lubricants in plasma sprayed coatings remains a major challenge due to the significant loss of solid lubricant particles during spraying. This leads to reduced tribological performance. To improve the retention of solid lubricants in plasma sprayed coatings, this study explores the possibility of coating solid lubricant powder, i.e., graphite, with an electroless Ni–P layer. Electroless plating was done for different time intervals, and it was observed that increasing the plating time led to improved coating uniformity and better particle coverage. Furthermore, it was seen that Ni–P coated graphite powders exhibited improved flowability and higher particle density compared to uncoated powders. Plasma spraying was performed using Ni–P coated graphite powders on Inconel substrates, and it was observed that the presence of the Ni–P layer reduced solid lubricant loss and prevented degradation, resulting in higher retentions. To evaluate the tribological performance of the coatings, sliding wear tests were conducted using a ball-on-flat test configuration. The tribological performance of the coatings under different test conditions, emphasizing the role of third bodies in modifying friction and wear behaviour, will be presented.

We report the synthesis of novel aluminum(III) and gallium(III) heteroleptic complexes, [M(TFB-tBuA)(O^tBu)₂] (M = Al, Ga), derived from tris(diethylamido)metal(III) precursors and the fluorinated β-ketoenamine ligand H-TFB-tBuA in the presence of tert-butyl alcohol. Both complexes exhibit high volatility, subliming at 60-70 °C under 1 mbar, and serve as effective molecular precursors for the low-pressure (10^-2 mbar) chemical vapor deposition of Al₂O₃, Ga₂O₃, and Al-doped Ga₂O₃ thin films. These results demonstrate the potential of a fluorinated β-ketoenamine ligand H-TFB-tBuA in designing volatile, thermally stable aluminum- and gallium precursors for high-quality oxide coatings via CVD.

Metal-oxide interfaces are ubiquitous in modern electronic devices, where they must simultaneously provide mechanical robustness and efficient heat dissipation to ensure reliable operation throughout the device lifetime. These requirements become increasingly important at the nanoscale, as the growing density of interfaces and the resulting complexity of interfacial thermal transport pose significant challenges for materials design. As a result, multilayer architectures, combining distinct adhesion and functional layers, are widely use to balance mechanical stability and thermal dissipation.

However, while trends in metal-oxide adhesion strength can be rationalized using descriptors such as the oxide formation enthalpy of the metal, ΔH, the degree of metal-O:2p hybridization governed by the occupation of d-states, or the covalency of the oxide, no comparably intuitive framework exists for understanding thermal boundary conductance (TBC). In this work, we present a systematic experimental study of metal-oxide TBC across a series of metals (Au, Pt, Cr, Ti, and Al), spanning weakly oxidizing metals with filled d states to strongly oxidizing metals with empty d states. The oxide systems range from the predominantly covalent SrTiO3 to the ionic MgO, with intermediate Al2O3. Our findings identify a set of descriptors that link interfacial bonding characteristics to TBC. These insights provide a rational basis for the design and optimization of metal-oxide interfaces with improved thermal management in nanoscale electronic devices.

Nanoglasses are nanostructured amorphous solids with internal interfaces, promise mitigating shear localization  and tuning their functional surface properties. In this work, we investigate the growth mechanisms and structure-properties relationships of Pd₇₇Fe₃Si₂₀ nanoglass thin films with different nanostructural lengths. We selected this composition owing to its excellent glass-forming ability and its noble character.

We grew thin films by magnetron sputtering on different substrates and with different deposition parameters to gain insights into the effect of surface diffusion and the energy of impinging atoms/clusters on the structure of nanoglass thin films. We used surface-sensitive methods, including GI-SAXS, AFM, KPFM, and XPS/UPS, to characterize the structural, chemical, and electronic properties of our thin films. We find that promoting the mobility of the impinging particles results in smoother thin film surfaces with shorter characteristic structural lengths. Conversely, reducing surface diffusion at the substrate and increasing the working gas pressure yields rougher, thin film surfaces and coarser characteristic structural lengths. In all cases, the thin film surfaces are covered by a thin native silicon oxide and correspondingly a subsurface layer enriched in palladium, that may enable to tune the work function of nanoglass thin films. Furthermore, we apply AFM-based methods to probe the small-scale plasticity of deposited nanostructured thin films.

 The identified process-structure-properties relationships provide a roadmap to tailor the structure of nanoglass thin films for their applications in different scenarios, such as protective layer against corrosion and wear, or for electronics and catalysis.
 

Keywords:metallic glasses; nanoglass;  surface, interfaces, and thin films; growth mechanisms.

Nanoscale gap engineering in metallic thin films has been widely investigated as an effective approach for amplifying sensing signals. In our previous nanogap-based systems, however, uncontrolled crack formation, limited control over nanogap dimensions, and poor reproducibility were frequently encountered. These limitations arose from the inherently stochastic nature of nanogap formation, which hindered predictable and reliable device operation.

 In this work, we introduce sonication-assisted nanogap engineering (SANG) as a reliable and scalable strategy for the controlled formation of palladium (Pd) nanogaps in thin films. Mild ultrasonication generates uniformly distributed seed cracks, which reproducibly evolve into sub-20 nm nanogaps upon hydrogen absorption. Importantly, the sensing behavior is not solely dictated by nanogap formation itself but can be systematically engineered through design-oriented control of thin-film mechanics. By tailoring the mechanical balance between the Pd nanogap layer and the underlying polydimethylsiloxane (PDMS) support, the nanogap opening dynamics and the resulting sensing response can be deliberately tuned, enabling predictable and reproducible device performance.

 This design concept is further extended to geometry-controlled SANG thin films, in which patterned nanogap architectures redistribute stress during hydrogenation and effectively suppress localized crack propagation. Such geometrical regulation enhances response linearity and signal predictability while preserving the intrinsic sensitivity associated with nanogap-based transduction mechanisms.

 The nano-engineered thin-film sensors were evaluated using a capacitive readout scheme and demonstrated an ultra-low limit of detection of 3 ppm at room temperature, along with fast and reversible response and recovery times of approximately 20–30 s. Furthermore, the devices exhibited excellent repeatability over more than 100 consecutive sensing cycles, maintaining stable signal amplitudes across a wide hydrogen concentration range. Collectively, these results demonstrate that controlled nanogap formation combined with mechanical and geometrical thin-film design provides a robust pathway toward predictable and reproducible sensing behavior, highlighting the potential of nano-engineered thin films for reliable gas-sensing and related functional applications.

 Advanced functional semiconductor nanostructures that integrate magnetic and electronic functionalities have attracted significant attention for next generation spintronics devices. In particular, high-quality ferromagnetic Co-based Heusler alloy/Ge heterostructures provided a promising platform for high-performance and room-temperature spintronic properties owing to high carrier mobility and compatibility with Si technologies [1-4]. However, the previous works limited the devices with a submicron contact distance between spin injector and detector. For further enhancement in the magnitude of spin signals at room temperature, it is essential to reduce the Ge channel length in the lateral devices. In this study, we explore spin transport at room temperature in Ge-based lateral spin-valve devices with a contact distance less than 100 nm.

 By using molecular beam epitaxy (MBE), an undoped Ge (111) buffer layer was grown on a Si (111) substrate, followed by epitaxial growth of a phosphorus doped n-Ge layer as a transport channel. Next, a ferromagnetic Co-based Heusler alloy was grown by MBE with an ultrathin Fe insertion layer. The heterostructure was processed into nanoscale lateral devices by electron-beam lithography and Ar ion milling with contact distances ranging from 30 to 100 nm, these sizes are one-tenth of these in our previous work [3]. Four-terminal nonlocal spin transport measurements revealed clear and reproducible spin signals at room temperature. Notably, the magnitude of the spin signals was enhanced up to twice as those in our previous work [4]. These results indicate that Ge-based spintronics structures have potential for applications in high-performance semiconductor spintronics devices at room temperature. We will discuss the growth, fabrication process, and spin transport properties in detail.

 The authors would like to thank Dr. Kenta Moto for his experimental support. This work was partially supported by JSPS KAKENHI (24H00034) and JST-ASPIRE (No. JPMJAP2413), MEXT X-NICS (Grant No. JPJ011438), and Spintronics Research Network of Japan (Spin-RNJ).

[1] K. Hamaya, et al., J. Phys. D: Appl. Phys. 51, 393001 (2018).

[2] M. Yamada, et al., Appl. Phys. Express 10, 093001 (2017).

[3] Y. Fujita, et al., Phys. Rev. B 100, 024431 (2019).

[4] M. Yamada, et al., NPG Asia Mater 12, 47 (2020).

Crystalline In2O3 Deposited by PEALD for 3D Ferroelectric Field Effect Transistors Applications

Jaewon Park1, Hyun-Suk Kim*

1Dept.of Energy and Materials Engineering, Dongguk University, 30 Pildong-ro 1(St), Jung-gu, Seoul 04620, Korea

Oxide semiconductors are promising materials for electronic devices due to their electrical, optical, and structural properties. Their high mobility, transparency in the visible light spectrum, and low leakage current make them ideal as active layer in thin-film transistor (TFT). Among them, indium oxides have been extensively studied due to their superior mobility. The thickness of the In₂O₃ layer is a key factor in determining electronic transport properties, significantly affecting TFT performance. Therefore, a comparative analysis of TFTs with varying In₂O₃ thicknesses is essential. Oxide semiconductors can be fabricated via sputtering, solution processing, and atomic layer deposition (ALD). Among these, ALD provides precise thickness control, high uniformity, and excellent step coverage. Plasma-enhanced ALD (PEALD) further improves upon thermal ALD by enabling low-temperature deposition because the plasma can break down precursor molecules and promote surface reactions even at lower temperatures, enhancing surface reactions, and reducing impurities, making it ideal for high-density integrated circuits and 3D structural devices.

In this study, high-quality ultra-thin In₂O₃ films were deposited at 150°C using the self-limiting PEALD growth mechanism. The properties of the In₂O₃ films, including chemical structure and electrical characteristics, were analyzed using XPS, Hall-effect measurements, ellipsometry, and TEM. Furthermore, thermal annealing was employed to induce crystallization, enabling the study of its impact on material properties and device performance. The structural evolution of the annealed films was examined using X-ray diffraction (XRD) to assess crystallization behavior and phase formation. Indium Oxide is integrated into 3D Ferroelectric Field Effect Transistors (FeFET) for advanced memory and logic applications. The vertical stacking of ferroelectric FeFET structures enables high-density, energy-efficient non-volatile memory, contributing to next-generation AI hardware. This integration facilitates the development of more efficient and high-performance electronic systems, contributing to advancements in ultra-low power AI processing technologies.

References

1. Sung-Hwan Choi. IEEE (2020). 168-171.

2. Si, Mengwei, et al. "Scaled indium oxide transistors fabricated using atomic layer deposition." Nature Electronics 5.3 (2022): 164-170.

3. Kim, Hyun Sung, et al. "High performance solution-processed indium oxide thin-film transistors." Journal of the American Chemical Society 130.38 (2008): 12580-12581.

4. Meng, You, et al. "Low-temperature fabrication of high performance indium oxide thin film transistors." RSC Advances 5.47 (2015): 37807-37813.

The integration of two-dimensional (2D) semiconductors with metal nanostructures provides a versatile strategy for tailoring optical responses and enhancing photocarrier generation via plasmon excitation. In this study, Au nanowires (AuNWs) were integrated with MoS2 monolayers to investigate the light-matter interactions in the AuNW-MoS2 integrated systems. Large-area MoS2 monolayers were obtained using the metal-assisted atomic spalling technique. AuNWs were first prepared on a polydimethylsiloxane (PDMS) film by drop casting and subsequently dry-transferred onto the MoS2 monolayers using the PDMS film as a transfer medium. The optical properties of single- and double-AuNW configurations were comparatively investigated through polarization-dependent photoluminescence measurements. In addition, micro-Raman spectroscopy was employed to examine the strain states and doping levels in the MoS2 monolayers induced by AuNW integration. To study photocurrent characteristics, Ag electrodes were fabricated to form planar metal/AuNW-MoS2/metal device structures. Scanning photocurrent mapping measurements were then carried out to elucidate the influence of AuNWs on spatially resolved photocarrier generation and collection processes. These results clarify how plasmonic AuNWs modulate optical absorption and photocarrier transport in MoS2 monolayers, providing insights into plasmon-mediated light-matter interactions in metal-2D semiconductor integrated systems.

This work reports an optimized, highly sensitive, and selective carbon monoxide (CO) gas sensor with a detection limit of 1 ppm, based on n-ZnO/p-CuO core–shell heterojunction nanostructures integrated onto porous laser-induced graphene (LIG). The LIG was fabricated by laser direct writing on a polyamide sheet, followed by the hydrothermal growth of ZnO nanorods and the deposition of a CuO shell using pulsed laser deposition (PLD). By optimizing the CuO shell thickness, the sensor exhibits a fast response time of 8.06 s and a recovery time of 1.38 s. The optimized LIG/ZnO/CuO sensor shows a response of 275% toward 1 ppm CO, which is nearly six times higher than that of the LIG/ZnO sensor (46%) under identical conditions. Furthermore, excellent selectivity toward CO is achieved in the presence of interfering gases such as NO, H₂, NH₃, and NO₂. The sensor also demonstrates good repeatability over multiple gas exposure cycles and stable performance over time. The structural, morphological, chemical, and electrical properties of the samples are systematically investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrical I–V measurements. Owing to the optimized sensing performance, ultra-low detection limit, and reliable quantification under mixed gas environments, the flexible LIG/ZnO/CuO-based gas sensor is well suited for environmental monitoring and smart industrial applications.

Nanostructured transition metal oxides are promising electrocatalysts for alkaline water splitting due to their abundance, stability, and tunable surface properties. In this work, nanostructured cobalt oxide thin films were deposited on Silicon and Ni-foam substrates by metal–organic chemical vapor deposition (MOCVD) and investigated as electrocatalysts for the hydrogen evolution reaction (HER) in alkaline media. The cobalt β-diketonate adducts [Co(hfa)₂ ·tmeda] was used as precursor source since it exhibited suitable thermal behavior for controlled film growth. Phase-selective deposition was achieved, with pure CoO films forming on Ni-foam at 550 °C, while both CoO and Co₃O₄ phases were obtained on Si(100) substrates depending on deposition temperature, highlighting the critical role of the substrate in directing phase formation. Electrochemical measurements in 1 M KOH demonstrate a marked enhancement of HER activity for CoO thin films on Ni-foam compared to the bare substrate, with performance improving as a function of deposition time. Kinetic analysis indicates that the hydrogen evolution reaction proceeds via a Volmer-limited mechanism. These results underline the importance of balancing nanostructure and thickness to maximize electrocatalytic efficiency and confirm MOCVD as a scalable technique for the fabrication of CoO/Ni-foam electrodes for hydrogen evolution reactions.

The authors thank the European Union (NextGeneration EU) for support within the PRIDE project (grant no. RSH2A_000037).

Ruthenium (Ru), owing to its high electrical conductivity and exceptional chemical stability, is capable of maintaining the metallic phase at temperatures of at least 300 °C under typical atomic layer deposition (ALD) conditions, and has therefore attracted increasing attention as a potential alternative electrode material to conventional metals in the semiconductor industry. Among various ruthenium precursors, bis(cyclopentadienyl)ruthenium (RuCp_₂) is particularly promising due to its suitable volatility, high thermal stability, and controllable reaction behavior. When combined with oxygen or surfaces deprived of oxygen, RuCp_₂ enables controlled Cp ligand elimination rather than complete oxidation, thereby suppressing premature precursor decomposition and mitigating carbon contamination during ALD.

In this work, density functional theory (DFT) calculations are employed to systematically investigate the adsorption behavior, as well as the thermodynamic and kinetic characteristics of RuCp_₂ in different configurations and its interaction with O_₂ on various substrate surfaces. The surface models in investigation include (i) TiN(100) surfaces with varied surface states, such as hydrogen-passivated surfaces, or mildly oxygen-induced surface during the nucleation stage, and (ii) stable Ru/RuOₓ(001) surfaces. The results reveal that variations in adsorption configurations and surface terminations lead to significant differences in adsorption geometries, binding energies, and activation barriers. These findings provide a mechanistic basis for understanding nucleation delay in Ru ALD and offer insights into Cp ligand dissociation via oxygen or hydrogen transfer mechanisms. Overall, this study elucidates the surface chemistry in the early stages of Ru ALD using cyclopentadienyl precursors and further establishes a theoretical foundation for improving the selectivity and process compatibility of Ru ALD on TiN substrates.

Thermally reconfigurable magnetic anisotropy is key to adaptive spintronic and microwave devices [1-3], with in-plane uniaxial anisotropy enabling deterministic and low-power magnetization control [4-7]. However, in most metallic thin films, the anisotropy decreases monotonically with temperature, degrading coercivity and resonance stability [8]. Achieving positive or non-monotonic temperature-controlled magnetic anisotropy (TCMA), therefore, remains a critical challenge for temperature-robust magnetic technologies. This study investigates the magnetic and dynamic properties of 20 nm-thick compositionally graded FeGa–B thin films deposited on YZ-cut LiNbO₃ (LNO) substrates. We examine two distinct interfacial configurations: an FeGa-rich interface (Sample A) and a B-rich interface (Sample B). Both configurations exhibit well-defined in-plane uniaxial magnetic anisotropy (UMA) with two-fold symmetry. Temperature-dependent magnetometry and ferromagnetic resonance (FMR) reveal a reversible interchange of easy and hard axes, with magnetic isotropy crossovers at 306 K and 282 K for Sample A and Sample B, respectively, driven by anisotropic thermal expansion of the substrate. We demonstrate a large, non-monotonic TCMA, defined as the rate at which the anisotropy increases or decreases per unit change in temperature. We observe a 2000–2370% increase in magnetic anisotropy within a narrow 60–70 K temperature range, achieving TCMA values of 30–40% K⁻¹ (representing a 10–15× modulation). Complementing this non-monotonic tunability, the films exhibit high saturation magnetization (M_S ≈ 1032–1160 emu/cm³) and exceptionally low, temperature-independent Gilbert damping (α ≈ 2.3–3.0 × 10⁻³) across both interfacial configurations. A quantitative stress model yields a large positive magnetostriction (λ_S ≈ 41–48 ppm). These results establish strain-mediated, thermally adaptive anisotropy as a robust and scalable platform for temperature-tunable magnetic architectures in high-frequency spintronic, sensing, and microwave applications.

References:

[1] Andrieu, S. et al. Phys Rev Mater 2, 064410 (2018).

[2] Dieny, B. & Chshiev, M. Rev Mod Phys 89, 025008 (2017).

[3] Jia, Z. et al. ACS Nano 19, 9452 (2025).

[4] Liu, J., Zhou, L., Li, S., Zhao, E. & Tang, N. Phys Rev B 109, L060404 (2024).

[5] Park, Y. K. et al. Phys Rev Mater 8, 044405 (2024).

[6] Matsumoto, R. & Imamura, H. Phys Rev Appl 14, 021003 (2020).

[7] Imamura, H., Nozaki, T., Yuasa, S. & Suzuki, Y. Phys Rev Appl 10, 054039 (2018).

[8] Callen, H. B. & Callen, E. J Phys Chem Solids 27, 1271 (1966).

Understanding the mechanisms by which oxygen and other ambient species modify phosphorene remains a key challenge, with the impact of the layer thickness and point defects still unknown. Despite its promise as a solid-state lubricant, detailed nanoscale understanding of layer-dependent defect formation, surface reactivity, and potential degradation is still limited. In particular, the possible multilayer-dependent degradation behaviour of phosphorene in the presence of common environmental species such as hydrogen (H), oxygen (O), and hydroxyl (OH) has received little attention. In this work, we perform a systematic density functional theory (DFT) investigation to explore how these chemical species interact with monolayer to 4-layer phosphorene, including systems with and without phosphorus vacancies. Our findings show that H, OH adsorption is energetically not favourable in any layer configurations, while O shows strong exothermic interactions across all thicknesses, regardless of the presence of defects, with the bilayer showing the most favourable interaction with these species. Structural responses, including changes in bond lengths and interlayer spacing, were quantified and found to depend on both the type of adsorbate and the number of layers. The presence of vacancies induces localized distortions but does not compromise the overall structural integrity. Bader charge calculations show charge transfer between phosphorene layers and adsorbates. Overall, our results set a foundation for further work on phosphorene by providing a detailed, layer-by-layer understanding of phosphorene's chemical reactivity in ambient environments and highlight the need to consider layer number, intrinsic defects and environmental species in models of phosphorene.

Altermagnetism is a new magnetic phase of matter identified recently on the basis of theoretical studies [1,2]. Due to the fully compensated magnetic moment combined with the presence of spin polarised electronic bands altermagnetic materials attract a lot of attention as candidates for perspective applications in spintronic devices. Among the variety of altermagnetic materials MnTe in its native NiAs-type hexagonal structure (α-MnTe) is a canonical altermagnet [1-3], previously considered as an antiferromagnet and extensively studied in the past. Initially it has been studied in the form of bulk crystals, then as epitaxial layers, since it can easily be grown by molecular beam epitaxy (MBE). MnTe can occur in several crystalline polytypes: α, β, γ and δ phases ascribed to hexagonal NiAs type, hexagonal wurtzite, cubic zinc blende and cubic rock-salt structure, respectively. In normal conditions hexagonal α is a typical crystallographic structure of MnTe; zinc-blende γ phase occurs only in epitaxial layers grown on suitable substrates. Rock-salt structure (δ phase) is metastable and can be stabilized e.g. by pressure;  whereas wurtzite β-MnTe to our knowledge has been reported only in nonhomogeneous MnTe thin films as a small admixture of secondary crystalline phase regions. Here we report the MBE growth of β-MnTe monocrystalline thin films deposited directly on GaAs(111) substrates and we show how to switch from nearly pure β-MnTe to α-MnTe by slight modifications of the MBE growth conditions. As for the altermagnetic properties of β-MnTe, there is no consensus, yet to our knowledge. By analogy to altermagneric wurtzite MnSe it cannot be excluded, [4] but there is no definite proof for that yet, neither from theory nor from experiment.

[1] Libor Šmejkal, Jairo Sinova, and Tomas Jungwirth, Phys. Rev. X 12, 031042 (2022).

[2] Libor Šmejkal, Jairo Sinova, and Tomas Jungwirth, Phys. Rev. X 12, 040501 (2022).

[3] K. P. Kluczyk, K. Gas, M. J. Grzybowski, P. Skupiński, M. A. Borysiewicz, T. Fąs, J. Suffczyński, J. Z. Domagala, K. Grasza, A. Mycielski, M. Baj, K. H. Ahn, K. Výborný, M. Sawicki, and M. Gryglas-Borysiewicz, Phys. Rev. B 110, 155201 (2024).

[4] Michał J. Grzybowski, Carmine Autieri, Jaroslaw Domagala, Cezary Krasucki, Anna Kaleta,  Sławomir Kret,  Katarzyna Gas, Maciej Sawicki, Rafał Bożek, Jan Suffczyński, and Wojciech Pacuski, Nanoscale 16, 6259 (2024).

Environmental exposure, especially moisture penetration, continues to be a primary factor in the long-term deterioration of solar cells. This study examines sputtered undoped ZnO thin films as an inorganic encapsulating layer to enhance device stability under accelerated ageing circumstances. RF magnetron sputtering was used to deposit ZnO films on solar cells at two different pressures, 0.02 and 0.04 mbar. X-ray diffraction showed that polycrystalline ZnO had formed, and atomic force microscopy showed that the surface shape changed with pressure and then again after being exposed to humidity. X-ray photoelectron spectroscopy showed that the number of oxygen species on the surface went up after being in a humid atmosphere for a long time. Contact angle measurements showed that hydrophobicity decreased slightly after being stored at 50 °C and 80% relative humidity for a long time. These results show that undoped ZnO thin films work well as moisture-resistant encapsulation layers that make solar cells more reliable.

Recently, the interest of rare earths (RE)-doped fluorides has increased in scientific research. These materials show several properties, as low phonon energies and high transparency and they are employed in many applications like bioimaging, optics and photocatalyst. This technology is, also, largely used in solar cells. In fact, a RE-doped fluoride acts as energy conversion layer and absorbs a larger range of solar energy spectrum, enhancing the efficiency of photovoltaic panels. Typically, these systems are binary and ternary fluoride films, composed of an inorganic host based on alkaline metals, like lithium or sodium doped with luminescent species such as europium or erbium.

The optimization of these layers containing luminescent species represents a crucial aspect in order to improve their properties. Several studies about dopant species, material composition and chemical structure of host have been reported.

In this contest, we describe the synthesis of new cesium-based metalorganic complexes, CsY(hfa)4∙2tetraglyme doped with rare earths, RE = Yb(III), Er(III), Nd(III), Eu(III); Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and tetraglyme = 2,5,8,11,14-pentaoxa-pentadecane. The compounds show high stability, good thermal properties and high solubility in ethanol. These adducts represent single sources precursors and they are employed in a sol-gel/spin coating approach for the deposition of doped fluoride-based layers.                        The films have been characterized in terms of structure, morphology and composition using X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX). In addition, their luminescent properties have been investigated through photoluminescent measurements.

C. B. thanks the University of Catania within the Erasmus+Study program.

Keywords:EUV pellicle, pellicle reliability, Zirconium silicide, Co-sputtering, 

Extreme ultraviolet (EUV) lithography pellicles require exceptionally high transmittance to minimize exposure energy loss. While MoSi₂ is currently the dominant material for EUV pellicle applications, ZrSi₂ has attracted growing interest due to its superior EUV transmittance. However, most previous studies have focused on single-material systems, primarily examining optical properties, thermal durability, and hydrogen plasma resistance, with limited attention paid to improving oxidation resistance through compositional control. In this study, composition-engineered zirconium silicide thin films were investigated to enhance EUV pellicle reliability and practical applicability.

Zirconium silicide thin films were deposited on silicon substrates with a 1000 Å dry oxide layer using Zr–Si dual-target co-sputtering. Film composition was controlled by adjusting sputtering parameters and target power ratios, and the results were compared with films deposited using a single ZrSi₂ target. The effect of ZrSi₂ sputtering power on film stability was examined. Nitrogen gas was introduced during both Zr–Si co-sputtering and ZrSi₂ sputtering to form zirconium silicon nitride films, enabling evaluation of nitrogen incorporation on oxidation resistance. In addition, films were stored under ambient conditions or in a vacuum desiccator at 750 mmHg to assess environmental stability. Co-sputtering of ZrSi₂ and Mo under nitrogen atmosphere was further explored to develop Mo–Zr silicide-based EUV pellicle materials.

Oxidation behavior was evaluated using the time-dependent change in sheet resistance as an indicator of material degradation. The time required for a 20% increase in sheet resistance (t20%) was defined as the characteristic oxidation time. The results show that sputtering power, nitrogen incorporation, and storage environment significantly influence t20%, indicating that oxidation behavior can be effectively tuned through composition control.

Overall, composition-tunable zirconium silicide thin films were successfully fabricated by co-sputtering, with selected compositions exhibiting improved oxidation stability compared to low-power ZrSi₂ films. Nitrogen incorporation and vacuum storage further suppressed oxidation, while preliminary results indicate that Mo-containing Mo–Zr silicide films offer enhanced oxidation resistance, demonstrating strong potential for improving EUV pellicle reliability.

The monolithic integration of III-V semiconductors such as GaAs on silicon substrates is a key strategy to achieve high-efficiency, low-cost photovoltaic devices. Theoretical models predict that a GaAs/Si tandem cell could reach an efficiency of 29.2% under the AM1.5G spectrum, while also enabling the development of cost-effective triple-junction architectures [1]. However, the heteroepitaxy of GaAs on Si is hindered by a 4.1% lattice mismatch, anti-phase domain formation, and dislocation propagation, all of which degrade the material’s electronic and optical properties.

To address these challenges, we developed the Epitaxial Lateral Overgrowth on Tunnel Oxide from nano-seeds (ELTOn) method, which enables defect-free integration of GaAs on Si through selective epitaxial growth from nanometric openings (< 90 nm) in an ultra-thin tunnel oxide layer (< 2 nm). This approach produces strain-free, epitaxial GaAs microcrystals with excellent electrical connectivity via tunneling through the oxide, offering a robust pathway for monolithic III-V/Si integration [2]. To maximize photovoltaic efficiency, we aim to achieve quasi-continuous GaAs coverage on silicon. While electron beam lithography (EBL) has shown promising results, the interfacial silica layer must remain ultra-thin to preserve electronic transport. We are therefore developing nanosphere lithography (NSL), a scalable and low-cost surface texturing method that allows precise pattern transfer onto the SiO₂ surface while maintaining its integrity and enabling localized, electrically connected crystal growth.

For the development of a functional GaAs/Si tandem cell, precise control of GaAs doping is essential. Due to the micrometric size of the crystals, conventional measurements are not applicable. We have developed a contactless characterization technique based on the temperature-dependent bandgap variation, investigated via microphotoluminescence. Using Pässler’s analytical four-parameter model [3]—an improvement over Varshni’s semi-empirical relation [4]—we account for bandgap narrowing in doped materials and ensure accurate estimation of physical parameters [5]. We first validated this method on homoepitaxial GaAs grown layers, with crystal orientations chosen to mimic heteroepitaxial growth on silicon, to investigate the influence of the V/III precursor ratio on residual doping [5]. This technique will be applied here directly to GaAs microcrystals obtained via NSL.

This work represents a critical step toward demonstrating an high efficiency monolithically integrated GaAs/Si tandem solar cell, while maintaining compatibility with industrial, low-cost silicon substrates.

[1] D. Mencaraglia et al., 36th European Union Photovoltaic Solar Energy Conf. Proc. (EU PVSEC), 2019, pp. 753-756

[2] C. Renard et al., Sci. Rep. 6 (2016) 25328

[3] R. Pässler, Phys. Status Solidi B (1999) 216, 975

[4] Y. P. Varshni, Physica 34 (1967) 149

[5] D. Mencaraglia et al., Phys. Status Solidi (A) (2024) 2400609

Understanding carrier dynamics is crucial for developing advanced semiconductor materials and optoelectronic devices across fields ranging from photovoltaics and light-emitting diodes to sensors and emerging quantum materials. While steady-state photoluminescence (PL) provides valuable information on optical quality, it often falls short in revealing the full picture of how charge carriers recombine, migrate, and interact with local defects.

Time-resolved photoluminescence (TRPL) and lifetime imaging techniques offer deeper insights by resolving carrier lifetimes, recombination pathways, and diffusion behavior with high temporal and spatial resolution. Combining TRPL with intensity-dependent measurements helps disentangle radiative and non-radiative processes and quantify how excitation conditions influence carrier transport, key parameters for optimizing material design and device performance.

In this contribution, we demonstrate how PicoQuant’s MicroTime 100 confocal TRPL microscope system enables detailed characterization of carrier diffusion and recombination dynamics in a wide range of semiconductor materials. Using hybrid perovskites as a showcase, given their broad relevance from photovoltaics to photodetectors, we illustrate how time- and space-resolved PL mapping can connect structural heterogeneity to electronic behavior. The same approach applies to diverse materials such as III-V semiconductors, 2D materials, quantum dots, and organic semiconductors.

This flexible measurement platform supports researchers aiming to optimize fabrication processes, reveal defect-related loss channels, and better understand fundamental transport mechanisms, all essential steps for advancing next-generation optoelectronic devices and functional materials.

The widespread use of antibiotics has caused significant concerns regarding their residues in food, as these residues may pose risks to human health and cause substantial economic losses. Consequently, the development of rapid, sensitive, and cost-effective methods for detecting low concentrations of multiple antibiotics in food samples is essential. In this study, MXene fibers were fabricated by coating commercial nylon yarns with different MXenes, and subsequently employed as sensing units in an impedimetric electronic tongue (e-tongue). An e-tongue is an analytical instrument that operates under the concept of global selectivity in which cross-sensitivity arises from the ability of each sensing unit to respond differently to various compounds present in the sample, rather than being selective for a single analyte. The collective response of all sensors generates a unique signal pattern or fingerprint for each analyzed sample, which can be differentiate by specific data processing techniques. Specifically, MXene-coated nylon fibers were fabricated using titanium carbide and carbonitride compositions (Ti3C2Tx, Ti3C1.75N0.25Tx, and Ti3C1.5N0.5Tx, where Tx stands for surface terminations) and employed as low-cost electrodes for an impedimetric e-tongue. These MXenes were selected because variations in their carbonitride structures and surface terminations give rise to distinct electrical behaviors, enabling the generation of complementary sensing responses for the e-tongue. Additionally, their inherently high electrical conductivity makes them particularly suitable as sensing elements in devices operating by electrical impedances. These MXene-fiber-based e-tongue was then employed to detect and differentiate trace amounts of three antibiotics, namely cloxacillin (CLO), tetracycline (TET), and streptomycin (STR), in cow and goat milk samples. Analysis of the electrical resistance data enabled the system to discriminate among the antibiotics and to detect their presence in real milk samples at concentrations as low as 10 nM. The use of low-cost MXene-modified nylon fibers as electrodes, which can be fabricated using rapid and straightforward methods, improves the scalability and practical applicability of the e-tongue system for dairy products.

Two-dimensional (2D) materials such as α-molybdenum trioxide (α-MoO₃) have attracted increasing attention for ultraviolet (UV) optoelectronic applications due to their wide bandgap, layered crystalline structure, high dielectric constant, and strong sensitivity to thermal treatments. Despite their promise, conventional integration routes often rely on costly or complex fabrication processes, which limits accessibility for low-resource laboratories. In this work, we present a low-cost and reproducible approach to synthesize, integrate, and characterize α-MoO₃ microstructures for proof-of-concept electronic devices.

α-MoO₃ microstructures were synthesized via Joule heating and subsequently mechanically exfoliated to obtain thin flakes. These flakes were transferred onto pre-patterned devices with metal contacts to enable electrical characterization. Structural and morphological analysis was performed using Raman spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), confirming the formation and transfer of α-MoO₃ flakes onto the contact region. Functional characterization included current–voltage (I–V) measurements and photoresponse evaluation under UV illumination. Additionally, thermal treatments in air and under vacuum were carried out to investigate the impact of atmospheric conditions on conductivity and device behavior.

Overall, this study establishes a practical experimental route for the preliminary integration of α-MoO₃ flakes into simple electronic structures, supporting its potential for future sensing and UV photodetection applications. Current efforts focus on baseline structural and functional characterization as a foundation for subsequent device optimization.

Thermochromic Liquid Crystals (TLCs) are a material whose structure and optical properties change with temperature. This makes them a useful material in temperature measurement applications. Characterising the response of TLCs under various conditions is crucial to ensuring their effective implementation in practical applications. The use of transmission measurements to characterise TLC performance under varying conditions has not been fully explored. In addition, the extent of undesirable phase change caused by overheating, and whether a threshold for permanent damage exists, remains poorly characterised. This paper aims to study the effects of film thickness, hysteresis, and overheating on the performance of TLCs using a light transmission setup. Here, performance refers to the behaviour of %Transmission vs Wavelength spectrum. An inflection wavelength vs temperature graph can additionally be derived to analyse TLC behaviour. A Polarization Light Microscopy (PLM) setup was also used to analyse the structural change of TLCs during heating and cooling. R35C10W TLCs were applied to a clear surface using a thin film applicator. The thickness was confirmed using profilometer and a thin film measurement system. Light transmission through the sample, as a function of temperature and wavelength, was measured using a Spectrophotometer.  Temperature was controlled using a customised sample holder with a a Peltier-Thermistor feedback loop. Measurements were repeated for different TLC film thicknesses. Initial results show a reduction in transmission magnitude for film thickness, hysteresis and overheating effects are currently being measured.  Data analysis techniques will be employed to assess changes in TLC performance due to above effects. Changes to the TLCs structure will be observed under the PLM setup during temperature change. Image processing techniques will be used to enhance and clarify visualisation of structural changes within the TLC film. A full uncertainty analysis will also be completed. These results establish practical limits on TLC film thickness and thermal cycling limits and will provide design guidelines for TLC-based thin-film temperature sensing. 

The rapid expansion of the digital information ecosystem has intensified the demand for scalable and physically secure encryption technologies. While software-based encryption is cost-effective and easily deployable, it remains vulnerable to attacks, whereas conventional hardware-based approaches offer stronger security at the expense of scalability and manufacturing complexity. Nano-engineered optical coatings provide a compelling alternative by exploiting tailored light–matter interactions for optical security. However, their practical deployment is often hindered by lithography-dependent fabrication routes.

Here, we present a scalable, self-assembly-driven thermal processing strategy for the deterministic design of reconfigurable nano-engineered thin-film coatings. The approach harnesses thermomechanical instabilities arising from thermal expansion mismatch and surface energy minimization to generate ordered 1D, 2D, and 3D microstructures. By systematically controlling film thickness, interfacial energetics, and processing temperature, we achieve precise control over microstructure geometry, orientation, and periodicity across diverse thin-film material systems. A universal mathematical framework is developed to quantitatively describe microstructure evolution and to establish predictive design rules linking thin-film mechanics to functional coating architectures.

Moving from materials design to device realization, we demonstrate a 16-pixel hybrid optical encryption device based on chalcogenide glass thin-film coatings, in which each pixel encodes information through a distinct microstructural motif. The device exhibits an exceptionally low decryption probability (~10⁻⁵³), high information density, and robust reconfigurability under repeated thermal and mechanical cycling. This work establishes thermo-mechanically programmed thin-film coatings as a viable and scalable platform for high-security optical encryption, exemplifying how nano-engineered coatings can be rationally designed and translated into real-world device applications.

Vacuum-based synthesis of chalcogenide perovskites (CPs) is a promising route for high-quality thin films, yet achieving high crystallinity at device-compatible temperatures below 600 °C remains a challenge. While sulfur excess is known to lower the crystallization temperature, the impact of the sulfur's chemical state during initial precursor deposition is often overlooked.

We investigate the growth and crystallization of BaZrS_₃ using a two-step process: reactive sputtering of Ba-Zr-S amorphous precursor films followed by post-sulfurization. Specifically, we compare two distinct reactive sulfur sources during the sputtering stage: thermally cracked elemental sulfur (S_x), delivered as a high-flux beam, and molecular hydrogen sulfide (H₂S), introduced as a diffuse reactive gas.

Using combinatorial synthesis and high-throughput characterization, we demonstrate that although the S_x source generates a higher sulfur partial pressure while maintaining the target in the transition zone, the H₂S-derived precursors result in superior crystallinity and a Ba:Zr ratio that is closer to the ideal 1:1 ratio when annealed at 600 °C. In contrast, precursors sputtered with the Sx beam were consistently Zr-rich. Comparative studies on binary Ba-S films suggest that H₂S provides a favorable reactive environment for Ba incorporation during the initial deposition.

Our results suggest that the "chemical memory" of the precursor film is just as critical as the final thermal budget. We demonstrate that by optimizing the sulfur source during reactive sputtering, we can achieve high-quality crystalline films at moderate temperatures. These findings offer a practical strategy for producing high-performance chalcogenide films at 600 °C, demonstrating that industrial scalability need not come at the expense of material quality.

High-k TiOxNy-based MIS devices have been developed using DC reactive magnetron sputtering on n-type Si substrates. The layers were obtained using a gas mixture of O2/N2 ambient. The MIS structure exhibited excellent capacitance-voltage (C–V) and current-voltage (I–V) characteristics. 

The physical parameters, such as fixed charge density (Qeff), dielectric constant (k) of the layers, flat-band voltage (VFB), interface defect density (Dit), etc., of the device were evaluated from C-V and I-V measurements. A minimum value of flat band shift (~0.5V) with a lower Qeff (-5.7x1011 C/cm2) has been achieved. Also, for this sample, the C-V measurements showed a very small hysteresis and very low-frequency dispersion. The energy distribution of defect states was evaluated, and it was maximum towards the bottom of the conduction band. The defect density has been tailored by means of the elemental composition change. The defects were further studied using deep-level transient spectroscopy (DLTS). The DLTS results showed that the defect distribution across the interface has been composition dependent and are multiple defect levels that are closely spaced, for instance at 0.38 eV, 0.47 eV and 0.52 eV. An ideality factor of 1.48 was obtained from the forward bias I–V characteristics. The TiOxNy films showed a high dielectric constant of ~ 50. The TiOxNy/Si devices showed superior electrical properties before and after the annealing as a result of the nitrogen incorporation in the oxide bulk and at the interface. The study demonstrated the tuneablity of electrical parameters of the interface of the device with the variation of composition. A detailed analysis is presented, keeping in view of tuning of electrical characteristics of the interface with respect to O2/N2.

The Smart Surfaces group at ISSMC‑CNR is actively engaged in the development of Slippery Liquid‑Infused Porous Surfaces (SLIPS) [1], an emerging class of bioinspired materials that we tailor to fabricate coating to reduce ice accretion, a persistent challenge across multiple industrial sectors, including aviation [2]. SLIPS replicate natural non‑stick mechanisms by integrating a porous inorganic ceramic scaffold, chemically functionalized with fluoroalkyl silane molecules, and subsequently infused with a polymeric lubricant. This architecture produces a stable, low‑adhesion liquid interface capable of repelling contaminants and significantly reducing ice buildup [3–4]. The group’s multidisciplinary research activities encompass the design, fabrication, and performance evaluation of hybrid SLIPS coatings under both ambient and sub‑zero conditions. These activities include Round Robin testing to assess ice adhesion strength and droplet dynamics, providing interlaboratory validation of coating performance. In parallel, icing phenomena are investigated through modelling and controlled experimentation conducted in an icing wind tunnel housed within a cold climate chamber, enabling the reproduction of real‑world operating conditions, such as those encountered on aeronautical air intakes. Over the past five years, these efforts have been integrated into the ICELESS consortium, a collaboration with specialists from Università degli Studi di Napoli Federico II and Politecnico di Torino. The project aims to develop a multilayered, bioinspired ice‑control system that emulates the functionalities of human skin, particularly its synergistic combination of protection, regulation, and responsiveness. Within this framework, passive and active strategies are combined to address the limitations of current anti‑icing technologies, particularly with regard to energy consumption and adaptability.
The multilayer platform integrates complementary technologies, including: i) Nanostructured coatings for passive anti‑wetting and anti‑icing behavior; ii) Biochar‑based smart heaters enabling efficient, localized de‑icing; iii) Ultrasound actuators to mechanically disrupt frost; iv) Embedded electronics and sensors for continuous monitoring; v) Machine‑learning modules for data‑driven optimization and autonomous control.
The final objective of the ICELESS initiative is the realization of a self‑regulating anti‑icing platform capable of minimizing energy use while improving flexibility and responsiveness to variable environmental conditions. By combining bioinspired surface chemistry, smart materials, and active control technologies, the project aims to deliver a transformative solution that surpasses the performance constraints of current ice‑mitigation systems.

[1] Wong, T.S. et al. 2011, 477, 443-447
[2] Subramanyam, S. B. et al. Langmuir 2013, 29, 13414
[3] Corozzi, A.et al. Coatings 2021, 11, 77
[4] Veronesi, F.et al. Surface & Coatings Technology 2021, 421,127363

Hafnium-doped Zinc oxide (HZO) thin films with a thickness of ~50 nm were deposited on Si (100) and glass substrates at 250 °C using atomic layer deposition (ALD). Post-deposition rapid thermal annealing (RTA) was carried out in the temperature range of 300-450 °C with an interval of 50 °C to systematically investigate the effect of annealing on the structural, optical, and electrical properties of the films. The HZO films were characterized using grazing-incidence X-ray diffraction (GIXRD), scanning electron microscopy, atomic force microscopy, spectroscopic ellipsometry, photoluminescence spectroscopy, Kelvin probe measurements, Hall-effect measurements, current–voltage (I-V) analysis, and impedance spectroscopy.

GIXRD analysis confirmed that the HZO films are polycrystalline with a hexagonal wurtzite structure with a predominant (100) preferred orientation. The films exhibited high optical transparency, with an average transmittance exceeding 80% in the visible and near-infrared (NIR) regions. The optical transmittance increases with annealing temperature, reaching an average value of ~ 95% for film annealed at 450 °C. Hall effect measurements reveals that the as-deposited film exhibit a minimum resistivity of 1.5 mΩ·cm and a carrier concentration of 2.48 × 1020 cm^-3. With increasing annealing temperature, the resistivity increases while both the Hall mobility and carrier concentration decrease, indicating annealing-induced modification of defect states and carrier scattering mechanisms. Photoluminescence measurements show a systematic reduction in emission intensity with increasing annealing temperature, suggesting suppression of defect-related radiative recombination. The work function of the HZO films was determined using Kelvin probe measurements, providing further insight into their surface electronic properties, with a change of work function in the range, 4.76-4.82 eV. In addition, the electrical behavior of Al/HZO/Si/Al heterostructures annealed at different temperatures was investigated using I-V and impedance spectroscopy measurements, revealing clear annealing-dependent transport characteristics of the interface.

These results indicate that post-deposition annealing significantly influences the optoelectronic balance of ALD-grown HZO thin films, leading to enhanced optical transparency accompanied by a reduction in electrical conductivity. This behavior underscores the importance of optimizing annealing conditions to achieve an appropriate trade-off between transparency and conductivity for transparent conducting oxide applications in photovoltaic devices. Detailed results will be presented at the conference.

This study investigates the combined effects of a hydrogen environment and cyclic loading on the structural integrity of pipeline steels and pressure vessels. The microstructural evolution and diffusion behavior in polycrystalline BCC-Fe and Inconel alloys were analyzed using Molecular Dynamics (MD) simulations. Two hydrogen concentrations (H/Fe = 0.005 and 0.01) were examined under 6 and 12 loading cycles to characterize hydrogen segregation, dislocation density, and Mean Square Displacement (MSD). The results indicate that hydrogen atoms preferentially segregate at grain boundaries (GBs) and dislocation cores. Notably, increasing hydrogen concentration decreases dislocation density, indicating a significant pinning effect that hinders dislocation multiplication. Additionally, the decline in MSD with increased hydrogen content confirms enhanced interactions between hydrogen atoms and lattice defects, limiting atomic mobility. In contrast, increasing the number of cycles from 6 to 12 has a minor effect on overall dislocation density compared to the effect of concentration. This research provides atomistic insights into hydrogen-induced damage mechanisms under cyclic stress, providing a theoretical foundation for predicting the lifespan of hydrogen energy infrastructure.

Recombination of the photo-generated charge carriers at the silicon surface is one of the major factors limiting the efficiency of silicon solar cells. To mitigate the surface recombination losses, many passivating contacts has been proposed over the years, which usually require 10 to 15 nm thickness for effective silicon surface passivation. However, for efficient charge collection, a high level of silicon surface passivation is required together with low contact resistivity.

Titanium oxide (TiO₂) is used as an electron contact for silicon solar cells. In this study, we demonstrate a high level of silicon surface passivation by atomic layer deposited ultrathin TiO₂ films. To evaluate the correlation between the film thickness and the passivation quality, TiO₂ films of various thicknesses were deposited on undiffused silicon substrates. The surface passivation was activated by post-deposition annealing in hydrogen ambient. A minority carrier lifetime of 1.54 ms is achieved corresponding to a TiO₂ thickness of 2.5 nm. X-ray diffraction measurements were performed for structural analysis, which revealed that the films are rutile in nature. Electrical properties of the films are studied in detail by electrochemical impedance measurements.

The results demonstrate that the ultrathin TiO₂ films are capable of providing excellent silicon surface passivation comparable to the other state of the art passivating layers, together with an uninterrupted collection of the charge carriers.

The mechanisms governing silicon surface passivation by thin hafnium oxide (HfO₂) films on p-type silicon deposited using plasma enhanced atomic layer deposition (PEALD) at different ALD cycles was investigated. The films with 10 and 50 ALD cycles (3 nm and 7 nm) exhibited thickness dependent passivation behavior. The as-deposited HfO₂ films showed poor surface passivation with a high interface defect density (Dᵢₜ ~1012 cm-2 eV-1). After thermal treatment, the passivation quality improved with a remarkable reduction in the Dᵢₜ by approximately two orders of magnitude (~1010 cm-2 eV-1) and also reduction in hysteresis and trap charges for the 7 nm film, indicating effective chemical passivation. The reduction in positive fixed charges after post-annealing is attributed to structural and chemical reconfiguration, as confirmed by XPS analysis. The films were further systematically characterized by FTIR, and electrical properties were studied in detail using frequency dependent C-V, G-V measurements and impedance spectroscopy. The results demonstrate that PEALD-deposited HfO₂ is a promising candidate for silicon surface passivation at relatively lower deposition temperatures.

Inorganic multilayer films of radiative cooling can overcome issues like photothermal degradation and lack of selectivity in the infrared spectrum. In this work, we propose an inorganic multilayer film strategy that adopts a simple film structure, namely, SiNx/(L/H/L/H)/SiNx/Ag/glass(substrate) (where L and H represent low and high refractive index materials, respectively), to achieve high performance of daytime radiative cooling. The film structure utilizes impedance mismatch to enhance solar reflection and complementary spectral contributions between different materials to enhance emissivity in the atmospheric window. The effectiveness of this design was demonstrated by using a multilayer film composed of SiO₂, TiO₂, and SiN_x. This film possesses a high reflectivity of 91.6% in the solar spectrum and selective radiation in the atmospheric window (8−13 μm) with an emissivity of 90.9%. Our calculation shows that the film temperature can achieve a steady-state temperature of 10 K below the ambient temperature under common solar radiation. The prepared multilayer film is tested under real outdoor temperature conditions, demonstrating significant subambient cooling effects. This study introduces an effective strategy for daytime radiative cooling using inorganic multilayer films. 

Aluminum-doped zinc oxide (ZnO:Al), owing to its wide band gap, high optical transparency, and enhanced electrical conductivity, has attracted considerable attention in optoelectronic applications. When the heterojunction is formed with p-Si (ZnO:Al/p-Si), the ZnO:Al layer effectively suppresses the surface dead layer that is commonly present in silicon homojunction devices. This suppression significantly enhances the ultraviolet photoresponse, leading to an improved photosensitivity and response speed in photodetectors.

In this study, ZnO:Al/p-Si heterojunction was fabricated using RF magnetron sputtering. The ZnO:Al films were developed at varying RF powers in the range, 100-200 W at room temperature to explore the opto-electronic characteristics of the devices. The influence of RF power on structural, optical, and electrical properties were analysed using different techniques. Grazing incidence X-ray diffraction (GIXRD) analysis confirmed that the films crystallized in a hexagonal wurtzite structure and the RF sputtering power affected the crystalline quality of ZnO:Al films. SEM and AFM analyses reveal dense and homogenous distribution of small grains on the surface of the film. The films exhibited high optical transmittance (>80%) in the visible region with a wide band gap of 3.39 eV, as studied using UV-Vis-NIR spectroscopy. The films showed a minimum electrical resistivity of 1.39x10^-4 W-cm at the sputtering of 100 W. The photoresponse behaviour of ZnO:Al/p-Si heterojunction diodes was systematically investigated under varying illumination intensities at a wavelength of 355 nm. The current vs voltage characteristics showed that increasing illumination intensity affects the reverse current. The fabricated diodes exhibited a high responsivity of 129 mA/W. The combined increase in reverse current and high responsivity confirms that ZnO:Al/p-Si device simultaneously exhibits photovoltaic and photoconducting characteristics. Also, time-dependent photocurrent measurement revealed that the transient response is strongly influenced by the illumination intensity, as well the deposition power. This suggests efficient carrier dynamics and fast response times, making the device suitable for optoelectronic applications such as photodetectors and solar cells.

Metal-semiconductor (MS) contacts are crucial part for semiconductor devices. Their performance is primarily dominated by the barrier at the contact interface, which varies with different deposition methods and its parameters. Although nickel is widely employed for forming schottky contacts on p-type silicon, achieving sufficiently low barrier heights remains a significant challenge for efficient hole transport. In this study nickel (Ni) metal films were deposited on p-type silicon substrates using DC magnetron sputtering at different power ranging from 40W to 100W, to investigate the influence of plasma power on the electrical properties of Ni/p-Si device including, interface quality and its performance. Structural and topographical characterization via GI-XRD and AFM revealed that surface of the film is smoother at lower powers. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics showed that the barrier height is directly influenced by the DC sputter power. The higher DC sputter power lowers the work function of deposited Ni films, which reduced the barrier height (Φ_b) and ideality factor (n) from 0.517 eV to 0.478 eV and 2.95 to 2.17. The surface damage from plasma resulted the change in energy distribution of the interface states over the band-gap of Si, as evaluated from the I-V characteristics by taking into account of the bias dependence of the effective barrier height (Φ_eff). The interface defect density (D_it) was found to be lower (8.35×10¹³ cm^-2 eV^-1) at the power of 80 W. Impedance spectroscopy (EIS) analysis has further elucidated the interface transport mechanisms at different sputter power, which was studied using equivalent circuit parameters of the Ni/p-Si diode. These findings highlight the optimized DC sputter power as a key parameter for the fabrication of efficient carrier transport schottky contacts with improved interfaces for the application of various semiconductor devices such as silicon solar cells, photodetectors, field-effect transistors, etc.

High-quality 2D transition metal dichalcogenides (TMDs) with a controlled number of layers are an emerging platform for next-generation optoelectronics. Here, we report the synthesis of MoSe2 and WSe2 films on quartz and sapphire substrates via the selenization of pre-deposited MoOx and WOx layers using atmospheric pressure thermally assisted conversion (TAC). The composition and structure of the synthesized layers were validated by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, while transmission electron microscopy (TEM) and optical spectrophotometry provided further morphological and optical characterization. Finally, we demonstrate the integration of these films as transparent conductive electrodes in polymer-dispersed liquid crystal (PDLC) light shutters. This cost-effective synthesis approach paves the way for new technological applications of few-layer MoSe2 and WSe2, particularly in the field of ITO-free electro-optics.

Acknowledgements: We acknowledge the Bulgarian Science Fund support under the project numbers КП-06-H-58/12 and КП-06-КОСТ/24. Financial support from the Research equipment of distributed research infrastructure INFRAMAT (part of Bulgarian National roadmap for research infrastructures) supported by Bulgarian Ministry of Education and Science is also acknowledged. Research equipment of the project № BG16RFPR002-1.014-0006 "National Centre of Excellence Mechatronics and Clean Technologies" was used for experimental work financially supported by European Regional Development Fund under "Research Innovation and Digitization for Smart Transformation" program 2021-2027.

Two-dimensional (2D) materials have gained significant attention for their exceptional physical properties and wide applications for next-generation electronic, spintronic, and optoelectronic devices. This study presents the synthesis and characterization of van der Waals heterostructures composed of graphene and platinum diselenide (PtSe2), with two distinct stacking configurations: PtSe₂/Graphene and Graphene/PtSe₂. The proposed systems provide a platform to investigate how interfacial interactions and stacking order influence the overall optoelectronic properties. The heterostructures were analysed using Atomic Force Microscopy (AFM), Raman spectroscopy, and UV-Vis-NIR spectrophotometry. The analyses confirm the successful fabrication and structural integrity of the heterostructures, revealing that the optical and vibrational properties are dependent on the specific layer arrangement. Our findings highlight the potential for tuning the system's behaviour through structural design, demonstrating a viable pathway for engineering novel electronic and optoelectronic devices.

Acknowledgements

Acknowledgements: We acknowledge the Bulgarian Science Fund support under the project number КП-06-H-68/1. Financial support from the Research equipment of distributed research infrastructure INFRAMAT (part of Bulgarian National roadmap for research infrastructures) supported by Bulgarian Ministry of Education and Science is also acknowledged. Research equipment of the project № BG16RFPR002-1.014-0006 "National Centre of Excellence Mechatronics and Clean Technologies" was used for experimental work financially supported by European Regional Development Fund under "Research Innovation and Digitization for Smart Transformation" program 2021-2027. 

Area-selective atomic layer deposition (AS-ALD) is a promising patterning strategy for future semiconductor integration, particularly in high-aspect-ratio (HAR) structures where conventional etch-based approaches face scaling limitations [1]. Although self-assembled monolayers (SAMs) have been widely explored as molecular inhibitors for AS-ALD, their evaluation in confined HAR geometries remains limited [2].

Here, we report a tunable HAR testbed platform based on a lateral trench structure for evaluating SAM-enabled area-selective TaN deposition. The testbed consists of SiO2/Mo multilayer stacks fabricated by plasma-enhanced chemical vapor deposition of SiO2 and sputtering of Mo films. A sandwich-structured geometry enables controlled exposure of Mo sidewalls through independent adjustment of the Mo film thickness and etchant-driven lateral under-etch depth, allowing the formation of HAR features without reliance on advanced lithography.

An alkylphosphonic acid SAM was employed as a representative molecular inhibitor using a solution-based process, exploiting selective P–O–metal chemisorption on Mo relative to SiO2 surfaces [3]. Subsequent thermal TaN ALD using pentakis(dimethylamido)tantalum and NH3 was performed, and the feasibility of SAM-enabled AS-ALD of TaN on HAR Mo sidewalls was evaluated using microstructural and compositional analyses. This work establishes a versatile HAR Mo testbed for probing SAM-assisted AS-ALD and provides a practical platform for assessing area-selective deposition strategies relevant to back-end-of-line interconnect scaling.

[1] R. Valliyil et al., J. Vac. Sci. Technol. A 39, 021002 (2021).

[2] M. J. M. Merkx et al., Appl. Surf. Sci. 607, 155032 (2023).

[3] E. Cianci et al., Chem. Mater. 31, 1004–1013 (2019).

Atomic layer deposition (ALD) enables conformal modification of complex porous substrates via sequential self-limiting reactions, yet precursor infiltration into high-surface-area networks often remains limited, especially for low-reactivity molecules with low sticking probability. Here, we revisit static ALD and develop a combined experimental–numerical framework to clarify how precursor residence time governs mass transport, surface reaction, and infiltration uniformity in porous media.

Porous alumina was used as a model substrate with diethylzinc (DEZ) and tetraethoxysilane (TEOS) representing precursors with markedly different sticking behavior. By introducing a controlled residence period between exposure and purge steps, we systematically quantified mass gain and infiltration depth. To interpret the trends, a transient diffusion–reaction model was constructed to simulate precursor concentration and surface-coverage evolution inside cylindrical pores. Model fitting enabled quantitative extraction of precursor-dependent parameters, including the sticking coefficient and an effective site-engagement parameter (effective denticity).

Extending residence time produced only marginal changes for highly reactive DEZ, whereas it substantially increased TEOS uptake and penetration depth. The analysis further indicates an optimal residence time that balances infiltration efficiency against process throughput. These results highlight the chemistry-dependent impact of static ALD operation and provide a generalizable framework for predicting and designing precursor infiltration in porous materials.

Controlled vapour-phase deposition of metals is essential for the fabrication of thin films used in electronics and photovoltaics, but it remains a costly and complex process. Recently, our experimental collaborators (Prof. Ross Hatton, Warwick Chemistry) demonstrated a new approach to selective deposition using a thin organofluorine layer to prevent metal adsorption in specific regions during vapour deposition. As the exact nature and strength of the interactions between various metals and organofluorines compounds was unclear, we utilised electronic structure calculations based on density functional theory (DFT) to unravel the atomistic details of these interactions and how they influence selective deposition. In particular, we found that the condensation of zinc onto a surface can be made highly selective, as its interactions are extremely weak and dominated by dispersion forces. 

We then employed classical molecular dynamics simulations to explore the morphology of the organofluorine surface and its impact on metal adsorption and growth. The simulations revealed that the structure and mobility of the organofluorine surface play an important role in the distinctly different adsorption behaviors observed for zinc and silver - which are not captured by single-molecule models. These results highlight the importance of intermolecular interactions and surface morphology in controlling metal condensation during thin-film growth. 

Together, this combined experimental and theoretical approach provides new insight into the atomistic and nanoscale mechanisms governing selective metal thin-film deposition, and has important outcomes for the rational design of photovoltaics and nano-engineered coatings. 

References: 

P. Bellchambers, L. Ammon, A. Fitkin, M. Dingley, M. Walker, S. Abrahamczyk, C. Pritchard, G. C. Sosso, R. A. Hatton, Zinc Grid Based Transparent Electrodes for Organic Photovoltaics. Adv. Energy Mater. 2025, 2405148. https://doi.org/10.1002/aenm.202405148 

J. Lee, S. Varagnolo, M. Walker, R. A. Hatton, Transparent Fused Nanowire Electrodes by Condensation Coefficient Modulation. Adv. Funct. Mater. 2020, 30, 2005959. https://doi.org/10.1002/adfm.202005959 

P. Bellchambers, C. Henderson, S. Abrahamczyk, S. Choi, J.-K. Lee, R. A. Hatton, High Performance Transparent Silver Grid Electrodes for Organic Photovoltaics Fabricated by Selective Metal Condensation. Adv. Mater. 2023, 35, 2300166. https://doi.org/10.1002/adma.202300166 

The rapid evolution of next-generation immersive display technologies, such as virtual and augmented reality (VR/AR), has created an urgent demand for ultrahigh-resolution displays. A pixel density of at least 3,000 pixels per inch (PPI) is required to suppress the "screen-door effect" where pixel gaps become visible at near-eye distances. This requirement necessitates the miniaturization of thin-film transistors (TFTs) to the 1-µm channel length regime.

In this work, we demonstrate high-performance 1-µm short-channel SATG In-Sn-Zn-O (ITZO) TFTs incorporating an Al₂O₃/SiO₂ dual-layer gate insulator (GI) heterostructure. ITZO was selected as the active channel material for its exceptionally high field-effect mobility and on-state current, which originate from the efficient electron transport pathways formed by the extensive overlap of In/Sn 5s orbitals at the conduction band minimum. However, fully capitalizing on these superior material attributes in highly scaled devices remains a significant challenge. Scaling SATG TFTs to the 1-µm level typically triggers severe short-channel effects (SCEs), such as negative threshold voltage (V_th) shifts and drain-induced barrier lowering (DIBL), caused by the lateral diffusion of carriers from n+ source/drain regions.

To overcome these challenges, we strategically implemented an Al₂O₃/SiO₂ stacked GI, which balances high gate capacitance with effective leakage suppression. Our optimized 1-µm SATG ITZO TFTs achieve outstanding electrical characteristics: a field-effect mobility of 38.76 cm²/Vs, a steep subthreshold swing of 0.08 V/decade, and an on/off current ratio of ~10⁸. Remarkably, the devices exhibit negligible DIBL (≈0 mV/V) and superior bias stability, with a V_th shift of only +0.23 V under negative bias stress (NBS).

Significantly, this study extends beyond the mere realization of 1-µm scale device operation. While several studies have reported the electrical characteristics of few-micron-scale SATG oxide TFTs, systematic investigations correlating GI film quality and interfacial engineering with performance to elucidate enhancement mechanisms remain scarce. Therefore, we conducted a comprehensive analysis to uncover these critical impacts. The fundamental mechanisms were further elucidated using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). The analysis reveals that the dielectric stack effectively passivates dangling bond-related defects at the GI–channel interface. Furthermore, it reinforces the structural integrity of the underlying SiO₂ bulk. Consequently, the high-performance 1-µm-channel SATG ITZO TFTs and the underlying mechanisms identified in this study represent substantial advancements, offering significant implications and value that extend to the broader field of future semiconductor industries.

Organic-inorganic perovskite solar cells (PSCs) have attracted a huge interest in the emerging photovoltaic field owing to their tunable band gap, high absorption coefficient, long diffusion length and high carrier mobility. At present, high efficiency PSCs are usually fabricated by spin coating process. However, spin coating has issues such as the use of toxic solvents, high solution waste and not suitable for large-area devices. Therefore, in this work, we deposited high quality perovskite film using a two-step evaporation (PVD)/blade coating method, which is scalable to large-area PSCs. Firstly, the difference of lead iodide (PbI2) films by PVD and spin coating process was investigated. It is found that the spin-PbI2 film possesses a porous structure that is highly beneficial for the penetration of organic salt. However, the PVD-PbI2 film is compact, leading to the inferior morphology of the obtained perovskite films by reacting with organic salts at room temperature. Therefore, we developed a temperature-assisted crystal growth to modulate the crystal growth and the morphology, and the high-quality perovskite films could be acquired by PVD and blade coating method. Consequently, a champion efficiency of 19.8% was realized, which is one of the highest values prepared with this strategy. Theses results suggest that two-step PVD and blade coating method offer a feasible way for the industrial production of perovskite solar cells in the future.

Two-dimensional (2D) transition metal dichalcogenide (TMD) lateral heterostructures provide a versatile platform for highly integrated and energy-efficient electronic and optoelectronic devices. Their atomically thin geometry and seamless in-plane heterointerfaces enable precise electrostatic control of carrier transport, making them attractive for reconfigurable device architectures[1]. Here, we use a water-assisted one-pot chemical vapour deposition method for the monolithic growth of MoSe₂–WSe₂ multijunction lateral heterostructures with controlled domain sizes and layer thicknesses[2]. Raman and photoluminescence spectroscopy confirm high crystallinity, sharp interfaces, and excellent optical quality of the as-grown heterostructures. Field-effect transistors fabricated on individual domains exhibit intrinsic n-type and p-type transport characteristics in MoSe₂ and WSe₂, respectively, enabling seamless in-plane p–n junction formation. Electrical measurements across the heterointerface show clear diode-like behaviour, validating high-quality lateral junctions. Beyond conventional diode operation, the same heterostructure platform demonstrates gate-reconfigurable multifunctional behaviour, including bipolar junction transistor action and electroluminescence, realized within a single monolithically grown structure. These results highlight the potential of lateral TMD heterostructures as a unified materials platform for reconfigurable, multifunctional all-2D in-plane devices, paving the way for scalable integration in next-generation low-power electronics.

Reference:

1. Chakraborty, S. K., et al. Seamless in two dimensions: prospects of lateral heterostructures from integration to quantum devices. npj 2D Mater Appl 9, 94 (2025).

2. Sahoo, P. K., et al. “One-pot growth of two-dimensional lateral heterostructures via sequential edge-epitaxy”. Nature 553, 63–67 (2018).

Amorphous metal-oxide semiconductor (MOS) thin film transistors (TFTs) have become indispensable elements in modern large-area flat-panel (or flexible/foldable) displays, shaping the progress of display technology over the past decade. Their widespread adoption is largely due to a combination of exceptional properties, including relatively high carrier mobility, excellent optical transparency, uniform performance across large areas, and stable electrical operation. Among the various materials investigated, MOS such as indium-gallium-oxide (In-Ga-O), indium-zinc-oxide (In-Zn-O), zinc-tin-oxide (Zn-Sn-O), indium-zinc-tin-oxide (In-Zn-Sn-O), and indium-gallium-zinc-oxide (In-Ga-Zn-O) have been extensively studied as active n-channel materials, demonstrating significant potential for high-performance oxide TFTs. Despite these advancements, the reliance on indium and gallium poses economic and sustainability challenges. Both elements are scarce and costly, which limits their long-term industrial use in large-area electronic applications. To address this, alternative materials with comparable electronic performance are being explored. Tin (Sn) stands out as a particularly attractive candidate, as it is abundant, environmentally benign, and possesses electronic characteristics and ionic radii similar to indium. This makes it a viable replacement in the development of cost-effective and sustainable oxide TFTs.

In this context, transparent zinc-tin-oxide (a-ZTO) thin films integrated into TFTs have shown promising results. Optimized flexible a-ZTO TFTs demonstrate a high saturation mobility(μsat), a low subthreshold swing (SS), and an impressive ON/OFF current ratio (ION/IOFF). Furthermore, these devices exhibit excellent bias stress stability and reliable performance under a range of environmental conditions, making them suitable for practical deployment in display backplanes. The superior electrical performance of a-ZTO TFTs is closely linked to the better quality of the films. High film density and smooth surface morphology contribute to reduced oxygen-related defects, resulting in improved conduction pathways for efficient electron transport. This, in turn, enhances the switching behavior and long-term operational stability of the a-ZTO TFT. The demonstrated performance and stability of a-ZTO TFTs highlight their strong potential as a next-generation semiconductor material. By combining affordability, abundance, and excellent electrical characteristics, a-ZTO stands as a leading contender to drive advancements in large-area flat/flexible panel display technologies.

The growing demand for high-data-rate communications in space missions drives the need for radiation-tolerant and high-performance optical materials. Optical fiber components such as amplifiers, laser systems, lidar, and navigation instruments are widely used in space technologies due to their reliability, availability, and cost effectiveness. As data transmission requirements continue to increase, the development of functional materials capable of maintaining optical performance under harsh space environments becomes critical.

In this work, erbium-based thin films were developed as functional optical layers and coatings for space applications. Erbium and erbium oxide thin films were synthesized using pulsed laser deposition (PLD) and characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy. Cross-sectional microstructural analysis was performed using focused ion beam (FIB) preparation combined with high-resolution transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS). Ion–solid interactions and damage profiles were investigated using Monte Carlo simulations based on the SRIM/TRIM code.

Structural and chemical analyses confirmed the formation of crystalline erbium oxide phases with controlled stoichiometry and surface composition. The films exhibit characteristic Er³⁺ 4f–4f optical transitions, demonstrating strong and stable photoluminescence in the UV-visible regions.

Morphological analysis shows uniform film growth, while spectroscopic measurements indicate that the optical response is strongly linked to the local chemical environment of Er³⁺ ions. These results highlight the potential of erbium-based thin films as radiation-resilient optical materials suitable for space communication systems. The findings contribute to the development of durable photonic coatings and functional layers capable of supporting next-generation space and terrestrial optical technologies.

The integration 2D van der Waals heterostructures with nonplanar photonic platforms offers new opportunities for controlling excitonic and phononic properties beyond conventional planar substrates. Here, we report the direct growth of vertical MoS₂/WS₂ heterostructures on optical fiber substrates using a solution-assisted CVD approach, alongside growth on SiO₂/Si for comparison. The heterostructures are synthesized in a single uninterrupted growth process without sample transfer.

Raman spectroscopy reveals clear substrate-dependent modulation of phonon modes in the heterostructures. For MoS₂, the in-plane E′ mode in the heterostructure grown on optical fiber exhibits a blue shift of approximately 1.6 cm^-1 relative to its counterpart on SiO₂/Si, while the out-of-plane A′ mode remains largely unchanged. A similar but weaker blue shift is observed for the E′ and A′ modes of WS₂. Importantly, the characteristic mode separations for both materials remain constant across substrates, confirming the preservation of monolayer thickness. In addition, fiber-supported heterostructures display enhanced resolution of second-order Raman modes, particularly the 2LA mode of WS₂, suggesting reduced substrate-induced damping and modified dielectric screening on the curved fiber surface.

Photoluminescence measurements further demonstrate pronounced substrate-driven excitonic modulation. For heterostructures on SiO₂/Si, the MoS₂ and WS₂ intralayer excitonic peaks appear at approximately 1.82 eV and 1.93 eV, respectively, exhibiting modest red shifts relative to standalone monolayers due to interlayer electronic interactions. In contrast, heterostructures grown on optical fibers show a MoS₂ excitonic peak at ~1.79 eV and a WS₂ peak at ~1.96 eV. Notably, the WS₂ exciton in the fiber-supported heterostructure is blue-shifted by ~ 60 meV relative to standalone WS₂ on fiber, indicating a substantial reconfiguration of excitonic recombination pathways.

In addition to intralayer exciton modulation, a low-energy emission feature at 1.35 eV is observed in fiber-supported heterostructures but is absent on planar substrates. Power-dependent photoluminescence analysis shows that this emission saturates at higher excitation power, consistent with recombination involving spatially indirect states. The energetic position and substrate selectivity of this feature support an interpretation that involves enhanced interlayer coupling.

Overall, this study demonstrates that optical fibers act as active substrates that significantly influence both phononic and excitonic properties of vdW heterostructures. By directly integrating MoS₂/WS₂ heterostructures onto curved fiber surfaces, we show that substrate geometry can serve as an effective parameter for tuning lattice vibrations, excitonic energies, and interlayer interactions. These findings open new opportunities for incorporating 2D heterostructures into fiber-based photonic and optoelectronic platforms.

In the present contribution we report on the epitaxial growth and characterization of thin refractory high entropy alloy films within the W-Nb-Ta-V-Mo system (W, W-V, W-Nb-V and W-Nb-Ta-V-Mo). Films are deposited by magnetron co-sputtering at ultra-high vacuum conditions using a variety of power schemes, including direct current, radio frequency, and high-power impulse magnetron sputtering. Growth experiments are carried out over a wide temperature range (300 – 1100 K) on MgO(001) substrates. Synthesis conditions are adjusted for obtaining equimolar compositions, as established by time-of-flight elastic detection recoil analysis (ToF-ERDA). ToF-ERDA data also show that the films are ultra clean containing miniscule fractions of O, H, and C impurities (< 1 at.%). Comprehensive structural characterization by means of x-ray diffraction (XRD) methods – including Bragg-Brentano, pole figure, and reciprocal space mapping measurements – shows that at all deposition conditions films grow epitaxially on the MgO(001) substrate with orientation relationship (001)film||(001)MgO;[110]film||[100]MgO. This orientation relationship is also confirmed by electron backscatter diffraction (EBSD). XRD rocking-curve measurements indicate that the films exhibit considerable mosaic spread with peak broadening (full width at half maximum-FHMW) of the order of 1-2 degrees. Investigation of the top-view morphologies by scanning electron microscopy (SEM) shows that films grown at 800-1000 K exhibit micrometer-size holes (seemingly associated with thermal stresses), whereas films grown at lower temperatures exhibit rather smooth surfaces. The overall results of our work provides the foundation for synthesizing high quality epitaxial layers of high-entropy alloys that can serve as platforms for understanding fundamental physical properties (including thermal stability and radiation resistance) in this class of technologically important materials.       

Precise resistors are essential components in many electronic systems and should maintain stable physical and electrical properties throughout the complete process flow. Tantalum nitride (Ta_xN_y) materials are particularly well suited for these applications due to their excellent thermal stability and tunable resistivity [1].

This work aims to provide a deep understanding of properties of 45 nm-thick Ta_xN_y thin films, deposited by reactive physical vapor deposition (PVD) with nitrogen concentration varying between 10 and 55 at.%. Additionally, this study investigates the impact of a post-deposition annealing treatment at 400 °C for 20 minutes.

After reactive PVD deposition, secondary ion mass spectrometry (SIMS) analyses permit us to identify two distinct zones as well as a surface region with a constant nitrogen concentration of 10, 27, and 55 at.% N, and a sub region near the underlayer SiO₂ layer interface where nitrogen concentration sharply increases. This increase is likely due to nitrogen adsorption occurring at the early stages of deposition. Grazing incidence X-ray diffraction (GIXRD) results reveal three distinct Ta_xN_y phases corresponding to the increasing nitrogen content of each sample: a body-centered cubic TaN_0.1 phase, a hexagonal Ta₂N phase, and a face-centered cubic δ-TaN phase, consistent with the SIMS findings. Electrical measurements show that film resistivity increases with nitrogen concentration, with average values within 300 mm Si wafers of 147 ± 13, 236 ± 4 and 274 ± 5 µΩ.cm respectively.

After annealing, SIMS analyses demonstrate nitrogen diffusion near SiO₂ interface, decreasing with the increase of nitrogen content, and becoming negligible at the highest level. Furthermore, no change is observed in nitrogen concentration at the top surface of Ta_xN_y layer. Regarding GIXRD, only the low nitrogen sample exhibited a shift of diffraction peaks towards lower angles, indicating slight lattice expansion after annealing, while patterns for the medium and high nitrogen samples remain unchanged. Resistivity increased from 274 ± 5 to 316 ± 6 µΩ.cm for the nitrogen-rich sample after annealing, whereas no major changes are detected for other samples

 All experimental results will be presented and discussed in this paper to establish the best process conditions for high stability precise resistor integrations.

1.         M. Cheviot et al., Surf. Coat. Technol., vol. 284, pp. 192–197 (2015).

Nitride-based hard coatings, such as titanium nitride (TiN), are widely used in industrial applications, including cutting tools, due to their exceptional hardness, chemical stability, thermal resistance, wear resistance, and fracture toughness. Enhancing these properties through ternary compositions, such as titanium zirconium nitride (TiZrN), could improve performance under abrasive and high-stress conditions.

This work examines the impact of nitrogen partial pressure (NPP) on the structural and mechanical characteristics of TiZrN coatings. The samples were deposited by reactive magnetron sputtering in an industrial-scale system equipped with a segmented Ti–Zr rotating cathode, enabling Ti/(Ti+Zr) variations along the chamber height. The synthesis of the coatings was carried out at five distinct NPP values — 0.008 Pa, 0.018 Pa, 0.040 Pa, 0.100 Pa, and 0.200 Pa — under constant argon pressure (0.300 Pa). Reference binary TiN and ZrN films were deposited under similar conditions. The chemical composition was determined by EDS, while the film texture and phase composition were characterised by XRD. Nanoindentation provided hardness and elastic modulus values, and K_IC (critical stress intensity factor in mode I), an indicator of fracture toughness, was measured via microcantilever bending tests.

Results indicated that the highest nitrogen incorporation occurred at a NPP value of 0.200 Pa. All deposited coatings exhibited a single-phase face-centred cubic (NaCl-type) structure, confirmed by characteristic (111), (200), and (220) reflections. Higher titanium content consistently led to a decrease in lattice parameter. Growth rate decreased markedly with rising NPP, from approximately 26 nm/min at the lowest pressure to 9 nm/min at the highest. All coatings displayed a pronounced columnar microstructure independent of composition or nitrogen pressure.

Mechanical performance showed a clear dependence on NPP and Ti/(Ti+Zr) ratio. Both hardness and elastic modulus reached their maximum values of 31 ± 1 GPa and 440 ± 5 GPa, respectively, at 0.040 Pa (Ti/(Ti+Zr) = 0.5), thereby markedly outperforming binary TiN (hardness = 25 ± 3 GPa). These properties improved from the lowest NPP up to 0.040 Pa before decreasing at higher pressures. Fracture toughness of reference TiN was 2.2 ± 0.4 MPa·m^1/2. Addition of zirconium resulted in a substantial toughness enhancement in the ternary system, with values increasing from 2.6 ± 0.2 MPa·m^1/2 at 0.008 Pa to 2.8 ± 0.3 MPa·m^1/2 at 0.040 Pa, then levelling off at higher NPP.

The presented results demonstrate that careful adjustment of nitrogen partial pressure during deposition offers an effective strategy for tailoring the microstructure and mechanical performance of TiZrN coatings for advanced industrial tooling applications.

Life Cycle Assessment (LCA) provides a rigorous analytical framework for quantifying the environmental performance of products and processes across all maturity stages. While established for industrial systems, its integration at low Technology Readiness Levels is essential for driving sustainability-informed Research & Development. By identifying environmental hotspots during early-stage development, LCA enables targeted optimization of experimental protocols and material design, ensuring that mitigation strategies are implemented before scale-up. 

This study quantifies the environmental footprint of a laboratory-scale Metal Organic Chemical Vapor Deposition (MOCVD) process for TiO₂/Al₂O₃ coatings, using a cradle-to-gate LCA approach in compliance with ISO 14040 and 14044 standards. The functional unit was defined as a 16 cm² S235J0 steel substrate coated with approximately 200 nm of TiO₂ and 400 nm of Al₂O₃.

System boundaries included reactor heating and evacuation, nitrogen carrier and dilution flows, precursor provision (TTIP, ATI) with container management, reactor cleaning, and post-synthesis N₂ annealing; substrate manufacture and end-of-life stages were excluded to isolate process-specific impacts. Primary data were collected at ICMATE-CNR (Padua) and integrated with Ecoinvent 3.10 and literature-derived secondary data.

Life Cycle Impact Assessment (LCIA) was performed using SimaPro 9.6.0.1 and the Environmental Footprint (EF) 3.1 method. Results identified electricity and nitrogen consumption as the dominant environmental hotspots, primarily during heating and evacuation. Conversely, metalorganic precursors contributed less than 1.2% of the total impact. Evaluated mitigation strategies included the adoption of renewable energy, the optimization of process durations and substrate amounts, and the replacement of the nitrogen-based trap with an alternative abatement system. The combined implementation of these strategies achieved an 83.7% reduction in overall environmental impact. These findings underscore the importance of incorporating LCA into early materials development, providing a robust basis for sustainable design and facilitating the transition to industrial-scale production.

Acknowledgements: This research was funded by the European Union – NextGeneration EU from the Italian Ministry of Environment and Energy Security POR H2 AdP MMES/ENEA with involvement of CNR and RSE, PNRR - Mission 2, Component 2, Investment 3.5 "Ricerca e sviluppo sull’idrogeno". WP2.2 - LA2.2.4 - Rivestimenti di condutture per il trasporto H2: Sviluppo di coating ossidici, metallici e ibridi e processi per la loro deposizione. CUP: B93C22000630006.

Threading dislocations (TDs) propagating across a gallium nitride layer grown on a foreign substrate can be blocked and/or deflected by employing an intrinsic interlayer. In this contribution, the role of a structured interlayer comprising micro-voids in reducing the TD density and in manipulating the residual stress in the top part of the GaN coatings is illustrated. The whole stacks were grown using high-temperature vapor phase epitaxy (HTVPE) on (0001)-oriented sapphire substrates that were first covered by a seed layer. The structured interlayers were produced via changing the parameters of the HTVPE process. For each parameter set, which involved mainly the total chamber pressure, the H₂/NH₃ flow rate ratio, and the temperatures of the substrate and the Ga melt, two samples were fabricated—one without and one with a top layer. Scanning electron microscopy studies confirmed that the variability of the parameters of the HTVPE process allows for the generation of different microstructure features within the interlayers—from facetted voids up to the 3D columnar structures. The X-ray diffraction investigations indicated that these features can help to reduce the TD density, especially in thicker top layers. Furthermore, it was found out that the kind of microstructure features present in the interlayers mainly affects the dependence of the decrease of the TD density in the thickness of the top layer. Moreover, based on the results of the micro-Raman spectroscopy, the impact of the interlayer on the depth and lateral profile of the residual stress will be discussed.

A comparative investigation was conducted on the oxidation behavior and corrosion mechanism of silicon carbide (SiC) ceramics with different additives in a wet environment (75 vol.% H₂O/25 vol.% air) within the high-temperature range of 1000–1200 °C. The results demonstrate as follows: Pure SiC ceramics exhibit markedly different oxidation morphologies, with numerous cracks on the surface of the resulting oxide layer. In contrast, the oxide layers surface of SiC ceramics doped with 10 wt.% (Al₂O₃-RE₂O₃) additives are covered with β-Y₂Si₂O₇, δ-Gd₂Si₂O₇, and β-Yb₂Si₂O₇ crystals, which efficiently inhibits oxide layer cracking. Meanwhile, the introduction of water vapor significantly accelerates the oxidation reaction of SiC-10 wt.% (Al₂O₃-RE₂O₃) ceramics at 1000 °C and 1100 °C, facilitating the formation of a protective silica (SiO₂) passivation layer that efficiently suppresses the material’s further oxidation. However, at 1200 °C, water vapor induces corrosion of the SiO₂ oxide layer, which in turn results in substantial mass loss. Surface scanning electron microscopy (SEM) observations after 10 h of corrosion at 1200 °C reveal that the surface porosity of the oxide layers follows the descending order: SiC-10 wt.% (Al₂O₃-Y₂O₃) ceramics (26%), SiC-10 wt.% (Al₂O₃-Gd₂O₃) ceramics (10%), and SiC-10 wt.% (Al₂O₃-Yb₂O₃) ceramics (5%). The thickness of the porous oxide layer on the surface of SiC-10 wt.% (Al₂O₃-Yb₂O₃) ceramics is only 3 μm. Corrosion kinetic analysis demonstrates that SiC-10 wt.% (Al₂O₃-Y₂O₃) ceramics exhibit the highest weight loss rate (≈2.6×10⁻² mg·cm⁻²·h⁻¹), whereas SiC-10 wt.% (Al₂O₃-Yb₂O₃) ceramics display the lowest weight loss rate (merely 2.8×10⁻⁴ mg·cm⁻²·h⁻¹). The oxidation activation energy of SiC-10 wt.% (Al₂O₃-Yb₂O₃) ceramics in wet atmosphere is 174 kJ/mol, the highest among the three SiC-10 wt.% (Al₂O₃-RE₂O₃) ceramic composites. This confirms that SiC-10 wt.% (Al₂O₃-Yb₂O₃) ceramics exhibit superior corrosion resistance. This superior performance stems from the flaky rare-earth pyrosilicate (β-Yb₂Si₂O₇) crystalline layer formed on the surface of SiC-10 wt.% (Al₂O₃-Yb₂O₃) ceramics, which significantly reduces surface water adsorption. Furthermore, the flaky morphology minimizes the contact between H₂O molecules and the SiO₂ oxide layer, thus improving the corrosion resistance of SiC-10 wt.% (Al₂O₃-Yb₂O₃) ceramics under wet conditions.

Increasing performance or durability of materials at moderate temperature requires the development of new ceramic coatings, including more elements or specific chemical compositions. However, the composition space can be wide and the development of machine learning could be thus appropriate to provide indications of relevant composition to limit experimental work.

It was decided to create our own database of ternary coatings: Al_xCr_1-xN, Al_xTa_1-xN and Cr_xTa_1-xN. These coatings are deposited by magnetron sputtering in a reactive atmosphere, with variable power applied on the two metallic targets involved. For each system, five compositions are obtained with a thickness close to 1 micrometer, on silicon substrate. Each coating is annealed in air at temperatures between 400 °C and 900 °C, leading to 72 samples. Then, the chemical composition is obtained by EDS, crystalline phases identification is performed by XRD, topography and cross-section are observed with SEM.

The influence of the metallic stoichiometry on coating structures and oxidation behavior is studied. Exploratory data analysis with visualization tools are used to extricate evolution trend. And at last, machine learning classification techniques are evaluated to suggest next compositions to be deposited.

This study investigates the fabrication of hollow, double-shell submicron fibers using a combination of electrospinning and atomic layer deposition (ALD). The hierarchical structures consist of an inner Al₂O₃ shell and an outer transition metal oxide (TMO) shell – specifically, cobalt, nickel, or iron oxides. The synthesis protocol comprises four steps: (1) electrospinning of poly(vinyl alcohol) (PVA) templates; (2) low-temperature ALD of an Al₂O₃ sacrificial scaffold; (3) high-temperature annealing to remove the polymer core; and (4) thermal ALD of the functional TMO layer. To preserve the structural integrity of the PVA templates, the initial Al₂O₃ layer was deposited at 60 °C. After polymer removal (500 °C in air for 24 h), the TMO layers were deposited at 230 °C using metallocene precursors (MeCp₂) and ozone (O₃). Structural and chemical characterizations were carried out by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The SEM imaging confirmed the formation of uniform hollow double-shell morphologies, while the XPS and XRD verified the elemental composition and crystallinity of the TMO/Al₂O₃ interface. Owing to their high specific surface area and tunable shell composition, these submicron structures show strong potential for applications in heterogeneous catalysis and chemical sensing.

Acknowledgment. This work was financially supported by the Bulgarian National Science Fund, Project No. KP-06-N88/7.

Metastable phases in functional thin films often exhibit superior properties compared to their thermodynamically stable counterparts, yet remain underexploited because conventional thermal processing (e.g., furnace heating, hot-plate annealing) relies on conduction and convection heat transfer that simultaneously heats the film and the substrate. This substrate-coupled processing restricts temperatures to the substrate's thermal stability limits, preventing access to metastable phases on low-thermal-stability substrates for diverse applications. Additionally, the slow cooling rates inherent to conventional methods provide sufficient time for thermodynamic relaxation, generally favoring stable over metastable phases.

We introduce Flash Photonic Heating (FPH) as a transformative platform enabling kinetic control of metastable phase formation through ultra-fast heating and cooling rates (10⁶-10⁷ °C/s, compared to 0.01-1 °C/s for conventional furnace annealing), made possible by substrate-decoupled processing via direct photonic absorption of the film, while the substrate remains unharmed.

Using Bi₂O₃ thin films prepared by pulsed laser deposition (PLD) and doctor-blade coating, we establish that identical material composition requires dramatically different FPH parameters based on microstructural differences. Despite nearly identical optical absorption, porous doctor-blade films undergo the α→β transformation with a single sub-millisecond pulse (total energy: 3 J/cm²), whereas compact PLD films require multiple sequential sub-millisecond pulses with repetitions (total energy: 20 J/cm²). Both undergo the same phase transformation when peak power reaches ~30 kW/cm², while millisecond-duration pulses at lower peak powers (~2-5 kW/cm²) yield thermodynamically stable α-Bi₂O₃. This reveals that pulse duration and peak power determine the crystallization pathway, while microstructure-dependent thermal transport properties dictate the energy and pulse strategy required.

The metastable β-Bi₂O₃ exhibits a narrower bandgap (2.35 eV vs. 3.15 eV for α-Bi₂O₃) and enhanced charge separation. Microstructural analysis and thermal simulations confirm that sub-millisecond, high-peak-power pulses induce melt-recrystallization mechanisms, achieving film surface temperatures exceeding 1950°C while maintaining glass substrates below 100°C.

This established framework enables the rational design of FPH processing parameters to control polymorphism across diverse thin film systems, from functional oxides to refractory materials, providing a transformative platform for accessing metastable phases with enhanced properties for energy and advanced materials applications.

Aluminum nitride (AlN) belongs to the class of ultrawide bandgap (UWBG) semiconductors that has wurtzite-structured nitride with a direct bandgap of 6.12 eV [1]. Its piezoelectricity has already established AlN as a key material in microelectromechanical systems (MEMS), particularly in radio-frequency (RF) filters. The electrical properties of AlN have been studied extensively through both experimental and theoretical approaches. For example, improvement in the piezoelectric properties of AlN has been reported through the co-addition of Mg with different transition elements [2–4]. Theoretical calculations predicted that co-addition of magnesium (Mg) and gold (Au) into AlN may yield the highest piezoelectricity among the examined combinations of Mg with different transition elements [2]. In this study, MgAu-doped AlN thin films were fabricated, and their electrical properties were examined. Contrary to theoretical predictions, the MgAu-doped AlN thin film did not exhibit piezoelectricity. However, it showed significant enhancement in electrical conductivity, suggesting that the functional scope of AlN‑based thin films may extend beyond MEMS and potentially include broader electronic applications such as UWBG electronic or optoelectronic applications. Therefore, the effect of adding Mg and Au into AlN on electrical conductivity was further investigated herein. 

All thin films were deposited on Si (100) wafer via reactive sputtering by using RF sputtering system (Kenix, Japan). The concentration of each element was controlled by adjusting the power of cathodes for each corresponding target during thin film deposition. The concentration of each element in thin films was investigated by using energy dispersive spectroscopy (Horiba, Japan). The current-voltage (I-V) characterizations were done at room temperature by using electrometer unit (Keysight, USA).

The I-V characteristics of AlN indicates low current below the detection limit of the unit (10^-13 A) at ± 5V, confirming its insulating nature. Incorporating Mg into AlN resulted in a slight increase in current, while Au-doped-AlN thin films exhibited a larger increase, demonstrating that addition of either Mg or Au into AlN enhanced its electrical conductivity. However, co-addition of Mg and Au into AlN resulted in substantially higher current values, approximately 10¹⁰ times higher than that of pure AlN, suggesting significant enhancement in electrical conductivity. This considerable increase in electrical conductivity warrants further investigation into the underlying enhancement mechanism to elucidate the synergistic behavior resulting from the co-addition of Mg and Au.

Acknowledgement: This work was supported by JSPS KAKENHI Grant No. JP25K07841

REFERENCES

[1] Taniyasu et al, Nature, 441 (2006) 325.

[2] Hirata et al, JSAP Spring Meeting 2022, 23P-P06-1.

[3] Uehara et al, Appl. Phys. Lett., 111 (2017) 112901-1.

[4] Anggraini et al, Scr. Mater., 22 (2019) 9.

Heterostructures composed of Bi₂Se₃ and Nb, including Bi₂Se₃/Nb and Nb/Bi₂Se₃/Nb geometries, are promising platforms for superconducting proximity effects and quantum device applications. For such systems, maintaining the intrinsic properties of each layer while forming a well-defined interface is essential. However, the Bi₂Se₃/Nb interface is highly susceptible to interfacial reactions and degradation of Bi₂Se₃ film quality. Although cleavage-based approaches have been reported to access clean interfaces, their applicability is limited by poor process reproducibility and device compatibility. In this work, the effects of Bi₂Se₃ deposition conditions on film quality and Bi₂Se₃/Nb interfacial characteristics are systematically investigated by varying the substrate, post-deposition annealing temperature, and the repetition number of Bi and Se deposition cycles. Bi₂Se₃ thin films with a thickness of approximately 20 quintuple layers were grown by alternating thermal evaporation of Bi and Se in a vacuum chamber below 10^-7 Torr. Nb superconducting thin films were deposited by DC magnetron sputtering. For Bi₂Se₃ deposited on Nb, annealing above 175 °C significantly enhances the diffusion of oxygen and Nb into the Bi₂Se₃ layer, resulting in dominant Bi-O and Nb-Se bonding and a reduction in Bi₂Se₃ thickness. In contrast, annealing at temperatures below 150 °C suppresses oxygen and Nb diffusion, preserving Bi-Se bonding. An interfacial layer of approximately 5 nm, attributed to an Nb_xSe_y phase, is consistently observed over the investigated annealing temperature range. This behavior is distinctly different from Bi₂Se₃ deposited on SiO₂, where Bi₂Se₃ remains stable without interfacial layer formation even above 200 °C, demonstrating the critical influence of Nb on Bi₂Se₃ film quality and interfacial chemistry. Furthermore, when Nb is deposited on Bi₂Se₃, an ultrathin interfacial layer of approximately 1 nm, also attributed to an Nb_xSe_y phase, is observed. The influence of the Bi/Se deposition repetition number is also examined. Increasing the repetition number effectively suppresses Nb diffusion into the Bi₂Se₃ layer, whereas a low repetition number leads to noticeable Nb diffusion and a deviation from stoichiometric Bi₂Se₃. The superconducting transition temperature of the underlying Nb layer remains above 8.7 K, indicating that Nb superconductivity is preserved during Bi₂Se₃ growth. These results provide practical guidelines for process-compatible engineering of Bi₂Se₃/Nb heterostructures for superconducting and quantum device applications.

This work was supported by Electronics and Telecommunications Research Institute (ETRI) grant funded by the Korean government [25YB1900] and was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No. RS-2025-02311266).

The relentless scaling down of semiconductor feature size is closely intertwined with the advancement of extreme process technology such as nanometer or atomic scale deposition and patterning. From that point of view, controllable atomic layer etching (ALE) has emerged as one of the key extreme technologies for the fabrication of gate-all-around (GAA) channel, i.e., a gate stack of dielectric (SiO2, HfOx) and metal surrounding a nanoscale channel, of GAA- or complementary FET. The controllability of ALE is usually achieved by taking advantage of self-limiting surface reaction, a naturally diminishing chemical reaction either by decreased diffusivity or activity of reactants.        

In the present study, SiO2 thin films were prepared on 6-inch Si(100) wafers of three dimensional microstructures prior to ALE. We applied optimized hybrid ALE, a combined process of the remote plasma-assisted activation of radicals and in turn their thermal reaction on SiO2 surface. The hybrid ALE follows a cyclic sequence comprising (i) surface modification using trimethylaluminum (TMA), (ii) selective fluorination of the modified SiO2 surface by SF6 radicals, and (iii) subsequent removal of fluorinated layer during the following TMA exposure. Our hybrid process is superior to conventional dry etching from the point of view of physical damage and surface roughening because direct ion bombardment, an energy transfer process between colliding particles, can be avoided or substantially reduced at least.         

As a result, we not only obtained the uniformity of etched thickness more than 98 % on a 6-inch wafer scale but ascertained that self-limiting mechanism can also be exploited in the present hybrid ALE for dielectric materials. In addition, we noted that isotropic etching can be realized well even in a GAA-like structure, demonstrating the applicability of the proposed process to complicated 3D nano-device architectures. In conclusion we demonstrated that an optimized heat-plasma hybrid ALE can be applied to nano scale cutting-edge transistors beyond proof-of-concept satisfying wafer-scale process stability and quality simultaneously.

Acknowledgments This work was supported by the Electronics and Telecommunications Research Institute (ETRI) grant funded by the Korean government [26ZB1410]

Magnetron-sputtered thin films can differ markedly from their bulk counterparts, highlighting the need to understand how deposition-induced non-equilibrium effects influence their microstructure and stability.

Fe–Cr alloys serve as a useful model for studying aspects relevant to stainless steels, such as the native oxide layer; however, the properties of sputtered films require detailed characterization first.

In this work, the influence of composition on the microstructure of co-sputtered Fe-Cr thin films is investigated, with a focus on the formation and stability of solid solutions across a range of Cr-to-Fe ratios. Structural analysis was performed using X-ray diffraction (XRD), where a random intercalation model was employed to fit the diffraction data and quantify lattice parameter evolution with composition. These findings were correlated with morphological and compositional analyses via scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS), providing insight into elemental distribution and film homogeneity. These techniques were also employed to assess the effect of a 773 K annealing treatment on sputtered films of different composition.  The results reveal a systematic variation in microstructure with composition and demonstrate the compositional limits for stable solid solution formation under thermal load. This work contributes to the understanding of phase behavior and microstructural evolution in Fe-Cr alloy thin films.

In this work, the investigation behavior of double chromium-copper coating deposited onto samples of alumina ceramics during heating in a vacuum at temperatures of 900 ÷ 1100 °C with holding at these temperatures from 5 to 20 min was investigated. The thickness of the chromium layer was 150 nm and the thickness of the copper layer was 1,5 µm.

The study found that heating the continuous initial coating on alumina ceramics at 900 °C in the time interval of 5 – 20 min did not lead to noticeable changes in it. With an increase in the annealing temperature to 1000 °C, the film gradually began to lose its integrity, but even after a 20-minute holding, the area of ruptures in the film did not exceed 10% of its total area.

After 5 min annealing at 1050 °C, the film was almost continuous, after 10 min, the process of film destruction accelerated a little, and after 20 min, it broke up into large fragments, which were still connected to each other, covering 70% of the surface area of the alumina sample. Annealing at 1100 °C significantly intensified the process of film destruction. Thus, after 5 min annealing, the film covered about 90% of the surface area of the sample, after 10 minutes 65%, and after 20 minutes of annealing, the film occupied only 58% of the surface area of the sample.

Thus, the double coating Cr-Cu can be used to join alumina ceramics at temperatures up to 1050 °C with the duration of the brazing or pressure welding process up to 20 min, and even at 1100 °C it is possible to carry out these joining processes, but limit holding time to 10 min.

The results of the work are differ from these obtained previously for the leucosapphire so the substrate structure influences the coating destruction processes.

According to the research results, the destruction curves of the studied double chrome-copper coating were built, so it is possible to determine the main technological parameters (temperature and holding time at this temperature) for processes where the Cr-Cu coating on alumina ceramics will be used.

The protection and functionalization of metallic surfaces is a major technological challenge for a wide range of industrial sectors, including energy, transportation, electronics and healthcare¹. Beyond simple protection, modern surface engineering aims to impart advanced functionalities to metals, such as enhanced corrosion resistance, controlled wettability, optical responses or improved biocompatibility. In this context, micro- and nano-structured coatings have attracted increasing interest due to their ability to tailor surface properties² through both chemical composition and topographical design.

Sol-gel chemistry represents an attractive route for the fabrication of multifunctional coatings, offering low-temperature processing, compositional versatility and the possibility to introduce barrier, protective or insulating layers on metallic substrates². However, the practical deployment of sol-gel coatings on metals is strongly limited by adhesion issues³. The intrinsic mismatch between metallic bonding at the substrate surface and the covalent network of sol-gel films often results in weak interfacial interactions, leading to cracking or delamination under mechanical stress. To overcome this limitation, a hybrid surface engineering strategy combining dry processes and sol-gel deposition is investigated. The approach relies on the introduction of tailored interfacial layers exhibiting strong affinity for metallic substrates, combined with sol-gel formulations optimized for interfacial reactivity. The adhesion mechanisms at the metal/sol-gel interface are systematically studied, with particular emphasis on the role of surface chemistry and interlayer composition³. Both purely inorganic and hybrid organic–inorganic sol-gel coatings are deposited on metallic substrates with controlled surface finishes, allowing a direct comparison of their adhesion behavior and mechanical robustness⁴. In addition, intermediate layers based on silicon or titanium, as well as hydroxyl-rich surface treatments, are introduced to promote the formation of durable chemical bonds across the interface.

Once robust adhesion is achieved, the sol-gel layers can be further structured using micro- and nano-patterning techniques⁴ such as optical lithography or nano-imprinting, enabling the fabrication of functional surfaces with controlled topography. This combined strategy provides a versatile pathway toward adherent, micro- and nano-structured sol-gel coatings on metals, opening new perspectives for durable and multifunctional surface treatments in demanding industrial applications⁵.

References :

[1] Hussein H.M. et al, Engineering Failure Analysis, 152, 107092 (2023).

[2] Durand H. et al. ACS Applied Bio Materials, 5, 4718-4740 (2022).

[3] Ramezani M. et al. Metals, 13, 21478 (2023).

[4] Valour A. et al, Advanced Materials Interfaces, 46, 1458 (2022).

[5] Crespo-Monteiro N. et al, Materials, 15, 5516 (2022).

Nanotribological Properties of Hybrid Graphene Oxide-Titania Nanotextured Surface

Debottam Datta,*,1 Enrico Gnecco,2 J. P. Singh,3 Nitya Nand Gosvami 4

1 School of Interdisciplinary Research, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India

2 Marian Smoluchowski Institute of Physics, Jagiellonian University, 30348 Krakow, Poland

3 Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India

4 Department of Material Science and Engineering, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India

* Corresponding Author: Debottam.Datta@sire.iitd.ac.in (Debottam Datta)

Biological species, including snakes, fish, and lizards, intelligently control friction and drag forces through their inherent macro- and nanoscale skin textures [1]. Inspired by such biological systems, artificial nanotextured surfaces have been developed in recent years to address real-world engineering challenges associated with sliding interfaces. However, micro- and nanotextured surfaces are susceptible to frictional losses arising from dominant surface forces- such as electrostatic, capillary, and van-der-Waals interactions- due to their high surface-to-area ratio [2]. Consequently, understanding and controlling failure mechanisms and nanoscale frictional behaviour in these textures is essential for achieving the desired tribological performance. In this study, a bio-inspired nanotextured surface is fabricated on a glass substrate by depositing tilted titania nanorods via glancing angle deposition (GLAD). The textured surface is subsequently coated with a solid lubrication layer comprising thin graphene oxide (GO) sheets to develop a hybrid surface. The nanotribological properties of both the hybrid and bare titania surfaces are investigated using friction force microscopy (FFM). The results reveal pronounced anisotropic friction on both the hybrid and bare nanotextured surfaces, due to the asymmetric nanorod patterns. The nanoscale frictional properties are substantiated by additional nanomechanical measurements, which explain the variation in nanotribological properties between the hybrid and bare titania textured surfaces. Furthermore, the hybrid surface exhibits higher wear resistance than bare nanorods due to the shielding effect of the GO layers [2]. Overall, this work demonstrates that bio-inspired GO-coated titania nanotextures provide valuable insights into the role of solid lubrication coatings in tailoring the friction and wear behaviour of micro- and nanotextured surfaces.

References:

1. D. Datta, E. Gnecco, J. Singh, N.N. Gosvami, Enhanced Frictional Anisotropy and Wear Resistance via Bioinspired Hybrid Graphene Oxide-Titania Nanopatterned Surfaces, ChemRxiv (2025).

3. D. Datta, E. Gnecco, N.N. Gosvami, J.P. Singh, Anisotropic Stick–Slip Frictional Surfaces via Titania Nanorod Patterning, ACS Appl Mater & Interfaces 16(33)(2024) 44193-44201.

There is short characteristics of PIXE spectroscopy. Standard setup of the method is effective for material volume element diagnostics owing to the proton penetration depth in conventional conditions of ion beam analytical facilities application is 5-20 mm. But the PIXE conventional spectroscopy can be reoriented into the surface elements diagnostics by use the phenomenon of radiation fluxes waveguide-resonance propagation. The modification implies including into the PIXE setup a Si polished reflector with central hole, which diameter is equal to ion beam cross-section and two Ti strips with thickness 100 nm on edges of inside reflector surface. In the work Ti and studies surface completes the planar waveguide-resonance slit, which is able to lead out the X-ray fluorescence yield characteristic of thin film surface layer, only. Report presents experimental data confirmed absence of X-ray fluorescence yield of target volume elements.

A. Gharbi^1,2, B. Caussat³, H. Vergnes³, B. Qaddah², P. Vilasi²,​​​ A. Saboundji⁴, A. Zhang⁵, M. Vilasi¹, T. Belmonte¹

¹Université de Lorraine, CNRS, IJL, 2 Allée André Guinier, BP 50840, F-54000 Nancy, France

²IRT M2P, 4 rue Augustin Fresnel, 57007 Metz, France

³LGC, Université de Toulouse, INPT-ENSIACET, 4 Allée Emile Monso, BP 44362, 31030, Toulouse Cedex 4, France

⁴Safran Tech, rue des jeunes bois, 78772, Magny-Les-Hameaux, France

⁵IHI Bernex AG, Industriestrasse 211, CH‑4600 Olten ‑ Switzerland

Nickel-based alloys are widely used in high temperature structural components in the aerospace field for their excellent properties such as sufficiently high heat resistance strength, excellent mechanical strength and resistance to high-temperature oxidation. Among these alloys, the Directionally Solidified nickel-based superalloy, DS200+Hf, is widely used for turbine blades. The DS200 has a chemical composition similar to MAR-M200, with the addition of Hafnium.

Despite its favorable properties, additional surface protection is required to extend the lifetime of turbine blades by improving their resistance to oxidation and corrosion. Historically, several methods have been commonly used for the deposition of aluminide coatings, including pack cementation, out-of-pack cementation, slurry techniques, and Chemical Vapor Deposition, CVD. Among these, the CVD method is particularly attractive due to its high flexibility in controlling process parameters. It is based on the deposition of a thin layer of solid material on a substrate, from gaseous reactants through chemical reactions in the gas phase and on solid surfaces.

In the first part of this thesis work, a laboratory-scale CVD reactor was designed and implemented. Aluminide coatings were deposited on the surface of DS200 samples at atmospheric pressure. The effects of deposition temperature, treatment duration, and precursor gas flow rate on the coating microstructure, chemical composition, and formation mechanism of aluminide coatings were investigated.

In parallel with the experimental study, numerical simulations were started to provide a deeper understanding of the CVD process designed in this thesis. These simulations are based on ANSYS Fluent, a tool grounded in Computational Fluid Dynamics, CFD. This approach enables the study of fluid flow behavior, heat and mass transfer, as well as chemical reactions that may occur within the system, taking into account possible interactions with solid surfaces. It involves solving the conservation equations of total and species mass, momentum, and energy within a domain defined by a 3D mesh. Through this numerical approach, it is possible to optimize the experimental parameters of the CVD process and to achieve a better understanding of the physical and chemical mechanisms governing aluminide coatings growth.

Integrating metallic conductive layers on polymer substrates is a critical challenge in flexible electronics, requiring a balance between mechanical compliance and electrical performance. This study investigates the electromechanical properties of metal layers deposited on polymer substrates using Atomic and Molecular Layer Deposition (ALD and MLD) interlayers to enhance interfacial stability, compatibility, and adhesion.

Previous studies show complementary benefits: ALD alumina interlayers (optimal at 5 nm thickness) between polyimide substrates and aluminum films improve ductility, delay cracking, and maintain conductivity under large deformation [1]; MLD alucone films using longer-chain organic precursors (1,10-decanediol vs. 1,6-hexanediol) transition from brittle to ductile behavior [2]. Combining both techniques exploits these advantages. Model interlayers are fabricated in a custom-built hot-wall ALD chamber to investigate the influence of interlayer architecture on mechanical performance and thermal stability.

To identify the optimal organic precursor (that can both enhance adhesion between the metal film and the polymer substrate, and accommodate eventual bending/stretching), two sample batches are prepared. Polyimide substrates undergo acidic hydrolysis to expose terminal -OH groups, then receive: 10 cycles of ALD-alumina (whose precursors are trimethyl aluminum and water), 35 cycles of MLD-alucone (using trimethyl aluminum with 1,6-hexanediol for batch one and with 1,10-decanediol for batch two), and 15 cycles of ALD-alumina. This final layer prevents polymer chain degradation upon air exposure. Samples are then coated with an aluminum thin film (circa 150 nm) deposited via physical vapor deposition (PVD). 

The performance as a function of interlayer type will be evaluated with in situ micromechanical tensile testing, correlated with high resolution microscopy. Moreover, the debonding of coating and substrate is studied by controlling the degradation of artificial MLD interlayers via thermal annealing at different heating rates [3], which is promising to lower adhesion as diols degrade at 200-300°C.

[1] Byloff et al., From Mechanics to Electronics: Influence of ALD Interlayers on the Multiaxial Electro-Mechanical Behavior of Metal – Oxide Bilayers. Adv. Funct. Mater. (2025)

[2] Niemelä et al., Molecular layer deposited alucone thin films from long-chain organic precursors: from brittle to ductile mechanical characteristics. Royal Soc. of Chemistry (2020)

[3] Gałko and Sajdak, Trends for the Thermal Degradation of Polymeric Materials: Analysis of Available Techniques, Issues, and Opportunities. Appl. Sciences (2022)

The combined effects of global population growth toward nearly 9.7 billion by 2050 and the rapid expansion of artificial intelligence and data centers are driving a sustained rise in electricity demand (~2.8% per year), requiring accelerated deployment of stable and low-carbon energy solutions [1–2]. Although SOFCs (Solid Oxide Fuel Cells) offer high efficiency power generation, their deployment is limited by Yttria-Stabilized Zirconia (YSZ) electrolytes, whose critical raw material supply [3] and thickness-dependent ohmic losses, limiting the electrochemical performance of the system. This situation motivates the development of alternative materials. The goal of the present work is to synthesise oxygen-vacancy-rich zirconia thin film by a low-pressure plasma-based reactive magnetron process with a metallic zirconium target in Ar/ O₂ mixture. Monitoring the target voltage evolution with oxygen flow rate allows identification of the so-called transition regime in which the material is expected to contain oxygen vacancies. As this regime is inherently unstable, i.e. the process parameters will drift in time and so the film chemistry, precise and real-time control of the target surface chemistry and oxygen partial pressure is essential [4]. Through process optimization, films are deposited in the transition zone at 100% signal. For film thicknesses ranging from approximately 300 to 800 nm, photoluminescence bands appearing at around 370 nm and 447 nm thus revealing the presence of surface defects and/or oxygen vacancies [5-6]. Structural analysis by grazing-incidence X-ray diffraction confirms the presence of a pure cubic zirconia phase, therefore stabilized by oxygen vacancies at room temperature.

Acknowledgements

This work is being used as part of the European CLUED-O project, funded by INTERREG France-Wallonie-Vlaanderen.

REFERENCES

1-World Energy Council 2013 - World Energy Scenarios: Composing energy futures to 2050

2-International Energy Agency – Analysis and forecast to 2026

3-European Commission - Study on the Critical Raw Materials for the EU-2023

4-Raza’s Thesis - University of Mons (2017)

5-Damir R. Islamov et al., Materialia 15(2021) 100979

6-Smits K. et al., Journal of physics : Conference series 93(2007) 012035

Adhesion between thin films and their substrates is one of the key factors governing the functional performance and mechanical stability of coatings used in demanding environments. Insufficient adhesion can lead to premature delamination, compromising both protection and functionality. Therefore, experimental methods capable of reliably quantifying interfacial strength are essential for the development and optimization of deposition processes. Among these methods, the pull-off adhesion test stands out as a direct and widely adopted approach for thin-film adhesion characterization. In this work, the development of a pull-off testing system for evaluating the adhesion of transition metal nitride thin films deposited on steel substrates is described. Steel samples with an approximate diameter of 50 mm were used both as substrates during deposition and as adapted supports for the tensile testing configuration, enabling a robust and reproducible mechanical setup. The performance of the system is assessed in terms of sensitivity, reliability, and applicability under different experimental conditions.
The results demonstrate that the developed pull-off system is suitable for characterizing the adhesion of thin films deposited on steel, offering good reproducibility and sufficient resolution to discriminate between different deposition and surface preparation conditions. The analyses indicate that plasma surface treatments, variations in bonded area, and film growth parameters have a significant influence on the measured adhesion strength, as well as on the observed failure mechanisms. The identification of fracture modes, including adhesive failure at the film–substrate interface and cohesive failure within the film or adhesive layer, highlights the complexity of the detachment process and underscores the importance of controlling both deposition conditions and test geometry. Overall, the proposed system proves to be a promising tool for systematic adhesion studies of thin films, contributing to the optimization of nitride-based coatings and to the advancement of technological applications that require high mechanical reliability.

Selective references:

Bull, S. J. and D. Rickerby, New developments in the modelling and simulation of the scratch test. Surface and Coatings Technology, 1990. 42(1–2): p. 149–164.

Mittal, K. L., Adhesion measurement of thin films and coatings. Surface and Interface Analysis, 1976. 1(1): p. 125–142.

New Zr(IV) and Hf(IV) complexes were synthesized and applied as molecular precursors for chemical vapor deposition (CVD) of Zirconium-, Hafnium-, and mixed Hafnium-Zirconium-Oxide (HZO) coatings. Reaction of tetrakis(diethylamido)metal(IV) complexes (M = Zr, Hf) with the fluorinated β-ketoenamine ligand (Z)-4-(tert-butylamino)-1,1,1-trifluorobut-3-en-2-one (H-TFB-tBuA) and tert-butyl alcohol produced new heteroleptic [M(TFB-tBuA)₂(O^tBu)₂] zirconium (Zr-1, M = Zr) and hafnium (Hf-1, M = Hf) complexes. Both compounds possess excellent thermal stability up to 250 °C and exhibit volatility suitable for chemical vapor deposition of ZrO₂ and HfO₂ thin films in a low-pressure (10^-2 mbar) chemical vapor deposition reactor. The vapor pressure and thermal stabilities of both Zr-1 and Hf-1 are compatible for the co-deposition of individual metal oxides, enabling direct synthesis of phase-pure HZO films with a tunable Zr:Hf ratio. The co-evaporation without preferential decomposition of either precursor was attributed to the matched decomposition profiles of Zr-1 and Hf-1, enabling the single-step deposition of mixed-metal HZO films.

Electrochromic (EC) devices tune their colour under the application of an external field through redox reactions. With the rapid advancement of electrochromic technology, providing thin films that offer superior performance and sustainability holds significant promise for practical applications of electrochromic devices (buildings, smart windows, displays). Devices that rely on ion transport often show long-term degradation because repeated cycling can cause irreversible ion trapping or accumulation in the host, ultimately limiting device lifetime. In this study, we address this challenge by deliberately engineering the balance between crystallinity and morphology of sputter-deposited NiO through systematic post-annealing. The optimized NiO film is then fabricated as an all-solid-state electrochromic device, where it delivers fast switching with outstanding durability, retaining stable operation beyond 40,000 cycles while maintaining an ultrahigh coloration efficiency (99.3 cm² C⁻¹). These results demonstrate that controlled microstructural tuning can suppress irreversible ion accumulation, enabling sustainable, long-life NiO-based complementary electrochromic devices for practical smart-window and display applications.

Keywords: Electrochromism, smart window, fast switching, sustainable

Materials with tunable Metal-Insulator-Transition are of great interest for a wide range of applications including thermal sensors, electronic switches, adaptive infrared camouflage, smart windows, etc.. Among them, Vanadium dioxide (VO₂) undergoes a fully reversible first order metal–insulator transition (MIT) from M1 monoclinic phase (P2₁/c) to a high-temperature tetragonal phase (P4₂/mnm) at around 68 °C. Modulate phase transition of VO₂ by chemical doping (M in M :VO₂) is thus of high fundamental and technological interest. Earlier studies based on chemical synthesis routes pointed out a decrease in transition temperature down to RT for Nb addition [1] while an opposite trend (i.e. increase in transition temperature up to 130 °C) was observed for Fe doping [2]. Being restricted for each synthesis to one composition led to limited and lightly accurate M/V composition determination.

Herein, focusing on a high throughput study using sputtering technology, the influence of dopant on the crystallinity and morphology of the doped vanadium oxides based thin films, was further evaluated. For this purpose, we have used a combinatorial synthesis and more precisely a magnetron co-sputtering approach to deposit M-V-O thin films from M and V metallic targets in a reactive atmosphere onto 4-inches wafer substrates, through a shadow mask, allowing the simultaneous deposition of 76 samples with different compositions all over the substrates surface. High throughput characterisation techniques were then combined to map the evolution of thin films properties over the wafer, such as structure (XRD) and morphology (Profilometry, SEM). Composition impact on the optical and electronic properties of M :VO₂ sputtered films will be discussed.

References

[1] S. Guan et al., Chemistry of Materials, 2019, 31(23), 9819–9830

[2] J.-L. Victor et al., Journal of Physical Chemistry Letters, 2021, 12, 7792–7796

Acknowledgements : This work has been supported by the ANR, Agence Nationale de la Recherche, France 2030 with the reference 22-PEXD-0008.

The influence of 5,5-dimethylhydantoin (DMH) and ethylenediaminetetraacetic acid (EDTA) as complexing additives on Zn–Ni alloy electrodeposition is systematically investigated in deep eutectic solvent (DES)–based organic electrolytes using an integrated experimental and first-principles modeling framework. Zn–Ni coatings are characterized by scanning electron microscopy, X-ray diffraction, and nanoindentation to establish correlations between electrolyte chemistry, microstructural evolution, crystallographic texture, and mechanical response. Cyclic voltammetry is employed to elucidate the electrochemical behaviour and deposition kinetics of DES electrolytes containing organic additives.

Density functional theory calculations provide the mechanistic foundation of the study by offering atomistic insight into metal-additive interactions in the DES environment. Computed dissociation energies reveal that, in DMH-containing electrolytes, Ni forms more stable complexes than Zn, thereby promoting preferential Zn release during alloy deposition. In contrast, EDTA-based DES electrolytes favour Ni dissociation over Zn, thereby enhancing Ni availability at the electrode–electrolyte interface. These theoretical predictions are consistent with experimental transport behaviour, where EDTA-containing DES baths exhibit higher Ni diffusivity and produce coatings with Ni contents approaching 16 wt%.

Texture analysis further demonstrates that increasing the DMH concentration from 0.1 to 0.5 M induces a pronounced transition in preferred orientation from {110}〈001〉 to {001}〈100〉. Conversely, coatings deposited from EDTA-containing DES electrolytes consistently display dominant {110}〈001〉 texture components across all investigated concentrations.

Overall, this work establishes a theory-guided strategy for tailoring additive chemistry in Zn–Ni alloy electrodeposition using organic DES electrolytes. The combined experimental–computational approach provides a transferable framework for designing sustainable, high-efficiency coating processes relevant to advanced surface engineering, intermetallic alloy development, and environmentally responsible electrochemical manufacturing.

High-energy planetary ball milling is a promising mechanical coating technique for depositing metal-oxide films on small components, though achieving uniform thickness and full coverage remains challenging. Titanium dioxide (TiO₂) is widely used in photocatalysis, protective coatings, energy devices, and surface engineering due to its high activity, chemical stability, non-toxicity, and low cost. However, TiO₂ layers produced by mechanical coating in planetary mills are typically limited to ~0.01–0.015 mm, which is insufficient for applications requiring higher mechanical integrity and thickness, including oil and gas environments. In this study, we investigate TiO₂ film growth on aluminum balls and quantify the influence of key processing parameters on coating development. Rotational speed (200–850 rpm), milling duration, and the addition of polyvinylidene chloride (PVDC) as an organic binder were systematically evaluated. Coating formation was assessed using mass gain, thickness estimation, and visual surface inspection. At low rotational speed (200 rpm), TiO₂ formed thin, discontinuous deposits. In contrast, intermediate speeds (400–600 rpm) combined with appropriate milling times produced dense, uniform TiO₂ films with good adhesion. PVDC improved nucleation and compaction, yielding smoother and more continuous coatings. Excessive speed (850 rpm) and/or extended milling led to surface roughening, non-uniform growth, and partial delamination. Under optimized conditions (≈600 rpm, ~4–7 h, with PVDC), the average coating thickness reached ~0.3 mm, substantially exceeding the thickness typically reported for mechanical coating approaches (0.01–0.015 mm). These results demonstrate a cost-effective and scalable route to produce thick, adherent TiO₂ coatings suitable for surface engineering, corrosion protection, optics, energy devices, and petroleum-related applications.

The development of efficient and durable technologies for hydrogen production, storage, and transport is a cornerstone of the current transition toward sustainable energy systems. However, significant materials‑related challenges still limit the deployment of hydrogen at large scale, particularly concerning reversible solid‑state storage and the integrity of metallic infrastructures exposed to hydrogen. Our research group is currently pursuing two complementary lines of investigation to address these issues.

We explore High Entropy Alloys (HEAs) as promising materials for solid‑state reversible hydrogen storage. In this framework, MgAlVCrNi and TiZrHfNbV coatings a few micrometers thick were deposited using a novel Glancing Angle Deposition–Magnetron Sputtering (GLAD‑MS) approach. This technique enables the controlled growth of porous, nanostructured columnar architectures—such as slanted, vertical, zigzag, or helicoidal motifs—designed to enhance hydrogen transport through open pathways and improve absorption kinetics. A dedicated GLAD‑MS configuration was developed, and the resulting coatings were thoroughly analysed in terms of morphology, crystallographic structure, and microstructural stability, providing insights into structure–property relationships relevant for hydrogen uptake.

In parallel, we investigate mitigation strategies for hydrogen embrittlement (HE) in metallic infrastructures involved in hydrogen transport. Since hydrogen atoms can readily diffuse into metals such as steels, Al‑ or Mg‑based alloys, and titanium, causing severe degradation, we focus on the development of ceramic hydrogen‑permeation‑barrier (HPB) coatings. Ti‑Al‑N based films were deposited by both DC and High Power Impulse Magnetron Sputtering (HiPIMS), optimized for density and chemical stability, and subsequently characterized before and after exposure to hydrogen environments. The results provide fundamental insights into the coatings’ behaviour under hydrogen permeation and highlight their potential as effective protective barriers. Overall, these studies andvance material solutions capable of supporting safe, efficient, and long‑term hydrogen storage and transport technologies.

Acknowledgements: This research was funded by: - PNRR - Mission 4, Component 2, Investment 1.1 – Bando Prin 2022 - Directorial Decree n. 104 of 02-02-2022; Project HEADSTONE CUP B53D23008820006 - identification code 2022KS2RAC Funded by the European Union - Next generation EU. - European Union – NextGeneration EU from the Italian Ministry of Environment and Energy Security POR H2 AdP MMES/ENEA with involvement of CNR and RSE, PNRR - Mission 2, Component 2, Investment 3.5 "Ricerca e sviluppo sull’idrogeno". WP2.2 - LA2.2.4 - Rivestimenti di condutture per il trasporto H2: Sviluppo di coating ossidici, metallici e ibridi e processi per la loro deposizione. CUP: B93C22000630006.

Despite the technological relevance of nitrides and sulfides in optoelectronic applications, multi-anionic sulfonitrides remain largely unexplored. Indeed, we interrogated computational materials discovery databases for stable ternary sulfonitrides (excluding O, H, and C) and only found 12 materials. Consequently, we argue that the field of multi-anionic sulfonitrides thin films is a wide-open research area with significant potential for discovery. In this work, we report the first thin-film synthesis of a sulfonitride, β-Zr2SN2, a material predicted to have potential as an ambipolar transparent conductor.

We have developed a custom-made deposition setup targeted towards the synthesis of sulfonitride thin films. In our setup, β-Zr2SN2 thin films are deposited by reactive sputtering of Zr in an Ar/N2/H2S gas-mixture, followed by a rapid thermal annealing (RTA) process in N2 gas. During the 2-step process transfer, we prevent air exposure and oxidation by fully integrating the reactive sputtering chamber and the RTA oven into an overarching N2-filled glovebox system. Using this setup, we mitigate the incorporation of O impurities in the films, and achieve a crystalline thin films with optical-grade smoothness.

We find that the transparency of the film increases drastically after crystallization in the RTA oven, driving a blue shift of the absorption onset to the UV/visible edge. DFT calculation of the band structure and dielectric constants reveals a wide range of momentum- and dipole-forbidden transitions in β-Zr₂SN₂, while retaining sharp optically inactive bands hosting very light holes and electrons. This decoupling of the electronic and optical properties enables the coexistence of high carrier mobility (m* ≈ 0.5me), high transparency (abs. onset = 2.9 eV) and high refractive index (n = 2.95), above state-of-the-art TiO2 and SiC-6H (n = 2.55 – 2.65). This makes it one of the few materials exhibiting such combinations of properties, unlocking applications in high reflectance optics, metasurfaces, transparent electronics, and integrated photonics.

TiAlN-based coatings are widely employed as tool coatings for the machining of difficult-to-cut engineering materials due to their good mechanical properties and high oxidation and wear resistance. Multilayers are often created to combine these properties, resulting in coatings with enhanced overall performance. However, their growth dynamics and texture evolution, particularly the role of the substrate, remain insufficiently understood.

This work explores the growth aspects of TiAlN-based single-layer and multilayer coatings deposited by HiPIMS on Si wafers and WC-Co substrates. Three single layers were deposited: TiAlSiN with Al/Ti ratios of 1 and 1.5, and TiAlN with an Al/Ti ratio of 1. Based on these single layers, two nanoscale multilayer systems with a 1:1 layer thickness ratio were deposited at 450 °C.

The single layers exhibited either cubic or hexagonal phases depending on their composition, while the multilayers preserved the phases of their constituent layers. The preferred orientation of the single layers was not affected by the substrate type. However, the addition of 3 at. % Si to the TiAlN composition altered the texture from (220) to (111) regardless of the substrate. In contrast, the multilayers developed orientations distinct from those of the single layers and demonstrated substrate dependence. Preferential (420) growth was observed for multilayers on silicon wafers, whereas TiAlN diffraction peaks were not clearly detected on the WC-Co substrate in the Bragg-Brentano configuration. Microstructural analysis revealed uninterrupted columnar growth and crystalline domains larger than the bilayer thickness in cubic-cubic multilayers, suggesting the absence of successive re-nucleation mechanisms. No preferential growth was observed at the coating/substrate interface. In contrast, the columnar growth structure was disrupted in the hexagonal-cubic multilayer system. The multilayer structures were confirmed by annular dark-field scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy.

High-entropy alloys (HEAs), introduced over 20 years ago, are multicomponent alloys with at least five principal elements (5–35 at.% each) that leverage high configurational entropy to stabilize simple solid-solution phases. HEA thin films produced by techniques such as magnetron sputtering extend this concept into coatings, where the large compositional space and tunable lattice distortion allow precise control of phase formation, microstructure, and functional properties, enabling tailoring of material properties for diverse targeted applications. Large δ parameters enhance hydrogen-storage capacity by increasing the H/M ratio up to 2.5.
Previous studies [1] of refractory HEA films deposited by magnetron sputtering determined the crystallization sequence, ranging from amorphous films through single-phase nanocrystalline to multi-phase polycrystalline structures.  The crystallization process is primarily driven by the changes in the substrate temperature, as the plasma environment during magnetron sputtering deposition features low-energy particles (~0.15 eV) with mostly thermal characteristics. At low deposition temperatures, atoms lack energy for establishing long-range order, remaining randomly distributed. With increasing temperature, in the intermediate range, atomic mobility enables a stable single-phase structure with limited elemental redistribution. At high temperatures, enhanced diffusion causes elemental segregation and intermetallic phase formation [1].
In this work, we investigate the growth of HfNbTiVZr-based thin films deposited by DC magnetron sputtering at various temperatures, using different substrates (MgO, Al2O3, Si) and equimolar (HfNbTiVZr, δ = 6.8 %) and non-equimolar (Hf0.75Nb0.75TiV1.25Zr1.25, δ = 7.5 %) target compositions. Crystalline structure was characterized by XRD, surface morphology by AFM, and chemical composition  and oxidation states by XPS. For both target compositions, amorphous structure is stable at higher deposition temperatures compared to HfNbTaTiZr films, characterized by lower misfit parameter (δ ≈ 5 %), thus larger lattice misfit inhibits crystallization. By increasing deposition temperature (in-deposition annealing) or via post-deposition annealing at 750 °C, multi-phase structure was formed [2]. 
[1] P. Hruška, S. A. Irimiciuc, S. Cichoň, M. Vondráček, D. Prokop, L. Fekete, J. Lančok, F. Lukáč, J. Drahokoupil, B. L. Božiček, L. Einfalt, M. O. Liedke, M. Butterling, E. Hirschmann, A. Wagner, Microstructural evolution of single-phase HfNbTaTiZr high-entropy alloy thin films. J. Alloys Compd., 1039 (2025), Article 183003 
[2] S. A. Irimiciuc, P. Hruška, S. Cichoň, M. Vondráček, L. Fekete, F. Lukáč, J. Lančok, Understanding the growth of refractory high-entropy alloys by magnetron sputtering via in situ plasma diagnostics. Surface and Coatings Technology, 515 (2025), Article 132610

In the present study, Zn-Co coatings are electrodeposited on a mild steel substrate using a deep eutectic solvent (DES) composed of choline chloride and ethylene glycol, providing a sustainable alternative to conventional aqueous electrolytes. The coatings are subsequently subjected to post-deposition annealing at 200°C for varying durations (20, 40, and 60 mins) to examine the influence of thermal processing on phase evolution and microstructural stability. X-ray diffraction and grazing-incidence XRD analysis reveals the presence of Zn-Co intermetallic and shows that annealing progressively promotes the formation of Zn-Fe intermetallic phases, primarily Fe₃Zn₁₀ and FeZn₁₃ at the interface, reflecting thermally driven elemental redistribution across the coating-substrate interface. Scanning electron microscopy (SEM) reveals pronounced grain coarsening, with the initially nodular surface morphology evolving into well-defined, polygonal recrystallized grains at longer annealing times. Cross-sectional energy-dispersive spectroscopy (EDS) line scan confirms enhanced diffusion of Zn into the steel substrate and localized redistribution of Co within the coating during prolonged thermal exposure. The development of a thick Zn-Fe interface layer, together with diffusion-induced porosity at extended annealing durations, indicates microstructural instability arising from coupled diffusion and phase transformation processes. These results highlight the strong relationship between post-deposition thermal processing and interfacial reactions in Zn-Co coatings, offering insights relevant to the design of thermally stable and durable protective coatings.

The current work examines the effects of the ionic surfactants CTAB and SDBS on the
structural, tribological, and electrochemical characteristics of ZnCo coatings, synthesized from a
ChCl-EG-based deep eutectic solvent. The role of surfactants in altering the nucleation process
has been elucidated using chronoamperometry. The surfactant-assisted coatings depict distinct
crystallite size, surface morphology, and roughness as characterized by X-ray diffraction,
scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. The
nano-indentation and wear analyses indicate that the incorporation of surfactants leads to a dense
microstructure, exhibiting increased hardness and less volumetric wear loss. The corrosion
efficacy of the coatings is markedly enhanced by surfactants, with icorr values of 23.9 μA/cm²
and 29.6 μA/cm² for samples treated with CTAB and SDBS, respectively, compared with 49.1
μA/cm² for the coating without surfactants. The time-of-flight secondary ion mass spectrometry
(ToF-SIMS) approach confirms that oxides and chlorides are the primary corrosion products.

Electrodeposition of Zn–Mn alloy coatings from a choline chloride and ethylene glycol based deep eutectic solvent: microstructural, electrochemical, and mechanical characteristics

Debasis Nayak*, Juan David Matallana Guerrero, Anjali Kumari, Siddhartha Das, Karabi Das

Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur, West Bengal, India

*Corresponding Author: Debasis Nayak (debasisnayak@kgpian.iitkgp.ac.in)

Abstract: -

Electrodeposited Zn alloy coatings have offered significant corrosion protection to steel substrates, primarily due to the formation of dense and adherent corrosion products under aggressive environments. Numerous studies have investigated the electrodeposition of Zn–Mn alloy coatings from aqueous electrolytes and the influence of various processing parameters on the resulting coating properties. However, very limited studies have reported the electrodeposition of Zn–Mn alloy coatings from non-aqueous electrolyte. In the present study, Zn–Mn alloy coatings were successfully deposited on steel substrates using the pulsed current electrodeposition technique from choline chloride and ethylene glycol based deep eutectic solvent. A systematic study was carried out to evaluate how variations of the manganese content in the electrolyte affect the microstructural, mechanical, and electrochemical behavior of the coatings. Cyclic voltammetry analysis revealed that increasing manganese content in the electrolyte bath reduced the potential gap between Zn and Mn reduction. From Scanning Electron Microscopy and Energy Dispersive Spectroscopy it was found that the manganese content of the coating was approximately 26 wt.%, while variations in Mn content in the bath had a negligible effect on the coating morphology. X-ray diffraction analysis indicated that the ε-phase (MnZn₃) predominated in Zn–Mn alloy coatings with manganese contents ranging from 10 to 26% in the coating, and its proportion increased progressively with increasing Mn concentration in the bath. The increased formation of the corrosion-resistant ε-phase with higher manganese content contributed to the improved corrosion behavior of the coating. A significant enhancement in hardness was observed, increasing from 75.25 ± 4.47 VHN for pure zinc coatings to 264 ± 12.2 VHN for the Zn–Mn alloy coating. Overall, increased manganese incorporation significantly improved both corrosion resistance and hardness, thereby extending the service life of metallic substrates.

Keywords: Deep eutectic solvent, Electrodeposition, Zn-Mn alloy, Corrosion resistance.

Tailoring structural and optical properties of Ta2O5 thin films via radio frequency magnetron sputtering for high-refractive index transparent materials

Aïmane Cheikh1, Christophe Labbé1, Xavier Portier1, Philippe Marie1, Cedric Frilay1, Olivier Debieu2, Julien Cardin1

1 CIMAP Normandie Université, ENSICAEN, UNICAEN, CEA, UMR CNRS 6252, 6 Boulevard Maréchal Juin, 10450 Caen Cedex 4, France

2 CRISMAT, Normandie Université, ENSICAEN, UNICAEN, UMR CNRS 6508, 6 Boulevard Maréchal Juin, 10450 Caen Cedex 4, France

Tantalum pentoxide (Ta₂O₅) films have garnered significant attention in advanced technologies due to their remarkable optical and dielectric properties. With a high refractive index n, low extinction coefficient k, and high transparency in the visible spectrum, Ta₂O₅ thin films might be well-suited for modern optical coating applications, including augmented reality (AR) glasses. In this study, we investigated the refractive index (n) and absorption coefficient (k) of Ta₂O₅ across the visible spectrum, with a particular focus on how these optical properties relate to its structural characteristics1.

Ta₂O₅ thin films were deposited using magnetron radio frequency sputtering on double-side polished silicon (Si) wafers and subsequently annealed via Rapid Thermal Annealing (RTA) at various temperatures. X-ray diffraction (XRD) measurements revealed the onset of Ta₂O₅ crystallization beginning at 650°C, predominantly forming an orthorhombic phase (β-Ta₂O₅) with a minor hexagonal phase. Transmission electron microscopy (TEM) further confirmed this crystallization, showing that the crystallized Ta₂O₅ thin films overlay a thin SiO₂ layer.

Optical properties were assessed using Variable Angle Spectroscopic Ellipsometry (VASE) and spectrophotometry. For annealing temperatures between 750°C and 850°C, a reduction in transmittance to 71% was observed, likely due to an increased trap density and the formation of active color centers associated with oxygen vacancies. These effects were accompanied by an increase in the extinction coefficient (k) starting from 3 eV, which reduced the optical transparency window to the range of 1.5 to 3.5 eV, as well as a decrease in the refractive index (n). In contrast, samples annealed with a lower thermal budget at 650°C exhibited a higher refractive index (n) of approximately 2.20 around 2 eV and a negligible extinction coefficient (k) up to 5 eV, resulting in a wider transparency window with an average transmittance of 78% between 1.5 and 5 eV.

In conclusion, the rapid annealing treatment at 650°C effectively optimizes Ta₂O₅ thin films, achieving a higher refractive index and minimal optical absorption across a broad spectrum. This enhancement in optical transparency paves the way for numerous advanced optical coating applications, including augmented reality technologies.

[1] A. CHEIKH, Journal of alloys and compounds 1040 (2025) 183273

Powder metallurgy processes, like Spark Plasma Sintering (SPS), allows to obtain metal parts with a fine and homogeneous microstructure and improved properties. In this process, the sintering is obtained by the simultaneous application of a pulsed current, making it possible to heat the powder, and of a uniaxial pressure. The powder is isolated from direct contact with the graphite tooling (mould, punches) by a sheet of graphite. Two issues can be identified: first, the carbon contamination of the powder leading to the formation of highly carburized layers on the surface, or even to the diffusion of carbon at the grain boundaries deeper in the part, and second, the bulk composition is dependent of the one of the initial powder.

In order to solve the contamination issue, one may apply by PVD of a thin protective layer on the graphite sheet. Indeed, magnetron sputtering makes it possible to produce films with a particular stoichiometry (from single element to multi elements alloys), having a controlled thickness and covering the graphite sheet in a homogeneous and conforming manner.

Secondly, coating the powder particles can also allow tuning finely the composition of the base powder. It paves the way to the synthesis of alloy with specific phase composition and improved properties thanks to the very fine microstructure.

In this study, part of the project OEDIPUS ANR-23-CE08-0028, these two approaches are applied to the sintering of iron-based powders.

The POLARISS project (ANR-22-CE08-0021) aims to develop the next generation of cutting tools for cryogenic machining processes (milling, turning, drilling). These tools, often of complex geometry, are mounted on a carousel substrate holder that can operate in static mode, with single rotation, or with dual rotation. The samples are positioned at different heights on the carrier bars. Under identical process conditions (i.e., constant temperature, bias voltage, target power, and working pressure), the deposited films may still display different behaviors, sometimes falling outside the expected property ranges.

This work investigates, both experimentally and numerically, the evolution of chromium film properties as a function of position inside the chamber and of the carousel rotation modes. The control parameters to be studied include film thickness, morphology (surface and cross-section), composition (with particular attention to oxygen incorporation as a contaminant), residual stress, and structure.

In the static case, Simtra and Virtual Coater are used to study material fluxes and film growth. For the rotating cases (single and dual rotation), only Virtual Coater is employed. Numerical and experimental results will be systematically compared.

The current global context, marked by growing concern over environmental issues stemming from the overexploitation of conventional energy resources, is driving a research effort focused on developing more sustainable, adaptable, and efficient photonic and photovoltaic devices [1-2]. In recent years, the increasing need for energy-efficient connected devices have heightened the importance of indoor photovoltaics (IPV), motivating the development of novel materials and functionalities for sustainable IPV cells [3,4]. Among the explored systems under investigation for these purposes, several materials show notable potential: selenium (Se) as an efficient light‑harvesting semiconductor and antimony (Sb) and bismuth (Bi) for introducing additional optical and electronic functionalities into the developed devices [5].

This work focuses on the optical characterization of thin films based on Se, Sb, and Bi in order to better understand the properties and possible role that they may have on the development of an IPV-cell. These films were deposited on Transparent Conductive Oxides (TCOs) by vapor transport deposition (Se) or Pulsed Laser Deposition (Sb, Bi). By using spectroscopic ellipsometry we have determined their dielectric optical function that give access to the determination of the band gap energy and absorption coefficient. We correlate the optical properties to the composition and morphology of the films. These results contribute to the understanding and optimization of semimetal‑based thin films for next‑generation IPV devices, supporting their integration into autonomous, low‑power electronic systems.

This study was carried out at the Optical Characterization of Materials Service (SCOM) of the Institute of Optics (IO-CSIC), using advanced techniques such as spectroscopic ellipsometry [6], reflectance, and transmittance [7] measurements.

References:

[1] M. García-Pardo et al., ‘Active analog tuning of the phase of light in the visible regime by bismuth-based metamaterials’, Nanophotonics 9, 885 (2020).

[2] G. Tagliabue et al., ‘Photonic solutions help fight climate crisis’. Nat. Photon. 18, 879–882 (2024). 

[3] J.P. Tiwari, ‘Outlook and future directions for indoor photovoltaics: modern societal needs and challenges’, Energy Fuels 39(21), 9623-9640 (2025).

[4] Z. Wei et al., ‘Low-cost and high-performance selenium indoor photovoltaics’, J. Mater. Chem. A 11, 23837-23843 (2023).

[5] F. Chacon-Sanchez et al., ‘Building conventional metasurfaces with unconventional interband plasmonics: a versatile route for sustainable structural colour generation based on bismuth’, Adv. Opt. Mater. 12(10), 2302130 (2024).

[6] J.A. Woollam et.al, ‘Spectroscopic ellipsometry from the vacuum ultraviolet to the far infrared’. AIP Conf. Proc. 29 January 2001; 550 (1): 511–518.

[7] A. Ruiz-Perona et al., ‘The effect of annealing temperature on Cu2ZnGeSe4 thin films and solar cells grown on transparent substrates’. J. Phys. Mater. 4 034009.

DC reactive sputtering was implemented to successfully deposit zirconium oxynitride thin films from a zirconium metallic target, argon as plasma gas and nitrogen and oxygen as reactive gases. Both reactive gases were simultaneously and independently pulsed with a rectangular signal during the film deposition by means of the reactive gas pulsing process (RGPP). A constant pulsing period was used for O₂ and N₂ with a delay time of a few seconds between each reactive gas starting injection. O₂ and N₂ duty cycles (α_O2 and α_N2, respectively) were systematically changed from 0 to 100% of the pulsing period. From real time measurements of the Zr target potential and total sputtering pressure, it was shown that some operating conditions can be reached to alternate the reactive sputtering process between elemental, nitrided and oxidized sputtering modes.

Playing with O₂ and N₂ duty cycles leads to a substantial increase of the deposition rate and adjustable film compositions compared to a conventional injection of the reactive gases (i.e., constant flows) with rates approaching that of the pure Zr metal. These reactive gases duty cycles also allow extending the working range of deposition conditions suitable to modify the optical properties of ZrON films from absorbent (colors in the bulk) to interferential. Analyses of Zr target potential and total sputtering pressure during reactive gas pulsing show that the process needs to be periodically changed between 3 modes: elemental, nitrided and oxidized to get high deposition rates.

Last but not least, a two-dimensional qualitative diagram based on O₂ and N₂ duty cycles as the two key parameters was proposed. Occurrence of different reactive sputtering regimes was clearly identified, with transitions involving periodic alternations between two or three process modes. These results demonstrate that independent pulsed injection of O₂ and N₂ using the RGPP technique is an effective approach for controlling the reactive sputtering process and for producing an extended range of ZrON thin films with changeable properties, especially optical reflectivity in the visible range and film colors in the L*a*b* space related to their chemical composition.

Janus magnetic particles are a subset of microparticles consisting of asymmetric magnetic coatings on non-magnetic colloidal substrates, such as silica. Janus particles provide a versatile platform for field-driven actuation, directed assembly, and microrobotic systems [1]. FePt-based Janus caps are particularly attractive to researchers due to their large magnetocrystalline anisotropy, thermal stability, and biocompatibility [1,2]. Despite growing experimental and theoretical interest, establishing a quantitative structure–property relationship for Janus magnetic particles remains challenging across simulation, theory, and experimentation.

From a modeling perspective, micromagnetic simulations typically assume idealized geometries and homogeneous material properties. In curved thin films, magnetic energy contributions are inherently geometry-dependent, with exchange, magnetocrystalline anisotropy, and demagnetizing energies responding differently to variations in curvature. When proceeding to experimental validation using ensemble techniques, such as SQUID magnetometry, the measured response reflects an average over many particles and microstates. This intrinsic simulation-experimental discrepancy complicates direct comparison between simulations and experiments.

Here, we bridge the simulation–experiment gap for curved thin films by investigating FePt-based Janus caps. Micromagnetic simulations were used to study FePt/SiO2 Janus particles with diameters ranging from 1 to 20 µm and a nominal FePt cap thickness of 60 nm. Simulations performed using OOMMF predict a pronounced cap-diameter-dependent evolution of the hysteresis behavior, driven primarily by changes in demagnetizing and exchange energies. In contrast, SQUID magnetometry reveals strongly overlapping normalized hysteresis loops across all particle diameters.

We attribute this simulation–experiment discrepancy to size-dependent dewetting and morphological evolution of the FePt caps, introducing thickness variations, lateral free surfaces, and partial magnetic decoupling. These three effects redistribute the relative contributions of exchange, magnetocrystalline anisotropy, and demagnetizing energies, reducing their individual sensitivity to nominal cap diameter and leading to an apparent equalization of the ensemble magnetic response. Our results highlight the critical role of morphology-induced energy redistribution in curved magnetic thin films and the necessity of incorporating realistic, non-ideal geometries for predictive modeling of Janus magnetic materials.

1. Bozuyuk, U. et al., Adv. Funct. Mater.

2. Wu, X. W. et al., Appl. Phys. Lett. 2003.

3. Donahue, M. J.; Porter, D. G., OOMMF User’s Guide, NIST, 1999.

Vanadium dioxide has attracted considerable interest since the early 2000s due to its thermochromic properties, which are promising for solar radiation regulation and sensing applications. At 68 °C, VO₂ undergoes a fully reversible displacive phase transition from an insulating and infrared-transparent state to a metallic and infrared-reflective state [1]. However, the synthesis of phase-pure VO₂ remains challenging because of the complexity of vanadium oxide stoichiometry, with more than fifteen stable oxide phases.

In this work, VO₂ thin films were deposited at room temperature by magnetron sputtering using a V₂O₅ ceramic target in pure argon atmosphere. Sputtering from a V₂O₅ target is an effective method for depositing vanadium dioxide due to the chemical stability of the target during the reaction [2], while limited range of oxygen/argon ratio and target poisoning make the growth of pure VO₂ thin films difficult with reactive sputtering of metallic vanadium.

The influence of the sputtering power applied to the V₂O₅ target was systematically investigated, revealing its strong impact on the vanadium oxide phases formed after annealing. The films were subsequently crystallized by post-deposition rapid thermal annealing (RTA) under vacuum and characterized by X-ray diffraction and Raman spectroscopy. Particular attention was also paid to the optimization of the annealing conditions in order to obtain highly crystallized VO₂ thin films with thickness below 100 nm, while avoiding dewetting and over-reduction phenomena.

The thermochromic behavior of the films was investigated by temperature-dependent FTIR transmittance measurements, which revealed pronounced and reversible infrared transmittance modulation across the metal-insulator transition. These results demonstrate that V₂O₅ sputtering with optimized RTA conditions represents an efficient strategy for synthesizing high-quality thermochromic VO₂ thin films.

[1] Eyert, 2002, "The metal-insulator transition of VO₂: A band theoretical approach", Annalen der Physic

[2] Singh & al, 2025, "Exploring phase transition dynamics in VO₂ films: The role of substrate temperature", Currend Applied Physics

High-entropy alloy (HEA) thin films represent a versatile class of advanced coatings in which mechanical performance and surface functionality are achieved through compositional design. Functionalisation of HEAs with intrinsically antimicrobial metals provides an effective strategy for mitigating microbiologically influenced corrosion (MIC), while maintaining high hardness and corrosion resistance in aggressive environments.

MIC is a major challenge in marine, energy, and industrial systems, where microbial attachment and biofilm formation accelerate localized corrosion, material degradation, and maintenance costs.

HEA thin films deposited by physical vapor deposition (PVD) techniques exhibit uniform microstructures and chemically active surfaces that suppress microbial attachment and biofilm development. The functional response arises from the interplay between compositional complexity, phase constitution, and surface chemistry, linking antimicrobial activity with improved resistance to corrosion and wear.

Functionalisation of HEA coatings for MIC mitigation via PVD offers a materials-based approach that does not rely on additional surface treatments or biocidal layers. This strategy highlights the potential of HEA thin films as multifunctional protective coatings for marine, energy, and industrial applications, and reinforces the role of high-entropy design concepts in advanced surface engineering.

The growing demand for energy efficiency and system durability calls for nano-engineered surface coatings capable of operating reliably in corrosive, humid, and freezing environments. Despite offering unprecedented geometric freedom for the development of enhanced heat transfer components by metal additive manufacturing (AM), there is a lack of scalable and robust surface engineering strategies which severely limits the functional performance of AM stainless steel 316L (AM-SS), particularly in applications requiring precise control of liquid–solid interactions.

Here, we report a scalable micro/nanoengineering strategy for micro/nanoengineered functional surfaces on AM-SS, leveraging intrinsic two-dimensional sub-grain features unique to the AM process to construct three-dimensional hierarchical architectures. Guided by insights into the surface chemistry and compositional heterogeneity of pristine AM-SS, a selective electrochemical etching approach is developed to remove chromium-enriched nanoscale sub-grain boundaries, yielding previously unexplored microneedle array structures. Subsequent conformal surface functionalization via a one-step oxidation treatment generates FeO(OH) nanosheets, forming a hybrid nano-engineered surface layer with tailored interfacial properties.

The resulting surfaces exhibit ultra-low water adhesion, enhanced mechanical and chemical durability, and a 98% reduction in corrosion rate compared to untreated AM-SS. In addition, they enable jumping-droplet condensation and maintain 23% frost-free surface area at −15 °C, demonstrating robust performance under freezing conditions. When further integrated with a low-surface-energy lubricant, the hierarchical structures function as a stable nanoengineered slippery coating, enabling sustained dropwise condensation of low-surface-tension liquids such as ethanol—behavior unattainable on microstructured conventional stainless steel.

Importantly, the process is scalable to application-relevant geometries, as demonstrated on AM-SS tubes using copper foam cathodes, where efficient ethanol condensation is achieved. This work establishes a design framework for nanoengineered coatings and surface architectures on AM metals, enabling multifunctional, durable interfacial control for energy and thermal management applications

As oxide- and nitride-based multilayer dielectric thin films in advanced semiconductor devices exhibit greater structural complexity, the importance of reliable surface preparation has become increasingly significant for nanoscale structural and electrical characterization. Deeply recessed features in complex patterned architectures near large-area test element group (TEG) regions generate pronounced topographic variations during CMP-based delayering, leading to localized over-polishing and non-uniform material removal that degrade analysis fidelity. In this work, we present a wax-assisted planarization approach as a robust surface engineering strategy to enhance delayering stability. By temporarily filling recessed features, the wax acts as a mechanically supportive layer that suppresses localized over-polishing, particularly at pattern intersections. Because the wax is applied at relatively low temperatures, the method introduces minimal thermal budget to the dielectric stack. Our approach provides a practical and reproducible pathway for consistent sample preparation, contributing to the reliability of advanced characterization techniques for multilayer dielectric systems in semiconductor failure analysis.

Tantalum nitride (TaNx) thin films are widely employed in microelectronics, protective coatings, and diffusion barrier applications due to their excellent thermal stability, mechanical robustness, and tunable electrical properties. In this work, the evolution of the structural, electrical, optical, and mechanical properties of TaNx thin films is systematically investigated as a function of deposition conditions and nitrogen incorporation. Variations in growth parameters lead to significant changes in film stoichiometry, phase composition, and crystallographic texture, promoting transitions between metallic Ta-rich phases and more resistive nitride-dominated structures. These structural modifications strongly influence charge transport behavior, with electrical resistivity evolving in response to increased disorder and phase transformation. Optical characterization reveals changes in reflectance and absorption associated with modifications in electronic structure, while mechanical analysis highlights the role of composition and microstructure in determining hardness and adhesion performance. The results demonstrate a strong correlation between deposition-induced microstructural evolution and the multifunctional properties of TaNx thin films, providing valuable guidelines for tailoring their performance in advanced electronic, optical, and protective applications.

Ti-C-N films are of technological and scientific interest due to their multifunctionality as hard, wear-resistant and protective coatings. Titanium carbonitride coatings with higher carbon content will contain an amorphous carbon (a-C) phase forming nanocomposites with Ti(C,N) crystallites separated by a-C. X-ray photoelectron spectroscopy (XPS) is especially useful for quantification of carbon in a-C vs Ti(C,N). This is important as it provides a measure of the phase ratio, which governs mechanical and electrical properties. Due to the surface sensitivity of XPS, surface oxide and contamination peaks can obstruct peak analysis of the bulk signal. Therefore, samples are commonly etched with Ar⁺ ions to enable analysis of the bulk of the film. However, this may lead to the introduction of spectral artefacts.

Ti-C-N coatings with carbon content between 12 and 34 at.% were deposited by reactive DC magnetron sputtering. Film analysis with XRD, SEM, TEM, Raman spectroscopy and XPS confirmed that the films consist of crystalline Ti(C,N) with the amount of a-C increasing with carbon content. XPS spectra were acquired using synchrotron radiation with photon energies of 6.6 and 2.2 keV, i.e. probing different information depths. Difference spectra were used to extract true bulk information and provide artefact-free reference spectra. Comparison with spectra acquired after sputter etching with different Ar⁺ energies revealed substantial spectral artefacts caused by sputter damage, also when using low energy (200 eV) Ar⁺. Based on the observed spectral artefacts, we propose that ion bombardment causes nitrogen depletion and subsequent knock-on implantation of carbon from the a-C phase into the carbonitride. This leads to changes in both the phase ratio and the stoichiometry of the carbonitride. Furthermore, we show that the use of a gas ion cluster sputtering with Ar₁₀₀₀⁺ and Ar₅₀₀⁺ also causes sputter damage, although the damage mechanism may be different. It is interesting to note that Ar⁺ etching in Ti(C,N)/a-C results in more severe damage than reported in literature for related materials such as TiC, TiN and TiC/a-C, where it was found that spectra obtained after low-energy ion etching remain representative of the material. Our results suggest that this is not the case for Ti(C,N)/a-C. The tuneability of the functional properties of Ti(C,N)/a-C has great potential to tailor coatings to specific applications. Reliable quantification of the phase ratio is therefore crucial for coating development. Thus, artefact-free spectra obtained with different photon energies are required for characterisation.

During the operation of servo valves, the surface of the spool is subjected to erosion wear by solid particles. Therefore, coatings are applied to the spool surface to enhance erosion resistance. First, two coatings, DLC and CrAlN, were prepared on the surface of the spool by physical vapor deposition (PVD). Then, the microscopic morphology and mechanical and erosion resistance properties of the two coatings were comparatively studied. The results showed that the erosion wear rate on the surface of the DLC- and CrAlN-coated spools decreased by 48 % and 65 %, respectively, compared with those of the uncoated spools. In particular, the surface of the DLC coating is smoother and denser, while the CrAlN coating has larger particles on its surface. Additionally, both coatings significantly enhanced the mechanical properties of the spool surface. The adhesion of the coatings on the spool was reduced compared to the 40Cr substrate. Both coatings significantly enhanced the erosion resistance of the spool surface of the servo valve.During the operation of servo valves, the surface of the spool is subjected to erosion wear by solid particles. Therefore, coatings are applied to the spool surface to enhance erosion resistance. First, two coatings, DLC and CrAlN, were prepared on the surface of the spool by physical vapor deposition (PVD). Then, the microscopic morphology and mechanical and erosion resistance properties of the two coatings were comparatively studied. The results showed that the erosion wear rate on the surface of the DLC- and CrAlN-coated spools decreased by 48 % and 65 %, respectively, compared with those of the uncoated spools. In particular, the surface of the DLC coating is smoother and denser, while the CrAlN coating has larger particles on its surface. Additionally, both coatings significantly enhanced the mechanical properties of the spool surface. The adhesion of the coatings on the spool was reduced compared to the 40Cr substrate. Both coatings significantly enhanced the erosion resistance of the spool surface of the servo valve.

Opportunities of functional oxide based analog devices for edge artificial intelligence (AI) inference accelerators are significant, as they promise energy-efficient and low-latency hardware for Internet-of-Things (IoT) applications. However, their practical deployment is fundamentally challenged by device relaibility and state-dependent weight updates, which originate from stochastic filamentary switching or unstable interface modulation and directly limit inference accuracy at the hardware level. This work addresses this challenge through a materials-designed switching landscape, rather than through pulse engineering and algorithmic compensation at the circuit level, or through complex fabrication routes that are incompatible with CMOS integration. Using a WO₃/TiN structure formed through a simple process, we engineer a transport regime that intrinsically suppresses state-dependent weight updates. Consequently, identical low-voltage programming pulses result in uniform weight updates with high programmability, maintained across cycles and devices, directly satisfying a core requirement for inference hardware. This materials-driven approach provides a scalable pathway toward reliable analog AI inference accelerators for IoT applications.

Transparent conducting oxides (TCOs) are key components in optoelectronic devices; however, the high cost and scarcity of indium-based materials motivate the development of low-cost alternatives with comparable performance. In this work, ZnO:Al/Cu/ZnO:Al (AZO/Cu/AZO) multilayer transparent electrodes are investigated as indium-free TCO candidates. The influence of RF sputtering power on the structural, electrical, and optical properties of the AZO layers is systematically studied, while the effect of Cu interlayer thickness is analyzed to optimize the trade-off between conductivity and optical transparency. The results reveal that increasing RF power improves the crystallinity and carrier transport in AZO films, leading to a significant reduction in sheet resistance. Simultaneously, the Cu thickness plays a critical role in enhancing electrical conductivity through metallic percolation, while excessive thickness degrades optical transmittance due to increased absorption and reflection losses. An optimal Cu thickness is identified, yielding a maximum figure of merit (FoM), calculated using standard Haacke and related criteria. The optimized AZO/Cu/AZO multilayer exhibits optoelectrical performances comparable to, and in some cases exceeding, those of conventional high-cost TCOs such as indium tin oxide (ITO). These findings demonstrate the strong potential of RF-sputtered AZO/Cu/AZO multilayers as low-cost, scalable transparent electrodes for photovoltaic and optoelectronic applications.

Photovoltaics in nanoscale have not yet reached their full potential and many avenues of research remain to be explored to obtain optimal energy conversion efficiency. In particular, when fabricating heterostructures based on thin films of various materials — both inorganic and organic — and integrating them with electrodes deposited onto junctions, numerous challenges arise. There are not only technical issues. They exist at the level of different surface morphology of films forming heterojunction, possible energy level alignment mismatch, differences in optical and thermo-mechanical properties of materials, etc.
In this work we discuss technical and physical problems arising during fabrication a nano-organic heterostructure and after that, during electrical measurements.  For that purpose, we created ITO (100 nm)/CuPc (30 nm)/C60 (20 nm)/Al (50 nm) samples. We obtained them by the physical vapor deposition method in ultra-high vacuum system. We characterized surface morphology, electrostatic, electronic, optic, and mechanic properties in nanoscale for each layer using several scanning microscopy methods and photoelectron spectroscopies. For imaging the surface and analyzing the morphology we used Atomic Force Microscopy (AFM). For determination of the Young Modulus, we used PeakForce Quantitative Nanomechanical Mapping Microscopy (PeakForce QNM). Scanning Kelvin Probe Microscopy (SKPM) measurements allowed us mapping of the contact potential difference (CPD) across all interfaces. These methods were applied ex-situ on samples. For in-situ methods we used X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS). XPS helped us to identify element composition and chemical bonding in each layer. UPS gave information about the work function, HOMO levels, and ionization energies. Both methods were used for constructing energy level diagrams, identifying interfacial shifts, and determining the energy offset between organic materials. We imaged surfaces, mapped local density of states and extracted transport bandgaps in organic semiconductors by the Scanning Tunneling Spectroscopy (STS). We determined also optical bandgaps for ITO and organic layers by the UV–Vis Spectroscopy. At the end we tested electrically our samples.

Our project is summarized with conclusions concerning thin films deposition technology, the influence of their morphology on potential electrical breakdown and short-circuit issues between aluminum and ITO electrodes, as well as challenges related to electrode deposition, masking, and electrical measurements of nano-heterostructures.
The conference fee is covered by EU funds FSD - 10.25 Development of higher education focused on the needs of the green economy European Funds for Silesia 2021-2027: The modern methods of the monitoring of the level and isotopic composition of atmospheric CO2 (project no.FESL.10.25-IZ.01-06C9/23-00).

Functional films with daytime passive radiative cooling (DPRC) capability are playing an increasingly critical role in outdoor thermal management by enabling effective cooling without external energy input. However, achieving advanced cooling performance typically relies on precise and complex optical designs, which often overlook the engineering of thermal conductivity. For outdoor equipment with cooling requirements, the utilization of DPRC materials with low thermal conductivity impedes the efficient dissipation of internal heat, resulting in increased equipment temperatures—an outcome that is clearly at odds with the original purpose of radiative cooling. In this work, we propose a design strategy for DPRC functional films with high thermal conductivity. This strategy efficiently incorporates enhanced thermal conductivity into DPRC thin films through two approaches: constructing thermal conduction pathways within optical scatterers to couple radiative and conductive heat transfer, and designing an integrated architecture that combines heat-conducting and cooling functional layers. We developed a micron/nano hierarchical BN@ZnO composite filler conducive to Mie scattering by constructing efficient thermal conduction pathways on optical scatterers. This filler not only significantly enhances solar spectral reflectance but also, through its unique hierarchical structure—where ZnO nanorods bridge BN micron sheets—substantially improves the thermal conductivity of the composite material. The high thermal conductivity of the composite material enhances the effective utilization of the cold source. The BN@ZnO/cellulose acetate thin film achieves a practical cooling of 6.3 °C for outdoor operating equipment with internal heat sources. Furthermore, by coupling the phase inversion of cellulose acetate with a nano/micro Ag wire–driven self-stratification process, we developed Janus composite films formed in situ rather than through post-assembly. This film consists of a porous cellulose acetate layer exhibiting high DPRC performance and an Ag layer with high thermal conductivity, enabling substantial cooling—exceeding 10 °C—for heat-generating electronic devices operating outdoors in hot urban environments. We believe that this study provides a new materials design paradigm for the synergistic integration of optical regulation and thermal conduction in multifunctional films, and offers a practical strategy for the development of sustainable and green energy materials.

     In the field of detection applications, the development of tungsten oxide-based inks for screen printing on multifunctional thin films is of great interest.

     This work aims to characterize electrically sensing layers that were screen-printed using WO3 inks on PET flexible substrate. These inks contained WO3 grown onto commercial SiO2/ATO (Antimony Tin Oxide) particles by co-precipitation methods. A fraction of the resulting particles (SiO2/ATO/WO3) underwent a thermal treatment at 500°C at 5 hours. Different inks were then produced combining functional particles with a binder system consisting of nitrocellulose in 2-buthoxyethyl acetate, with different ratios (ATO : WO3) varying between 0.75 : 1 and 3.5 : 1. The ink viscosity was adjusted to about 6000 cP for optimal printability.

     Structures were printed through 77 threads cm-1 mesh screens, and cured for 30 minutes at 80ºC. This resulted in thicknesses ranging from 5 to 15 microns.

     The resistivity of these films was characterized using a temperature-controlled four-point probe station. In this study, we analysed the influence of temperature, light and humidity, as well as the long-term stability. It appeared that:

     - Visible light does not electrically affect our different samples: exposed to daylight, or not (an opaque glove box covering the equipment), the same resistivity was measured for a given sample.

     - Temperature has a significant influence, resulting in an 8% decrease in resistivity between room temperature and 100 °C, regardless of the film. This decrease in resistivity as temperature increases has also been observed over a wider temperature range using a cryoprobe station down to -70 °C. We also observed a hysteretic behaviour and this hysteresis was smaller for annealed inks, indicating a greater structural homogeneity.

     - Long-term electrical measurements indicate a significant increase in resistivity over time (10% after more than a day). Two parameters could be involved in this change: temperature and humidity.

     To separate the influence of these two parameters mentioned before, the temperature was set at 23°C and the applied current intensity optimized to minimize a local rise in temperature. A slight flow of nitrogen gas was introduced inside the glove box, in order to modify the humidity level (0% - 30%) during the electrical measurements.

     Consequently, it was observed that the resistivity decreases as relative humidity increases, with a maximum sensitivity of 0.4 ohm.cm / %RH for annealed samples whose cycling yielded more stable and reliable curves.

     Tungsten oxide inks could then be excellent candidates for the development of cost-effective, local humidity sensors in numerous applications (healthcare, housing, materials…).

Calcium-phosphate (Ca–P) coatings on titanium represent a class of functional surface modifications with potential applications in bio-related and protective technologies. Among various surface engineering routes, micro-arc oxidation (MAO) is a plasma-assisted process enabling the in-situ formation of nano- and micro-structured oxide-based coatings incorporating calcium and phosphorus species directly from the electrolyte. The resulting coating architecture and mechanical integrity are strongly governed by both the processing parameters and the structural state of the metallic substrate.

In the present study, Ca–P coatings were synthesized on titanium substrates using MAO under different electrical regimes, leading to distinctly different surface morphologies and pore architectures. The adhesion and mechanical stability of the nano-engineered coatings were systematically evaluated by scratch testing, including the determination of critical loads and failure characteristics.

To gain insight into the mechanisms of coating degradation and delamination, focused ion beam (FIB) cross-sectioning was performed in the scratch track regions, allowing direct visualization of coating–substrate interfaces and damage evolution at the micro- and nanoscale. The results reveal a clear correlation between MAO processing conditions, coating architecture, and adhesion behavior.

These findings highlight the role of plasma-assisted surface engineering in controlling the structure–property relationships of functional thin films and provide guidelines for the design of mechanically reliable nano-engineered coatings for advanced applications.

The development of structurally controlled hybrid coatings based on transition metal oxides and carbon nanostructures is of considerable interest for nano-engineered surfaces, where uniformity, interfacial stability, and reproducibility of thin-film architectures play a key role. In this work, an approach to the fabrication of NiO/CNT composite coatings is presented, based on a combination of PE-ALD and CVD techniques.

NiO thin films were deposited by PE-ALD on Al₂O₃ surfaces using NiCp₂ as the metal–organic precursor and O₂  plasma as the oxidant. The deposition was carried out on SENTECH equipment in a typical ALD cyclic mode, consisting of sequential pulses of NiCp₂ and O₂ plasma separated by nitrogen purge steps. The GPC was approximately ~0.3 Å per cycle and was determined by spectroscopic ellipsometry based on NiO thickness measurements after different numbers of deposition cycles. Atomic force microscopy revealed that the deposited NiO films exhibit high uniformity and conformally replicate the surface morphology of the substrate. Elemental and optical analyses confirmed the formation of the NiO phase.

CNT deposition was carried out using two technological approaches. In the first approach, prior to the onset of CVD growth, the NiO surface was preliminarily reduced to metallic nickel in a hydrogen atmosphere. After completion of the reduction step, CNT growth was performed using a 10% acetylene–argon gas mixture. In the second approach, no preliminary reduction of the NiO film was applied. In this case, the reduction of NiO to the metallic state occurred during the initial stage of the CVD process due to hydrogen generated by the thermal decomposition of the acetylene, followed by the formation of catalytically active nickel sites and CNT growth.

CNT growth proceeded predominantly via a base-growth mechanism, which is attributed to the strong anchoring of nickel nanoparticles on the oxide film surface. After reaching a certain CNT layer thickness, the growth process became self-limited due to restricted diffusion of acetylene toward the catalytic sites located at the base of the structure. The quality of the formed CNTs was confirmed by Raman spectroscopy, revealing a low intensity ratio of the defect-induced D band to the graphitic G band (I_D/I_G ≈ 0.1), indicating a low density of structural defects in the carbon phase.

The proposed approach enables the reproducible fabrication of NiO/CNT composite coatings with controlled nanostructure. The high degree of structural ordering of the carbon nanotubes and the conformal nature of the oxide sublayer make such coatings suitable as functional interfacial layers in micro- and nanoelectronic devices. In particular, these architectures can be considered promising for thermal management and heat-spreading applications in silicon chips, as well as in integrated sensing and nanoelectronic systems.

 In this study, molecular dynamics simulation is conducted to investigate the evolution of subsurface damage in laminated CoCrFeNiMn high-entropy alloys. The deformation behavior and tribological mechanism are studied. The results indicated that the subsurface damage can be improved with an increase in cutting temperature. The recrystallization process and the lubricant effect in the amorphous structure at the top layer are two primary reasons for this phenomenon. The amorphous layer almost disappears in the subsurface sample and is advantageous for subsurface damage as the cutting temperature is higher than 1100 K. The slip motion and dislocation nucleation in the surface sample promote plastic deformation. The pile-up collections ahead of the cutting tool increase with the increasing cutting temperature. The phase transformation indicated by the presence of HCP, BCC, and amorphous structure is recorded at the cutting layer. The Shockley partial is the primary dislocation for all cases. The deformation of the surface sample is reduced, and the frictional coefficient is decreased at higher cutting temperatures, which is advantageous for surface deformation.

Thin films, both organic and inorganic, on stretchable substrates enable lightweight, conformable devices that can bend and stretch with their environment, opening applications in wearable health monitoring, soft robotics, flexible displays, and resilient sensors for curved or moving surfaces. Achieving this requires a solid understanding of how microstructure, charge transport, and mechanically induced strain are linked. We investigate the use of in situ tensile‑testing grazing incidence wide angle X-ray scattering (GIWAXS) to track how film microstructure evolves under strain and to better connect processing, structure, and electromechanical performance. Our experimental setup integrates a Deben tensile rig directly into the XMaS beamline at ESRF and the P03 beamline at PETRA III (DESY), enabling real-time GIWAXS measurements during controlled uniaxial load of films on stretchable substrates.

Our approach is validated using a ~70 nm 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) film deposited on polydimethylsiloxane (PDMS). GIWAXS patterns are collected under uniaxial strain up to 30%. Preliminary analysis confirms a well-textured film and indicates strain-induced microstructural evolution, observed as shifts in the q-vector of several thin-film reflections. Refinement of Bragg peaks is used for quantification of micro-strain and uniaxial loading in AFM for assessment of microstructure development in real space.

Photovoltaic/photothermal (PV/T) systems enable the graded utilization of solar spectrum by transmitting visible light to photovoltaic cells for electricity generation while absorbing or reflecting near-infrared light for heat production. By constructing a Ag-based optical microcavity (with the film structure of Substrate/Ag1/Si₃N₄/SiO₂/Si₃N₄/Ag2/Si₃N₄/W-WOₓ), our team has, for the first time, developed a short-wave pass filter (SPF) with high visible transmittance (an average transmittance of 0.60 at 380-780 nm), high near-infrared absorptance (an average absorptance of 0.86 at 780-2500 nm), and high mid- to far-infrared reflectance (an average reflectance of 0.67 at 2500-20000 nm and 0.91 at 8000-20000 nm). It was achieved by coupling the intrinsic spectral selectivity of W-WOₓ and ultra-thin Ag films, along with interference mechanisms and surface plasmon resonance effects. Such SPFs exhibit a higher thermal equilibrium temperature, thereby improving the efficiency of thermal conversion efficiency in PV/T systems.

By adjusting the optical constants and thicknesses of Ag (from 8 nm to 12 nm for Ag2 layer) and W-WOₓ (from 30 nm to 0) layers, the intrinsic optical properties of the films and the interference central wavelength of the SPF were altered. Thus the absorbing band narrows and the reflecting band widens gradually, until the near-infrared transformed from high absorptance to high reflectance band (other bands remained unchanged). After heat treatment at 200 °C in air for 72 h, the optical properties of the SPF remained stable. This work elucidates the relationships among film structure, micro-structure, and optical property, offering new insights for the design of SPFs and contributing to enhanced efficiency in PV/T systems.

During the rapid advancement of nanoelectronic devices, embedded SiGe source–drain strain technology has been widely adopted as an effective approach to enhance device performance. With the emergence of new device architectures and three-dimensional solutions, such as stacked nanosheet channel devices and CFETs, integrating strain engineering into these advanced processes requires continuous optimization. This work employs epitaxial buffer-layer technology to modulate strain distribution in SiGe/Si multilayer nanosheet structures. Compressive strain is maintained in the SiGe channel layers, while tensile strain is preserved in the Si channel layers. By leveraging the selective etching between SiGe and Si, compressively strained p-type nanosheet FETs (P-NSFETs) and tensile-strained n-type nanosheet FETs (N-NSFETs) are simultaneously fabricated on the same silicon substrate. The buffer layer also allows the growth of SiGe channels with higher Ge content, facilitating selective etching, well-defined nanosheet geometries, and improved fabrication yield. Figure 1 shows (a) the key process conditions used to control selective etching and prevent channel bending, and cross-sectional images of the ultrathin SiGe/Si multilayer structure obtained by (b) high-resolution TEM (HRTEM) and (c) scanning TEM with high-angle annular dark-field (STEM-HAADF). Well-defined atomic-layer structures and excellent epitaxial quality are observed. In parallel, HfO₂/ZrO₂ superlattice (SL) thin films are developed as high-k gate dielectrics. Alternating layers of HfO₂ and ZrO₂ are stacked (0.5 nm per layer) to form a total thickness of approximately 5 nm. Cross-sectional TEM images of metal–insulator–semiconductor (MIS) capacitors (Figure 2) confirm the structural integrity and uniformity of the gate stack. The lower diffusion coefficient of ZrO₂ suppresses oxygen vacancy migration, reducing interface trap density and improving dielectric stability. The combination of strain-engineered multilayer nanosheets and nano-engineered oxide superlattices demonstrates a clear structure–property relationship, enabling reliable integration into nanosheet FET CMOS inverters.

Figure Captions

Fig. 1. (a) Key process conditions used to control selective etching and prevent channel bending. Cross-sectional images of the ultrathin SiGe/Si multilayer structure obtained by (b) HRTEM and (c) STEM-HAADF reveal well-defined atomic-layer structures and excellent epitaxial quality.

Fig. 2. Cross-sectional TEM images of MIS capacitors with (a) HfO₂/ZrO₂ superlattice dielectric stacks composed of alternating 0.5-nm-thick HfO₂ and ZrO₂ layers, and (b) conventional HfO₂ dielectric stacks. The superlattice exhibits a well-defined multilayer structure with a total thickness of approximately 5 nm.

Keywords

Nanosheet FETs, Strain engineering, SiGe, Superlattice HZO, CMOS inverter, Nano-engineered thin films

Soil nutrient monitoring increasingly depends on rapid, reliable, and low-cost analytical approaches to support precision agriculture and sustainable fertilizer management [1,2]. In this study, microfluidic impedimetric electronic tongues are explored as an alternative, relying on sensor arrays in which each sensing unit exhibits distinct interfacial electrical properties, enabling differential response to complex soil matrices [3]. Within this framework, the glancing angle deposition (GLAD) technique enables the growth of nanostructured metal nitride thin films with controlled thickness, geometry, and surface morphology, providing a direct route to tune sensitivity, reproducibility, and electrical and mechanical robustness [4]. Chromium nitride (CrN), boron nitride (BN), and titanium nitride (TiN) nanostructured films were deposited onto gold interdigitated electrodes via GLAD, defining distinct film–electrolyte interfacial environments. These interfaces were evaluated in aqueous solutions containing representative soil macronutrient ions (e.g., K⁺, NO₃⁻, and NH₄⁺) at multiple concentrations. The films were integrated into an impedimetric platform, and frequency-dependent impedance spectroscopy (1 Hz–10⁶ Hz) was employed to analyze the impedance spectrum, from which resistive, capacitive, and dielectric loss contributions were extracted to assess interfacial polarization and dielectric relaxation phenomena [5]. The results reveal that each nitride film produces a characteristic interfacial dielectric signature: CrN exhibited the most resistive and least polarizable behavior, whereas BN and TiN showed enhanced capacitance, stronger dielectric losses, and faster relaxation dynamics, associated with increased ion accessibility and interfacial charge accumulation. Overall, the results demonstrate that GLAD-engineered nitride thin films provide an effective strategy to tailor interfacial dielectric response, establishing a direct link between thin-film deposition and electrical behavior, and highlighting their potential for soil sensing applications in precision agriculture.

[1]https://doi.org/10.1016/j.agsy.2016.07.001.

[2]https://doi.org/10.3390/agriculture10120653.

[3]https://doi.org/10.1088/978-0-7503-3687-1.

[4]https://doi.org/10.1021/acssensors.5c00921.

[5]https://doi.org/10.1038/srep34843.

Oil-water separation membranes with engineered surface wettability have emerged as promising solutions for mitigating oil spill contamination. Among them, mesh-based membranes are particularly attractive due to their cost-effectiveness, mechanical flexibility, and scalability. However, their practical deployment remains limited by a persistent material challenge in achieving durable coating adhesion and long-term structural stability under realistic operating conditions. In this work, we present a systematic material-fabrication strategy to develop robust and durable coatings on stainless steel mesh (SSM) substrates by addressing interfacial failure as the primary factor governing membrane stability. An intermediate O₂ plasma activation step is introduced to generate chemically active surface functionalities, thereby significantly enhancing coating-substrate interactions and overall membrane stability. Graphene oxide (GO) coatings were initially explored for their inherent advantages as 2D materials, including high surface area and abundant oxygen functionalities. While those membranes exhibit high initial separation efficiency (SE), their long-term durability is limited by weak interfacial adhesion between stacked GO sheets and the substrates. Plasma-induced surface functionalization improves adhesion, highlighting the critical role of interface chemistry, while revealing the intrinsic durability limitations and scalability constraints associated with multistep GO-based fabrications. Building on this understanding, copper oxide (CuO) coatings were subsequently fabricated via one-step solution-combustion synthesis, enabling rapid, energy-efficient membrane fabrication with minimal processing complexity. Although CuO-coated membranes offer favorable wettability and high flux, performance degradation in acidic environments highlights the limitations of single-oxide architectures. This insight drives the development of a mechanically and chemically reinforced nanocomposite design. Accordingly, a CuO-ZrO₂ coating was developed by combining combustion synthesis with plasma pre-treatment. The resulting membrane exhibits SEs exceeding 99.5% with a maximum flux of 91000 L m^-2 h^-1 and retains SEs above 98.8% even after 30 separation cycles, indicating excellent chemical durability and recyclability. This enhanced performance is attributed to the synergistic combination of CuO-induced wettability with the mechanical rigidity and chemical inertness imparted by ZrO₂. Overall, this study illustrates how interfacial engineering, guided by iterative materials understanding, can drive the transition from laboratory-scale coatings to scalable, robust membranes for next-generation oil-water separation technologies. 

Recently, nanostructured materials based on metal oxide composites have been the focus of considerable scientific research in view of developing modern gas sensors suitable for room-temperature operation and the detection of low concentrations of specific gases. Many factors should be considered while composite nanostructures for sensor elements are designed, such as active surface, physicochemical characteristics of the surface, electrical conductivity, nanocrystal size, surface energy, etc. Each of these factors significantly depends on the selection of materials, deposition methods, and the process parameters used in deposition. The development of effective and low-cost nanostructured gas sensors from metal-oxide composites is still an open topic; further studies are thus required for their optimization. One possibility for developing a technology suitable for fabrication of sensor elements is to use the advantages of well-developed methods for depositing thin films and structures through their combined application.

In this work, composite porous metal-oxide structures based on well-known metal oxides, such as ZnO and SnO₂, were produced by the successive implementation of pulsed laser deposition (PLD) and magnetron sputtering (MS) bearing in mind possible gas sensor applications. Porous ZnO (or SnO₂) nanostructures were prepared by using PLD at atmospheric pressures in air. The deposition led to the fabrication of highly porous nanostructures composed of nanoparticles. The as-deposited porous metal-oxide structure was covered by a thin SnO₂ (or ZnO) film prepared by MS. The influence was studied of the synthesis parameters of PLD and MS on the morphology, structure and physicochemical properties of the sample's surface. Preliminary gas-sensor tests were conducted to determine the behavior of the sensors consisting of composite nanostructures under exposure to different gases (CO, acetone vapor, ethanol, ammonia, etc.). The possible mechanism of gas detection is also discussed.

Acknowledgements: The authors acknowledge the financial support of the project KP-06-N87/8 “Development of sensor elements based on composite metal-oxide thin films and nanostructures” under the “Competition for financial support of basic research projects – 2024” Program of the Bulgarian National Science Fund.

Compensating defects and dopant–vacancy clustering limit n-type activation in GeSn, a metastable alloy thin-film platform for mid-infrared optoelectronics. Here we study post-growth doping of Ge and GeSn thin films by combining remote plasma-enhanced chemical vapour deposition (RPECVD) with ion implantation and controlled annealing, and we use magnetotransport as a sensitive probe of processing-induced defects.

Ge and GeSn films (2–10 at.% Sn) were grown by RPECVD and implanted with P, As and Sb, followed by rapid thermal annealing (RTA, 400–650C) or laser annealing. Structural recovery and defect evolution were assessed using Rutherford backscattering spectrometry (RBS) and transmission electron microscopy (TEM). Electrical activation and transport were characterised by Hall-effect and magnetoresistance measurements. Transport anomalies were interpreted with effective-medium / resistor-network modelling to connect macroscopic magnetotransport signatures to spatially inhomogeneous conduction expected from compensating defect landscapes.

Across the explored processing window, RBS/TEM indicate near-complete recrystallisation and low extended-defect densities in the implanted layers. However, equilibrium thermal processing can promote dopant redistribution and deactivation: in particular, high-temperature RTA leads to Sb surface segregation. In samples exhibiting poor activation (lower-temperature RTA and GeSn), magnetotransport reveals linear magnetoresistance and anomalous Hall response, consistent with electronically inhomogeneous transport arising from compensating defects and donor deactivation. In contrast, laser annealing provides a non-equilibrium pathway that limits diffusion during dopant incorporation and suppresses dopant–vacancy clustering relative to equilibrium annealing, offering improved prospects for achieving highly conductive n-type layers while preserving the quality of metastable GeSn.

These results highlight post-growth ion implantation plus non-equilibrium laser processing as a practical nano-engineering route for functional GeSn thin films and demonstrate magnetotransport as a rapid diagnostic of defect-driven inhomogeneity to guide process optimisation for mid-IR devices.

High-temperature resistant separators with rapid lithium-ion transport are crucial for ensuring lithium battery safety and overcoming application bottlenecks in extreme environments. Poly(ether ether ketone) (PEEK) is a promising material due to its intrinsic high-temperature resistance, excellent mechanical properties, and high electrolyte affinity. However, its poor solubility and high melting point have hindered the processing of high-performance PEEK separators and the effective regulation of their ion transport behavior. To address this challenge, we developed high-temperature resistant semi-crystalline PEEK separators (thermal shrinkage temperature > 200 °C) with tunable microstructures by integrating a reversible chemical modification strategy with crystallization engineering. This method effectively mitigates the severe swelling issue typical of conventional sulfonated PEEK separators, enabling stable cycling of lithium metal batteries at high temperatures (70 °C). Furthermore, a sulfonate group-modified semi-crystalline PEEK separator was designed via in-situ surface-sulfonation. This design ensures high structural stability while facilitating rapid and selective lithium-ion transport. The lithium metal battery assembled with this separator demonstrates stable cycling performance under high-temperature and high-rate conditions.

Quasi-2D perovskites are known for their long-term environmental stability. In this system, bulky spacers are expected to inhibit ion migration and reduce interfacial nonradiative recombination. However, it also presents challenges for charge transportation at the same time. As a result, the possibility and great potential of such quasi-2D perovskites for wide band gap (WBG) solar cells have rarely been explored. Here, we specialize in formamidinium-based quasi-2D WBG perovskites, obtaining a preferential crystal orientation perovskite film. To obtain better performance, the interfacial quantum wells (QWs) regulation strategy for a higher preference of a low-dimensional perovskite interface layer is proposed. The interfacial QWs are adjusted by the preference binding capacity of the solvent and long-chain molecules. The importance of interfacial QW distribution for charge transportation and stability is further investigated in this work. The quasi-2D 1.70 eV perovskite solar cells achieved by the regulation strategy exhibit an efficiency of 20.18% with a VOC of 1.27 V and maintain 95% initial performance under 1 sun illumination over 500 h of stable operation.

All-solid-state Li-S batteries (ASSLSBs) are attractive candidates for high-energy-density and environmentally sustainable energy storage systems. However, their practical deployment remains constrained by lithium dendrite formation and interface instability with solid-state electrolytes (SSEs) when using lithium metal as anodes. Herein, we propose a sulfur-oxidant-driven anodization strategy to construct a stable and ionically conductive interface on lithium. By anodically reacting P4S16 with lithium metal in 1,2-dimethoxyethane (DME), a conformal thiophosphate (Li3PS4) interphase is deposited in situ on the lithium surface. This solid electrolyte film exhibits high ionic conductivity (0.19 mS cm-1), controlled thickness, and robust interfacial contact with lithium metal, which collectively suppresses lithium dendrite propagation and parasitic reactions during cycling. As a result, symmetric cells employing this LPS/Li electrode demonstrate stable cycling over 600 hours at 1 mA cm-2 in liquid electrolyte systems. Furthermore, when LPS serves as the solid-state electrolyte, symmetric solid-state cells assembled with two LPS/Li electrodes demonstrate a stable cycle life exceeding 1000 hours at 1 mA cm-2 due to well-improved interfacial compatibility. When integrated into ASSLSBs, with the LPS interphase as the solid-state electrolyte and Li metal as the anode, the cell delivers a high specific capacity of 1351 mAh g-1 at 0.1 C with a capacity retention of 89.3 % after 50 cycles. This study introduces an unprecedented sulfur-oxidant-induced anodization process, providing a simple and effective interfacial-engineering strategy to develop next-generation ultrathin all-solid-state lithium-sulfur battery technologies.

The continuous scaling of semiconductor technology demands advanced nanoelectronic devices that can simultaneously achieve high integration density, strong electrostatic control, and reliable operation. Among various emerging architectures, one-dimensional nanowire-based device structures have attracted significant attention due to their superior gate controllability. In particular, GaN-based nanodevices exhibit great potential for power and high-frequency applications because of their high breakdown voltage, high electron mobility, and excellent thermal stability. However, a comprehensive understanding of the temperature-dependent electrical behavior of ultra-scaled GaN nanodevices remains limited.

This lack of understanding poses critical challenges for practical device operation, including performance instability and long-term reliability degradation, especially in extremely miniaturized structures where carrier scattering mechanisms and interface trap effects become dominant.

In this work, these challenges are addressed by fabricating a wrap-gate nanodevice based on a one-dimensional GaN nanowire with a height of approximately 56 nm and systematically investigating its temperature-dependent electrical characteristics over a range of 100–300 K. Advanced electron-beam lithography and self-limiting growth processes were employed to achieve highly uniform, horizontally aligned nanowire structures. Key electrical parameters, including drain current, transconductance, threshold voltage, subthreshold swing, Ion/Ioff ratio, on-resistance, and carrier mobility, were quantitatively analyzed.

The experimental results demonstrate that the drain current increases with increasing temperature in the low-bias regime (V_gs < 2 V), whereas an opposite trend is observed in the high-bias regime (V_gs > 2 V). Furthermore, the threshold voltage and on-resistance increase with temperature, while the carrier mobility and Ion/Ioff ratio decrease. These temperature-dependent behaviors are attributed to the combined effects of electron–phonon scattering, surface trap states, and the interplay between core and surface conduction channels in the one-dimensional nanowire architecture.

This study provides a quantitative understanding of temperature-dependent electrical transport in ultra-scaled 56 nm one-dimensional GaN nanowire nanodevices and offers critical physical insights and design guidelines for the development of high-performance, highly reliable GaN-based nanoelectronic devices for future extreme-scaling and harsh-environment applications.

High-purity perovskite precursors are crucial for minimizing defect density and enhancing the performance of perovskite solar cells (PSCs). This study introduces an aqueous synthesis method for producing ultrapure formamidinium lead iodide (FAPbI₃) microcrystals as perovskite precursors. The approach enables kilogram-scale production with an average purity of 99.994%±0.0015%, achieved by removing key impurities such as calcium (Ca²⁺), sodium (Na⁺), and potassium (K⁺) ions from low-purity raw materials. The purified precursors significantly reduce carrier trap states, extend carrier diffusion lengths, and improve film quality. As a result, p-i-n structured PSCs fabricated using these precursors achieve a power conversion efficiency (PCE) of 27.2% and retain 94% of their initial PCE after 1000 hours of continuous illumination at 50°C. This work demonstrates a scalable, cost-effective, and environmentally friendly route to high-purity perovskite precursors, advancing both the efficiency and stability of PSCs.

Graphene-based materials are promising two-dimensional (2D) nanomaterials for advanced field-effect transistor (FET) biosensors due to their exceptional electrical conductivity, large surface area, and strong affinity for biomolecules. This study presents a FET platform featuring a graphene-modified source–drain channel designed for label-free detection and immobilization of DNA nucleobases. The π-conjugated structure of graphene enables strong π–π stacking interactions with the aromatic rings of nucleobases, promoting stable adsorption and effective electronic coupling between DNA molecules and the conductive channel. These interactions induce modulations in charge carrier density, resulting in significant and reproducible shifts in the FET transfer characteristics. Real-time monitoring of these electrical variations allows direct detection of DNA bases without requiring labeling or amplification. Experimental data demonstrate distinct electrical responses for individual nucleobases, indicating potential for selective and sequence-specific recognition. The platform operates under ambient conditions and exhibits high sensitivity, fast response, and compatibility with miniaturized and flexible substrates, supporting integration into portable and low-power diagnostic devices. This approach leverages the intrinsic properties of graphene to enable efficient and scalable biosensing, marking a step forward in the design of electronic platforms for nucleic acid analysis. The proposed sensor architecture holds promise for applications in point-of-care diagnostics, personalized medicine, environmental monitoring, and bioanalytical research. Overall, this study highlights the versatility of 2D graphene materials in biosensor engineering and their potential to advance next-generation bioelectronics technologies.

Acknowledgements: This work was supported by the project “National Platform for Semiconductor Technologies”, Contract No. G 2024-85828/390008/27.11.2024, SMIS Code 351364, funded by the European Regional Development Fund (ERDF) under the Operational Programme for Smart Growth, Digitization and Financial Instruments (POCIDIF), Priority 4 – Development of Strategic Technologies for Europe (STEP). Additional funding was provided by the Romanian Ministry of Education and Research, through CCCDI-UEFISCDI, project PN-IV-P7-7.1-PED-2024-0386, Contract No. 79PED/2025.

The production, use, and recycling of tires pose significant environmental challenges, requiring the development of more sustainable materials and improved life-cycle strategies. One proposed solution is a detachable tread system that can be replaced independently of the tire carcass, representing a first step toward enhanced sustainability, tire performance, and intelligent integration while reducing environmental impact. In this context, extending the service life of the tire carcass is essential, as it can remain functional provided that degradation caused by environmental agents such as moisture and ultraviolet (UV) radiation is prevented.

To improve the UV resistance and longevity of rubber, silicone coatings were applied as stabilizing and protective layers. Due to the inherently low surface energy of rubber and the difficulty of achieving coating adhesion, an atmospheric cold plasma treatment was applied, increasing the surface energy by approximately 250%. After plasma activation, silicone nanoparticles dissolved in a solvent were deposited onto the rubber surface by spraying. Upon solvent evaporation, a nanometric silicone layer remained, providing effective protection against UV radiation.

NR-SBR rubber specimens (natural rubber and styrene–butadiene rubber) were coated with silicone and subsequently cured before being subjected to UV ageing for up to 1500 h. Tensile tests revealed that uncoated rubber experienced a stiffness increase of approximately 20%, becoming brittle, whereas silicone-coated rubber showed only a 4% increase in stiffness while maintaining flexibility. These results demonstrate the effectiveness of silicone-based nanocoatings in mitigating UV-induced degradation and support the development of advanced protective coatings to extend the service life of rubber materials in demanding environments.

 The rapid expansion of high-frequency communications, autonomous technologies, and electrified transportation is pushing EMI shields to become thinner while delivering multiple functions. Conventional approaches mainly focus on increasing DC conductivity, either by developing better conducting phases or by dispersing 0D and 1D conductive fillers in polymer matrices. Although these composite routes are well established, they face practical limits: added fillers often demand high loading and thickness, can degrade thermal transport, and tend to produce shielding that relies heavily on reflection rather than absorption.

 Here we present a design strategy based on an RC circuit viewpoint, where the effective conductivity at high frequency is governed not only by resistance but also by interfacial capacitance. We engineer an all–monolayer, two-dimensional nanomatrix in which densely stacked nanosheets form face-to-face nanocapacitor networks. This architecture amplifies interfacial capacitance and drives conductivity to rise with frequency, enabling exceptionally high thickness-normalized shielding effectiveness even when the DC conductivity remains low. At comparable DC conductivity, the resulting performance (dB/mm) exceeds that of typical composites by nearly two orders of magnitude. The films further combine high thermal conductivity with intrinsic nonflammability.

 Functionality can be programmed through composition and structure. The platform accommodates a broad set of 2D building blocks, spanning both conventional van der Waals materials and non–van der Waals systems. Introducing structural gradients improves impedance matching and suppresses surface reflection. Finally, a spray-processable ink enables conformal, CMOS-compatible coatings on practical hardware.

 Overall, this work shifts the design logic of EMI shielding from a purely conductivity-centered paradigm to one that leverages capacitance engineering, and it establishes scalable 2D nanomatrix assemblies as a versatile route beyond the constraints of conventional composite strategies.

Energy conversion, such as photovoltaic (PV), is key to renewable sources. As the Seebeck effect-driven thermoelectric (TE) energy conversion emerges, with materials having varied efficiencies, further options become available. One option is the photothermoelectric (PTE) energy conversion, where the application of the artificial light absorbers (ALH) creates a large photothermal (PT) temperature gradient (DT) to produce useful electrical power.

Research on PTE has led to several interesting applications, such as photodetectors (PD)^{1,2 ,} actuators³, battery charging4, among others. Here, we report on two kinds of scalable dark PT light harvesters that produced remarkable PTE powers, surpassing most of the available reports. First, a composite of Cs₄CuSb₂Cl₁₂ (CCSC) perovskite, with bulk MoS₂ (ALH1). Next, is a dark and small band gap TE material, Bi₂Te₃ nanosheets (ALH2). We demonstrate remarkable PTE powers under common desktop lamp and solar irradiation. The optimum ALH1 is a 75 % composite of CCSC and 25 % MoS₂, obtained from a comparison of pure CCSC (100 %), pure MoS₂ (0 %), and other compositions, which produced a high (ΔT) of ~30 °C, and maximum PTE power density of 3.26 mW cm^-2 under 450 mW cm^-2 of a 3000 K lamp. The Bi₂Te₃-coated TEG device, produced an unprecedented PTE voltage of 553 mV, and could charge a 40 mAh (3.7 V) Li-ion battery  within 180 s under a common desktop 3000 K lamp (0.45 W/cm²).

In summary, PT efficient, dark, scalable artificial light harvesters (ALH) were designed and synthesized. Coated on TEG modules these ALHs could generate PTE powers when illuminated under sunlight, lasers and common desktop lamps. We demonstrate charging of Li-ion batteries with the PTE power generated therein.

References:

1. V. Sridhar, C. T. Wu, S. Chattopadhyay ACS Appl. Mater. Inter. 17 39584 (2025).

2. M. Dai, X. Zhang, Q. J. Wang, Adv. Funct. Mater. 34, 2312872 (2024).

3. P. Zhou, J. Lin, W. Zhang, Z. Luo, L. Chen, Nano Research 15, 5376 (2022).

4. Y. Wang, W. Sha, M. Xiao, Y. Fang, P. Zhu, Z. Wang, S. Wang, W. Zeng, J. Zhao, L. Ruan, Chem. Engg. J. 489, 151571 (2024).

A development of stretchable electrodes with excellent elasticity, conductivity and long-term durability is of paramount importance in a variety of highly deformable next-generation electronics Applications. The liquid metal-based stretchable electrodes have recently emerged as a promising candidate for high performance stretchable electrodes. Herein, we introduce the bi-layered stretchable electrode where the lower and upper layers are composed of solid metal and thin liquid metal films, respectively. In previous studies, the upper layer comprised of thick liquid metal films, which indispensably limits the electrical conductivity of bi-layered electrodes. This approach enables to increase a volumetric fraction of highly conductive solid metallic layer, which consequently improves the overall electrical conductivity of stretchable electrodes. It also enables the electrodes to be embedded in elastomers, improving their stability. The resulting stretchable electrodes maintained their own stretchability and long-term durability while securing significantly a higher conductivity. The fabricated electrode shows a stable resistance variation under 30,000 stretching cycles, proving its long-term durability.

Thermochromic vanadium dioxide is a promising material for temperature-adaptive control of thermal radiation because it undergoes a reversible insulator-to-metal transition near 68 °C. This transition induces pronounced changes in optical properties in the mid-infrared region, enabling dynamic emissivity modulation without external energy input. However, practical implementation is often limited by the difficulty of obtaining ideal single-phase vanadium dioxide films on glass substrates.

In this work, we demonstrate temperature-adaptive thermal emission control using a Fabry–Pérot thin-film cavity composed of vanadium dioxide, a dielectric spacer, and a metallic back reflector. The cavity structures were fabricated using scalable thin-film deposition and annealing processes. By integrating vanadium dioxide into a resonant cavity architecture, strong temperature-dependent modulation of infrared absorption and emission is achieved even with ordinary multiphase films.

A key finding of this study is that the maximum emissivity is obtained before the vanadium dioxide layer fully transforms into the metallic state when the film thickness exceeds a critical value. This behavior originates from partial phase coexistence within the vanadium dioxide layer, which enhances optical absorption through resonant field confinement inside the cavity. As a result, substantial emissivity modulation can be realized at temperatures significantly lower than those required for complete phase transition.

These results show that high-performance dynamic thermal emitters can be achieved through cavity-level optical design rather than relying on ideal material quality. The proposed thin-film cavity approach relaxes material constraints and provides a practical route toward scalable temperature-adaptive thermal management technologies, including energy-efficient building envelopes and infrared emission control.

The long wavelength infrared atmospheric window from 8 to 14 μm is important for thermal imaging, thermal management and optical security. Conventional approaches to spatial emissivity control often require micro or nanofabrication, which limits scalability and increases cost. Here we report a lithography free platform based on planar cavity metasurfaces combined with the nonvolatile phase change material Ge2Sb2Te5(GST). The approach enables large area patterning, multispectral information storage, and programmable emissivity control using thin film deposition and laser processing.

The device architecture uses a metal back reflector and a GST thin film to form a planar Fabry-Perot cavity. Amorphous GST is relatively transparent in the infrared, whereas crystalline GST exhibits higher absorption. This contrast strengthens cavity enhanced absorption and produces a large change in emissivity. We locally crystallize GST using pulsed laser irradiation, which allows spatially record emissivity patterns. Because GST is nonvolatile, the written thermal patterns remain stored without power.

To extend the concept beyond single band thermal images, we design the structure to store visible and infrared information independently in a single device. The lower cavity controls infrared emissivity, while the upper layer provides visible patterning and remains effectively transparent in the infrared. This functional separation enables concurrent multispectral readout without mutual interference. For practical manufacturing, we adopt metal mask based selective deposition and laser direct writing rather than complex lithography.

A key challenge for strong absorption is the need for relatively thick GST layers, while many lasers have limited effective penetration depth. To overcome this limitation, we develop a UV laser-based process that controls crystallization depth through thermal diffusion. By tuning laser fluence through writing parameters, we achieve continuous emissivity control rather than only binary switching. In our demonstrations, the average emissivity within the atmospheric window can be tuned over a wide range from 0.15 to 0.77. This enables multi-level encoding and supports more advanced security functions.

These results establish a scalable pathway to planar, laser programmable metasurfaces that combine infrared emissivity engineering with multispectral information storage. The platform is suitable for anti-counterfeiting and multispectral imaging.

Rapid progress in memory technologies, artificial intelligence (AI), autonomous systems, and the Internet of Things (IoT) has intensified the demand for highly energy-efficient semiconductor devices. However, conventional field-effect transistors (FETs) employing positive-capacitance gate dielectrics are fundamentally limited by a subthreshold swing (SS) of 60 mV/dec, which restricts further scaling of low-power operation. To circumvent this theoretical barrier, researchers have proposed device concepts such as Negative Capacitance FETs (NCFETs) and Tunnel FETs (TFETs), both offering the potential for reduced operating voltage and faster switching behavior.

Among various dielectric materials, hafnium oxide (HfO2)-based thin films have emerged as promising candidates for NCFET applications due to their stable ferroelectricity at the nanoscale, excellent CMOS compatibility, and robust chemical reliability compared to conventional ferroelectrics. The intrinsic non-centrosymmetric structure of ferroelectric materials allows them to exhibit both positive and negative capacitance states, with the transient negative capacitance phase appearing during polarization reversal. To stabilize this state and suppress hysteresis, a high‑k dielectric layer is often placed in series with the ferroelectric layer, thereby improving the overall device stability and switching efficiency.

The performance of thin‑film transistors (TFTs) is largely governed by the electrical quality of their active channels. Although two‑dimensional (2D) semiconductors such as MoS2 and WSe2 demonstrate excellent electrical properties, amorphous oxide semiconductors (AOSs) are particularly advantageous due to their high carrier mobility, large-area uniformity, and compatibility with low-temperature fabrication. Among AOSs, indium‑gallium‑zinc‑oxide (IGZO) stands out for its extremely low off‑state current, which is beneficial for minimizing leakage and standby power losses.

In this work, oxide semiconductor‑based NCFETs with an Hf0.5Zr0.5O2 (HZO)/Al2O3 gate stack and an IGZO channel are demonstrated. The HZO ferroelectric layer induces a negative capacitance effect that enables steep subthreshold swing, while the Al2O3 dielectric layer provides capacitive matching that stabilizes the ferroelectric response. Among IGZO NC‑FETs with varying Al2O3 thicknesses, the HZO (10 nm)/Al2O3 (5 nm) structure shows the best electrical characteristics, with an off‑current of 10-9 A, subthreshold swing values of 27.59 and 30.91 mV/dec in forward and reverse sweeps, and a negligible hysteresis of ~10 mV even under repeated voltage stress. These results demonstrate that capacitance matching between the HZO ferroelectric and Al2O3 dielectric layers stabilizes the intrinsically unstable negative capacitance effect and relaxes the trade‑off between steep SS and hysteresis, positioning the gate‑stack‑engineered IGZO NC‑FET as a promising candidate for low‑power and energy‑efficient electronics.

1. INTRODUCTION

In recent years, research toward the realization of low-power devices has been actively pursued, and one such approach is the use of interface dipole modulation (IDM) at heterogeneous oxide interfaces [1]. IDM has been confirmed in Al₂O₃/TiOₓ/SiO₂ stack structures [2], and has also been reported in Al₂O₃/SnOₓ/SiO₂ stack structures [3]. Previous studies have suggested that IDM may be related to changes in the Sn–O bonding states in the SnOₓ modulation layer. However, the effect of SnOₓ film thickness on the electrical properties has not yet been sufficiently investigated. In this study, Al₂O₃/SnOₓ/SiO₂ stack structures with varying SnOₓ modulation layer thicknesses were fabricated, and the thickness dependence of the electrical properties was examined by capacitance–voltage (C–V) measurements.

2. EXPERIMENTAL

Al₂O₃ layers with a thickness of 7.0 nm and SnOₓ layers with thicknesses ranging from 0.1 to 1.0 nm were deposited by atomic layer deposition (ALD) on n-Si(100) substrates covered with a 7.1 nm-thick SiO₂ layer formed by thermal oxidation. The fabricated Al₂O₃/SnOₓ/SiO₂ structures were annealed at 300 °C in an Ar atmosphere, followed by the formation of Al gate electrodes and a subsequent annealing at 300 °C in an Ar atmosphere.

Capacitance–voltage (C–V) measurements were carried out at a frequency of 100 kHz with a sweep voltage of up to ±10 V.

3. RESULTS and DISCUSSION

C–V measurements of the Al₂O₃/SnOₓ/SiO₂ structures with average SnOₓ thicknesses of 0.1 nm and 0.2 nm exhibited counterclockwise hysteresis. The hysteresis width increased with increasing applied voltage and reached a maximum value of approximately 0.22 V. Considering the voltage dependence of the hysteresis width and the band alignment, these behaviors differ from the previously reported IDM operation and are likely attributable to charge trapping effects. This suggests that an extremely thin SnOₓ layer may adopt an island-like structure.
On the other hand, in the Al₂O₃/SnOₓ/SiO₂ structures with SnOₓ thicknesses of 0.4 nm and 0.6 nm, hysteresis behavior similar to that reported for IDM operation was observed, suggesting that the SnOₓ thickness may influence IDM behavior.

4. CONCLUSIONS

These results indicate that an appropriate SnOₓ thickness, at which the SnOₓ modulation layer can form a continuous film, is important for the occurrence of IDM behavior. The present study provides a guideline for optimizing the SnOₓ thickness in Al₂O₃/SnOₓ/SiO₂ stack structures and is expected to contribute to the development of low-power devices based on interface property control.

References

[1] N. Miyata, Sci. Rep. 8, 8486 (2018). [2] Y. Kirihara et al., Appl. Phys. Express 15, 111003 (2022). [3] Y. Kirihara et al., Appl. Phys. Lett. 126, 101601 (2025).

Color customization of photovoltaic (PV) modules is a key requirement for the widespread adoption of building-integrated photovoltaics (BIPVs) in urban environments, where architectural harmony is as critical as energy performance. In this study, we we present a synthesis-driven and fully inorganic photonic glass approach for durable PV colorization based on metal oxide nanospheres.. The durability of the proposed colorization strategy arises from the use of fully inorganic metal oxides and structural color generation mechanisms, which inherently avoid photobleaching and chemical degradation commonly observed in organic dye-based coatings. Vanadium pentoxide (V₂O₅) and molybdenum trioxide (MoO₃) are selected due to their intrinsic optical selectivity, chemical stability, and suitability for long-term outdoor operation, offering a robust alternative to conventional organic dyes. Monodisperse metal oxide nanospheres are synthesized by a solution-based route and deposited onto PV cover glass using large area applicable ultrasonic spray coating method. The synthesis process enables controlled particle size distribution and near-stoichiometric compositions, while potential deviations from ideal stoichiometry (oxygen-rich or oxygen-deficient states) are considered due to their known influence on optical absorption behavior.The resulting 2–3 µm thick photonic layers generate angle-independent structural color through Mie scattering. Structural phase and surface morphology of both the nanoparticles and the coated layers are systematically analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Device-level performance is examined by integrating the colored photonic layers onto 15 cm × 15 cm mini-PV panels, followed by electrical characterization using current–voltage (I–V) measurements. While the uncoated reference device defines the baseline performance, the V₂O₅ coated green panel maintains more than 90% of the reference PCE, whereas the MoO₃ coated blue panel retains only ~60%. Overall, the results highlight the critical role of synthesis and stoichiometry control in minimizing optical losses while achieving stable and visually appealing coloration. Metal oxide photonic glass coatings therefore represent a scalable and materials-driven pathway for expanding color palettes in durable BIPV applications.

This work was financially supported by the Scientific and Technological Research Council of Türkiye (TÜBİTAK) under Grant No 123F372.

High-touch surfaces are recognized as important vectors for pathogen transmission and are commonly encountered in public transport, schools and healthcare settings. Current mitigation strategies rely mainly on routine cleaning and disinfection using chemical agents. Although effective, these approaches provide temporary solutions, as surfaces can be rapidly re-contaminated between cleaning cycles. As a result, antimicrobial surface coatings have emerged as a promising complementary strategy to conventional hygiene practices. However, in the light of product innovation within a Safe and Sustainably by Design (SSbD) approach, assessing release of active materials to the environment or quantifying human exposure is one important step. In this study, a novel class of light activated antimicrobial coatings incorporating micron-sized upconverting particles (Li2CaSiO4:Pr,Na) into water-borne coating formulation was investigated ¹. These coatings convert visible light into ultraviolet radiation, which inactivates microorganisms through physical damage to DNA without relying on conventional biocidal agents. Although this approach offers promising antimicrobial performance, understanding potential particle release during real-world use is necessary to ensure user and environmental safety. Therefore, particle release was evaluated under simulated dermal contact and cleaning conditions using a crockmeter to reproduce controlled rubbing motions mimicking repeated dermal contact and disinfection. Rubbing cycles ranged from 10 to 1250 double passes. Experiments were performed using cotton wipes as a surrogate of human fingers under dry conditions, water-wetted conditions, artificial sweat, and selected disinfectants. Released material was collected on wipes, digested using an optimized acid digestion protocol, and quantified by inductively coupled plasma mass spectrometry. Release increased with increasing cycle number, with initial release attributed to loosely bound surface material followed by continued particle release during prolonged rubbing. Dry rubbing resulted in higher release compared to wet conditions, likely due to reduced friction at the coating-wipe interface in the presence of moisture. After 1250 cycles, approximately 1% and 0.2% release was observed under dry and wet conditions respectively. Overall, these findings provide insight into the stability of upconverter particles and their interaction with the coating matrix during prolonged use, supporting the evaluation of antimicrobial coatings within a Safe and Sustainable by Design (SSbD) framework ².

References

1.               Schröder, F., Fischer, S. & Jüstel, T. X-ray and VUV excitation studies on Pr3+ activated Li2CaSiO4. J. Lumin. 235, 118046 (2021).

2.               Tunali, M., Voelker, D., Burkart, C., Schwirn, K. & Nowack, B. Recommendations for making the European Commission’s Safe and Sustainable by Design framework practicable for biocides. Sustain. Chem. Pharm. 48, 102221 (2025).

Electrochemical nanosensors have emerged as a key technology of modern analytical chemistry, offering high sensitivity and rapid response times by facilitating efficient charge transfer at nanostructured electroactive sites. Their practical performance is largely determined by the density and accessibility of electroactive surface area as well as the interfacial chemistry that governs analyte adsorption, selectivity, and electron-transfer kinetics. Block copolymer (BCP) self-assembly provides a robust route to engineer these active regions with nanoscale precision, allowing systematic control of site distribution and surface functionality without complex lithographic processing.

In this study, we utilize such benefits of BCP self-assembly to demonstrate a high-performance sensing platform based on gold nanoparticle (AuNP) arrays on indium tin oxide (ITO) substrates. We focus specifically on the role of surface functionalization in tuning electrochemical characteristics and enabling multiplexed detection. Self-assembled PS-b-P4VP thin films were employed as templates to form ordered gold nanoparticle (AuNP) arrays through selective infiltration into P4VP-rich domains. After template-directed AuNP formation, the AuNP arrays were independently modified with different functional layers, each designed to impart different interfacial properties such as hydrophilicity, electrostatic interaction, and specific affinity toward target analytes. By comparing these functionalized interfaces, we systematically elucidated how surface chemistry modulates charge-transfer resistance, capacitive behavior, and faradaic response in complex mixed-analyte environments. Our findings reveal that the chemical nature of the interface is a decisive factor for suppressing non-specific signals while amplifying target-specific electron transfer. This work highlights that the synergy between nanoscale structural templating and tailored surface chemistry provides a scalable strategy for achieving high selectivity in electrochemical sensing. Ultimately, this work offers a practical and versatile pathway toward developing robust nanosensor platforms for advanced bioanalytical applications.

The effectiveness of solar cell window layers is significantly influenced by deposition conditions and surface modification techniques. This research concentrates on customising the optical, surface characteristics of undoped ZnO thin films via regulated sputtering pressure and subsequent plasma treatment for self-cleaning solar cell applications. RF magnetron sputtering was used to form ZnO films on glass, silicon substrates at different working pressures. The films were then exposed to plasma for different amounts of time. Atomic force microscopy showed that both changes in pressure and plasma treatment changed the roughness of the surface in a systematic way. Kelvin probe force microscopy showed that the surface potential also went down. Optical tests showed that the material constantly had good transmittance in the visible range. After being exposed to plasma, the transmittance increased and the reflectance decreased. Ellipsometric investigation showed that the refractive index and extinction coefficient changed as the surface was changed. Wettability tests showed that the water contact angle went up following plasma treatment, which means that the surface is better at cleaning itself. The findings confirm that plasma engineering is viable method for creating multifunctional ZnO window layers for advanced solar cell applications.

Structural coloration has garnered significant attention as a robust alternative to chemical pigments. While a variety of nanostructures, including metasurfaces, have been proposed, they often face limitations in scalability, durability and cost. Conversely, planar Fabry-Perot (F-P) cavities based on metal-insulator-metal (MIM) layers are promising but typically suffer from poor color purity due to their subtractive nature-manifesting as broad reflection dips rather than peaks-and often exhibit chromatic discrepancies between reflection and transmission.

To overcome these limitations, we propose a lithography-free design strategy that leverages Fano resonance to invert the spectral profile from a reflection dip to a narrow peak. By integrating a broadband absorbing Ge2Sb2Te5 (GST) layer atop an Ag-SiO2-Ag F-P cavity, we couple the discrete cavity mode with the broad continuum state of the absorber. This structure not only aligns the chromaticity of reflection and transmission (dual-mode capability) but also utilizes the GST layer as an active medium for versatile optical modulation. Specifically, we demonstrate that controlling the laser pulse energies enables two distinct lithography-free patterning regimes: a 'stealthy' mode for optical security, where subtle tonal changes render patterns visible only at specific angles, and an 'erasure' mode that fully bleaches the structural color.

Furthermore, we introduce a capping layer with one or more thin dielectric layers that significantly enhances color saturation and expands the gamut with a negligible influence on the crystallization of the underlying GST. Based on this optimized structure, we demonstrate highly pure R/G/B colors with a narrow bandwidth of ~50 nm and a maximum efficiency of ~80%. Notably, our device successfully addresses the low saturation issue in the red spectrum-a persistent challenge in conventional structures-achieving a color gamut that exceeds the standard sRGB space.

Managing water production while ensuring oil production remains a significant challenge in mature, heterogeneous reservoirs. Chemical autonomous inflow control devices (AICDs) offer a promising approach to passive inflow regulation; however, their effectiveness depends heavily on the design of specialized inserts that respond to their environment. In this context, we introduce, for the first time, an innovative multi-shell core system, C-AICDs, featuring selectively dissolvable core-shell-coated material composites that respond effectively to variations in downhole harsh conditions. In this work, we developed oil/water-selective dissolvable core–multi-shell (CMS) composites tailored for use as chemical AICD elements. The CMS architecture is based on a compact core surrounded by three concentric shells, each designed to operate across different oil-to-water ratios while remaining mechanically stable under harsh conditions. By tuning the materials' hydrophilicity/hydrophobicity of each shell, we program a sequence of dissolution events coupled to the surrounding fluid composition at different conditions. Dissolution tests at 80 °C in 100% crude oil, 70:30 oil: water and 30:70 oil: water mixtures reveal distinct, phase-selective dissolution behavior. The outer shell dissolves on the order of days in oil-rich environments. In contrast, the intermediate and inner shells are progressively activated in more water-rich environments, enabling staged exposure of successive layers. Cross-section imaging and mechanical probing confirm the sphere's structural integrity and that interfacial adhesion is preserved throughout the designed sequence. These results demonstrate that tailored polymer–mineral multishell composites can function as robust, environmentally triggered dissolvable elements under reservoir-relevant conditions. The proposed CMS concept provides a versatile platform for next-generation smart AICD components. It can be extended to other time-programmed controlled materials and release systems operating in harsh multiphase fluids.

Corrosion remains a major industrial challenge, with global costs estimated at ~3.4% of global GDP, driving large economic losses and safety and sustainability concerns. Conventional protective coatings can lose anticorrosion performance once mechanically damaged (e.g., cuts or scratches), motivating engineered functional coatings for surface protection that can autonomously restore barrier properties at the defect site.

However, many established self-healing or anticorrosion strategies rely on materials and chemistries that raise health and environmental concerns, such as hexavalent chromium–based inhibitors and microencapsulation routes employing formaldehyde-based shells and/or reactive diisocyanates. In this context, linseed oil provides a more environmentally friendly alternative to commonly used reactive healing agents. Upon release from microcapsules at a scratch or cut, its unsaturated chains undergo crosslinking upon exposure to oxygen, forming a polymerized film that fills and seals the defect, thereby restoring the barrier protection against corrosive media.

Here, we developed a sustainable self-healing coating concept and improved the environmental profile of the microencapsulation step using a straightforward solvent-evaporation method in three complementary ways: biopolymer shells (PCL and PLA), greener solvent systems as alternatives to conventional chlorinated solvents (e.g., dimethyl carbonate replacing dichloromethane), and linseed oil as the healing agent. The microcapsules were incorporated into industrially relevant resin matrices (e.g., epoxy and alkyd formulations) and applied to carbon steel substrates. The microcapsules were characterized by optical microscopy, SEM, and FTIR. Encapsulation efficiency was determined by solvent extraction of the core followed by quantification of the recovered linseed oil. We showed that microcapsule morphology and key characteristics could be tuned through emulsifier selection and the oil-to-polymer ratio, enabling controlled encapsulation and compatibility with the coating matrix. Healing was assessed by scratch tests followed by immersion in NaCl solution and compared with control coatings without microcapsules. Importantly, the incorporation of these microcapsules enabled the coating to recover protective performance after damage, mitigating corrosion initiation at the defect. Overall, this approach supports longer service life of metallic components while reducing maintenance needs and associated environmental impact, providing a pathway toward autonomous anticorrosion protection for industrial applications.

Two-dimensional (2D) semiconducting materials have recently attracted considerable attention as potential building blocks for next-generation electronics. Their layered crystal structure, held together by weak van der Waals interactions, allows the formation of atomically thin 2D layers. In particular, indium selenide (InSe) is considered as promising representative 2D semiconductor which exhibits high electron mobility exceeding (>10³ cm² V⁻¹s⁻¹) and a thickness-dependent band gap. To date, most studies have primarily focused on charge transport properties in mechanically exfoliated 2D semiconductor flakes. However, from a technological perspective, the scalable synthesis of uniform, wafer-scale 2D semiconductors with precise control over defect density, surface roughness, and grain boundaries remains critically important. As a result, the fabrication of high-quality and large-area 2D semiconductor thin films continues to represent a major challenge in materials science.

Promising route for producing wafer-scale 2D semiconductors is annealing-induced crystallization from the amorphous phase. In the case of InSe, however, the presence of multiple competing crystalline phases, including In₄Se₃, InSe, In₂Se₃ and In₆Se₅​, significantly complicates precise control over crystallization and the realization of mono-phase InSe films over large areas.

In this work, we systematically investigate the phase transformation behavior of thermally evaporated amorphous InSe thin films under controlled annealing conditions and assess the resulting structural and electronic properties. Both in situ and ex situ characterization techniques were employed to monitor the evolution of the amorphous InSe film structure during annealing in an inert atmosphere. Our results demonstrate that stoichiometric crystalline InSe thin films can be achieved by annealing within a temperature window of 335–350 °C. Furthermore, we examine the kinetics of laser-induced local crystallization in amorphous InSe thin films. The pronounced differences in optical and electrical properties between the amorphous and crystalline phases lead to distinct light–matter interaction behaviors. Notably, the substantial resistivity contrast associated with crystallization highlights the potential of InSe thin films for emerging applications, including photonic integrated circuits and phase-change memory devices.

Acknowledgment. This research was funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103225).

The deployment of proton exchange membrane water electrolysis (PEM-EL) for sustainable hydrogen production requires anode electrocatalysts combining high activity with long-term stability in strongly acidic and oxidative environments. Although IrO₂ and RuO₂ remain benchmarks for the oxygen evolution reaction (OER), their scarcity and cost motivate the exploration of noble-metal-free, earth-abundant alternatives. Tungsten oxide (WO₃) is a chemically robust material whose electronic structure can be tuned via defect engineering and electrochemical reduction, making it an attractive platform to investigate structure-property relationships for acid-stable OER electrodes.

Preliminary results of WO₃ thin films obtained by Radio Frequency Magnetron Sputtering (RFMS) on FTO Substrates show a good repeatability and adhesion. Film thickness, structure and electrochemical behavior were systematically investigated. X-ray diffraction shows that deposition without additional heating (25-30°C) yields amorphous WO₃, whereas substrate heating at 400°C leads to the formation and co-existence of crystalline triclinic, monoclinic and cubic phases, motivating further mapping of crystallinity evolution as a function of temperature. Electrochemical characterization by cyclic voltammetry reveals that amorphous WO₃ exhibits pronounced electrochromic behavior associated with the W⁶⁺/W⁵⁺ redox couple, with high currents and vivid coloration, while crystalline WO₃​​​​ seems less active and presents very mild redox coloration.

OER activity was evaluated by linear sweep voltammetry in acidic electrolyte. While platinum (Pt) displays early onset potential and high current density, both amorphous and crystalline WO₃ films underperform compared to bare FTO, indicating that WO₃ currently behaves as a passive overlayer rather than an active OER catalyst. These results demonstrate that solely crystallinity is an insufficient deposition parameter to activate WO₃ towards OER, and highlight the central role of electronic structure and defect chemistry.

Based on these findings, ongoing work focuses on further parametrization of RFMS deposition conditions aiming towards the modification of the material’s electronic structure, in order to outline design principles for noble-metal-free, acid-stable oxide electrodes for PEM water electrolysis.

Generally, plasma polymers are considered amorphous materials due to their multifunctionality and crosslinked structure. Herein, we report the discovery of crystalline fluorescent nanoparticles in plasma polymer films containing amino groups (amine PP). Cyclopropylamine (CPA) mixed with argon was used to deposit the films in a radio frequency (RF) capacitively coupled discharge at 50 Pa. The films with varying nitrogen content, functional groups, and crosslinking were prepared at different RF powers [1]. Since the films deposited
at low power were partially soluble, the nanoparticles can be released into water. Thanks to it, the cells cultivated on the amine PP films uptake the particles and fluoresce [2]. Since amine PP coatings can be used to make materials more suitable for cell attachment and proliferation [1, 3] and the particles are not cytotoxic, they can be used to image cells during biological experiments. Analysis by X-ray photoelectron spectroscopy and infrared spectroscopy revealed that the particles and the films have similar compositions (17 at.% nitrogen), with a subtle increase in the particles’ oxygen content, attributed to oxidation during extraction. The round particles had an average size of 7.5 nm, as determined from atomic force microscopy. Surprisingly, high-resolution transmission electron microscopy revealed that the crystalline particles are of two types, with lattice spacings of 0.29 nm and 0.34 nm, the latter corresponding to graphite. The particles show excitation-dependent emission with the peak emission energy linearly depending on the excitation energy until 4.2 eV beyond which the maximum emission energy stays constant at around 3.8 eV. The excitation-dependent fluorescence resembles the optical properties of nitrogen-doped carbon quantum dots synthesized from glucose and ethylenediamine by the microwave hydrothermal method [4].
References
[1] Anton Manakhov et al. Plasma Processes and Polymers 14 (2017), 1600123.
[2] Martina Janusova et al. Applied Materials Today 47 (2025), 102965.
[3] Ivana Nemcakova et al. International Journal of Molecular Sciences 21 (2020), 9467.
[4] I. Jennifer Gomez et al. J. Phys. Chem. C 125 (2021), 21044–21054.

In our research, we focused on the preparation of thin films of High-temperature superconductors based on YBaCuO. For that purpose we used novel PVD thin film deposition method Ionized jet deposition, which has several benefits over conventional method for HTS preparation.
High-temperature superconductors based on YBaCuO structure are ceramic materials, that is why it is difficult to manufacture them as bulk material and the process of crystalization is very slow and energetically demanding. In order to achieve economical approach to manufacture large quantity of superconducting wires and cables, it is necessary to utilize some form of thin films deposition method. Our method of choice was Ionized jet deposition, the novel thin film deposition method, with huge industrial potential.

During the experimental phase we have been able to produce several specimens of HTS with promising superconducting properties. However, further development is needed for the process to be optimized for production. The goal is to develop industrial-ready manufacturing process for large-scale production of HTS wires for energetics and power transmission.

The conventional state-of-the-art method for HTS thin films preparation is Pulsed laser deposition and Magnetron sputtering. But both of them suffer from various obstacles, e.g. production speed, cost and scalability. Recently, Ionized Jet Deposition (IJD) is getting attraction for its simplicity and potential for industrial applications. This new method could fundamentally change the way HTS wires are produced and decrease their cost.
Ionized jet deposition relies on a strong electron pulse induced by high voltage primary source in an evacuated chamber. This electron pulse ablates the target material, which is then deposited onto the surface of the substrate and creates thin film of the target material. The process can be controlled by varying gas during the deposition, changing acceleration voltage as well as altering substrate temperature.

However, the deposition of high-quality YBaCuO films is extraordinary challenging and relies strongly on the correct deposition parameters and stoichiometry as well as post-deposition treatment and annealing.
Nevertheless, we have proven that using IJD it is possible to overcome the challenges and create superconducting thin-films with sufficient quality and properties and we believe that in the near future it can be deployed for industrial production.

Among metals used in biomedical applications, titanium and titanium alloys are the most widely used for orthopedic, dental, and cardiovascular implants. Owing to their high biocompatibility, low in density, high mechanical strength, and relatively low Young’s modulus, titanium-based materials provide an optimal balance between mechanical performance and biological compatibility. However, following implantation, bacterial adhesion to surface can lead to infection, responsible for at least 5% of surgical revisions. In addition, over time, friction between titanium-based biomaterials and surrounding bone tissue can release microparticles that may induce inflammatory responses. To address these issues, surface treatments of titanium implants have been developed to enhance both mechanical and biological properties. Among surface modification strategies, diamond coatings are particularly attractive due to diamond expected unique properties, including very high hardness, chemical inertness, biocompatibility, and low friction coefficient. In particular, NanoCrystalline Diamond (NCD) thin films, characterized by their nanometric grain size and low surface roughness, are promising candidates for applications requiring smooth surfaces while preserving the bulk properties of the biomaterial.

In this work, we report the synthesis of NCD coatings on Grade 2 titanium (>99% Ti) and Grade 5 titanium alloy (Ti–6Al–4V, 90% Ti, 6% Al, 4% V). The coatings were deposited by Microwave Plasma Assisted Chemical Vapor Deposition (MPACVD) using a Distributed Antenna Array (DAA) reactor composed of 16 plasma sources arranged in a two-dimensional (2D) matrix, operating using a CH₄/H₂/CO₂ gas mixture at low pressure and low temperature. The NCD films properties were first investigated on 2D substrates using physicochemical techniques, demonstrating the formation of continuous, uniform, and high-quality coatings with thicknesses ranging from 200 to 300 nm on both titanium-based substrates. The nanomechanical testing demonstrates the superior hardness of NCD-coated substrates compared to bare samples. Under applied moving loading, penetration resistance is markedly higher for NCD/Ti systems, with the NCD films remaining adherent at the nanoscale. This enhanced hardness suggests that the diamond coating could potentially reduce wear of the biomaterial under dynamic forces, maintaining a strongly adherent surface layer. With respect to biomedical performance, in vitro biological evaluations reveal no cytotoxic effects of the NCD coatings. Finally, the successful demonstration of three-dimensional growth using the DAA reactor highlights the feasibility of extending this NCD coating process to complex-shaped implants and prostheses with curved surfaces and sharp edges, offering significant potential benefits for the long-term performance of medical devices.

The performance of immunosensors critically depends on the quality of surface functionalization and on the homogeneous and efficient immobilization of antibodies onto the transducer substrate. While numerous strategies have focused on improving antibody orientation, less attention has been devoted to the systematic optimization of surface coverage during each step of the functionalization process, despite its strong impact on sensor sensitivity and reproducibility.

In this work, we present a comprehensive strategy to optimize nano-engineered functional coatings for immunosensors by dissecting each stage of the surface modification protocol. Silicon transducer substrates were sequentially functionalized using organosilane chemistry, crosslinking agents and protein-based blocking layers, leading to the covalent immobilization of anti-IL6 antibodies. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were systematically employed to characterize surface topography, roughness, chemical composition and homogeneity after each functionalization step. This detailed surface analysis enabled the identification of incomplete coverage, chemical heterogeneities and inefficient reaction conditions, which were subsequently corrected through targeted modifications of the functionalization parameters.

Based on this rational optimization, significant improvements in surface uniformity and antibody coverage were achieved, resulting in enhanced immunosensor performance. The optimized coatings led to an increase in detection sensitivity of approximately 19% and a reduction of the limit of detection by about 16%, as demonstrated using an optical immunosensor for interleukin-6 detection. Importantly, the results reveal that increasing the amount of immobilized antibody does not necessarily improve sensor performance, highlighting the central role of controlled surface chemistry and nano-engineered interfaces.

In addition to AFM and XPS, synchrotron-based Fourier transform infrared (FTIR) spectroscopy using polarized light at different incidence angles was employed to gain complementary insight into the molecular organization and orientation of immobilized antibodies on the functional coatings.

Overall, this study demonstrates how the rational design and detailed characterization of nano-engineered surface coatings can be used to systematically improve immunosensor efficiency.

Commercial membranes often exhibit difficulties in rejecting specific ionic species due to their usual negative charge and are furthermore prone to fouling. To overcome these distinct issues, this study proposes functionalizing the membrane surface via plasma polymerization to enhance rejection and  minimize fouling.

The surface of a thin-film composite membrane featuring a polyamide active layer was modified via cold plasma polymerization using either poly(allylamine) or maleic anhydride. Membrane characterization included surface charge analysis through zeta potential measurements and determination of mean pore size by fitting neutral solute rejection data with a steric hindrance model. Additionally, tangential filtration experiments involving various cationic and anionic pollutants and a model foulant were performed to compare the performance of pristine and modified membranes.

Zeta potential measurements reveal that electrical properties are significantly altered by both grafting. In the case of poly(allylamine) the isoelectric point shifting towards basic pH. This results in a charge reversal from negative to positive at 2.5 < pH < 4 after just 5 minutes of deposition, attributed to the positive amine groups introduced to the surface. In the case of maleic anhydride, the opposite is observed: the pie shifts to acidic pH values due to the grafted carboxyl groups. Structural properties are also affected: the mean pore radius is roughly halved from 2.45 nm to 1.32 nm for poly(allylamine) and reduced to 0.77 nm after maleic anhydride grafting. In both cases, membrane permeability decreases by 30% due to the deposit of the polymer.

Filtration experiments with multi-ionic solutions reveal that changes in membrane properties result in a marked increase in the rejection of multivalent cations (Ba²⁺, Ni²⁺, Co²⁺, and Cr³⁺). In contrast, Li⁺ and Pb²⁺, which exhibited low retention with the pristine membrane, remained only weakly rejected by the modified membrane. While the limited impact on lithium rejection was anticipated given its low charge (monovalent co-ion), the behaviour of lead is unexpected. A specific investigation suggests that standard ionic properties are insufficient to explain this phenomenon.

For the membrane with maleic anhydride deposition, we also observe an improvement in the retention of multivalent cations, which is certainly due to the steric effect, but we particularly observe negative retention of lithium and lead due to their positive charge.

Finally, the BSA fouling study indicates that poly(allylamine) deposition does not prevent flux decline during filtration. However, it facilitates more efficient removal of the fouling layer during rinsing, resulting in reduced irreversible fouling and a slightly higher recovered normalized flux. In contrast, the membrane modified with maleic anhydride exhibits a smaller reduction in flow during BSA filtration, and most notably, the initial flux is fully restored after washing.

Nanostructured plasmonic–dielectric composites offer a promising route to polarization‑selective optical coatings and tuneable anisotropic responses. This work investigates the dichroic and plasmonic behaviour of glancing‑angle‑deposited (GLAD) Au nano‑islands embedded within a‑SiN thin‑film stacks. A 5‑nm Au layer was deposited at a 70° glancing angle onto a 72‑nm a‑SiN underlayer and subsequently annealed at 400 °C and 600 °C to induce controlled morphological restructuring. Following annealing, all samples were coated with a 13‑nm a‑SiN capping layer to preserve the Au morphology and ensure film stability. AFM images made prior the top a-SiN deposition show a well-defined tilted columnar growth. Polarization‑resolved transmission and reflection spectra (400–1000 nm) reveal a clear difference in resonance wavelength in transmission, including a sign inversion at wavelengths longer than the localized plasmon resonance, and a broad polarization‑dependent contrast in reflection extending from the plasmonic peak (≈570–590 nm) to about 900 nm. The dichroic contrast decreases systematically with annealing temperature due to thermally driven reshaping of the uncapped Au nano‑islands. This trend is consistent with AFM measurements of the Au nanostructure morphology at different annealing temperatures. Together, these results demonstrate that polarization‑resolved optical spectra serve as a sensitive, non‑destructive probe of nanoscale morphology, enabling estimation of the degree of nanostructuring as a function of annealing temperature.

The engineering of bioactive surfaces is a key approach for controlling interactions between materials and biological systems, particularly the binding of biomolecules required for biosensing, tissue engineering, and other fields. The introduction of functional groups through techniques such as plasma treatment or deposition is considered an effective method for preparing bioactive surfaces [1]. The presence of amino groups and unsaturated bonds was a key factor for the excellent reactivity of plasma polymer (PP) films towards antibodies in the case of imunosensors [2]. Another approach to binding biomolecules involves the use of free radicals, which have already been successfully employed to covalently bind complex molecules, such as proteins, to surfaces exposed to energetic ion bombardment [3]. Although a larger reservoir of reactive species in conventional polymers can be generated only by high-energy ions, plasma deposition of thin films offers two possibilities. Bilek's group is again using the principle of radicals' generation via ions [4], but Yasuda already proposed in the 70s that radicals formed in plasma can be trapped in the PP structure [5], and he classified monomers by their ability to form PP with radicals [6]. He attributed the highest radical concentrations to the monomers of group I with triple bonds or aromatic structure, e.g., C₂H₂. We deposited PP films by plasma-enhanced chemical vapor deposition (PECVD) from a cyclopropylamine (CPA)/Ar mixture under gentle ion bombardment. Based on Yasuda's classification, CPA belongs to group II, resulting in PP with a moderate concentration of free radicals. Despite that, the radical concentration in our films was about 3× higher than in the films from C₂H₂/N₂ plasma with gentle ion bombardment [4]. When increasing the discharge power 5×, we achieved similar radical concentrations as when Bilek et al. applied a high bias of at least -500 V [4]. Thus, we concluded that engineering the bioactive PECVD films via radicals offers more knobs to play with.

The radical concentrations in the PP films deposited from CPA at higher power remain high for a long storage time. Therefore, we investigated the decay kinetics, accounting for diffusion and recombination. Fitting the data revealed the presence of two types of radicals, differing in their diffusion coefficients. In agreement, the EPR spectra could be better fitted when considering two radicals differing chemically in their g-factors. 

References:

[1] C. Karthik et al., Biomedical Engineering. 26, (2023).
[2] E. Makhneva et al., Surface & Coatings Technology. 290, 116-123 (2016).
[3] M.M. Bilek et al., Proceedings of the National Academy of Sciences. 108, 14405-14410 (2011).
[4] B. Akhavan, et al. Applied Materials Today 16 (2019), pp. 456–473.
[5] N. Morosoff, et al. Sci-Chem A10:3 (1976), 451-471.
[6] H. Yasuda. Journal of Polymer Science Macromolecular Reviews 16.1 (1981), pp. 199–293.

The increasing demand for multifunctional semiconductor materials has driven significant interest in systems that combine sensing and photocatalytic functionalities. Such materials are particularly relevant for environmental monitoring, where gas detection and photocatalytic degradation are complementary approaches. In this context, the present study focuses on the fabrication and comprehensive characterization of dysprosium-doped tin dioxide (SnO 2 :Dy) thin films prepared by spray pyrolysis for multifunctional environmental applications. The films were deposited on glass substrates with Dy concentrations ranging from 0 to 7 wt%, and their structural, morphological, and compositional properties were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X- ray spectroscopy (EDS), and atomic force microscopy (AFM). The analyses revealed that Dy incorporation significantly influences the crystallinity, surface morphology, and dopant homogeneity of the films. An optimal Dy content was identified, leading to enhanced structural quality and a more developed surface, which are key factors governing both gas sensing performance and photocatalytic activity. The gas sensing properties of the SnO₂:Dy thin films were evaluated toward low NO₂ concentrations down to 1 ppm [1]. The sensors exhibited high sensitivity at an optimal operating temperature of 250 °C, along with excellent selectivity against common interfering gases such as CO, H₂, ethanol, and toluene. In parallel, the photocatalytic performance was assessed through methylene blue degradation, where the Dy-doped samples showed significantly enhanced activity. The film containing 5 wt.% Dy achieved a degradation efficiency of approximately 91% while maintaining good stability and reusability over three successive photocatalytic cycles [2]. These findings highlight the strong potential of Dy-doped SnO₂ thin films elaborated by spray pyrolysis for stable and highly sensitive NO₂ detection, as well as for efficient photocatalytic degradation of organic pollutants, making them promising candidates for real-world environmental monitoring and industrial applications. This work highlights the design of nano-engineered SnO₂-based thin-film coatings, where controlled rare-earth doping enables the tuning of growth, surface morphology, and multifunctional performance for environmental applications

Keywords: SnO₂, Dysprosium, thin films, spray pyrolysis, NO₂ sensing, morphological properties, gas sensor, Methylen Blue, photocatalysis.

References:
[1]: Mezyen, M., Bitri, N., Riahi, I., Chaabouni, F., &amp; Llobet, E. (2025). Optimizing Sputtered SnO2: Dy Thin Films for NO2 Gas Detection. Chemosensors, 13(4), 121.
[2]: Mezyen, M., El Fidha, G., Bitri, N., Harrathi, F., Ly, I., &amp; Llobet, E. (2023). Visible light activated SnO 2: Dy thin films for the photocatalytic degradation of methylene blue. RSC advances, 13(44), 31151-31166.

Compact TiO₂ is a useful hole‑blocking and electron‑transport layer (ETL) for perovskite photoanodes, but its effectiveness depends strongly on synthesis conditions and layer thickness. We thermally oxidized electron‑beam‑evaporated Ti to form smooth, pinhole‑free c‑TiO₂ films (12–83 nm) and tested them as ETLs in back‑illuminated n–i–p CsPbBr₃ photoanodes for the oxygen evolution reaction.

Electrochemical measurements showed that films thicker than 51 nm fully covered the substrate and acted as effective hole‑blocking layers, reducing recombination and improving electron extraction. Water‑oxidation tests using linear sweep voltammetry revealed that a 51 nm TiO₂ layer produced the best performance: 4.2 mA/cm² at 1.23 V vs RHE and an ABPE of 0.93% at 0.8 V vs RHE, while maintaining more than 1.5 mA/cm² for over 4 hours without a catalyst. Thicker layers (65–83 nm) lowered photocurrent because of higher resistance.

Overall, these results show that both film quality and precise thickness control are crucial. Thermal oxidation of e‑beam‑deposited Ti provides a reliable way to make compact, transparent TiO₂ ETLs with the right balance of coverage, light transmission, and resistance for stable photoelectrochemical operation.

Here, we report a hybrid initiated and plasma-enhanced chemical vapor deposition (iCVD/PECVD) approach for the single-step fabrication of mechanically durable superhydrophobic nanocomposite coatings. This strategy enables precise control over surface chemistry and mechanical performance without the need for complex, multistep fabrication processes typically required for durable superhydrophobic coatings. Machine learning assisted optimization was employed to identify the critical deposition parameters such as substrate temperature, chamber pressure, filament temperature, and plasma power, necessary to achieve coatings with maximized durability and superhydrophobic performance.

Thin films of poly(acrylic acid-co-ethylhexyl acrylate) (p(AA-EHA)) were first deposited onto glass substrates via iCVD, followed by the deposition of a highly rough perfluorodecyl acrylate (p(PFDA)) top layer using PECVD. The thicker p(AA-EHA) base layer provided mechanical integrity and robustness, while the fluoropolymer overlayer imparted low surface energy and nanoscale roughness.

The structural and morphological properties of the coatings were characterized by FTIR, XPS, AFM, and SEM, while static water contact angles and sliding angles were measured to assess water-repellent behavior. The resulting nanocomposite coatings exhibited water contact angles exceeding 150° and sliding angles below 10°, attributed to the presence of long fluorinated side chains, and demonstrated excellent mechanical durability. Nanoindentation measurements further revealed that both the elastic modulus and hardness increased with increasing acrylic acid content.

Cu2ZnSnS4 (CZTS) materials are a promising absorber for sustainable thin-film photovoltaics due to its earth-abundant, non-toxic constituents and near-optimal band gap. Yet, device performance remains limited by a narrow compositional window, Cu-related deep defects and secondary phase formation. In particular, precise control of the copper content across the absorber thickness is critical for optimizing electronic properties and the absorber/back-contact interface.

Here, we report a compositionally graded CZTS absorber architecture fabricated by a solution-based sol–gel spin-coating approach, offering a low-cost and scalable alternative to vacuum-based methods. The absorber consists of three sequentially deposited layers with a controlled Cu gradient. The bottom layer is stoichiometric and the upper layers are Cu-poor, with Cu/(Zn+Sn) ratios ranging from 0.9 to 0.8. This design aims to suppress Cu-related deep defects while promoting favorable band alignment and charge collection near the back contact.

After thermal treatment at 450 °C (CTA, Ar), cross-sectional SEM analysis reveals a well-defined multilayer structure with good adhesion to the Mo back contact, demonstrating excellent process control. X-ray diffraction confirms the formation of a single-phase kesterite CZTS structure, with no detectable secondary phases throughout the graded absorber. UV–Vis spectroscopy shows a systematic shift of the absorption edge correlated with the copper gradient, evidencing band-gap modulation induced by compositional grading.

These results demonstrate that Cu grading implemented via sol–gel spin-coating enables effective band-gap engineering and defect control in CZTS absorbers, providing a versatile and scalable pathway toward improved kesterite-based thin-film photovoltaic devices.

Acknowledgement:

This research was funded by the Romanian Executive Unit for Financing Higher Education, Research, Development and Innovation (UEFISCDI), by the grant PN-IV-P7-7.1-PED-2024-1434.

Indium tin oxide (ITO) is a widely used material in optoelectronics, primarily due to its high electrical conductivity and optical transparency in the visible spectrum.[1] In organic photovoltaics (OPVs), ITO is employed as transparent electrode, typically the anode. However, device's performance can be substantially improved by engineering the surface properties of ITO, aiming: i) the fine tuning of ITO's work function with respect to the energy levels of the donor-acceptor layer, ii) to reduce the charge transport barriers between the material and device, iii) to protect ITO from chemical corrosion.[2] A promising strategy to achieve such aims is by growing a self-assembled monolayer (SAM) onto ITO using anchoring molecules with specific properties. In particular, it has been shown that the functionalization of ITO's surface with high dipole moment SAMs can lead to reduced work function ITO.[3] In this contribution, we evaluated by density functional theory (DFT) how the electronic properties of ITO can be tailored by low to giant dipole moment phosphonic acid molecular systems. In the first step, we evaluated the phosphonic acids with respect to their dipole moment, orbital isosurfaces, and ionization energies as calculated with an optimally tuned range-separated hybrid functional in order to accurately describe their charge transfer and electronic properties. Subsequently, we model a hydrogen-passivated ITO slab with 10% Sn doping concentration using the PBE functional. Then, we evaluated the slab-molecule system by probing different bonding sites on ITO with the phosphonic acids. Finally, we calculated their effect on ITO's work function. Our findings provide a predictive framework for designing transparent electrodes that enhance the stability and efficiency of OPVs, and in particular for the preparation of inverted device architectures.

1. U. Shankar, D. Oberoi, and A. Bandyopadhyay, Polym. Adv. Technol. 33, 3078 (2022).
2. N. R. Armstrong et al., Acc. Chem. Res. 42, 1748 (2009).
3. J. Hu et al., J. Polym. Sci. 60, 2175 (2022).

The approximation of radiative recombination spectra is essential in semiconductor physics because the shape and position of emission bands contain information about charge carrier transport and recombination processes. An adequate analytical description of experimental spectra allows quantitative determination of key material parameters, such as bandgap energy, carrier temperature, carrier concentration, minority carrier lifetime, and the influence of defects and structural inhomogeneities. Without proper approximation, spectral data remain a set of discrete experimental points, making reliable comparison between different samples and measurement conditions difficult. In addition, spectral modeling enables the separation of contributions from various recombination mechanisms, including interband, impurity-related and defect-assisted processes. This is especially important for thin films and nanostructures, where spatial potential fluctuations, lattice strain, and quantum confinement significantly affect emission spectra. From a practical standpoint, accurate approximation of radiative recombination spectra is crucial for both fundamental research and the optimization of semiconductor devices, such as light-emitting diodes, lasers, and photodetectors, where recombination processes determine device efficiency and performance.

The proposed probabilistic framework describing the formation of emission spectra in semiconductors during interband radiative recombination relies on three key assumptions. First,  radiative recombination is treated as a sequence of randon events associated with the recombination of nonequilibrium charge carriers, where photon emission occurs randomly and the emitted photon wavelength serves as the random variable. Second, the shape of the emission spectral line is governed by the probability density function of this random variable, which reflects the collective contribution of all nonequilibrium carrier transitions within a statistical ensemble of energy states.

This statistical ensemble comprises a large number of energy levels arising from spatial inhomogeneities in the material, as well as from variations in energy level occupation induced by thermal fluctuations. The third assumption asserts that the distribution of emitted photon wavelengths corresponds to a limiting distribution for extreme values. According to extreme value statistics, the asymptotic distribution for the minimum of a large set of independent random variables is given by the Weibull–Gnedenko distribution. Using this approach, experimental interband radiative recombination spectra of GaAs and InP thin films were successfully approximated. The close agreement between experimental data and theoretical predictions confirms the validity of the proposed probabilistic model for describing radiative recombination processes in semiconductor materials.

Titanium-based implants are widely used due to their mechanical strength, corrosion resistance, biocompatibility, and high long-term success rates, largely attributed to their ability to achieve osseointegration. However, challenges such as peri-implant inflammation, occasional hypersensitivity reactions, and long-term interfacial stability continue to drive research toward surface modification strategies. Surface coatings based on bioactive materials, including calcium phosphates and silica (SiO₂), have been extensively investigated to enhance bone-implant interactions. In particular, SiO₂ coatings improve corrosion resistance and promote cell adhesion, contributing to improved osseointegration. Recently, biosilica (BS) derived from natural sources has emerged as a sustainable and biologically relevant alternative to synthetic SiO₂. Marine sponge-derived BS exhibits unique hierarchical structures and osteoinductive properties, making it a promising candidate for biomedical coatings. Moreover, BS surfaces can be functionalized with bioactive molecules to further enhance biological performance. Curcumin, a natural compound with well-known antioxidant and anti-inflammatory properties, represents a promising functionalizing agent, although its low solubility and limited stability restrict direct biomedical use. Incorporation of curcumin into SiO₂-based systems has been shown to improve its stability and enable controlled release. In this context, this study aims to develop alginate-based coatings containing marine sponge-derived BS, with and without curcumin functionalization, for application on titanium substrates. The coatings were physicochemically characterized, and their in vitro biological performance were evaluated using human cell models to assess cytocompatibility, cell proliferation and osteogenic response. Scanning electron microscopy (SEM) revealed the presence of BS spicules, confirming the characteristic structure of the material. Fourier transform infrared spectroscopy (FTIR) identified SiO₂-specific bands, while additional absorption bands associated with curcumin were observed in the functionalized BS group. Wettability analyses indicated that, compared to uncoated titanium, samples coated with BS and curcumin-functionalized BS exhibited increased hydrophilicity. In vitro cytotoxicity assays using primary human osteoblast (HOb) cells showed no cytotoxic effects, confirming the biocompatibility of the coatings. Cell proliferation assays demonstrated enhanced cellular growth, particularly in samples containing higher concentrations of BS. In conclusion, BS functionalization with curcumin was successfully achieved, as confirmed by structural and spectroscopic analyses. The developed coatings exhibited improved surface bioactivity while maintaining cytocompatibility, highlighting their potential for applications in tissue engineering and biomedical coatings. Acknowledgements: CAPES – Finance Code 001.

The silver nanoparticles (Ag-NPs) are obtained by thermal evaporation on 
heated substrates at 350°C. The used substrates are corning glass and crystalline silicon wafer oriented 
(100). For the characterization we used the Scanning Electron Microscopy to define 
the morphological properties and the optical transmission technique to define optical 
absorbance spectral. The mean diameter of Ag-NPs is about 50nm. The equivalent film thickness is varied from 10nm 
nm. The Ag-NPs diameter distribution reveals two kinds of 
population types : small and thick ones. The optical absorbance spectrum 
reveals a band absorption due to the Localized Surface Plasmon Resonance. The 
LSPR absorption band is closely linked to the nanoparticle's morphological 
properties. The position of the LSPR band is centered at 450 cm-1.

Plasma polymers (PPs), thin organic films prepared by plasma-enhanced chemical vapor deposition (PECVD), can be used to engineer hydrophilic, bioactive, or adhesive surfaces. In addition to typical variations in deposition parameters (gas mixture, pulsing frequency, discharge power, and pressure), substrate placement relative to spatial gradients in reactive plasma species and substrate potential may also influence the final properties of deposited films. Previously, we deposited PPs from cyclopropylamine (CPA) in radio frequency (RF) capacitively coupled discharges and investigated their interactions with biomolecules [1] and cells [2,3]. CPA plasmas tend to produce a significant amount of nitrile (CN) molecules [4] that are incorporated in the films. Besides, CPA monomer is prone to making films with a substantial amount of trapped free radicals [5]. Before, we studied these structural properties in PPs deposited at the RF electrode that acquires a negative DC self-bias. Here, we modified the substrate potential, i.e., the ion energy, by placing the substrates at the floating potential of a 20 mm-high dielectric stack on the RF electrode. In this case, the energy of ions impinging on a growing film is reduced compared to the substrate on the RF electrode because of a little difference between the plasma and the floating potential (approx. 10 V). The parameter most affected by the change in the substrate potential was the deposition rate, which was surprisingly reduced. A more expected result was a reduction in free radical concentration, determined, namely, in the films deposited at the highest RF power, i.e., the highest self-bias. However, the question remains whether these changes in PPs' structure are solely due to the floating potential or whether spatial gradients in the plasma also contribute.

References

[1] Makhneva E., et al., Sens. Actuator B-Chem. 276 (2018) 447

[2] Janůšová, M., et al., Surf. Coat. Technol. 503 (2025) 131962

[3] Janůšová, M., et al., Appl. Mater. Today 47 (2025) 102965

[4] Buddhadasa M. et al., Plasma Process Polym. 14 (2017) e1700030

[5] Beliančı́nová B. et al., Proceedings of Int. Symposium on Plasma Chemistry 2025, P1.9.7

 Metal nanoparticles are often deposited on top of solar cells to improve their efficiencies via the surface plasmon resonance effect. However, their fragility greatly inhibits their stability and long-term effectiveness within the solar cells. Diamond has a vast range of exceptional physical and optical properties which enable it to provide resistance to physical, chemical, and thermal degradation whilst helping to reduce solar cell reflectance losses. This includes, high density, high stiffness (Youngs modulus), chemical inertness, scratch resistant, ultra-wide bandgap (5.47 eV), high refractive index (2.4), optical transparency, high radiation hardness and high thermal conductivity. Apart from being the hardest naturally occurring material, diamond can also be lab-grown which can even be done on non-diamond substrates e.g. silicon and silicon nitride, which are commonly used in solar cells. This project proposes the use of a protective diamond coating, grown over silicon solar cells thus fixing the nanoparticles in place to provide greater robustness and sustain improvements in long-term efficiency of the solar cell. We anticipate that these coatings can be utilised for extraterrestrial applications, with the potential for incorporation of the solar cells into small devices and wearable electronics.

Organic electronic technologies are rapidly reshaping modern device platforms by enabling flexible, lightweight, biocompatible, and multifunctional systems. Among these, organic field-effect transistors (OFETs) have garnered significant attention as versatile building blocks for sensing and actuation due to their molecular tenability, solution processability, and inherent signal amplification capabilities. The operational efficiency of OFETs is strongly influenced by surface and interfacial design, which plays a decisive role in charge transport, sensitivity, response behavior, and long-term stability.

In OFET architectures, organic semiconductors and dielectric layers serve as the primary functional components, and the strategic integration of advanced materials within these layers offers powerful routes for enhancing performance. This presentation focuses on embedding spin-crossover (SCO) nanomaterials into the dielectric layer to exploit their intrinsic bistable nature and cooperative switching between low-spin (LS) and high-spin (HS) states. These transitions can be triggered by external stimuli such as temperature, pressure, light irradiation, and electric fields. The characteristic hysteresis associated with SCO systems makes them particularly attractive for applications in non-volatile memory, data storage, and reconfigurable electronic platforms.

The incorporation of SCO nanomaterials within dielectric matrices introduces new dimensions of functionality, enabling enhanced sensitivity, stimulus-selective responses, and multimodal sensing capabilities. Such hybrid dielectric systems expand the functional scope of OFET-based devices, opening pathways toward highly precise and adaptive solid-state sensors. By combining functional nanomaterials, organic electronics, and advanced device engineering, this work highlights innovative design strategies that advance the performance and versatility of organic electronic devices. The concepts discussed provide a forward-looking perspective on the development of intelligent, responsive, and high-performance organic sensors and actuators.

Thin-film engineering of magnetic heterostructures offers an effective pathway to tailor magnetization dynamics for spintronic applications. In this work, we investigate the influence of interfacial design on magnetic damping in YIG-based thin-film heterostructures, focusing on YIG/Ag and YIG/SnTe multilayers deposited on GGG (111) substrates. Epitaxial growth of YIG thin films with thicknesses of 150 and 200 nm is confirmed by X-ray diffraction, revealing a single (444) reflection overlapping the substrate peak, while Ag and SnTe layers exhibit no detectable crystalline peaks, consistent with disordered growth induced by lattice mismatch.

Magnetic characterization demonstrates soft ferrimagnetic behavior with low coercive fields, weakly affected by the metallic overlayers, indicating preserved magnetic quality after thin-film integration. Magnetoimpedance measurements performed in the 0.5–1.7 GHz frequency range reveal clear ferromagnetic resonance (FMR)-driven features, with resonance field shifts and impedance peak evolution governed by the combined effects of strong skin depth and dynamic magnetic permeability.

A comparative analysis shows that YIG/Ag heterostructures exhibit narrow resonance peaks, indicative of low magnetic damping, whereas YIG/SnTe thin films display significantly broadened and reduced-intensity resonances. By fitting the magnetoimpedance response with Lorentzian functions, the FMR linewidth and effective damping parameter were extracted, revealing a systematic reduction of damping with increasing YIG thickness. Importantly, YIG/SnTe heterostructures present a pronounced enhancement of effective damping compared to YIG/Ag, attributed to increased spin pumping efficiency and higher effective spin-mixing conductance enabled by the strong spin–orbit coupling of SnTe.

These results demonstrate how thin-film and interface engineering can be exploited to control spin dissipation mechanisms in magnetic insulator-based coatings, highlighting the relevance of YIG/SnTe heterostructures for functional spintronic thin-film applications.

Silicon-based solar cells, the most popular class of photovoltaics, are susceptible to delamination, thermal fatigue, and solder joint corrosion due to moisture- and heat-induced degradation. Conventionally, to dissipate heat, photovoltaic modules are actively cooled by circulating fluids, such as water, air, and nanofluids. However, continuous fluid circulation in the long term leads to corrosion of the silver metal contacts and increased production and maintenance costs. Therefore, it is imperative to develop a cost-effective strategy that provides both radiative cooling and a moisture barrier simultaneously, thereby extending the lifetime of solar cells even in tropical climates. In our work, we fabricated and utilised polymer nanocomposite (PNC) films as encapsulants to provide a one-stop solution for heat- and moisture-induced degradation in silicon solar cells.

For this, we dispersed ~0.5wt.% of nanocrystalline zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles of 100-400 nm size range individually into polydimethylsiloxane (PDMS) mixture using polyethene glycol (PEG) as a surfactant and chloroform as solvent, and fabricated PNC films using the doctor-blade technique – a scalable route, followed by subsequent curing at 80 °C for 20 minutes. The fabricated PNC films of 500 microns thickness were used as blanket encapsulants for commercial mini-silicon solar cells, and the encapsulated cells, along with bare cells, were subjected to accelerated aging tests to predict long-term performance. By the end of the hot-air aging test, in which the cells were heated to 150 °C, the PNC-encapsulated cells retained more than 80% of their initial power conversion efficiency (PCE), whereas the unencapsulated cells retained only ~50% of their initial PCE. Moreover, when heated to 60 °C and 90 °C, the surface temperature of PNC-encapsulated cells was ~5˗8 °C lower compared to unencapsulated cells, highlighting the role of radiative cooling of the films. Furthermore, by the end of the damp-heat aging test (60 °C, 85% relative humidity for 1 week), the PNC-encapsulated cells retained more than 50% of their PCE, whereas the unencapsulated cells retained only ~17% of their PCE. The improved retention of PCE with encapsulated cells is attributed to reduced heat build-up due to the NIR-reflective properties of the dispersed metal oxide particles, which also create a tortuous pathway for water molecules, thereby resulting in a 23–28% reduction in water vapour permeation compared to pristine PDMS films. These results highlight the potential of the fabricated PNC films as effective encapsulants to mitigate degradation caused by both humidity and temperature, thereby providing a moisture-blocking and radiative-cooling encapsulant, paving the way to extend the lifespan of silicon photovoltaics even when deployed in harsh tropical climatic conditions where conventional encapsulants may fail prematurely. 

Nano-engineered coatings and thin films with dynamically tunable electronic properties are central to the development of next-generation energy-efficient electronic devices. Here, we report a versatile class of metal–phenolic network (MPN) thin films that exhibit thermally reversible insulator–metal transitions, enabled through precise nanoscale control of molecular packing and interfacial interactions. The MPN films are fabricated via facile, ambient, and scalable assembly routes, producing uniform coatings with thicknesses ranging from ~10 to 300 nm that can be deposited on diverse substrates.

The electrical switching behavior originates from thermally induced reconfiguration of π–π stacking within the organic ligands, which drives a transition from an ultra-high-resistance insulating state with near-zero current leakage to a highly conductive state with high Hall mobilities. The transition temperature is systematically tunable (354–504 K) through rational design of the film composition, including ligand structure, metal ion selection, metal-to-ligand ratio, and film thickness. In situ structural characterization and molecular dynamics simulations reveal that enhanced π–π interactions and electron delocalization underpin the observed conductivity switching.

Importantly, these nano-engineered MPN coatings combine ultrahigh ON/OFF ratios, sub-microsecond switching speeds, large-area scalability, and compatibility with electronic circuits and sensing platforms, without requiring high-temperature processing or vacuum-based deposition. This work establishes metal–phenolic networks as a designable thin-film materials platform, linking molecular-level nano-engineering with macroscopic device functionality, and opens new opportunities for energy-efficient thermal switching, sensing, and smart electronic coatings.

Reference:

Accepted paper: Wang, T.; Lin, Z.; McLean, B.; Mazaheri, O.; Jannat, A.; Guo, X.; Xu, W.; Richardson, J. J.; Yarovsky, I.; Zavabeti, A.; Caruso, F.
Engineering Temperature-Switchable Conducting Metal–Phenolic Network Films.
Advanced Materials 2025, accepted (December 2025).

Nano-engineered polymer thin films were fabricated by chemical vapor deposition (CVD) using copolymers of 2-ethylhexyl acrylate (EHA) and fluorinated acrylate units. The solvent-free CVD process enabled precise control over chemical composition at the nanoscale, allowing uniform and conformal deposition on both flat and fibrous substrates while preserving their intrinsic morphology and maintaining nanoscale surface roughness below approximately 20 nm. By systematically varying the copolymer composition, interfacial wetting and adhesion were tuned without altering surface topography, enabling isolation of chemistry-driven interfacial effects.

Increasing the fluorinated content led to the formation of superhydrophobic interfaces, providing a controlled platform to examine their impact on adhesion-related mechanical behavior. Mechanical characterization demonstrated strong and composition-dependent interfacial adhesion, with shear resistance typically ranging from ~100 to 300 N/cm² and peel strengths on the order of 0.5-1.5 N per 25 mm. Despite the nanoscale thickness of the coatings, robust load transfer across the interface was achieved, highlighting the dominant role of interfacial chemistry in governing macroscopic mechanical behavior. Importantly, the nano-engineered films exhibited high interfacial stability under aggressive environmental conditions. After prolonged exposure to humid and aqueous environments, more than 80% of the initial shear strength was retained, indicating enhanced mechanical robustness associated with fluorine-rich interfacial design. SEM analysis confirmed conformal coating of porous fibrous substrates without structural disruption, supporting the mechanical integrity of the thin-film architecture. Overall, this study establishes a direct link between nanoscale chemical design, interfacial interactions, and macroscopic adhesion performance. The presented nano-engineered thin-film system offers a versatile framework for investigating size-dependent interfacial mechanics and durability in advanced polymer coatings and thin films.

With the advent of metal halide perovskites into the world of emerging sustainable semiconductors, a host of previously unprecedented applications has materialised. Aside from their raging success in photovoltaics, perovskites as applied to light emitting diodes (LEDs) and displays have gained particular interest due to their extremely facile bandgap tunability, directional and narrow-linewidth emission characteristics, high brightness, superior efficiencies and colour purity among other desirable features. However, most of the world records in terms of device efficiency and stability have been achieved on lab-scale pixels processed using solution-based techniques, primarily spin-coating. However, with its inherent advantages of scalability, reproducibility and precise thickness control, vacuum-based thermal evaporation provides an edge over solution-processing for all optoelectronic applications.

Following recent advancements in vacuum thermal evaporation of perovskite solar cells in our group, we have employed this technique to fabricate highly luminescent red- and NIR-emitting perovskite films for efficient and operationally stable light emitting diodes (LEDs). By optimizing the growth conditions, we have been able to achieve previously unreported photoluminescence quantum efficiencies (PLQE) close to 20% under 1-sun equivalent conditions for red emitters. Moreover, no sign of unwanted halide segregation has been observed under continuous illumination, thereby resulting in stable PL emissions in the wavelength range of 630-640 nm (pure-red emission) and 770-790 nm (NIR). To understand the effect of deposition conditions on the resulting optoelectronic properties of evaporated perovskites, a range of characterization including intensity-dependent PLQE, fluence-dependent TRPL, PL imaging, temperature-dependent PL, THz spectroscopy and transient photoconductivity measurements have also been conducted. Furthermore, X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) have been employed to obtain information on the chemical composition and electronic properties of the evaporated films. Finally, by extensive screening of the charge injection layers, we have been able to demonstrate red LEDs with champion external quantum efficiency (EQE) ~4.78 % and turn-on voltage ~ 3V which exhibit unprecedented high luminance of > 3000 cd/m2. Concurrently, for NIR LEDs, we have been able to realise high EQE ~7 % with peak radiance > 90 W/m2/sr which is 30 times the current world record.

Corrosion of mild steel poses a persistent challenge across industries, with global
costs exceeding $2.5 trillion annually. Epoxy coatings are commonly used for
corrosion protection but often suffer from water permeation and degradation in
aggressive environments. This study introduces an advanced strategy to enhance
epoxy coatings using hexagonal boron nitride nanosheets (hBNNS) functionalized
with 3-aminopropyltriethoxysilane (APTES).
Bulk hBN was exfoliated into nanosheets through optimized ball milling, reducing
crystallite size from ~32 nm (~95 layers) to ~7.5 nm (~23 layers), as confirmed by
XRD. The nanosheets were then functionalized with APTES to improve dispersion
and compatibility with the epoxy matrix. Successful grafting was verified by XRD
(peak broadening and d-spacing increase from 0.335 nm to 0.336 nm), FTIR (Si-O-C
and Si-O-Si vibrational peaks), and XPS (silicon peaks and carbon increase from
3.96% to 10.98%, confirming Si-O-B bonding).
Epoxy nanocomposites were prepared with pristine hBN, exfoliated hBNNS (hBNNSBM),
and APTES-functionalized hBNNS (APTES-hBNNS) at 0.15, 0.25, and 0.5
wt.%. SEM of cryo-fractured surfaces showed that APTES-hBNNS composites had
more tortuous fracture paths, suggesting enhanced dispersion and interfacial
adhesion. Surface wettability tests revealed increased hydrophobicity, with the 0.25
wt.% APTES-hBNNS coating achieving the highest contact angle (~98°), compared
to neat epoxy (~81°) and hBNNS-BM (~89°).
Corrosion performance was evaluated via 90-day electrochemical testing in 3.5 wt.%
NaCl solution. Open circuit potential (OCP) showed that while neat epoxy degraded
to -0.6 V vs. SCE within 28 days, the 0.25 wt.% APTES-hBNNS coating maintained
stable, noble potentials (-0.056 V to -0.082 V). Electrochemical impedance
spectroscopy (EIS) confirmed enhanced barrier properties, with the 0.25 wt.%
APTES-hBNNS showing the highest low-frequency impedance (|Z|₀.₀₁ₕz ≈ 8.85 × 10⁹
Ω·cm² after 90 days), nearly three orders of magnitude higher than neat epoxy.
Equivalent circuit modeling further indicated sustained high coating resistance (Rc)
and charge transfer resistance (Rct).
The improved corrosion protection is attributed to: (1) better nanosheet dispersion
creating a more tortuous path for corrosive agents, (2) stronger epoxy–filler
interfacial bonding through APTES amine–epoxy linkages, and (3) enhanced
hydrophobicity reducing water uptake. The optimal filler concentration was 0.25
wt.%, providing maximum protection without the agglomeration seen at higher
loadings.
Overall, APTES-functionalized hBNNS emerges as a promising nanofiller for nextgeneration
epoxy coatings, offering significantly improved corrosion resistance for
mild steel in harsh environments. This work advances the design of durable
nanocomposite coatings with superior long-term performance.

Printed Electronic Technology have gained prominent growth in the fabrication of flexible electronic devices and health care recently. Conductive inks are a major part of these flexible electronic devices. Flexible printed electronics based on silver nanoparticles allow manufacturers to develop affordable, eco-friendly devices using a wide range of manufacturing techniques. Due to the unique optical, electrical, biological, and antibacterial properties of silver nanoparticles, conductive silver inks are frequently used for printed flexible substrates. Silver nanoparticles with homogeneous shape, size, crystal state, and good dispersion were synthesised via a chemical reduction technique. Formulation of the conductive ink using a minimal number of solvents, capping agents that aid in cost-effectiveness and nontoxic binders like gum arabic that help in an environmentally friendly process is also reported. The formulated ink was used to create a pattern on a flexible substrate and the resistance was measured using a two-point probe digital multimeter. Moreover, the electrical resistivity of the obtained silver conductive ink is controllable, under the sintering temperature and time @ 60ºC for 30 minutes, resulting in an optimal electrical resistivity of 1.29 × 10−6 Ω cm. Ink adhesion and conductive performance after cyclic bending were evaluated on samples printed on flexible photo sheet substrates that endured a thorough study.

Employing FAPbI₃ single crystals (SCs) are crucial to achieve high efficiency solar cells. However, under room temperature, metastable alpha phase FAPbI₃ SCs readily turn into delta phase within a few days under sealed environment (Sealed-δ-FAPbI₃). Here, we propose that open-environmental storage could inhibit these phase transition by encapsulating bulk alpha phase with amorphorus phase of the outside shell (Open-α-FAPbI₃). With improved crystallinity, trap-assisted carrier recombination was reduced with decreased defect concentration in perovskite film fabricated with Open-α-FAPbI₃. This was further verified by significantly increased charge carrier lifetime. The relative ratio of ionic conductivity and electronic conductivity substantially decreased by utilizing Open-α-FAPbI₃, contributing to long-term stability. [1] With improved electrical properties, the power conversion efficiency of perovskite solar cells fabricated with 2 month-aged SCs could exceed 24% and retain over 90% of their initial performance over 2000 hours. Our results demonstrate the possibility of perovskite SCs phase stabilization for its long-term usage.

Reference

[1] Jihyun Kim et al., Adv. Energy Mater., 2024, 14, 2402117

For tandem applications, stable wide-bandgap (WBG) perovskite solar cells (PSCs) are essential, yet Br-rich WBG perovskites often suffer from large open-circuit-voltage (V_OC) deficits driven by non-radiative recombination, as well as limited thermal robustness. Here, we investigate additive engineering in inverted (p-i-n) PSCs based on FA_0.8Cs_0.2Pb(I_0.6Br_0.4)₃ (bandgap = 1.77 eV). The additive promotes uniform crystallization and improved film quality, reducing trap-assisted recombination and stabilizing ion transport while suppressing halide phase segregation. To elucidate thermal degradation pathways, perovskite films were thermally aged at 65 ℃. In control films, annealing induces pronounced accumulation of SCN⁻, which is associated with the gradual emergence and lateral spreading of a secondary surface phase with a higher work function. In contrast, additive-treated films effectively regulate excess SCN⁻, suppressing secondary-phase formation and preserving interfacial energetics during extended heating. Consistent with these interfacial changes, additive-containing devices exhibit V_OC recovery after an initial thermally induced drop, whereas control devices continue to degrade. As a result, the additive-engineered devices achieve a champion power conversion efficiency of 19.73%, with V_OC = 1.31 V and a fill factor of 81.7%, alongside markedly improved long-term operational stability.

Angle-dependent PL tuning for white light generation in 1D Silicon-Microcavity structures via sol-gel processing

Prasenjit Prasad Sukul*,1,2 , Luis F Santos2, Rui M Almeida2, Giovanni Mattei 1

[1] Dipartimento di Fisica e Astronomia ‘G. Galilei’, Università Degli Studi di Padova, Via F. Marzolo 8, 35131, Padova, Italy

[2] Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Tecnico, Universidade de Lisboa,

 Av. Rovisco Pais, 1049-001, Lisboa, Portugal

* email: prasenjit.sukul@unipd.it

The present study investigates a symmetric one-dimensional (1D) photonic crystal (PC) microcavity with the structure (LH)nL2(HL)n where L and H denote alternating layers of low-refractive index (L, made by lanthanide-doped aluminosilicate glass, Al–SiO₂) and high-refractive index (H, made by titania, TiO₂) materials, respectively, and n is the number of period in the multilayer. The structure consists of two distributed Bragg reflectors with n=5 deposited on p-type single-crystal (100) silicon substrates and is fabricated via a sol–gel process for tunable white-light generation (WLG). The microcavity exhibits strong angle-dependent upconversion (UC) emission that closely agrees with the simulated reflectance spectra. The resulting chromaticity coordinates correspond to near-white light with a correlated color temperature (CCT) of 5592 K. The multilayer structure studied in this work consisted of 2×5 high/low index pairs with a double thickness defect (L) at the center. After film deposition, a final thermal treatment was performed at 900°C for 1 hour. The experimental reflectance curve at 10° off-normal shows a pass band at 620 nm, closely matching the simulated defect at 635 nm (Transfer Matrix Method, TMM). The pass band at 10° has a quality factor (Q) of 34, lower than the simulated Q of ~ 200, highlighting some limitations of the sol-gel deposition technique for 1D PCs. However, the expected spectral blue shifts of stop bands and defects were accurately observed. These results demonstrate the potential of sol–gel–derived 1D photonic crystal microcavities for tunable white-light generation, with promising applications in solid-state lighting, photonic color control, and optoelectronic display technologies.

Self-healing microelectronics are needed for costly applications with limited or without access. They are needed in fields such as space exploration to increase lifetime and decrease both costs and the environmental impact. While advanced self-healing mechanisms for polymers are numerous, practical ways for self-healing in metal films have yet to be found. A concept for an autonomous intrinsic self-healing metallic film system is developed, allowing the healing of cracks in metallic films on flexible substrates. The concept relies on stabilizing metastable thin films with high mixing enthalpy via segregation barriers. This allows the films to possess autonomous intrinsic self-healing capabilities triggered by cracking at temperatures not detrimental to flexible microelectronics. The effect will be shown on metastable Mo_1-xAg_x and Mo_1-xCu_x thin films, stabilized via a Mo segregation barrier. Without a segregation barrier, the system is known to exhibit spontaneous particle formation on the surface. This property is controlled and directed to heal cracks and partially restore the electro-mechanical properties of the multilayer system. This mechanism opens up the field of self-healing thin metallic films that could profoundly impact the design of future microelectronics.

The rapid rise of antimicrobial resistance (AMR), together with the continuous emergence of new viral pathogens, represents a major global health challenge and highlights the urgent need for alternative, non-antibiotic antimicrobial strategies. In this context, nanozymes (nanomaterials that exhibit enzyme-like catalytic activity) have emerged as a promising class of artificial catalysts capable of generating or modulating reactive species under external stimuli, thereby enabling controllable antimicrobial action without relying on conventional drugs.

Here, we present nitrogen-doped graphene acid (NGA) as a metal-free photoactive nanozyme that combines oxidase-like catalytic activity with efficient photothermal conversion under near-infrared (NIR) light irradiation. Upon light activation, NGA catalytically promotes the generation of superoxide while simultaneously producing localized heat, resulting in a synergistic antimicrobial mechanism that is effective against both bacterial and viral pathogens.

Biocompatible NGA-based coatings were fabricated and comprehensively characterized in terms of physicochemical properties, optical response, and catalytic performance. The coatings demonstrate long-term stability, preserved photo-catalytic activity over extended storage, and highly reproducible ROS and heat generation when activated using a clinically approved NIR light source. Importantly, the catalytic response is strictly light-triggered, allowing precise spatial and temporal control of antimicrobial activity.

In vitro and ex vivo assessments show that short irradiation times (on the order of minutes) are sufficient to significantly inhibit bacterial and viral spread on the coated surfaces. Notably, the coatings do not induce skin irritation, sensitization, or observable adverse effects, supporting their safety and suitability for clinical and translational applications.

Overall, this work establishes NGA as a robust photoactive nanozyme platform and demonstrates how catalytic, light-activated nanomaterials can be engineered into stable, biocompatible coatings. These results pave the way for the development of nanozyme-based catalytic strategies to combat AMR across a broad range of clinical and healthcare settings, including dental, and subdermal infections.

Surface-enhanced Raman spectroscopy (SERS) enables ultrasensitive molecular detection; however, it faces limitations in reusability and analyte specificity on conventional metal-based substrates. Photoinduced enhanced Raman spectroscopy (PIERS) addresses these issues by harnessing synergistic photoinduced charge transfer and plasmonic enhancements. Unlike traditional PIERS platforms, which often require UV activation, in this work, we introduce a vis-irradiation active PIERS platform comprising silver nanoparticles (AgNPs) decorated on sulfur vacancy-rich tin sulfide (SnS) nanostructures, fabricated via glancing angle deposition (GLAD), followed by controlled sulfurization and Ag deposition. The SnS framework acts as a semiconductor host, efficiently generating photoexcited electron–hole pairs under visible irradiation (400 nm), while intrinsic sulfur vacancies promote strong interfacial charge transfer. Concurrently, AgNPs contribute electromagnetic enhancement through localized surface plasmon resonance (LSPR). This hybrid PIERS substrate exhibits remarkable Raman signal amplification and allows label-free detection of various analytes, including probe molecules such as 1,2-bis(4-pyridyl)ethylene and p-aminothiophenol, as well as dyes like Rhodamine 6G, Crystal Violet, Methylene Blue (MB), and Methyl Orange (MO), achieving a detection limit as low as 10⁻¹¹ M. Additionally, the substrate demonstrates excellent photocatalytic degradation capabilities and recyclability. The proposed system offers a cost-effective, scalable, and reusable approach for next-generation PIERS platforms, with significant potential in real-time environmental monitoring, chemical sensing, and bioanalytical applications.

The deployment of hydrogen in energy and mobility systems motivates compact devices for the safety of operators in occupational context and users prevention. Because hydrogen is highly flammable (4-75% vol in air) and diffuses rapidly, early leak detection is essential for safe operation of hydrogen based systems. Nano-engineered thin film coatings in which metal nanoparticles spread onto an organic semiconductor layer exhibit suitable properties and potentialities as sensing layers for conductometric hydrogen sensors especially for leak detection at low operating temperature in ATEX environments. Here we report a room temperature conductometric sensor based on nanostructured copper phthalocyanine (CuPc) thin film decorated with palladium nanoparticles (Pd NPs), proposed as an alternative to common continuous palladium thin films that suffer from swelling, crack formation, and signal drift upon H₂ exposure. The nanostructured sensing layer is elaborated through the deposition of CuPc thin film by thermal evaporation on alumina substrate integrating Inter-Digitated Electrodes maintained at room temperature. This deposition method processing at room temperature allows to nanostructure the surface through self-organized CuPc building blocks. To enhance their sensitivity towards H₂, these nanosized layers are decorated with Pd NPs by a simple drop casting process. Structural and morphological analyses confirm the hybrid architecture: the nanostructured CuPc film enabling surface roughness, promotes improved Pd NPs dispersion compared to a deposition on a bare and smooth substrate, highlighting the role of organic layer on the improvement of nanoparticle distribution and stabilization. Electrical characterization shows linear I-V behavior consistent with typical ohmic behavior and reveals that the conductivity can be tuned through Pd loading while benefiting a high baseline resistance associated with the nanostructured CuPc thin film. These hybrid structures are then tested towards H₂ while optimizing the NP loads on the nanostructured film. The results we intend to discuss here will demonstrate that a synergistically effect takes place and results into a significant improvement of responses compared to phthalocyanine film or Pd NPs considered separately. Beyond, we will demonstrate that the sensitivity, repeatability and response time combined with lower LOD make these results very relevant for H₂ leak monitoring application. Furthermore, stability and humidity tests reveal the positive effect of nano-structuration in limiting these external. Such a device shows good repeatability, low cross-sensitivity to interfering gases and long-term stability. Overall, the study underlines that Pd nanoparticles dispersion and loadings on CuPc thin film are key design parameters for sensing coatings used in room temperature conductometric H₂ leak detection avoiding the poisoning and drift drawbacks that most hydrogen sensors based on palladium thin films suffer.

Germanium tin (GeSn) alloys have attracted interest in recent years as promising candidates for fabricating mid-infrared photodetectors operating up to 10 µm. However, the growth of GeSn alloy on Ge is challenging since the equilibrium Sn solid solubility in Ge is less than 1%, and lattice mismatch between Ge and GeSn causes threading dislocations during film relaxation to equilibrium lattice spacings. Both aspects severely degrade the photodetector performance made by defective GeSn alloy. The main aim of this study is to grow defect-free Ge-GeSn superlattices under conditions that provide strain compensation and hence substantially improve material quality.

Ge-GeSn superlattices of various compositions and thicknesses were grown by remote plasma-enhanced chemical vapour deposition at 300°C on Ge substrates. The films were fully characterised by double-crystal x-ray diffraction and mapping, atomic force microscopy, Rutherford backscattering and channelling (RBSC), and advanced cross-sectional transmission electron microscopy (TEM), along with energy-dispersive spectroscopy (EDS). Our results show that defect-free, fully-strained superlattices with more than 10 Ge-GeSn pairs can be grown if the Sn concentration is less than ~7%. At high Sn content, lattice relaxation occurs when the strain exceeds a critical value, and the layers become defective, along with significant phase separation. However, if the thickness of the individual Ge layers is increased, it is possible to decrease the integrated strain and grow defect-free superlattices at high Sn content.

In conclusion, high Sn content, defect-free, strain-compensated Ge-GeSn superlattices can be grown by altering Ge thickness to reduce the integrated strain, thus opening up the prospect of much improved photodetectors.

All-solid-state batteries (ASSBs) based on inorganic solid-state electrolytes (SSEs) are viable contenders for next-generation energy storage, as they address certain constraints of conventional lithium-ion batteries, such as safety and energy density, particularly if integrated with lithium metal anodes ^1-6. The development of SSEs must meet certain criteria, including high values of ionic conductivity (at least 10^-3 S cm^-1) and low values of electronic conductivity (under 10^-9 S cm^-1), while also demonstrating chemical and electrochemical stability when paired with 4V-class cathodes. Out of the several materials studied in the literature, halide SSEs demonstrate likely candidates matching several, if not all, of the mentioned requirements^1-6. Yet, these criteria are usually met using costly central metals 1, limiting their practical use. The choice of zirconium as the primary metal, along with anionic and cationic substitution, is proposed here as a solution to that limitation. As such, Li₂ZnCl₆ (LZC) was synthesized by a mechanochemical method in an argon atmosphere using stoichiometric halide precursors ^2-6. Compositions of anion/cation-substituted Li₂Zr_(1-x)(Ni_x or Sn_x)Cl_(6-y)Br_y were synthesized using similar methodologies to examine their influence on structural and ionic/electronic transport properties. Ionic and electronic conductivities were assessed by electrochemical impedance spectroscopy and direct current polarization in symmetric cell designs. Synthetized LZC demonstrates an ionic conductivity on the order of 10^-4 S cm^-1 and a low electronic conductivity of ~10^-11 S cm^-1. LZC exhibits a hexagonal close-packed trigonal structure (P 3m1) ^2,3,5. Raman spectroscopy and X-ray photoelectron spectroscopy were used for structural and chemical analysis. The implementation of LZC-based SSE in ASSB architectures is preliminarily addressed from a processing standpoint with thin-film LiFePO₄ cathodes deposited by sputtering, while the LZC electrolyte layer is layered via doctor blade coating. Lithium metal anodes are subsequently deposited by thermal evaporation, with current collectors also being deposited by sputtering, thereby completing the solid-state cell stack.

References

1 Asano et al, 2018, Advanced Materials.

2 Zhang et al, 2023, Journal of Energy Chemistry.

3 Kwak et al, 2021, Advanced Energy Materials.

4 Wang et al, 2021, Nature Communications.

5 Jeon et al, 2024, Journal of Power Sources.

6 Luo et al, 2022, ACS Applied Materials & Interfaces.

The two-step sequential deposition is promising for control of the crystallization and growth of compact perovskite by separating the deposition of PbI2 and organic salt. Furthermore, thermal evaporated-PbI2 has the potential for textured surfaces. However, the performance of inverted perovskite solar cells by the two-step sequential deposition lags far behind the counterpart fabricated by the one-step deposition from a precursor solution. Here, we found insight into anion exchange in the sequential thermal evaporation-solution process for high-quality perovskite films. The exchange process promotes mass transport and penetration of organic compounds into evaporated PbI2, optimizes phase purity, and enables a homogeneous halide distribution with inhibited phase segregation. The devices fabricated by evaporated-PbI2 as the bottom layer following the solid-solution interdiffusion process yield a champion efficiency of 24.43% (certified 24.18%), which is the highest inverted perovskite solar cells based on evaporated PbI2. Incorporating the scalable blading process for solid-solution interdiffusion, the device exhibits an efficiency up to 22.22%. The resulting conformable and scalable cells maintain 95% of the initial efficiency after operation for 682 h under one sun illumination. This anion-exchange strategy provides instructive significance for future large-area and monolithic perovskite-silicon tandem cells.

Blade-coating stands out as an alternative for fabricating scalable perovskite solar cells. However, it demands special control of the precursor composition regarding nucleation and crystallization and currently exhibits lower performance than the spin-coating process. It is mainly the resulting film morphology and excess PbI₂ distribution that influence the optoelectronic properties. Here, we find the effectiveness of introducing N-Methyl-2-pyrrolidone (NMP) to regulate the structure of the perovskite layer and the redistribution of PbI₂. The introduction of NMP leads to the accumulation of excess PbI₂, mainly on the top surface, reducing residual PbI₂ at the perovskite buried interface. This not only facilitates the passivation of perovskite grain boundaries but also eliminates the potential degradation of the PbI₂ triggered by light illumination in the perovskite buried interface. The optimized NMP-modified inverted perovskite solar cell achieves a champion efficiency of 24.5%, among the highest reported blade-coated perovskite solar cells. Furthermore, 13.68 cm² blading perovskite solar modules have been fabricated and demonstrate an efficiency of up to 20.4%. Our findings underscore that with proper modulation of precursor composition, blade-coating can be a feasible and superior alternative for manufacturing high-quality perovskite films, paving the way for their large-scale applications in photovoltaic technology.

The development of efficient photoanodes is critical for advancing photoelectrochemical water splitting as a viable clean energy technology. This work presents the fabrication of an indirect Z-scheme heterojunction photoanode consisting of sequentially deposited W18O49, Au, and Bi2O3 layers. Structural and chemical characterization confirmed the successful formation of a composite material containing crystalline monoclinic W18O49, metallic Au, and α- Bi2O3. Optical analysis revealed a significant enhancement in visible-light absorption, with the optimal composite (BO10) exhibiting a red-shifted absorption edge at 556 nm and a reduced bandgap of 2.23 eV. Under simulated solar illumination, the BO10 photoanode achieved a substantially improved photocurrent density of 1.52 mA cm⁻2 at 1.4 V vs. RHE, which is 69% higher than its Au-decorated W18O49 counterpart. Electrochemical impedance spectroscopy indicated a low charge-transfer resistance of ~150 Ω, confirming enhanced interfacial charge separation kinetics. Furthermore, the photoanode demonstrated excellent operational stability over 4 hours. These results underscore the efficacy of the Au-mediated Z-scheme heterojunction in synergistically improving light harvesting, charge carrier separation, and overall, PEC performance for solar water oxidation.

Tungsten trioxide (WO_­3) is a promising material for renewable energy utilization. It is cheap and abundant, thermally and electrochemically stable¹, and allows for reversible proton intercalation². At the same time, WO₃ allows for different thin-film deposition methods. Among these, spray pyrolysis is especially interesting, as it allows for the production upscaling³ while maintaining control of composition and morphology⁴. However, proton storage in thin films deposited by spray pyrolysis remains understudied. This is especially important as WO₃ can be used in proton-based batteries and fuel cells, electrochromic devices, and memristors. In some cases, a bulk proton storage is required, while in others a fast-switching mechanism is beneficial. In this work, we systematically study the influence of deposition parameters on proton storage capacity and bulk diffusion in WO₃ films, and contribute to a better understanding of proton intercalation dynamics in WO₃ thin films.

1.      Shinde, P. A. & Jun, S. C. Review on Recent Progress in the Development of Tungsten Oxide Based Electrodes for Electrochemical Energy Storage. ChemSusChem 13, 11–38 (2020).

2.      Guo, H. & Zhao, C. An Emerging Chemistry Revives Proton Batteries. Small Methods 8, 2300699 (2024).

3.      Sriram, S. R., Parne, S. R., Pothukanuri, N. & Edla, D. R. Prospects of spray pyrolysis technique for gas sensor applications – A comprehensive review. J. Anal. Appl. Pyrolysis 164, 105527 (2022).

4.      Workie, A. B., Ningsih, H. S. & Shih, S.-J. An comprehensive review on the spray pyrolysis technique: Historical context, operational factors, classifications, and product applications. J. Anal. Appl. Pyrolysis 170, 105915 (2023).

    This research presents a hydrothermal method for fabricating textured BaTiO3 (BTO) nanorod arrays with high crystallinity on fluorine-doped tin oxide (FTO) substrates by applying a polarization treatment to the samples to explore the feasibility of enhancing their piezoelectric properties. The preparation of highly textured BTO nanorod arrays using a two-step hydrothermal process was investigated in detail, including the spin-coating process for depositing the TiO2 seed layer, the influence of solution acidity on the hydrothermal synthesis of TiO2 nanorod arrays, and the formation mechanism of textured BTO nanostructures. The piezoelectric constants (d33) of the samples were determined using piezoresponse force microscopy. S-BTO, which has high crystallinity and preferential orientation, achieves a d33 as high as 85.4 pm/V after poling, which is 3.2 times higher than that without textured structures and poling. Our findings revealed that chemically controlling and inducing a preferential orientation in the crystal structure of piezoelectric materials with a seed layer and specific hydrothermal conditions can significantly enhance their piezoelectric properties after poling, making them excellent candidates for piezoelectric devices.

Keywords: BaTiO3 nanorod arrays, textured, hydrothermal, rhodamine B, piezocatalysis.

This study reports the strategic fabrication of BaTiO₃ (BTO) nanorod arrays decorated with silver (Ag) nanoparticles through a synergistic combination of hydrothermal and photoreduction methods, specifically designed to harness the piezo-phototronic effect for enhancing the degradation efficiency of rhodamine B (RhB) solution. A key innovation lies in the use of vertically aligned BTO nanorod arrays as a robust template, which provides a high surface-to-volume ratio and abundant nucleation sites, ensuring a more uniform and stable distribution of Ag nanoparticles compared to conventional bulk or powder counterparts. The resulting BTO–Ag heterostructure exhibits a significant longitudinal piezoelectric coefficient of 40 pm/V and demonstrates broadened visible-light absorption due to the surface plasmon resonance (SPR) effect from Ag nanoparticles. Under simultaneous simulated solar irradiation and ultrasonication, the BTO–Ag (0.03 M AgNO₃) composite achieves an optimal RhB degradation efficiency of approximately 86% within 120 minutes. This performance is driven by the piezo-phototronic effect, where the piezopotential in the BTO lattice acts as a dynamic gate to modulate the Schottky barrier at the interface. Furthermore, the integrated film-based architecture of the nanorod arrays not only prevents the aggregation of Ag nanoparticles but also facilitates effortless recovery and reuse of the catalyst, addressing the practical challenges of secondary pollution and energy-intensive recycling in wastewater treatment. The synergistic system of BTO–Ag nanorod arrays provides a promising paradigm for the development of high-performance and self-powered environmental purification technologies.

Keywords: BaTiO₃ nanorod arrays, Ag nanoparticles, hydrothermal, piezo-phototronic effect, RhB degradation.

In this study, the thickness and density of AlOx dielectrics were precisely controlled by tuning the anodizing voltage, and the correlation between the dielectric electrical properties and OCMFET device performance was systematically investigated. Increasing the anodizing voltage resulted in a linear increase in AlOx dielectric thickness, accompanied by a reduction in leakage current and an enhancement in breakdown voltage, thereby directly modulating the charge coupling efficiency through changes in the effective control gate–floating gate capacitance. High capacitance can be achieved under low anodizing voltage conditions. However, limited dielectric insulation stability leads to increased gate leakage and degraded device reliability. In contrast, high anodizing voltages increase the dielectric thickness, resulting in reduced capacitance and a limited amount of charge induced from the control gate to the floating gate. This, in turn, suppresses the threshold voltage shift and transconductance. These results confirm the existence of an optimal anodizing voltage range in which sufficient insulation characteristics and efficient charge induction are simultaneously achieved. Furthermore, interfacial charge stability was improved by introducing a TDPA-based self-assembled monolayer (SAM) on the floating gate surface. OCMFETs with simultaneously optimized dielectric and surface properties effectively amplified floating gate potential modulation under control gate operation, leading to highly sensitive changes in channel current. These results suggest that OCMFETs can be extended to multifunctional sensor platforms capable of detecting various external stimuli, including pressure, chemical, and biological signals, with high sensitivity.

The advancement of bio-devices, wearable electronics, and IoT applications requires highly reliable and miniaturized power systems. Conventional battery technologies face limitations in scaling, safety, and integration with semiconductor-based platforms. To address these challenges, we have focused on the development of microbattery using the NNFC Semiconductor–All-Solid-State Microbattery Platform. 

This platform integrates Physical Vapor Deposition (PVD), Chemical Vapor Deposition (CVD), rapid thermal annealing, and advanced encapsulation modules in a cluster-type configuration that supports wafer-scale fabrication up to 8 inches. A unique feature of the system is the ability to process all battery layers without atmospheric exposure, ensuring excellent interfacial quality and enhanced device reproducibility. By leveraging this environment, NNFC has demonstrated stable fabrication of all-solid-state microbattery arrays with the footprint ranging from 5.3 mm2 to 1 cm².

To implement the microbattery on a wafer, we applied photolithography and lift-off processes. In this way, not only a single full cell with a stacked current collector, active material, and electrolyte, but also a cell design in which multiple full cells are stacked vertically or arranged on a plane was implemented. The arrayed and multi-layered cell design provides tunable capacity and voltage outputs, enabling direct integration with diverse substrates and device architectures. These characteristics are particularly valuable for emerging applications: powering implantable or wearable bio-devices, supporting self-charging energy systems, and enabling flexible, lightweight IoT devices. Beyond electrochemical stability, the platform’s compatibility with semiconductor processes ensures seamless integration into microelectronics, expanding the design possibilities for next-generation systems. The resulting devices demonstrate strong compatibility with microelectronics and flexible substrates, making them suitable for applications such as bio-device systems, self-charging modules, and wearable IoT devices. This progress highlights the critical role of integrated infrastructure in accelerating the commercialization of micro-power systems for emerging technologies.

High carrier mobility III-V and Ge materials have been regarded as leading candidates to surpass the Si limit for future CMOS technology. Demonstrations of individual III-V or Ge devices with superior performance have been reported [1-6]. However, in order to take full advantage of high-mobility channels, III-V and Ge devices must be co-integrated on Si substrate at the nanometer scale. It is usually thought that co-integration can be achieved by selective epitaxy or direct wafer bonding. Indeed, many reports were focused on direct wafer bonding [4,5]. But Si CMOS compatible co-integration of defect free Ge and III-V fins simultaneously on Si was rarely reported.

In this work, for the first time, we demonstrated InxGa1-xAs and Ge fins co-integrated on standard bulk Si using InxGa1-xAs selective epitaxy and Ge directly etching to achieve defect-free III-V/Ge fins on standard Si wafers. Fig. 1 depicts the proposed heterogeneous integration architecture for Ge/III-V co-integration based on the defect-trapping concept using necked oxide trench and diamond-shaped pocket without thick buffer layer to effectively constrain the lattice defects at the bottom and reveal defect-free III-V/Ge fins on top for n/p FinFET operations. Detailed process flow and the characterization of Ge/III-V FinFETs on Ge/Si were described and the process challenges in Ge/III-V cross-contamination as well as the thermal budget of heterogeneous integration were also discussed in details.

References:

[1] Rinku Rani Das, et al., ,IEEE Access, Vol. 12, pp. 50556 – 50577, 2024

[2] M.-S. Yeh, et al., IEEE Journal of the Electron Devices Society, Vol. 6, pp. 1227 – 1232, 2018

[4] L. Czornomaz, et al., Proc. IEDM 2013, pp52-55, 2013

[5] K. Nishi, et al., Proc. VLSI Symp. Tech. Dig., 2015, p. T174, 2015.

[6] Heng Wu, et al., Proc. VLSI Symp. Tech. Dig., pp. 1-2, 2014.

With the rapid advancement of electronic devices, quantitative and high-precision characterization techniques for electronic materials have become increasingly important. Scanning capacitance microscopy (SCM) is widely used to evaluate dielectric properties, determine carrier polarity, and map nanoscale carrier concentration distributions. The reliability of these analyses critically depends on the quality and stability of the SCM signal. However, when a conductive probe contacts the sample surface, a contact potential difference (CPD) inevitably arises due to a mismatch in work functions between the probe and the sample. CPD is a subtle yet critical factor influencing SCM measurements, as it can reduce voltage modulation efficiency, shift the flat-band voltage, and induce charge transfer, thereby degrading SCM signal quality and image reliability. In this work, we systematically investigate the influence of CPD on SCM measurements by employing probe tips with different work functions. Oxide nanofilms deposited on p-type silicon substrates were used as samples. The probe work functions were calibrated by Kelvin probe force microscopy (KPFM) using a gold reference whose surface potential was independently determined by X-ray photoelectron spectroscopy. Three probes with distinct work functions were examined: a PtIr-coated tip (5.29 eV), a PtIr/Ti-coated tip (4.98 eV), and an Al/Ti/Au-coated tip (4.68 eV). Using these calibrated probes, the surface potentials of the oxide nanofilms were measured by KPFM to quantitatively assess the impact of CPD on SCM signal behavior. The SCM results show that significantly higher signal intensities and improved relative standard deviation (RSD) are achieved when a PtIr/Ti-coated tip is used to scan a thermally grown SiO₂ surface (sample A) and when an Al/Ti/Au-coated tip is used to scan an Al₂O₃/SiO₂ stacked film (sample B). An SCM setup exhibiting high signal intensity together with a low RSD enables high SCM sensitivity in regions of high carrier concentration. KPFM measurements indicate surface potentials of 5.45 eV for sample A and 4.85 eV for sample B. At thermal equilibrium, when the conductive tip contacts the sample surface, voltage modulation efficiency degrades if the CPD induces a reverse-bias condition that narrows the depletion region. In contrast, a CPD-induced forward-bias condition can enhance voltage modulation efficiency only when it drives carriers toward the depletion edge rather than into the inversion region. These results provide insight into CPD-induced SCM signal degradation and highlight the importance of probe work-function engineering for achieving high-quality, quantitative SCM measurements.

We report the synthesis of undoped and selenium-doped (0.5 and 1 wt.%) calcium-phosphate thin films by pulsed laser deposition using rich, renewable and inexpensive bovine-bone resources (BioCaP, BioCaP:Se0.5, and BioCaP:Se1). The deposited films were systematically compared in terms of mechanical response, structure, morphology, chemistry, wetting behaviour, dissolution resistance, and in vitro apatite-forming ability.

Adhesion tests showed a clear mechanical benefit of Se: Se-doped BioCaP layers reached bonding strength values ~1.5 times higher than undoped BioCaP and more than 3 times above the minimum threshold set by international standards. Selenium also lowered the friction coefficient and improved scratch resistance, underscoring a consistent strengthening effect.

X-Ray Diffraction revealed thin, crystalline BioCaP layers dominated by hydroxyapatite (HA) reflections. Fourier Transformed InfraRed (FTIR) Spectroscopy displayed the characteristic phosphate (PO43‒) vibrations and indicated that Se acts as a structural modifier within the HA lattice. Surface imaging showed rough, irregular films build from spherical/ovoid aggregates with broad size distributions; Se increased particle size and density, pointing to a dopant-mediated change in growth during deposition.

Wetting measurements captured a pronounced shift from hydrophobic Ti controls (contact angle, CA ~ 121°) to superhydrophilic behaviour (CA < 5°) for Se-doped films.

In aqueous media, all BioCaP films followed the expected sequence of initial dissolution followed by biomimetic CaP reprecipitation. Selenium accelerated nucleation and growth of apatite, with BioCaP:Se0.5 transforming most rapidly toward dense spherulitic layers. After 30 days in simulated body fluid, BioCaP:Se0.5 developed a compact acicular network of well-interconnected particles, consistent with advanced biomimetic mineralization. FTIR band narrowing further supported Se-driven acceleration of CaP nucleation and improved phase ordering, highlighting the beneficial role of Se in promoting biomineralization.

Beyond performance imparted by Se doping, the use of bovine-derived feedstocks emphasizes sustainability and cost effectiveness, positioning BioCaP:Se thin films as attractive, renewable alternatives to synthetic HA for bone-implant applications.

Acknowledgement: GD, GPP, VG, and LD acknowledge partial support from the Romanian Ministry of Education and Research, under Romanian National Nucleu Program LAPLAS VII—Contract No. 30N/2023.

Electric dipoles play very relevant role in semiconductors devices and may be investigated by thermally stimulated depolarization current (TSDC) technique, which successfully used for characterization of several materials, including semiconductors. TSDC refers to the depolarization current upon temperature rise, when field induced buildup of dipoles at room temperature is frozen by decreasing the temperature, These dipoles come from arrangement of charged defects, originally randomly oriented throughout the sample. The temperature increase gives rise to depolarization current bands, related to the return of dipole-like defects to the original distribution,

The heterostructure GaAs/SnO2, built by resistive evaporation of Er-doped SnO2 on top of GaAs semi-insulating substrate, is explored using TSDC. The possibilities for dipole formation are associated with native charged defects, such as the EL2 in the GaAs, oxygen vacancies and Er ions in the SnO2. The dipole relaxation activation energies are found in the range 0.2-0.3 eV, in good agreement with ionization energies of these defects. The main TSDC bands, located about 270 K, either for positive or negative polarization, reveal ionization energies of 213 meV for positive bias, and 218 meV for negative bias [1], which may correspond to the second ionization level of oxygen vacancies in SnO2. TSDC is also applied to this heterostructure in the presence of monochromatic light from a He–Cd laser (325 nm) and a InGaN LED (450nm). The characteristic current-voltage (I x V) curves are measured across the GaAs/SnO2 interface [2], yielding a diode-like rectifying behavior.  The effect of monochromatic light is analyzed by I x V curves in conjunction with TSDC data, considering the main types of defects. Photo-induced TSDC affects bands previously obtained in the dark, suggesting large shift on the thermal and optical activation energies of defects. This effect is stronger with the illumination of the LED (2.76 eV) compared to laser (3.80 eV). The LED excites only the GaAs layer while the laser is more effective to excite the SnO2, because the energy is slightly above the band-to-band transition, populating states available at the base of the SnO2 conduction band.

Dipole-like behavior has also been investigated in a heterostructure GaAs/SnO2 where the oxide is Eu-doped. Through resistivity measurements in the range 200-350K using optical filters with distinct cutoff wavelengths, the defects optical ionization energies were scanned and related with TSDC and interface electric dipoles. The current-temperature data for fixed bias of 5 V, using a filter with cutoff wavelength of 820 nm, shows a band at 270 K in good agreement with TSDC data, attributed to arrangement of oxygen vacancies in SnO2 in dipole-like structures.

Acknowledgement CNPq (proc. 303388/2022-6).

[1] F. T. Russo, D. H.O. Machado, L. V.A. Scalvi, Chemical Physics 573, 112004 (2023)

[2] F. T. Russo, L.V.A. Scalvi, Physica B 690, 416240 (2024)

SrSnO₃ (SSO) is an ultra-wide-bandgap (UWBG) perovskite semiconductor that has attracted considerable attention for next-generation power devices due to its high electron mobility. Despite growing interest, the epitaxial growth behavior of SSO films on SrTiO₃(001) substrates under sputtering conditions remains poorly understood. In this study, we grow thickness-dependent high-quality SSO films on SrTiO₃(001) substrates using off-axis RF magnetron sputtering. To examine the effect of plasma position on film growth, SSO films were grown at various plasma positions to identify optimal growth conditions. Using this optimized geometry, a series of SSO films with various thicknesses was deposited to track the evolution of epitaxial growth. Structural characterization using X-ray diffraction and reciprocal space mapping revealed a thickness-driven structural phase transition from a tetragonal to an orthorhombic phase occurring at approximately 10 nm. The emergence of the orthorhombic phase was further confirmed by the observation of half-order Bragg peaks and transmission electron microscopy (TEM), which revealed an a⁻b⁺c⁻ pattern of SnO₆ octahedral tilting. TEM also showed that dislocations are observed in the orthorhombic phase, whereas no apparent dislocations are detected in the tetragonal phase. These results provide the thickness-dependent structural relaxation behavior of SSO films grown on SrTiO₃ and its correlation with dislocation, thereby clarifying insight into their structural phase evolution and establishing a structural framework for understanding charge transport in stannate-based UWBG perovskite semiconductors.

Early disease detection and continuous health monitoring increasingly rely on sensing platforms capable of real-time operation with high sensitivity and energy efficiency. Consequently, wearable electronics and point-of-care diagnostic technologies require miniaturized, solid-state biosensors that enable label-free detection with high scalability. Ion-sensitive field-effect transistors (ISFETs), compatible with complementary metal–oxide–semiconductor (CMOS) manufacturing, provide a promising platform for integrating such sensing functionalities into compact systems.

As continued miniaturization begins to deviate from the traditional Moore’s law scaling paradigm, further improvements in sensitivity and multifunctional integration increasingly demand channel materials beyond silicon. Two-dimensional (2D) semiconductors therefore emerge as promising candidates for next-generation electronic and sensing platforms. Among them, MoS₂ offers an atomically thin channel, excellent electrostatic control, and strong potential for heterogeneous integration. Despite these advantages, the absence of dangling bonds on MoS₂ poses a fundamental challenge for dielectric integration, resulting in poor nucleation, high interface trap densities, and non-uniform coverage when conventional thin-film deposition techniques are employed. This interface bottleneck critically limits device reliability, reproducibility, and large-scale adoption.

Here, we present a systematic investigation of Al₂O₃ thin films deposited on MoS₂ using sputtering, e-beam evaporation, and atomic layer deposition (ALD), and elucidate the direct correlation between deposition route, interfacial quality, and device electrostatics in extended-gate, multi-gated ISFET architectures. Sputter-deposited Al₂O₃ films (50 nm) exhibit degraded gate modulation and compromised back-gate characteristics, attributed to plasma-induced damage and defect generation in the MoS₂ channel. E-beam evaporated Al₂O₃ of comparable thickness suffers from high leakage currents and a loss of back-gate control under top-gate biasing, indicative of poor dielectric integrity.

In contrast, conformal ALD-grown Al₂O₃ deposited using a TMA–ozone process in an oxygen-rich environment enables uniform nucleation, low leakage, and significantly improved interfacial quality. Optimized post-deposition processing, including a dilute HF-based contact-opening step, preserves channel integrity and minimizes process-induced degradation. ISFET devices incorporating ALD Al₂O₃ demonstrate excellent electrostatic control with I_ON/I_OFF ratios of 10⁶–10⁷ and leakage currents in the 10⁻¹² A range. Under top-gate operation, these devices further exhibit a super-Nernstian pH response approaching 972 mV/pH, highlighting how dielectric thin-film quality directly enables high-gain sensing. This work establishes ALD-based Al₂O₃ dielectric integration as a scalable and robust pathway for advancing 2D semiconductor electronics and biosensing platforms.

Electrical conductivity and ferromagnetism are simultaneously observed at the interface as the LaAlO3 (LAO) is deposited more than 4 unit cells on a TiO₂-terminated SrTiO₃ (STO) substrate even though both of materials are nonmagnetic insulators.  In this study, LaFeO₃ (LFO3)/CaFeO₃ (CFO3) multilayers, which is analogous to the LAO/STO heterostructure, are grown where the LFO3 and the CFO3 are antiferromagnetic insulators.  This study aims to elucidate the mechanisms of electrical conduction and magnetic phase transitions, as well as to control the antiferromagnetic-to-ferromagnetic phase transition by applying an electric field at room temperature.

The STO(001) substrate was cleaned, etched with buffered HF, and then annealed in air at 950°C for several hours.  The substrate surface with a confirmed step-terrace structure was used for the growth.  The both of LFO3 and CaFeOx (CFO) thin films were deposited on the substrate using the pulsed laser deposition (PLD) method.  After deposition, oxygen was introduced into the chamber up to 1 atm, and the substrate was cooled down to room temperature.

   From the results of RHEED oscillation, surface morphology depicted by SPM (scanning probe microscopy) and XRD (X-ray diffraction), the about 3 units CFO3 was grown first and then followed by the growth of Ca₂Fe₂O₅ (CFO2.5) because of the instability of Fe⁴⁺.  From the illustration of saturation magnetization per cm², Mst, at 300K depending on composition ration of CFO3 to CFO2.5 in CFO layer, maximum Mst was obtained at nearly 54% in LFO/CFO multilayers, although LFO3 and CFO3 are antiferromagnetic.  More than 70% of CFO3 in CFO layer, the Mst was almost zero.  In addition, from the Mst depending on the thickness of LFO3, the Mst showed abrupt jump up to 4.4 μB / Fe.  It is expected that the electron transfer at the interface occur to introduce the ferromagnetic interaction between Fe³⁺ (3d⁵) and Fe⁴⁺ (3d⁴).  In the case of CFO approximately 118 units film and CFO/LFO multilayers, where the thickness of CFO were 4.3 and 8.7 units and that of LFO was 18 units, the activation energy was approximately 0.2eV for all films.  This activation energy is considered to correspond to the energy required for electron transfer between the Fe³⁺ and Fe⁴⁺ 3d e_g orbitals.

 With planar silicon scaling reaching its physical limits, monolithic 3D integration has emerged as a critical solution to ensure continued bit-density growth in next-generation electronics. Amorphous Indium-Gallium-Zinc-Oxide (a-IGZO) is a strong candidate for vertically stacked 3D DRAM in this architecture. While its wide bandgap offers superior off-state leakage characteristics compared to conventional silicon, realizing ultra-low power high-density arrays requires further suppressing the residual thermally excited carriers that degrade the subthreshold swing (SS).

 In this work, we propose a novel graphene/a-IGZO hybrid transistor that exploits the low density of states (DOS) of the graphene Dirac source to achieve steep slope characteristics. Unlike conventional metallic sources with constant DOS, the graphene source functions as a "cold source," where the vanishing DOS near the Dirac point effectively filters out high-energy electrons. This mechanism drastically reduces the probability of carriers crossing the source-channel barrier in the off-state, thereby minimizing leakage current to the theoretical limit.

 Furthermore, we employ a plasma-induced channel engineering technique during the device fabrication process. This selective plasma treatment serves as a versatile approach to modulate the electrical properties of the a-IGZO channel, enabling precise control over key parameters such as threshold voltage (Vth) and carrier mobility. This capability enables the device characteristics to be optimized for specific device applications..

 Our experimental results demonstrate that the synergistic integration of the graphene cold source and the plasma-controlled a-IGZO channel leads to a significant reduction in off-current and a steep subthreshold swing. This study clarifies the carrier filtering mechanism through DOS analysis and suggests that this hybrid architecture presents a highly viable approach for next-generation low-power memory applications.

TiO₂ thin films are widely used as functional oxide materials due to their high chemical stability, wide-bandgap semiconducting nature, and pronounced optical properties. Their characteristics strongly depend on synthesis conditions and defect states, which makes accurate determination of optical parameters essential, taking into account possible structural heterogeneity. ALD enables the fabrication of TiO₂ thin films with high uniformity and precise thickness control; however, even under thermal ALD conditions, defect states related to oxygen vacancies and variations in the titanium valence state may form. The presence of such defects has a significant impact on the optical response of the films and requires the use of appropriate optical characterization techniques.

TiO₂ thin films were deposited by thermal ALD using TTIP and H₂O as precursors, with N₂ as the purge and carrier gas. The depositions were carried out on a SENTECH ALD system.

The optical properties of the TiO₂ films were investigated by spectroscopic ellipsometry using a SENTECH SER850 system over a wide spectral range of 240–1000 nm. The choice of this spectral range is of critical importance, as fundamental interband transitions of TiO₂ dominate in the ultraviolet region, whereas additional energy levels associated with defect states and oxygen vacancies characteristic of the ALD process may appear in the visible regions. Accounting for such a broad spectral range allows not only reliable determination of the optical constants of the films, but also high-precision thickness evaluation, since the accuracy of thickness determination by spectroscopic ellipsometry directly depends on the adequacy of the dielectric function model.

To interpret the experimental ellipsometric data, a parametric model of the complex dielectric function based on a three-oscillator Tauc–Lorentz approach was employed. In contrast to single-oscillator models, this approach accounts for multiple absorption-related energy levels formed in TiO₂ films as a result of defect-related and structural features inherent to ALD synthesis. Each oscillator represents a distinct energetic contribution corresponding to the fundamental absorption edge, sub-bandgap defect states associated with oxygen vacancies, and deep localized levels potentially related to different ionic states of titanium, which collectively determine the optical response of the films.

It is shown that the three-oscillator model provides a stable fitting procedure and good agreement between experimental and calculated data over the entire investigated spectral range, confirming its adequacy for describing the energy structure of TiO₂ thin films. A key advantage of this approach is the possibility of quantitatively evaluating the contribution of individual energy levels to the imaginary part of the dielectric function, thereby enabling assessment of the role of defect states in shaping the optical response.

Quantum dot light-emitting diodes (QLEDs) are central to next-generation display technologies. However, the performance of inorganic hole-injection layers (HILs), particularly nickel oxide (NiO), is often limited by inherently low electrical conductivity and severe interfacial exciton quenching at surface defect sites like NiOOH. In this study, we demonstrate a comprehensive interfacial engineering strategy by integrating Cu-doped NiO (Cu:NiO) with halide-functionalized self-assembled monolayers (SAMs) of (2-(9H-carbazol-9-yl)ethyl) phosphonic acid (2PACz).

Our approach is deeply rooted in density functional theory (DFT) calculations to elucidate the synergy between surface doping and molecular functionalization. DFT results reveal that Cu-doping on the NiO surface introduces impurity states within the bandgap, narrowing it by ~0.259 eV and serving as critical activation sites that enhance SAM adsorption energy from -1.016 eV (pristine NiO) to -2.693 eV (Cu:NiO). Systematic halogenation (Cl, Br, I) of the carbazole core significantly increases the molecular dipole moment from 1.97 D (pristine 2PACz) to approximately 4.5-4.7 D. This strong dipole elevates the Cu:NiO work function to 5.37 eV, effectively reducing the hole-injection barrier to the TFB transport layer to a mere 0.07 eV.

Beyond dipole tuning, we identify that the high polarizability of heavier halogens, particularly iodine, enhances van der Waals (vdW) dispersion forces. This physical interaction facilitates the formation of a dense, stable passivation layer. Ab initio molecular dynamics (AIMD) simulations further confirm the chemical robustness of the P-O-Ni/Cu linkages under thermal stress (400 K) and electrochemical injection conditions. Experimentally, I-2PACz treatment reduced the Ni³⁺/Ni²⁺ ratio from 3.84 to 3.25, confirming the effective passivation of NiOOH traps. Consequently, green QLEDs using I-2PACz-modified Cu:NiO achieved a record-high external quantum efficiency (EQE) of 26.95% (mean 19.53%) and a maximum luminance of 92,735 cd/m², which is 3.5 times higher than the unmodified control. This study underscores that the simultaneous optimization of interface polarizability and molecular anchoring is a scalable pathway toward high-efficiency, stable optoelectronic devices.

Keywords: QLED, Nickel oxide (NiO), Halide-functionalized self-assembled monolayer, Interface engineering, Density functional theory (DFT), Dipole moment, Polarizability, Hole-injection layer

Vanadium dioxide (VO₂) is a prototypical correlated oxide exhibiting a sharp insulator–metal transition (IMT) near 68 °C, enabling diverse applications such as smart windows and optoelectronic device through controlled tuning of its IMT characteristics. Precise control of IMT behavior in VO₂ films requires a systematic understanding of their surface morphology. In particular, elucidating the thermal evolution of surface cracks is critical for strain engineering, film stability, and IMT modulation in device applications. We systematically examine the role of surface morphology in the structural and electronic properties of epitaxial VO₂ films grown on TiO₂ substrates. AFM image analysis clearly demonstrates a growth-temperature-driven morphological evolution, from a continuous, crack-free film at low growth temperatures, to crack formation at intermediate temperatures, and finally to an island-like structure at high growth temperature. X-ray diffraction and reciprocal space mapping demonstrate that crack formation facilitates partial relaxation of out-of-plane lattice parameter. Temperature-dependent electrical transport measurements show that cracked films exhibit increased resistivity, higher IMT temperature, and a pronounced broadening of the transition region. These behaviors originate from the stabilization of strain-relaxed insulating domains. This study offers key guidelines for strain and morphology engineering to optimize VO₂-based electronic and optoelectronic devices.

Defect engineering is widely employed to enhance the functional performance of oxide-based thin films, but their impact on mechanical reliability in low-dimensional nanostructured systems remains unexplored. In this work, we systematically investigate the role of oxygen vacancies and nanorod architecture in governing the depth-dependent mechanical response of vertically aligned α-MoO₃ nanorod thin film grown on SiO₂/Si substrates by Pulsed Laser Deposition. By varying the oxygen partial pressure from 2.5 to 15 Pa, nanorod arrays with thicknesses ranging from 325 nm to 1600 nm were obtained, showing controlled tuning of nanorod morphology, oxygen vacancy concentration, and packing-density gradients along the film thickness. Correlative structural and defect characterization confirms the systematic evolution of defect density and nanorod architecture with growth conditions, utilizing lateral and cross-sectional FESEM, AFM, Raman spectroscopy, EPR, and XPS. Depth-resolved static, dynamic, and creep nanoindentation measurements reveal that oxygen vacancies are the dominant factor promoting time-dependent deformation and mechanical softening, while increasing nanorod packing density with depth leads to apparent hardening and reduced substrate influence in thicker films. Photoelectrochemical measurements further indicate that the same defect architectures governing mechanical reliability also influence functional response, highlighting an intrinsic performance and stability trade-off in defect-engineered oxide nanorod thin films. These results give an understanding of defect- and architecture-controlled mechanical reliability in low-dimensional oxide thin films and offer design guidelines for robust multifunctional oxide systems.

Molecular beam epitaxy (MBE) is the core technique for producing sharp and well‑controlled interfaces in semiconductor research, but achieving reproducible growth requires extensive calibration. Here, we explore an alternative route for defining metal–oxide interfaces by starting from chemically deposited precursors, offering a simpler and potentially scalable approach that could complement or partially replace MBE in selected applications [1,2].

In this context, our study examines the chemical deposition and thermal conversion of FeOOH and NiOOH layers on STO(001) and STO(111). These hydroxides undergo controlled reduction and structural rearrangement during annealing, yielding metallic Fe and Ni that align with the STO substrate. Such substrate‑guided transformations are important for catalysis, spintronics, and nanopatterned metallic architectures, where metal–substrate orientation strongly shapes functional properties.

Thin films were synthesized using chemical deposition methods optimized for uniform coverage and controlled nucleation. Their structural evolution was examined before and after annealing. Heating at 1000 °C for 4 h led to a substantial conversion of FeOOH and NiOOH into their metallic phases.

Low‑Energy Electron Diffraction (LEED) provided direct evidence for epitaxy: after annealing, the cleaned surfaces showed sharp diffraction spots, indicating that Fe and Ni adopt epitaxial orientations on both STO(001) and STO(111). This confirms that thermal conversion drives substrate‑guided ordering. X‑ray photoelectron spectroscopy (XPS) further supported this, showing a strong reduction of hydroxide components together with the growth of metallic Fe and Ni peaks.

The epitaxial stabilization of Fe and Ni on STO is technologically significant. These metals are central to magnetic devices, catalytic systems, and nanoscale patterning. Controlling their epitaxial growth enables interfaces with tailored magnetic anisotropy, improved catalytic activity, and optimized electron transport, while also providing a platform to study how reduced dimensionality, strain, and symmetry breaking affect spin behavior and scattering.

Using low‑cost precursors followed by thermal conversion offers a scalable route to high‑quality epitaxial metallic films without complex vacuum techniques. The method supports large‑area processing and could accelerate the development of spintronic components, catalytic layers with engineered active sites, and metallic templates for nanopatterning. Its generality also makes it applicable to other material families, including those with strong spin–orbit coupling or unconventional interfacial behavior.References

1.Nunn, William, et al. "Novel synthesis approach for “stubborn” metals and metal oxides." Proceedings of the National Academy of Sciences 118.32 (2021): e2105713118

2.Rouviller, Axel, et al. "Growth and characterization of strontium vanadate films deposited by reactive magnetron sputtering." APL Materials 13.6 (2025)

Beta-gallium oxide (β-Ga₂O₃) is a key material attracting significant attention in next-generation power electronics and ultraviolet (UV) photodetector applications due to its wide bandgap characteristics. In this work, we demonstrated lateral p-NiO / n-Ga₂O₃ heterojunction diodes (HJDs) featuring an interdigitated finger geometry. The devices were fabricated using β-Ga₂O₃ epilayers grown on sapphire substrates and NiO thin films deposited via RF sputtering.

First, mesa structures with an active area of 500×500 μm² were defined using an inductively coupled plasma reactive ion etching process. Subsequently, a Ti/TiN stack was sputtered on the cathode fingers, followed by thermal annealing at 500 °C to form an ohmic contact. For the anode fingers, a p-type NiO thin film was selectively sputtered by controlling the Ar/O₂ partial pressure, after which a Ni/TiN electrode stack was deposited.

The fabricated HJDs exhibited a turn-on voltage below 5 V and an on/off current ratio exceeding 10³, attributed to the suppressed reverse leakage current. In particular, the p-NiO layer effectively suppressed electric field crowding at the electrode edges, resulting in improved breakdown voltage characteristics. Furthermore, optical characterization confirmed solar-blind UV detection capabilities. Under 254 nm UV illumination, the HJD exhibited a photocurrent response with a photo-to-dark current ratio exceeding 10², while showing negligible response in the visible light region.

These results suggest that the low-cost lateral p-NiO / n-Ga₂O₃ heterojunction diode is a promising candidate for high-power electronics and reliable UV photodetectors.

Cation charges and crystal field splitting effects play key role in determining the crystal structure and cation distribution in spinels with the general formula AB₂O₄. The arrangement of divalent, trivalent and/or tetravalent cations between tetrahedral (Td) and octahedral (Oh) sites may range from fully ordered to highly disordered configurations. In normal spinels, divalent cations occupy Td-sites while higher-valence cations are octahedrally coordinated. In inverse spinels, higher-valence cations occupy the Td-sites and the Oh-sites are shared between divalent and higher-valence cations. Many spinels display partial inversion and cation disorder, resulting in intermediate configurations. In addition, Jahn-Teller interactions may induce a symmetry lowering from cubic to the tetragonal spinel [1].

These effects are well-known in bulk (Mn,Co)₃O₄ system. The end-members Mn₃O₄ and Co₃O₄, crystallize as a normal tetragonal and a normal cubic spinel, respectively. In the limited number of reports on thin films, intermediate compositions seem to exhibit various cations ordering and crystal structures but several compositions remain unexplored (especially in the Mn-rich part). Moreover, contradictions persist in the literature regarding the formal oxidation states of manganese near the MnCo₂O₄ composition [2]. To achieve a detailed understanding of the chemical and physical mechanisms governing electronic transport and magnetism in Co_xMn_3-xO₄, it is essential to investigate model oxides with well-controlled composition and crystallinity.

In this work, we report the epitaxial growth of Co_xMn_3-xO₄ thin films (6-20 nm), with a wide range of cationic stoichiometry, from Mn₃O₄ to Co₃O₄ compositions, by oxygen-assisted molecular beam epitaxy on different substrates (α-Al₂O₃ (0001) and MgAl₂O₄ (001)). According to the cationic compositions, the epitaxial relationships between the substrate and the oxide layer are analyzed in real time by using reflection high energy electron diffraction. In situ and ex situ X-ray photoemission spectroscopy analyses obtained on the Co 2p, Mn 2p and 3s core levels put on view different oxidation states for Co (Co²⁺, Co³⁺) and Mn (Mn²⁺, Mn³⁺ or Mn⁴⁺) depending of the Co/Mn ratio. Finally, X-ray diffraction allow to probe in detail the crystalline structure of the synthetized oxide (in plane/out of plane lattice parameter), lattice mismatch with the stoichiometry. The strains imposed by the α-Al₂O₃ substrate led to a cubic structure independently of the stoichiometry. In contrast, previous studies report a tetragonal distortion for Mn-rich compositions, occurring at x ≤ 1.78 in bulk [3] and extending to approximately x ≤ 2.2 in thin films grown on MgAl₂O₄ (001) substrates [2].

[1] K.E. Sickafus et al. J. Am. Ceram. Soc. 82 (1999) 3279

[2] M. D. Blanchet et al. : J. Phys.: Condens. Matter 33 (2021) 124002 ; J. Vac. Sci. Tech. A 41 (2023) 052703

[3] H. Bordeneuve et al. Solid State Sciences 12 (2010) 379

Chemical bath deposition is a widely used method for the growth of ZnO nanowires, yet it typically relies on hexamethylenetetramine (HMTA), which can release formaldehyde and raises health and environmental concerns. In this work, we clarify the role of HMTA in ZnO nanowire growth and assess the possibility of its removal from the process. Synchrotron-based X-ray near-edge absorption spectroscopy demonstrates that HMTA does not form complexes with Zn(II) species over a wide pH range. Instead, in agreement with thermodynamic calculations, [Zn(H₂O)₆]²⁺ and Zn(NH₃)₄²⁺ are identified as the dominant Zn(II) species under low- and high-pH conditions, respectively. While HMTA is required to obtain high–aspect ratio ZnO nanowires at low pH, it can be fully substituted by ammonia at high pH, leading to ZnO nanowires with excellent structural and optical quality. These results demonstrate that HMTA-free chemical bath deposition at high pH is feasible, representing a significant step toward greener synthesis routes for ZnO nanowires.

Owing to the multilevel storage and integrated sensing-storage capabilities enabled by the dual regulation of optical and electrical signals, optoelectronic memory devices have garnered growing attention. Weak light and low voltage are indispensable for achieving low-power consumption memory and detectors with high performance.

A novel optoelectronic memory was constructed based on a new architecture with amorphous Ga₂O₃ (a-Ga₂O₃) as photosensitive dielectric (PSD). Data writing and erasing are realized by using an optical pulse to switch on the PSD with low programming voltage and optical power density. Meanwhile, the device may be extended to other transistors for specific applications [1].

The PSD (Ga₂O₃)-based optoelectronic memory was found facilitating the fabrication process of solar-blind UV image arrays. A crossbar array with the above-mentioned structure as the pixel can complete clear imaging without extra switching elements. It manifests both remarkably sensitive weak-light detection and excellent imaging-memory-reading-refresh-reimaging cycle capabilities [2].

The interface hole traps in Ga₂O₃/Al₂O₃ dual dielectric layer is also proposed to increase the light absorption length and decrease dielectric capacitance, hence contributing to excellent weak-light detection and storage capability, even at a low output power of 0.8 µW/cm² and a short irradiation time of 20 ms.

[1] Rui Zhu et al, Nat. Commun. 14, 5396 (2023) (Feature Article)

[2] Rui Zhu et al, ACS Photonics 12, 555 (2025)

Wide-bandgap oxides (WBOs) provide an attractive platform for advanced optoelectronic applications due to their large bandgaps enabling UV operation, high transparency in the visible range, and excellent thermal stability. In this work, Ag inverted-nanocone (INC) arrays were fabricated via epoxy-assisted template stripping from Si nanocone masters and subsequently integrated with RF-sputtered ZnO thin films to form ZnO/Ag-INC hybrid systems. ZnO, as a representative WBO, offers a UV-range bandgap, robust thermal and chemical stability, and compatibility with low-temperature processing. The Ag INC arrays play a dual role as highly conductive electrodes and optical nanocavities, enabling efficient confinement of incident light. Finite-difference time-domain simulations revealed strongly concentrated electromagnetic fields within the Ag-INC cavities. The structural integrity and optical characteristics of the Ag-INC arrays were studied by scanning electron microscopy and reflectance measurements. Notably, the ZnO/Ag-INC hybrid systems exhibited broad reflectance dips in the short-wavelength visible region. Wavelength-dependent photocurrent measurements further elucidated the spectral dependence of photocarrier generation and collection in the hybrid systems under illumination. The combined optical and electrical investigations demonstrate that Ag-INC arrays  effectively enhance light-matter interactions in WBOs, highlighting their promise for UV–visible photodetector applications.

The purpose of this study is to optimize β-Ga₂O₃ inverters for high-efficiency power conversion applications. The research focuses on achieving stable enhancement-mode (E-mode) operation by modulating the gate-recess depth and selecting gate dielectrics among Aluminum Oxide (Al₂O₃), and Hafnium Oxide (HFO₂). The simulation incorporates several physical phenomena to reflect device behavior. These include Shockley-Read-Hall recombination, Fermi-Dirac statistics, and lattice temperature effects. Material properties of β-Ga₂O₃ are addressed through incomplete ionization of dopants. Carrier transport is described using Klaassen's mobility model and field-dependent mobility to analyze scattering and velocity saturation. For HfO₂, its ferroelectric properties are included to evaluate the internal polarization effects on the threshold voltage and channel control. The performance is evaluated by comparing the transient response and output voltage characteristics over time. The expected results indicate that the use of ferroelectric HfO₂ facilitates E-mode operation with a reduced gate-recess depth compared to Al₂O₃. By comparing the time-domain output results, the study identifies the specific combination of dielectric material and recess depth that produces the highest switching efficiency. The final results provide the structural and material parameters for β-Ga₂O₃ logic circuits based on switching speed and current density.

Oxide semiconductors have emerged as strong contenders for next-generation electronic applications such as displays, DRAM, and CMOS-based devices, owing to their advantages including high carrier mobility, low off-state leakage, and cost-efficient processing. Nevertheless, the realization of high-performance oxide devices conventionally depends on high-temperature post-annealing steps, which impose substantial thermal budgets and severely restrict their applicability to flexible electronics and advanced architectures such as DRAM and three-dimensional integrated circuits.

To overcome this thermal limitation, we introduce an innovative in-cycle argon (Ar) plasma treatment integrated directly into the atomic layer deposition (ALD) process of IGZO. The ion bombardment induced by the Ar plasma generates localized and instantaneous surface heating, enabling a form of “cycle annealing” that is confined solely to the channel layer. As a result, the necessity for high-temperature post-annealing is eliminated, significantly reducing both the overall thermal budget and process complexity. This localized treatment serves as an effective, high-performance alternative to conventional annealing processes used in IGZO fabrication.

The in-situ Ar plasma treatment actively modulates oxygen vacancy concentrations within the IGZO film during deposition, a role traditionally fulfilled by ex-situ thermal annealing, while simultaneously enhancing the electrical performance of the resulting TFTs. Importantly, this approach achieves high film quality without exposing the entire substrate to elevated temperatures. Experimental validation demonstrates that TFTs fabricated using the plasma-assisted ALD technique exhibit excellent performance, including on/off current ratios exceeding 10⁶ and field-effect mobilities greater than 50 cm²/V·s. In addition, devices processed with this localized annealing method show outstanding operational stability under both positive and negative bias stress conditions.

In summary, the proposed in-cycle Ar plasma treatment represents a simple yet highly effective localized annealing strategy for oxide semiconductor channel layers. This method enables the fabrication of high-performance oxide TFTs under low-temperature processing conditions and offers significant advantages for advanced integration schemes, particularly DRAM technologies, where minimizing thermal impact on underlying structures is critically important.

The realization of functional heterostructures based on 2D transition metal dichalcogenides (TMDs) has attracted growing research interest for next-generation electronic and optoelectronic devices. Owing to the atomic-scale thickness and tunable electronic properties, TMDs provide a versatile platform for heterointerface engineering; however, the extremely small physical volume of TMDs makes conventional doping strategies either ineffective or detrimental. To address this challenge, integration with oxide thin films can provide a promising approach to modulate the electronic and interfacial properties of TMDs. Among various oxides, transparent conducting oxides (TCOs) are particularly attractive due to their high electrical conductivity, optical transparency, and intrinsic thermal robustness up to several hundred degrees Celcius. In this work, large-area mono- and few-layer MoS2 flakes were prepared on SiO2/Si substrates using a metal-assisted spalling technique. Solution-processed ZnO thin films, representative of the TCO family, were prepared on top of MoS2/SiO2/Si and subsequently annealed in Ar ambient at different temperatures. Raman and photoluminescence spectra of MoS2 were compared before and after annealing to investigate strain and electrical modifications induced by ZnO. The optical characterizations confirmed the feasibility of forming thermally stable ZnO/MoS2 heterointerfaces. These results demonstrate that solution-processed TCOs provide a route for engineering TMD-based heterostructures, offering new opportunities for advanced optoelectronic devices.

​​​​​​Since the pioneering work by Nomura et al. on transparent and flexible thin‑film transistors based on oxide materials, research on flexible oxide devices has progressed rapidly. Most studies in this field employ plastic films as flexible substrates, necessitating low‑temperature processing due to their limited thermal resistance. Consequently, many efforts have focused on amorphous oxide materials, which can be deposited at room temperature while offering properties such as high carrier mobility. This has enabled significant advances in the application of amorphous oxide semiconductors to various flexible devices. In contrast, conventional applications of oxide materials often rely on their ability to integrate diverse electronic functionalities, which requires epitaxial thin films because of their strong anisotropy. However, the high processing temperatures needed for epitaxial growth have thus far prevented their use with flexible plastic substrates. This highlights the need for novel processes that can extend traditional oxide‑based functionalities to flexible device platforms. In this study, we propose a transfer process that enables epitaxially grown functional oxide thin films, initially deposited on appropriate substrates, to be transferred onto flexible plactic films. The feasibility of this approach was demonstrated using a perovskite‑type ferroelectric thin film transferred onto a plastic sheet. The results and their implications for future flexible device applications are discussed. 

The authors gratefully acknowledge financial support from the JSPS KAKENHI Grant-in Aid for Scientific Research (C) (grant no 23K04608) and the Cooperative Research Program of the Network Joint Research Center for Materials and Devices (grant no 20254024).  

In this study, we analyzed the defect transition phenomenon induced by self-heating stress in amorphous IGZO thin films depending on the indium composition ratio. Self-aligned top-gate coplanar IGZO TFTs were fabricated using high and low indium content thin films under the same process conditions, and the defect generation pathways were identified by changes in transfer characteristics under self-heating stress (SHS). Experimental results showed that In-poor films exhibited a monotonically positive shift in threshold voltage (V_TH) with increasing stress time, but subthreshold swing (SS) and field-effect mobility (μ_FE) do not show significant changes. In contrast, In-rich films exhibited a non-monotonic change in V_TH under high-field conditions, accompanied by increases in SS and μ_FE, suggesting a reduction in the effective channel length due to enhanced drain induced barrier lowering. From the experimental results, the abnormal behavior of the In-rich IGZO TFT under SHS conditions is possibly attributed to the diffusion of hydrogen atoms from the n⁺ IGZO source/drain extension region to the IGZO channel region. The higher oxygen vacancy (V_O) concentration in indium-rich IGZO provides a pathway for hydrogen dopants to readily diffuse into the IGZO. The diffused hydrogen initially acts as a shallow donor, but transitions to a deep acceptor like state over time. These results indicate that the Indium content in the oxide channel layer significantly affects electrical stability under SHS, highlighting the critical role of indium-dependent hydrogen-mediated defect transitions in reliability.

Ga₂O₃ is an ultra‑wide‑bandgap semiconductor with properties attractive for optoelectronic and power‑electronic applications. As in most metal oxides, achieving robust p‑type conductivity is still challenging; by contrast, n‑type doping is expected to afford controllable carrier densities. In this work, we study the thermodynamic equilibrium of point defects and charge carriers in Sn-doped Ga₂O₃ to achieve controllable n-type conductivity.  Specifically, we investigated the Ga₂O₃ crystal–vapor of one component  to optimize the growth/thermal processing processes. For the thermodynamic analysis, we employed the Kröger-Vink approach of quasi-chemical equations. We assumed that the primary compensating defect is the gallium vacancy. While Sn atoms are expected to occupy gallium lattice sites, we also took into account the possible incorporation of Sn atoms into interstitial sites. This may significantly influence the conductivity, as Sn in an interstitial position may exhibit amphoteric behavior, acting as either a donor or an acceptor depending on the local thermodynamic equilibrium (Fermi level). In our calculations, we also accounted for the formation of defect associates, which may further influence conductivity by creating shallower donor levels or neutralizing compensating centers. Calculations were performed across a range of partial pressures, temperatures, and Sn concentrations within the crystal. Consequently, we developed a triangular defect phase diagram to identify the optimal parameter space for controlled doping.

Metal-oxide-based semiconductors such as indium zinc oxide (IZO) and indium gallium zinc oxide (IGZO) have been widely adopted in thin-film transistors (TFTs), particularly for display applications. However, the high density of deep defect states commonly associated with oxygen deficiency in indium-based oxides leads to device instability, especially under prolonged electrical stress. While gallium incorporation has been shown to suppress oxygen vacancy–related defects, it also introduces increased photosensitivity to visible light, which is undesirable for many large-area electronic applications.

To address these challenges, this work investigates solution-processed silicon-doped indium oxide (In₂O₃:Si) as an alternative n-type oxide semiconductor, focusing on the role of silicon incorporation in defect suppression and device stability. In₂O₃:Si thin films were deposited by spray coating in ambient air at a substrate temperature of 360 ^oC from precursor solutions based on indium salts and silicon-containing dopants. The structural, optical, and morphological properties of the films were systematically characterised using UV–Vis absorption spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and atomic force microscopy (AFM).

Thin-film transistors employing solution-processed Y₂O₃ gate dielectrics, In₂O₃:Si semiconductor channels, and gold source/drain contacts were fabricated and electrically characterised as a function of silicon content. For optimised doping concentrations, the resulting TFTs exhibited high electron mobilities, low operating voltages, and well-defined transfer characteristics. Importantly, under prolonged negative and positive bias stress for up to 10,000 s, the devices demonstrated excellent electrical stability, with threshold voltage shifts slightly and no significant degradation in charge transport. The electron mobility showed only a minor reduction, indicating effective suppression of electrically active defect states.

These results demonstrate that silicon doping is an effective strategy for improving the stability of solution-processed In₂O₃ TFTs without introducing the photosensitivity issues associated with gallium-containing oxides, highlighting In₂O₃:Si as a promising semiconductor for stable, large-area oxide electronics.

High-k metal-oxide gate dielectrics are key enablers for low-power CMOS and thin-film transistor (TFT) technologies, offering a scalable alternative to conventional SiO₂. While widely studied oxides such as HfO₂, ZrO₂, and TiO₂ provide high dielectric constants, practical implementation is often limited by trade-offs between bandgap, leakage current, and processing compatibility. Composite dielectric systems provide an effective route to balancing these competing requirements.

In this work, we report on the solution processing and integration of two composite gate dielectrics - hafnium titanate (Hf_1-xTi_xO_y) and zirconium silicate (Zr_1-xSi_xO_y) - for use in ZnO-based TFTs. The dielectric films were deposited at moderate temperatures in ambient air and systematically characterised in terms of their structural, optical, and electrical properties. Both materials form smooth, amorphous films with wide bandgaps and low leakage behaviour, making them well suited for gate dielectric applications.

When incorporated into ZnO TFT architectures, both composite dielectrics enable low-voltage operation, high current modulation, minimal hysteresis, and enhanced charge-transport performance. The results demonstrate that solution-processed composite oxides can deliver a favourable balance between dielectric constant, leakage suppression, and interface quality.

Overall, this work highlights composite high-k dielectrics as promising candidates for low-temperature, solution-processed oxide electronics and provides a viable pathway toward scalable, CMOS-compatible TFT technologies.

A wide range of binary metal oxides, including Al₂O₃, Y₂O₃, ZrO₂, HfO₂, TiO₂, and Nb₂O₅, have been demonstrated as promising gate dielectrics for thin-film transistors (TFTs), offering clear advantages over conventional SiO₂. While high dielectric constants are essential for low-voltage operation, suitable gate dielectrics must also provide sufficiently large band offsets to suppress leakage currents, particularly when wide-bandgap oxide semiconductors are employed as channel materials. Achieving both high permittivity and wide bandgap within a single binary oxide, however, remains challenging.

An effective strategy to overcome this limitation is the use of composite or ternary oxide dielectrics, which enable independent tuning of dielectric constant, bandgap, and leakage characteristics. Several ternary systems have already demonstrated the potential of this approach by combining wide-bandgap and high-permittivity oxides into a single material platform.

In this work, we report on the deposition, characterisation, and device integration of Nb_1-xAl_xO_y composite gate dielectrics, systematically investigated as a function of the Nb-to-Al atomic ratio. The films were deposited by spray coating in ambient air at moderate substrate temperatures below 400 ^oC and were characterised using UV–Vis spectroscopy, FTIR, impedance spectroscopy, atomic force microscopy, X-ray diffraction, and field-effect measurements. The resulting Nb1-xAlxOy layers are smooth and uniform, exhibiting tunable dielectric constants and optical bandgaps depending on composition.

When integrated into TFTs employing ZnO semiconductor channels, Nb_1-xAl_xO_y gate dielectrics enable low leakage currents, steep subthreshold behaviour, high on/off current modulation, and electron mobilities exceeding 20 cm² V^-1 s^-1. These results demonstrate that Nb–Al–O composite oxides provide an effective balance between dielectric constant and bandgap, making them attractive gate dielectrics for low-temperature, solution-processed oxide electronics.

Indium tin oxide (ITO) is an n-type semiconductor with unique combination of high electrical conductivity and optical transparency in the visible spectrum, making it essential for optoelectronic technology [1]. A crucial parameter of ITO is a wide, tunable direct bandgap, typically in the range from 3.5 to 4.3 eV, strongly dependent on preparation methods and post-deposition treatments.

The aim of this work is to perform characterization of the direct and indirect bandgap changes of commercial ITO thin films after annealing at temperatures from 200 to 400 °C, in oxidizing, reducing and neutral gas atmospheres (O₂, CO2, air, N₂, N₂/H₂ mixture, and vacuum). The ITO films were deposited on glass substrates and had a thickness of 175 nm.

Two different methods were applied to determine the direct/indirect energy bandgaps of ITO, namely (i) optical method based on recording  transmission/reflection spectra in the ultraviolet - visible range, and then application of the modified Tauc approach [2], and (ii) photoelectric method, i.e. surface photovoltage spectroscopy (SPS), based on the registration of the contact potential difference changes under ultraviolet illumination, using a Kelvin probe. In the SPS experiment, the ITO samples were excited by a xenon lamp equipped with band-pass filters for different wavelengths from 254 to 350 nm, allowing controlled photoexcitation in the vicinity of the fundamental absorption edge of ITO and thus determining the band gap value [3].

The direct band gaps obtained from the optical method were found to lie in the range of 3.9 – 4.1 eV, depending on annealing atmosphere and temperature (markedly reduced after annealing in O2 and slightly increased after annealing in N₂/H₂ mixture due to O-related vacancy reduction/generation, respectively). Systematic differences between the band gap values obtained using optical and SPS methods were observed, indicating the enhanced sensitivity of SPS to surface states, defect-related energy levels, and band bending effects, which become increasingly relevant in nanoscale oxide films. Overall, the results demonstrated that SPS provides valuable complementary insight into the electronic properties of thermally processed ITO layers beyond that accessible through conventional optical characterization alone.

The conference fee is covered by EU funds FSD - 10.25 Development of higher education focused on the needs of the green economy European Funds for Silesia 2021-2027: The modern methods of the monitoring of the level and isotopic composition of atmospheric CO2 (project no.FESL.10.25-IZ.01-06C9/23-00).

[1] A. Kaźmierczak-Bałata et al. Materials 17(2024)4606
[2] A. Dolgonos et al. J. Solid State Chem. 240(2016)43
[2] B. Adamowicz, et al. Surf. Sci. 94(1991)247

Understanding how nanoscale structural variations influence the optical and electronic behaviour of semiconductor materials is critical for the development of next-generation photonic and electronic technologies. In this work, we apply four-dimensional scanning transmission electron microscopy (4D-STEM) as an advanced metrology approach to probe structure–property relationships in transparent conductive oxide (TCO) materials. This work is timely given the growing push for indium-free (In-free) TCOs in optoelectronic applications.

Our study focuses on aluminium-doped zinc oxide (AZO) superlattices fabricated by molecular vapour deposition (MVD). AZO is an emerging In-free TCO with relevance to displays, photovoltaics, and integrated photonics due to its tunable carrier concentration, optical transparency, and compatibility with CMOS processing. The interplay between Al doping, phase stability, and crystallographic ordering strongly governs these functional properties, motivating high-spatial-resolution structural characterisation.

Using precession-assisted 4D-STEM on a TESCAN TENSOR system, we can combine nanobeam electron diffraction with simultaneous elemental analysis using energy dispersive X-ray (EDX) analysis to obtain high-resolution phase, grain and orientation maps of focused ion beam (FIB) cross-sectional AZO films across Al doping concentrations ranging from 1 to 11 at.%. At low doping levels (1–2 at.%), the films exhibit predominantly wurtzite ZnO with a columnar structure, layered compositional order near the substrate, and a small number of large grains (10–15 nm) alongside many smaller grains. This layered order becomes progressively diffuse at higher doping levels (7 at.%) and is essentially absent at 11 at.%, where the film is largely amorphous with only small crystallites embedded within the matrix. Crystallite size decreases with increasing doping.

These results demonstrate the sensitivity of AZO’s structural architecture to doping and highlight how nanoscale structural changes can be correlated with functional properties critical for photonic and electronic device performance. Our findings establish 4D-STEM as a powerful quantitative metrology technique for semiconductor materials design and process optimisation in emerging In-free TCO technologies.

In transparent/oxide TFT platforms for display industry, high performance n-channel TFTs (e.g. IGZO) are well established. However, the absence of p-channel TFT platforms with comparable mobility, long-term stability, and reproducibility continues to limit CMOS development. TeO₂ is a wide band gap oxide that has emerged as a promising p-channel TFT candidate, following reports of high mobility p-type channel operation in two-dimensional β-TeO₂^[1]. Nevertheless, we still do not fully understand the origin of the unusually high mobility that has been reported, and concerns remain regarding reproducibility and the possible influence of impurities^[2]. Addressing these issues demands a deep understanding of the material itself, making it crucial to rigorously identify and interpret its quantum-mechanical properties. This is because most device characteristics ultimately originate from quantum-mechanical bonding mechanism. For example, hole mobility is governed by the valence-band-edge dispersion, which is controlled by the hybridization and overlap of atomic orbitals.

In TeO₂, Te forms four Te-O bonds while retaining a 5s² lone pair. This coordination environment cannot be explained by the conventional octet rule. In this study, using density functional theory (DFT) calculations and electronic structure analysis, we effectively explain the unusual bonding nature of crystalline (α, β, γ, and rutile) and amorphous TeO₂ materials by a multi-center interaction mechanism based on the donor-acceptor theory. The chemical bonding network was investigated by various quantum chemical methods, thereby providing deeper insight into the bonding mechanism. In particular, natural bond orbital (NBO) analysis offers a chemically intuitive perspective by decomposing the electronic structure into Lewis and non-Lewis components and by revealing hybridization characteristics and donor-acceptor stabilization energies. We extended our study to relevant variants, such as oxygen-poor TeO_2-x and doped TeO₂. By analyzing how changes in the bonding network translate into distinct quantum-mechanical signatures in a detailed and systematic manner, this study will provide the new insights toward developing high performance p-type semiconductors based on tellurium oxide system.

1.       Zavabeti, A., et al., High-mobility p-type semiconducting two-dimensional β-TeO2. Nature Electronics, 2021. 4(4): p. 277-283.

2.       Xiao, Z., et al., Is p-Type Doping in TeO2 Feasible? Chinese Physics Letters, 2025. 42(1): p. 016103.

Optical waveguides can use the properties of materials, among which the refractive index, to efficiently transport information with a minimum loss. Silica-based waveguides, such as the ones used in optical fiber, are cheap and efficient as long as the wavelength is not too far from the visible light. However, for mid-infrared or UV light, or higher powers, this method is limited as the wavelength and power of the source influence the phenomenon. To overcome this, specific materials, with adapted transmittances and refractive indexes, are needed.

For such applications, the good non-linear optical properties of TeO₂-based bulk glasses and ceramics^[i] can be interesting. However, they are usually prepared at high temperature from powder. This process is less convenient when the goal is to infiltrate small cavities and complex geometries. Moreover, infiltration of melted samples at high temperature is rapidly increasing the degradation of the equipment. Our aim was thus to lower the temperature of the inorganic conversion as compared to the melting of oxides. A liquid-based synthesis, for two compositions (pure TeO₂ and Zn-doped TeO₂), was developed from Te and Zn precursors. Indeed, a Pechini synthesis was tested successfully on tellurium oxide materials in order to obtain crystalline phases^[ii].

Our goal in this work was to understand the formation of Te- and Te-Zn- based materials using a modified Pechini synthesis, in order to succeed in the deposition of amorphous thin films at the internal wall of a hollow core fiber. For this, the reactions occurring during the synthesis were studied by in-situ Raman spectroscopy to follow the formation of different organometallic species in the liquid state. Then the temperature induced transformations were analyzed for both systems from drying to 650°C and the formation of the different intermediate phases was reported. The influence of the modification of the rheological properties on the formation of phases was identified, as well as the capacity to obtain a film suitable for a use as optical waveguides. Finally, the optical properties of the formed materials were measured to ensure that this synthesis method does not decrease the good performances of the original bulk TeO₂-based glasses.

[i] R.A.F. El-Mallaway, Tellurite Glasses Handbook: Properties and Data, CRC, Boca Raton, FL (2002).

[ii] MD. Bataliotti et al., J Sol-Gel Sci Technol., 103 (2022) 378–385.

 We show that short-channel self-aligned top-gate (SA-TG) coplanar indium–gallium–zinc oxide (IGZO) thin-film transistors (TFTs), operated with a negative back-gate bias, provide more desirable characteristics for use as driving transistors in organic light-emitting diode (OLED) pixels than long-channel devices. In particular, the short-channel IGZO TFTs (channel length L = 3 μm) biased at V_BG = −3.5 V exhibit a larger subthreshold swing (SS = 0.21 V/dec) than their longer-channel counterparts (L = 5 μm, SS = 0.16 V/dec), while maintaining a comparable threshold voltage (V_TH ≈ 0.7–0.8 V). Such a larger SS is advantageous for pixel-driving operation because it enables finer current modulation over a practical gate-voltage range, thereby improving grayscale controllability, especially at low gray levels where visual sensitivity is high.

 Beyond the transfer characteristics, the negatively back-gate-biased short-channel SA-TG coplanar IGZO TFTs also demonstrate markedly improved electrical stability relative to the long-channel devices under both positive gate-bias stress and hot-carrier stress conditions. The enhanced stability is consistent with more effective defect passivation in the IGZO channel associated with hydrogen supplied from the n⁺-IGZO source/drain extension regions in the SA-TG coplanar structure, which becomes more influential as the channel length is reduced. Overall, these results indicate that combining short-channel SA-TG coplanar IGZO TFTs with negative back-gate biasing offers a simple and practical route to achieve large-SS operation together with robust reliability, thereby broadening the design space and applicability of IGZO TFTs for OLED display backplanes.

Interfacial control of magnetic anisotropy is central to realizing ultra-low-power spintronic memory technologies. In voltage-controlled magnetoresistive random-access memory (VC-MRAM), the simultaneous achievement of robust perpendicular magnetic anisotropy (PMA) and a large voltage-controlled magnetic anisotropy (VCMA) coefficient remains a major challenge due to competing interfacial mechanisms. In this work, we demonstrate a systematic strategy to simultaneously enhance PMA and VCMA in CoFeB/MgO heterostructures through controlled insertion of an ultrathin iridium (Ir) layer and precise optimization of post-deposition annealing conditions. By varying the CoFeB and Ir thicknesses and annealing temperature within an industry-relevant processing window (290–335 °C), we identify an optimal regime at 310 °C where interfacial crystallinity and spin–orbit coupling are favorably balanced. The optimized CoFeB(x)/Ir(t_Ir)/MgO stacks exhibit strong perpendicular magnetic anisotropy alongside a maximum VCMA coefficient of −66.1 fJ V⁻¹ m⁻¹, while maintaining stable magnetic properties suitable for device operation. Hall-effect measurements confirm efficient voltage-induced modulation of magnetic anisotropy, and first-principles calculations reveal that controlled Ir positioning near the metal–oxide interface is critical for maximizing VCMA while suppressing deleterious interdiffusion effects. These results establish interfacial spin–orbit engineering as an effective pathway for enhancing energy efficiency in voltage-driven spintronic memory devices, providing practical design guidelines for next-generation low-power MRAM technologies.

Interfacial control of magnetic anisotropy is central to realizing ultra-low-power spintronic memory technologies. In voltage-controlled magnetoresistive random-access memory (VC-MRAM), the simultaneous achievement of robust perpendicular magnetic anisotropy (PMA) and a large voltage-controlled magnetic anisotropy (VCMA) coefficient remains a major challenge due to competing interfacial mechanisms. In this work, we demonstrate a systematic strategy to simultaneously enhance PMA and VCMA in CoFeB/MgO heterostructures through controlled insertion of an ultrathin iridium (Ir) layer and precise optimization of post-deposition annealing conditions. By varying the CoFeB and Ir thicknesses and annealing temperature within an industry-relevant processing window (290–335 °C), we identify an optimal regime at 310 °C where interfacial crystallinity and spin–orbit coupling are favorably balanced. The optimized CoFeB(x)/Ir(tIr)/MgO stacks exhibit strong perpendicular magnetic anisotropy alongside a maximum VCMA coefficient of −66.1 fJ V⁻¹ m⁻¹, while maintaining stable magnetic properties suitable for device operation. Hall-effect measurements confirm efficient voltage-induced modulation of magnetic anisotropy, and first-principles calculations reveal that controlled Ir positioning near the metal–oxide interface is critical for maximizing VCMA while suppressing deleterious interdiffusion effects. These results establish interfacial spin–orbit engineering as an effective pathway for enhancing energy efficiency in voltage-driven spintronic memory devices, providing practical design guidelines for next-generation low-power MRAM technologies.

Deciphering the coupling between various degrees of freedom (i.e., phonons, electrons, orbitals, and spin waves) is essential to understanding the material properties of complex oxides, particularly in systems where bond angles deviate from ideal configurations, such as strained oxide thin films and heterostructures [1]. However, precise individual control over these degrees of freedom has remained challenging. Recent advances in experimental techniques, such as narrow-bandwidth terahertz pulses, have enabled precise control over optical phonon modulation, thereby modulating material responses, for instance, magnetism, as observed in CoF₂ [2]. Here, we theoretically study the effect of phonon perturbation on orbital and spin degree of freedom in two magnetic oxides, NiO [3] and YCrO₃ [4]. We select these two magnetic oxides because their magnetic superexchange interaction pathways differ substantially. While NiO exhibits ideal 90- and 180-degree superexchange interactions, YCrO₃ shows significant deviations from these configurations, and multiple orbitals contribute to the nearest-neighbour exchange pathways.

We employ a Green’s function-based approach to obtain the orbital-resolved exchange interactions [5] and the spin waves. We find that, contrary to the commonly assumed linear relationship, exchange interaction has a quadratic dependence on phonon perturbations in NiO. This quadratic dependency arises from a change in the Ni-O-Ni bond angle from 180 degrees, changing the orbital overlap, which we explicitly quantify. We also find a small but finite magnitude non-diagonal contribution to the exchange interaction, which is forbidden in a non-perturbed configuration. In YCrO₃, deviation of bond angles from 180-degree (~135 degrees) results in complex orbital and exchange interactions. On phonon perturbation, the changes in bond angles nonlinearly modify the specific orbital interactions and exchange interactions and renormalize the spin waves by as much as ~2 meV. However, we find a relatively small magnitude of the spin-phonon coupling constant. Our results provide a quantitative understanding of phonon-driven renormalization of orbital and magnetic interactions in magnetic oxides, which have been difficult to measure using inelastic neutron scattering (INS), the workhorse of spin-wave measurements, because INS lacks temporal resolution required to capture changes at the picosecond time scale.

References.

1. Rondinelli, J. M.,N. A. Spaldin. Advanced materials 23(30) 3363-3381 (2011).

2. Disa, A. S., et. al., Nature Physics, 16(9), 937-941 (2020).

3. SS, Jayakrishnan, Bansal, D., PRB 111.10 (2025).

4. SS, Jayakrishnan, Bansal, D., PRB 112.21 (2025).

5. Korotin, D. M., et. al., PRB, 91(22), (2015).

High-quality superconducting ReBCO films, notably YBa₂Cu₃O_7-x (YBCO), critically depend on the choice of growth template. In practice, this is achieved either by a complex stack of buffer layers on a Hastelloy substrate for commercially available ReBCO tapes [1], or by using single-crystal substrates such as SrTiO₃, which are primarily employed in fundamental research [2]. This dependence limits substrate choice and motivates the exploration of more flexible growth strategies in which epitaxial film growth is independent of the underlying substrate. Realizing such an approach would open new opportunities for the application of ReBCO materials, particularly in small-scale devices.

In this work, we demonstrate the growth of epitaxial YBCO films on arbitrary substrates. The epitaxial template is provided by a layer of flexible, crystalline Ca₂Nb₃O₁₀ nanosheets deposited using the Langmuir–Blodgett technique [3]. These nanosheets are one unit cell thick and have sheet sizes ranging from approximately 200 to 250µm². Epitaxial YBCO domains form on top of the nanosheets. However, grain boundaries and in-plane domain misorientation are present, which significantly reduce the critical current density [4]. We address these challenges through process optimization, doping strategies, and materials engineering. Currently, we achieve a critical temperature of 89K and a critical current density of approximately 50kA/cm² at 77K. While this is two to three orders of magnitude lower than the performance of state-of-the-art ReBCO conductors, it represents a significant step toward substrate independent epitaxial growth.

Ongoing research focuses on a detailed investigation of grain boundary effects, specifically comparing the material properties within a single YBCO domain (grown on an individual nanosheet) to transport across grain boundaries between adjacent nanosheets. Comprehensive characterization is performed using a combination of four-probe scanning tunneling microscopy, electron backscattering diffraction in scanning electron microscopy, and electrical transport measurements.

The Langmuir–Blodgett deposition of nanosheets is scalable and substrate flexible. We aim to extend our approach to large area growth, including 4-inch wafers, and to a variety of substrates such as copper and silicon. This work presents a flexible and scalable route toward the growth of superconducting YBCO on varies substrates while maintaining competitive superconducting properties, enabling new possibilities for small superconducting devices and electronics, such as patterned coils and integrated superconducting circuits.

[1] Y. Zhao et al., Supercond. Sci. Technol. 32, (2019)
[2] G. Hammerl et al, Nature 407, 162 (2000)
[3] P.T.P. Le et al., ACS Appl. Nano Mater 3, 9 (2020)
[4] S.E. Babcock, Micron, 30,5 (1999)

Advanced strategies for tailoring transparency window in Correlated Transparent Conductors

A. CHEIKH1*, M. Rath1, U. Lüders1, A. Fouchet1, W. Prellier1, A. David1

1 CRISMAT (UMR6508 CNRS-ENSICAEN), Caen, France

Correlated transparent conducting oxide TCOs have gained significant attention due to their ability to overcome the limitations of conventional TCOs by combining high transparency and excellent electrical conductivity. SrVO3 (SVO) stands out as a high-performance TCO in the visible range1, leveraging vanadium, a more abundant and affordable element compared to indium in prototype TCOs, such as indium tin oxide (ITO). However, the functional properties of SVO have yet to undergo optimization to fully explore its technological potential.

This study aims to expand the optical transparency window of SVO through gradual doping to cover the UV-visible-NIR range while maintaining high electrical conductivity. In order to expand the transparency window of SVO, defined by the screened plasma frequency ωP* and the inter-band transition Ep-d1, we implemented two different strategies, including the control of band-filling and bandwidth tuning. The growth of the different compositions as thin films was achieved from two targets of the respective end members in order to ensure a high flexibility of the content. By controlling the number of pulses on each target and allowing the growth of less than one unit cell, the desired composition was grown by consecutive deposition from each target.

Regarding the band-filling strategy, one of the possible ways for this strategy is the use of SrTi1-xVxO3 thin film grown by laser-assisted deposition (PLD) on a SrTiO3 substrate. As STVO becomes richer in titanium (Ti), the transparency window expands, but such composition no longer retains the high electrical conductivity required for TCO applications2. For the bandwidth tuning strategy, we used the Ca1-xSrxVO3 thin film. Gradual substitution of Sr by Ca shows that ωP* remains localized in the IR range, expanding the transparency window region by pushing Ep-d into the UV region, leading to a wide transparency window covering the UV-vis-IR range2. 

As a result, through an appropriate choice of chemical doping and by exploiting the reinforcement of electronic correlations, we successfully expanded the transparency window size by around 11% surpassing that of SVO while retaining a high conductivity of approximately 2.3×104 (Ω.cm)-1 and a high charge carriers’ density of 2.93×1022 cm-3. This study shows that each strategy yields specific advantages based on the target optoelectronic application, illustrating the tunability of SVO’s functional properties through precise dopant engineering2.

[1] L. Zhang et al. Correlated Metals as Transparent Conductors. Nature Mater 2016, 15 (2), 204–210.

[2] A. Cheikh. Tuning the Transparency Window of SrVO3 Transparent Conducting Oxide. ACS Appl. Mater. Interfaces 2024, 16 (36), 47854–47865.

Tailoring structural and optical properties of Ta2O5 thin films via radio frequency magnetron sputtering for high-refractive index transparent materials

Aïmane Cheikh1, Xavier Portier1, Philippe Marie1, Cedric Frilay1, Olivier Debieu2, Julien Cardin1

1 CIMAP Normandie Université, ENSICAEN, UNICAEN, CEA, UMR CNRS 6252, 6 Boulevard Maréchal Juin, 10450 Caen Cedex 4, France

2 CIRISMAT, Normandie Université, ENSICAEN, UNICAEN, UMR CNRS 6508, 6 Boulevard Maréchal Juin, 10450 Caen Cedex 4, France

Tantalum pentoxide (Ta₂O₅) films have garnered significant attention in advanced technologies due to their remarkable optical and dielectric properties. With a high refractive index n, low extinction coefficient k, and high transparency in the visible spectrum, Ta₂O₅ thin films might be well-suited for modern optical coating applications, including augmented reality (AR) glasses. In this study, we investigated the refractive index (n) and absorption coefficient (k) of Ta₂O₅ across the visible spectrum, with a particular focus on how these optical properties relate to its structural characteristics1.

Ta₂O₅ thin films were deposited using magnetron radio frequency sputtering on double-side polished silicon (Si) wafers and subsequently annealed via Rapid Thermal Annealing (RTA) at various temperatures. X-ray diffraction (XRD) measurements revealed the onset of Ta₂O₅ crystallization beginning at 650°C, predominantly forming an orthorhombic phase (β-Ta₂O₅) with a minor hexagonal phase. Transmission electron microscopy (TEM) further confirmed this crystallization, showing that the crystallized Ta₂O₅ thin films overlay a thin SiO₂ layer.

Optical properties were assessed using Variable Angle Spectroscopic Ellipsometry (VASE) and spectrophotometry. For annealing temperatures between 750°C and 850°C, a reduction in transmittance to 71% was observed, likely due to an increased trap density and the formation of active color centers associated with oxygen vacancies. These effects were accompanied by an increase in the extinction coefficient (k) starting from 3 eV, which reduced the optical transparency window to the range of 1.5 to 3.5 eV, as well as a decrease in the refractive index (n). In contrast, samples annealed with a lower thermal budget at 650°C exhibited a higher refractive index (n) of approximately 2.20 around 2 eV and a negligible extinction coefficient (k) up to 5 eV, resulting in a wider transparency window with an average transmittance of 78% between 1.5 and 5 eV.

In conclusion, the rapid annealing treatment at 650°C effectively optimizes Ta₂O₅ thin films, achieving a higher refractive index and minimal optical absorption across a broad spectrum. This enhancement in optical transparency paves the way for numerous advanced optical coating applications, including augmented reality technologies.

[1] A. CHEIKH, Journal of alloys and compounds 1040 (2025) 183273

Titanium dioxide (TiO₂) is a well-established wide band-gap semiconductor valued for its electrical and optical properties, including low work function, its high dielectric constant, elevated refractive index, and minimal absorption in the visible range. These characteristics make TiO2 highly relevant for applications such as solar energy harvesting and photocatalysis. Among the polymorphs, anatase, rutile, and brookite, the anatase phase is particularly appealing due to its superior electron mobility, longer diffusion lengths, and extended carrier lifetimes. While bulk single crystals typically exhibit the best material parameters, thin films are essential for device integration. Achieving epitaxial thin films remains a challenge, as it requires precise control over crystallinity and microstructural quality.

In this abstract, we present the development of a plasma-enhanced atomic layer deposition (PEALD) process tailored for the epitaxial growth of anatase TiO₂ films on hydrothermally grown single-crystal TiO₂ flakes (~2 µm × 2 µm). The flakes, confirmed to be highly crystalline anatase by X-ray diffraction (XRD) and Raman spectroscopy, serve as substrates. Titanium tetraisopropoxide (TTIP) was used as the metal precursor, while oxygen plasma as a co-reactant in PEALD. Depositions were carried out under ultra-high vacuum conditions at substrate temperatures in a range around 300 °C. Films deposited below 300 °C exhibited an amorphous structure, while those grown at higher temperatures were polycrystalline. Raman spectroscopy validated the anatase phase of the deposited films. Atomic force microscopy (AFM) revealed smooth surfaces, with roughness values of ~7 Å for the flakes and ~4 Å for the deposited TiO2 films. High-resolution transmission electron microscopy (HR-TEM), in conjunction with XRD, confirmed the successful epitaxial alignment of the anatase TiO₂ films with the underlying single-crystal flakes.

The Rashba spin–orbit interaction (SOI) enables a direct interconversion between charge and spin currents, a key mechanism underpinning spintronic devices. The phenomenon originates from spin-split electronic bands induced by broken inversion symmetry, where the magnitude of spin-splitting directly governs spin-charge interconversion efficiency. The ability to electrically tune Rashba splitting thus offers a pathway toward low-power, voltage-controlled spintronic devices. In addition to the conventional linear Rashba effect, recent studies highlight the importance of nonlinear (cubic) Rashba contributions, which play a central role in nonlinear spin–charge conversion and quantum metric effects.

Although Rashba SOI has been widely explored in heavy-metal, light-metal interfaces remain less studied due to their weak atomic SOI. Surprisingly, recent experiments have revealed notable Rashba effects at Cu/Bi₂O₃ and Py/Bi₂WO₆ interfaces, suggesting that orbital hybridization with heavy elements can enhance spin–orbit coupling. Motivated by these observations, we perform first-principles DFT calculations to explore the Rashba effect at the interface between a light metal (Cu) and a heavy-element oxide (WO₃).

Using Cu(001)/WO₃(001) as a model heterostructure, we demonstrate that interfacing a light metal (Cu) with a band insulator (WO₃) induces an interface state exhibiting a robust Rashba spin-splitting. This splitting arises from the interplay between linear and cubic Rashba effects, driven by the strong spin–orbit coupling (SOC) of W atoms and enabled through W–Cu orbital hybridization at the interface. We have calculated the intrinsic Rashba coefficients—a linear term of ( $\alpha$_R) ≈ +0.5 eV·Å and a giant cubic term of ($\tilde{\alpha }$_R) ≈ –1.9 eV·Å³. We further show that the linear and cubic Rashba effects remarkably persist with sizable magnitude across the Cu(110) and Cu(111) orientations, confirming the robust and orientation-independent nature of this interfacial Rashba phenomenon. Our findings establish the Cu/WO₃ interface as a new light-metal/heavy-oxide platform for Rashba spintronics. The giant cubic Rashba parameter offers exciting prospects for nonlinear spin–orbit effects, tunable spin–charge interconversion, and oxide-based spin–orbitronic technologies.

Chromic properties in vanadium oxides such as VO2, V2O3, and related Magnéli are governed by a fundamental reconstruction of the electronic system driven by changes in electronic correlations, electron–phonon interaction, and crystal symmetry. As a result, thermochromism in vanadium oxides develops across a Peierls-Mott Metal-Insulator Phase Transition. Typically, the optical response of vanadium oxides is described using a generalized phenomenological Drude–Lorentz model, where the metal-insulator transition is associated with the suppression of the Drude contribution and redistribution of spectral weight among Lorentz oscillators. While this approach successfully reproduces experimental optical spectra, it provides limited physical interpretation for the microscopic origin of individual spectral contributions.

In this work, the chromic optical response of vanadium oxides was analyzed within the Green’s function formalism based on a Hubbard-Holstein model Hamiltonian. The dielectric function is evaluated in the pole of the two-particle Green’s function using linear-response theory. Although the resulting dielectric response exhibits a Drude–Lorentz-like form, its spectral components admit a clear microscopic interpretation in terms of correlation- and structure-driven spectral-weight redistribution. This framework provides a consistent microscopic description of thermochromism in vanadium oxides beyond purely phenomenological oscillator models. The theoretical results are validated by a comparative analysis with spectroscopic ellipsometry data. The analysis reproduces the experimentally observed thermochromic contrast, with the refractive index n remaining nearly unchanged (approximately 2.5 at 2 eV) in both insulating and metallic phases, while the extinction coefficient k decreases from approximately 0.16 to 0.12 across the transition.

Acknowledgements: CNCS-UEFISCDI, project number 18ROMD/20.05.2024, project PN-IV-P8-8.3-ROMD-2023-0186, within PNCDI IV and Ministry of Education and Research of the Republic of Moldova, subprogram 011207.

Ultra-wide bandgap β-Ga2O3 (Eg ≈ 4.9–5.3 eV) is a strong candidate for next-generation high-voltage electronics, yet the absence of reliable p-type doping motivates all-oxide p–n heterojunction strategies [1]. In this context, Ni1-xO is an attractive p-type partner, with hole conduction primarily enabled by Ni vacancies and a type-II band alignment with β-Ga2O3 making the reproducibility of thin, conductive Ni1-xO layers and their structural quality decisive [3,4]. State-of-the-art vertical NiO/β-Ga2O3 rectifiers already demonstrate a 1-10 kV range of blocking voltage [2,3,4].

Here, we report an experimental process window for reactive RF magnetron sputtering of Ni1-xO by systematically varying the O2 fraction in the sputtering gas mixture and the applied RF power. 20-200 nm thin films were deposited primarily on c-sapphire (0001) Al2O3 substrates, along with Sn-doped β-Ga2O3substrates, and characterized by crystal structure/texture (XRD), surface morphology (AFM), thickness (XRR, profilometer), resistivity, and Hall effect measurements.

The deposition kinetics scale strongly with power: at 50% O2, the growth rate increases from 0.13 Å.s-1 (50 W) to 1.28 Å.s-1 (200 W), enabling 60 nm films in 8 to 90 min. Additionally, the room-temperature resistivity decreases, from 5 Ω.cm (50 W) to low 0.9 Ω.cm (200 W), while maintaining low roughness (AFM RMS 1.0-1.6 nm). θ–2θ XRD patterns consistently show a single phase cubic NiO with a prevailing (111) preferred-texture, with d111=0.02436 nm and an epitaxial relation Ni1-xO [1-10] || Al2O3 [1-10] and Ni1-xO [11-2] || Al2O3 [110]; importantly, the (111) peak position shows no significant shift over 100-200 W at fixed O2, while rocking-curve broadening at the highest power suggests an increased mosaïcity consistent with enhanced ion bombardment. These results identify a power / fixed-O2 sputtering regime that simultaneously delivers thin, smooth, and low-resistivity Ni1-xO. And we will also present the first results of the characteristics of Ni1-xO onto β-Ga2O3 thin films.

References

[1] S. J. Pearton et al., Appl. Phys. Rev., 5, 011301 (2018)

[2] J.-S. Li et al., Appl. Phys. Lett. 121, 042105 (2022)

[3] H. Gong et al., IEEE Transactions on Electron Devices, 67, 8, 3341-3347 (2020)

[4] A. Taube et al., Mat. Sci. Semicond. Process., 184, 108842 (2024)

Vanadium dioxide has attracted considerable interest since the early 2000s due to its thermochromic properties, which are promising for solar radiation regulation and sensing applications. At 68 °C, VO₂ undergoes a fully reversible displacive phase transition from an insulating and infrared-transparent state to a metallic and infrared-reflective state [1]. However, the synthesis of phase-pure VO₂ remains challenging because of the complexity of vanadium oxide stoichiometry, with more than fifteen stable oxide phases.

In this work, VO₂ thin films were deposited at room temperature by magnetron sputtering using a V₂O₅ ceramic target in pure argon atmosphere. Sputtering from a V₂O₅ target is an effective method for depositing vanadium dioxide due to the chemical stability of the target during the reaction [2], while limited range of oxygen/argon ratio and target poisoning make the growth of pure VO₂ thin films difficult with reactive sputtering of metallic vanadium.

The influence of the sputtering power applied to the V₂O₅ target was systematically investigated, revealing its strong impact on the vanadium oxide phases formed after annealing. The films were subsequently crystallized by post-deposition rapid thermal annealing (RTA) under vacuum and characterized by X-ray diffraction and Raman spectroscopy. Particular attention was also paid to the optimization of the annealing conditions in order to obtain highly crystallized VO₂ thin films with thickness below 100 nm, while avoiding dewetting and over-reduction phenomena.

The thermochromic behavior of the films was investigated by temperature-dependent FTIR transmittance measurements, which revealed pronounced and reversible infrared transmittance modulation across the metal-insulator transition. These results demonstrate that V₂O₅ sputtering with optimized RTA conditions represents an efficient strategy for synthesizing high-quality thermochromic VO₂ thin films.

[1] Eyert, 2002, "The metal-insulator transition of VO₂: A band theoretical approach", Annalen der Physic

[2] Singh & al, 2025, "Exploring phase transition dynamics in VO₂ films: The role of substrate temperature", Currend Applied Physics

Oxygen deficiency in ZnO thin films is a key factor in tailoring their optical and electrical properties for applications [1, 2]. High oxygen-deficient zinc oxide thin films were synthesized by pulsed electron beam deposition and investigated by Rutherford backscattering spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, Hall effect, optical and photoluminescence measurements. At a high degree of deficiency of about 15%, leading to black (or dark) films, zinc oxide films were found to be amorphous. The optical properties are are mainly controlled by deep-level defect states that absorb visible light, whereas the electrical properties are governed by a higher electron concentration in the conduction band and a temperature-dependent resistivity characteristic of disordered metal oxide systems. These oxygen-deficient zinc oxide films exhibits enhanced violet and blue photoluminescence emission in the range 408-456 nm attributed to zinc interstitials and their extended states. We investigate how severe oxygen deficiences affect the optical and electrical properties of ZnO thin films, thus improving our understanding of the behaviour and performance of black amorphous ZnO thin films and their ability to foster innovative applications. [1] M. Nistor, D. Dobrin, F. Gherendi, J. Perrière, Nanoscale, 2025, 17, 23000; [2] M. Nistor, F. Gherendi, D. Dobrin and J. Perrière, J. Appl. Phys., 2022, 132, 225705.

Bismuth oxide (Bi_₂O_₃) is a versatile semiconductor material with unique properties, finding applications from electronics and energy storage to environmental remediation and sensing technologies. Its morphology, structure, surface topography, and electronic properties are critical for the stable functioning of thin film in target devices.

Presented results demonstrate the influence of selected fabrication parameters on the surface structure and electronic properties of Bi_xO_y thin films, along with their correlations. Thin films of 30 nm thickness were fabricated using physical vapor deposition on standard Si substrates by annealing previously deposited metallic bismuth layers in air or vacuum. Variable parameters of the fabrication process included post-deposition annealing temperature, ambient conditions, deposition rate and substrate temperature.

Several scanning microscopy techniques were employed. Atomic force microscopy was used to study surface topography, enabling the estimation of roughness, surface structure, and the size and distribution of surface features. Kelvin probe scanning microscopy was used to analyze surface electronic properties, visualizing changes in contact potential difference distribution at the layer-substrate interface and through grain boundaries. Scanning tunneling microscopy was used to study the energy band gap. XRD analysis confirmed bulk morphology and the degree of crystallization, identified polycrystalline phases, and correlated them with fabrication parameters. Photoelectron spectroscopies in X- and UV- range (XPS, UPS) were used to determine metallic and oxide phase content, verify chemical composition and as a complementary addition to electronic structure analysis.

Key findings include: selecting the optimal temperature range for obtaining a fully oxidized material, determining the effect of annealing temperature on crystallite formation, growth, and size, significantly greater substrate temperature impact on morphology versus the deposition rate, achieving electrically homogeneous layers, and energy gaps consistent with polycrystalline phases confirmed by XRD.

The results show how varying fabrication parameters during Bi_xO_y thin film production leads to structural and morphological changes, which in turn affect surface electronic properties.

This research was funded by National Science Centre, Poland project MINIATURA6 2022/06/X/ST5/01248. The conference fee is covered by EU funds FSD - 10.25 Development of higher education focused on the needs of the green economy European Funds for Silesia 2021-2027: The modern methods of the monitoring of the level and isotopic composition of atmospheric CO2 (project no.FESL.10.25-IZ.01-06C9/23-00)

The development of fuel cells is crucial for solving energy problems. Proton conductors are expected to be used as electrolytes in fuel cells, so high proton conductivity is required. Furthermore, thin-film deposition is also necessary for practical fuel cells. In this study, we focused on the inorganic oxide LiTaWO6. LiTaWO6 was synthesized using a solid-state reaction method. The raw materials, Li2CO3, Ta2O5, and WO3, were ground and mixed in a mortar for 30 minutes and then calcined at 800°C for 10 hours. The resulting sample was ground and mixed again in a mortar for 30 minutes and sintered at 800°C for 14 hours. The sintered sample was then ground and mixed and subjected to XRD analysis. The target product was identified as LiTaWO6. LiTaWO6 powder was proton-exchanged in nitric acid and TBA was added to obtain a nanosheet dispersion. The nanosheet dispersion was then laminated by suction filtration to form a free-standing film. The nanosheet freestanding film thus prepared was immersed in a 1M HCl solution for one day to exchange the TBA for protons, yielding an HTaWO6 nanosheet freestanding film. The XRD peak pattern in the out-of-plane direction of the HTaWO6 nanosheet freestanding film was measured to examine the interplanar spacing. Next, the conductivity in the out-of-plane direction of the HTaWO6 nanosheet freestanding film was measured at 80-40°C. The proton conductivity reached a high value of 10-3 S/cm at 80°C. Furthermore, a power generation test was performed by passing hydrogen gas and oxygen gas through both ends of the nanosheet freestanding film. The maximum power density was 60 mA/cm-2 at 80°C. The shape of the TaWO6 nanosheets was examined using an atomic force microscope (AFM) and a transmission electron microscope (TEM). A certain amount of the nanosheets existed as rolled tubes.

Transparent conducting oxides (TCOs) are key components in optoelectronic devices; however, the high cost and scarcity of indium-based materials motivate the development of low-cost alternatives with comparable performance. In this work, ZnO:Al/Cu/ZnO:Al (AZO/Cu/AZO) multilayer transparent electrodes are investigated as indium-free TCO candidates. The influence of RF sputtering power on the structural, electrical, and optical properties of the AZO layers is systematically studied, while the effect of Cu interlayer thickness is analyzed to optimize the trade-off between conductivity and optical transparency. The results reveal that increasing RF power improves the crystallinity and carrier transport in AZO films, leading to a significant reduction in sheet resistance. Simultaneously, the Cu thickness plays a critical role in enhancing electrical conductivity through metallic percolation, while excessive thickness degrades optical transmittance due to increased absorption and reflection losses. An optimal Cu thickness is identified, yielding a maximum figure of merit (FoM), calculated using standard Haacke and related criteria. The optimized AZO/Cu/AZO multilayer exhibits optoelectrical performances comparable to, and in some cases exceeding, those of conventional high-cost TCOs such as indium tin oxide (ITO). These findings demonstrate the strong potential of RF-sputtered AZO/Cu/AZO multilayers as low-cost, scalable transparent electrodes for photovoltaic and optoelectronic applications.

Oxide semiconductor Indium Gallium Oxide (IGO) thin film transistors have attracted considerable attention as key devices for large area displays and next generation electronic applications owing to their high carrier mobility and excellent process flexibility. To ensure device reliability and long term operational stability precise analysis of defect states within the band gap is essential. However conventional quantitative defect analysis techniques require electrical contacts which limits their applicability to practical process environments and large area thin film structures. In this study we propose a non contact optical approach for analyzing defect states in oxide semiconductor IGO thin film transistors.

In this work defect states in IGO thin film transistors were investigated by combining differential reflectance transient spectroscopy (DRTS) and time resolved photoluminescence (TRPL). Differential reflectance transient spectroscopy is a pump probe based reflectance technique that analyzes the temporal decay behavior of photo induced reflectance changes. Temperature dependent measurements were performed to probe the energetic characteristics of defect states in greater detail. By applying an inverse Laplace transform algorithm to reflectance decay signals measured at different temperatures multiple distributions of time constants with distinct activation energies were extracted. These time constants correspond to shallow level and deep level defect states located within the band gap enabling discrimination of their relative contributions and energy depths.

Time resolved photoluminescence measurements were further employed to directly probe carrier recombination dynamics in the time domain and to clarify the influence of defect states on carrier lifetime. The multi component decay behavior observed in TRPL reflects different recombination pathways associated with shallow and deep defect states identified by DRTS analysis. By correlating the energetic information obtained from DRTS with carrier dynamics measured by TRPL defect states that actively participate in carrier recombination can be selectively identified.

Through this combined temperature dependent optical analysis the energetic positions temporal behavior and impact of defect states on carrier dynamics in oxide semiconductor IGO thin film transistors can be comprehensively understood. The proposed non contact optical defect analysis approach provides a versatile analysis platform for investigating defect formation and evolution under different process conditions and can be effectively utilized for process optimization reliability enhancement and defect monitoring in large area oxide semiconductor thin film transistors.

This study investigates the fabrication and electrical characteristics of quasi-vertical Gallium Nitride (GaN) Metal-Insulator-Semiconductor (MIS) Schottky Barrier Diodes (SBDs) utilizing high-k aluminum oxide (Al₂O₃) as a dielectric layer. To address the limitations of traditional Metal-Semiconductor (MS) SBDs, specifically high leakage currents and limited breakdown voltages, Al₂O₃ thin films were deposited on GaN-on-Si substrates using Atomic Layer Deposition (ALD). The investigation compared standard MS SBDs with MIS structures featuring 20 nm and 30 nm Al₂O₃ layers. Key findings and performance improvements include: (i) Improved Breakdown and Leakage: the 20 nm Al₂O₃ MIS SBD achieved a breakdown voltage of 243 V, a significant increase from the 176 V observed in MS SBDs; (ii) Leakage Reduction: leakage current density at -3 V dropped from 9.24x10^-6 A/cm² (MS) to 4.98x10^-7 A/cm² (MIS), attributed to the insulating layer suppressing charge transport; (iii) Transport Mechanisms: I-V analysis confirmed that the 20 nm Al₂O₃ device exhibits Fowler-Nordheim (F-N) tunneling characteristics. In contrast, the 30 nm device displayed capacitor-like behavior, indicating the thickness limit for functional SBD operation; (iv) Barrier and Resistance Extraction: using thermionic emission theory and Cheung’s method, the Schottky barrier height (ϕ_B) was found to increase from 0.70 eV to 0.84 eV with the introduction of the oxide layer. While the MIS structure exhibited a slightly higher series resistance (18.18 Ω vs. 16.03 Ω), it maintained superior high-power performance; (v) Interface Analysis: C-V measurements validated the carrier concentration (~1x10¹⁶ cm^-3) and revealed that the insulating layer increases the built-in potential, further enhancing device stability. These results demonstrate that integrating high-k Al₂O₃ dielectrics into quasi-vertical GaN SBDs effectively balances the trade-off between switching speed and high-voltage reliability, positioning these devices as viable candidates for electric vehicles, 5G communications, and power systems.

Amorphous oxide semiconductors (AOSs) have emerged as pivotal materials for next-generation optoelectronics, primarily due to their superior carrier transport properties under normal operation, characterized by high field-effect mobility (μFE) and a steep subthreshold swing (S.S.). In this ideal regime, thin-film transistors (TFTs) exhibit rapid switching and minimal power dissipation, ensuring high-performance device integrity. However, the practical deployment of these devices is frequently hindered by abnormal operation, most notably the "hump effect" -a deleterious double turn-on phenomenon observed in transfer characteristics. This non-ideal behavior induces significant threshold voltage (Vth) instability and an excursion in off-state leakage current, which fundamentally undermines the operational reliability of integrated systems. Such abnormal operations are primarily rooted in the presence of intrinsic defects, such as oxygen vacancies (VO), which induce localized potential fluctuations and symmetry-breaking within the semiconductor matrix.

In this study, we investigate the fundamental origins of the hump effect by performing a comprehensive spatial analysis across the channel regions to identify localized defect densities. To overcome the limitations of conventional macroscopic electrical analysis, we employ Second-Harmonic Generation (SHG) as a sophisticated nonlinear optical probe. Unlike linear optical methods, SHG is uniquely sensitive to symmetry-breaking and localized electric fields at the interfaces, making it an ideal non-destructive tool for mapping the inhomogeneous distribution of defects. By conducting a systematic spatial analysis from the channel center to the peripheries, this optical diagnostic approach is synergistically combined with Photo-Induced Current Transient Spectroscopy (PICTS) for the quantitative assessment of deep-level trap densities.

By establishing a rigorous correlation between the spatially resolved SHG signals and macroscopic electrical signatures—most notably the Vth shifts in I-V curves—we elucidate that the accumulation of defects at the channel peripheries serves as the primary driver for parasitic conduction path formation. Our findings demonstrate that such double turn-on characteristics are critically fatal to semiconductor performance, necessitating precise spatial control of defect density to ensure industrial feasibility. This research offers vital insights into defect-mediated transport mechanisms, providing a strategic framework for suppressing the hump effect and enhancing the long-term stability of oxide-semiconductor-based electronic architecture.

The metastable corundum gallium oxide (α-Ga2O3) features advantageous properties in comparison to the thermodynamically stable monoclinic β-Ga2O3 phase, such as wider bandgap, which is beneficial for a range of applications. However, stabilization of phase-pure α-Ga2O3 thin films is still challenging with conventional deposition methods due to limited understanding of growth factor influence on film formation. In this work we investigated the impact of growth temperature (500-800°C) and film thickness on α- and β-Ga2O3 phase formation in thin films deposited heteroepitaxially on a-plane sapphire via reactive pulsed direct-current (DC) magnetron sputtering. The structure and morphology of the prepared films was studied using X-ray diffraction, scanning and transmission electron microscopy, selected-area electron diffraction and atomic force microscopy. It was determined that the growth of α-Ga2O3 phase is more favourable when the substrate temperature is increased, while polycrystalline β-Ga2O3 forms at lower deposition temperatures. Phase-pure α-Ga2O3 epitaxial films can be obtained up to some critical thickness, when the β-Ga2O3 phase formation starts due to exposed α-phase crystal facets of other than [110] orientation. A-plane sapphire substrates show merit for epitaxial stabilization of thicker single-phase α-Ga2O3 thin films, if the complex parameter space of the selected deposition method is considered.

[1] Butanovs, E. et al. Impact of temperature and film thickness on α- and β- phase formation in Ga2O3 thin films grown on a-plane sapphire substrate. Thin Solid Films 803, 140467 (2024)

Recently, 𝛽-phase gallium oxide (Ga₂O₃) has received much attention for applications in UV-light emitting diodes and detectors due to its ultra-wide bandgap (~ 4.9 eV) nature. The material also exhibits high thermal and chemical stability. It has been reported that intrinsic Ga₂O₃ often shows unintentional n-type behavior, which can be attributed to the oxygen vacancies. Ga₂O₃ can also be extrinsically doped n-type with Si and Sn. However p-type doping of Ga₂O₃ is still a challenge. GaN is another wide bandgap semiconductor which can be controllably doped p-type. There are reports of epitaxial growth of Ga₂O₃ on GaN. It will thus be interesting to study n-Ga₂O₃ /p-GaN heterojunctions for UV detector applications.

Here, we have deposited Si-doped Ga₂O₃ layers on p-type Mg-doped (0001)GaN/c-sapphire substrates using pulse laser deposition (PLD) technique. It is observed that the epitaxial quality of Ga₂O₃ film depends on the oxygen pressure inside the chamber and the substrate temperature during growth. The optimum growth conditions are obtained by analyzing the X-ray diffraction (XRD) data. It has been found that the grown Ga₂O₃ layer has monoclinic 𝛽-phase with (-201) growth orientation. Surface morphology and roughness of the films are investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques, respectively. This devices are found to show rectifying current-voltage characteristics, which suggests the formation of p-n junctions. Photo-responsivity of this detector found to be as high as 56.8 mA/W at 270 nm wavelength of the photons. This devices are also found to respond very fast; within a few milliseconds.

SrRuO₃ (SRO) is a 4d itinerant ferromagnet that serves as a platform to study the interplay of magnetic order, electronic correlations, and spin-orbit coupling (SOC) in correlated oxide metals. We investigate anisotropic charge transport in (110)-oriented epitaxial SrRuO₃ thin film, where crystallographic anisotropy facilitates symmetry-resolved charge transport along orthogonal in-plane directions. In the paramagnetic bad-metal regime above the Curie temperature T_c,on≈165 K, resistance along orthogonal in-plane directions exhibits strong anisotropy consistent with spin-fluctuation scattering. This anisotropy is significantly suppressed upon entering the ferromagnetic state, despite persistent structural inequivalence, indicating the emergence of isotropic electron–magnon and electron–electron scattering processes. The application of a magnetic field demonstrates a notable directional contrast in the magnetoresistance MR including a sign reversal along one crystallographic axis.  It remains negative along [001], but changes sign to positive along 110 below T⁰=145 K. Our results identify two sources of anisotropy in SrRuO₃ - non-topological scattering-driven anisotropy above the ferromagnetic transition and a Berry-curvature-driven contribution that emerges only in the ordered state, establishing the ferromagnetic transition as a critical regime for symmetry and topology-controlled transport.

Transparent conductive oxides (TCOs), grown by pulsed laser deposition (PLD) on fused silica were characterized with respect to their application as electrode to the photocatalyst Ta₃N₅. Ceramic targets, required for the PLD process, were prepared by solid state reaction of SnO₂ and In₂O₃ and of ZnO with Al₂O₃ resulting in doping levels of 2 at% Sn in In₂O₃ (ITO) and 2 at% to 5.1 at% Al in ZnO (AZO). The PLD thin films were structurally, electrically, and optically characterized. Growth parameters, such as deposition temperature, atmosphere and target stoichiometry, were systematically varied. Structurally the AZO films were found to grow dominantly along the c-axis. Electrically the AZO performed better when deposited in nitrogen atmosphere, achieving resistivities as low as ρ = 2.21 × 10⁻⁴ Ωcm, charge carrier densities as high as n = 1.76 × 10²¹ cm⁻³ and mobilities as high as 21.5 cm²/Vs. Optically all samples follow the Burstein-Moss shift with absorption edges ranging from 3.25 eV to 3.85 eV for free electron concentration between 3.38 × 10¹⁹ and 1.76 × 10²¹ cm⁻³ . From the optical and electrical parameters, Haacke’s figure of merit was calculated and the highest value for AZO was φ_TC = 26.1 × 10⁻³ Ω⁻¹. The ITO films deposited in nitrogen atmosphere had metallic indium incorporated into the structure. Their mobilities were therefore limited by the grain boundary scattering, and the films were not transparent. For the oxygen deposited samples, the resistivities were as low as ρ = 2.40 × 10⁻⁴ Ωcm, carrier densities as high as n = 8.31 × 10²⁰ cm⁻³, and mobilities as high as μ = 39.4 cm²/Vs. The oxygen deposited samples had an absorption edge range of 3.96 eV to 4.02 eV following the Burstein-Moss shift. The highest performing film had a figure of merit value at φ_TC = 44.8 × 10⁻³ Ω⁻¹. Sputtered Ta films were ammonolized creating Ta₃N₅. As-grown and TCO covered Ta₃N₅ thin films were tested with photoelectrochemical measurements. The photocurrent is determined with chopped light measurements, by turning the solar simulator on and off. Three measurements were done for each sample, then the difference in photocurrent is found from the first to the last measurement. In one system with TCO as a top layer the photocurrent decreased with 28 % and 32 % without a TCO top layer. This indicates that the TCO top layer improves the Ta₃N₅ photocatalytic system.

The Atomic layer deposition (ALD) technique is highly used for thin film deposition binary oxides and have huge potentials for deposition of complex oxides. Perhaps the most vital part of an ALD process is the properties of the precursors used, i.e. their ability to sublime, react and have sufficient thermal stability during the whole deposition. This becomes increasingly complex when multi component materials such as ZnFe2O4 are attempted to be deposited by ALD.  For multicomponent materials it is important that the deposition systems are chemically compatible and enable control of deposited stoichiometry by tuning the pulsing sequences. Such control may be challenging when the different precursors show very different growth rates, such as for the diethylzinc + water process compared to the iron(III) acetylacetonate + ozone process. We have therefore investigated the possible growth of ZnO using the precursors zinc acetate + ozone and zinc acetyl acetonate + ozone as precursor combinations. The goal is to develop precursor combinations that together with the iron-based process provide higher control of deposited composition and crystallinity for deposition of ZnFe2O4.

The zinc acetate + ozone process show similar same growth per cycle as the iron(III) acetylacetonate + ozone process, however, has challenges with organic residue during growth, indicating poor ligand removal. Also, to reach a self-limiting saturation requires extreme pulse times. The zinc(II) acetylacetonate precursor have reportingly been used in ALD, however, we observe that its applied sublimation temperatures should be revisited. We have investigated the suitability of both of these systems for growth of ZnO and for possible use to obtain ZnFe2O4.

Multiple quantum well (MQW) light-emitting diodes (LEDs) provide precise wavelength control, making them ideal light sources. However, achieving simultaneous short-wavelength infrared (SWIR, 1–3 μm) and mid-wavelength infrared (MWIR, 3–5 μm) emission from a single LED presents significant technical challenges due to lattice mismatch and reduced quantum efficiency when MQW structures with distinct bandgap energies are integrated onto a single substrate. As a result, most LEDs typically operate in only one IR band. In this study, we demonstrate monolithic multi-band MQW LEDs capable of simultaneous SWIR and MWIR emission using InAsSb, a material typically applied for MWIR emission. By incorporating InAsSb QWs, InAsPSb QBs, and metamorphic buffer layers and applying strain engineering, we achieved high-quality MQWs with atomically sharp interfaces and coherent epitaxy. This design overcomes the crystallographic and electrical challenges associated with differing bandgaps, allowing for simultaneous emission at 2.87 μm (SWIR) and 3.18 μm (MWIR) with output powers of 14 μW and 30 μW, respectively. Simulations indicate that reducing the QW thickness enhances quantum confinement effects, facilitating shorter-wavelength photon emission. To design LEDs with a broad emission range across the SWIR and MWIR bands, we developed a simulation-based fabrication feasibility map that incorporates both the peak emission wavelength and low strain energy, with parameters determined by the QW thickness and Sb composition. Consequently, we successfully fabricated another monolithic MQW LED capable of simultaneous emission at IR wavelengths of 2.63 μm and 3.34 μm. The fabricated monolithic multi-band MQW LEDs demonstrate stable, simultaneous SWIR and MWIR emission with precise strain compensation, enhanced quantum confinement, and high structural quality, offering a practical platform for compact, tunable, and efficient IR optoelectronic devices.

The structural and chemical properties of organic spacer cations play a decisive role in determining the stability and optoelectronic performance of two-dimensional (2D) organic-inorganic perovskites. Although the orientation of these cations is known to significantly affect charge carrier dynamics, a precise experimental determination of their molecular arrangement has remained challenging. In this work, we present a detailed investigation into the molecular orientation of spacer organic cations in 2D perovskite thin films using synchrotron-based angle-dependent X-ray absorption spectroscopy (XAS). By analyzing the intensity variations of specific resonance transitions as a function of the X-ray incidence angle, we quantitatively determine the tilt angles and preferential alignment of the organic moieties relative to the inorganic octahedra layers. Our results reveal that the molecular conformation of these cations is intrinsically linked to the interlayer distance, which in turn governs the out-of-plane charge mobility and the overall dielectric environment of the quantum well structure. This study provides a comprehensive molecular-level understanding of how the spatial orientation of organic cations can be tailored to optimize the optoelectronic properties of 2D hybrid perovskites. These findings offer a fundamental design principle for engineering high-performance and stable perovskite-based devices, such as solar cells and light-emitting diodes, through precise control of organic-inorganic interfaces.

The trade-off between responsivity and response speed remains a persistent bottleneck in high-performance photodiodes. Vertical p–i–n architectures have been proposed as an effective solution to this dilemma, allowing for a short carrier transit time without sacrificing the optical absorption area. However, their practical realization is limited by complex fabrication processes and stringent doping requirements. Here, we illustrate a doping-free p–i–n photodiode based on a 2D TMD van der Waals heterostructure, in which graphene transparent top electrodes enable a fully vertical device architecture, thereby overcoming these limitations. This structure maximizes optical absorption in the intrinsic layer, enables efficient photocarrier separation via a strong built-in field, and ensures effective carrier harvesting through a minimized vertical transit path directly to the electrodes. We strategically engineer the layer thicknesses to resolve performance trade-offs. The MoTe₂ intrinsic layer is tuned to enhance absorption at 1,310 nm while maintaining a rapid vertical carrier transit time, with the transport-layer thickness is optimized to extend full depletion across the intrinsic region for efficient transport dynamics of photogenerated carriers. Consequently, our device exhibits exceptional optoelectronic performance at 1,310 nm, achieving high responsivity surpassing 0.1 A/W and a rapid temporal response corresponding to a 3-dB bandwidth exceeding 50 kHz. our work resolves the responsivity-speed trade-off, presenting a promising alternative to conventional commercial devices that operates without the restriction of lattice mismatch and simplifies the fabrication process.

The photomagnetic effects of magneto-optical material offer a unique opportunity for nonthermal control of the magnetization dynamics and switching by changing the light polarization. While many previous works studied this phenomenon on continuous thin film [1], the understanding of the effect of nano-sized garnet structures on the magnetization precession speed and energy efficiency is still limited. Such study requires two conditions: to be able to nanostructure a thin garnet layer, and to sufficiently focus the optical pulse on it in order to modify the magnetization.

Here we address the challenge of etching garnet film with high resolution patterns and controllable dimensions. We consider garnet layers grown on a (001)-oriented GGG (Gallium Gadolinium Garnet) substrate by Pulsed Laser Deposition (PLD) technique [2]. We show systematic investigation of etching Bismuth Iron Garnet (BIG: Bi3Fe4.8Co0.1Ge0.1O12) using Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE), which has made its proofs as a good etching technique of garnet thin film [3]. Various size, shape and density of nanostructures under different etching conditions were studied in detail. This work provides a controllable process to obtain BIG nanostructures with high verticality and dimensions for future investigation on the magnetization switching, which can be applied in ultrafast nonthermal data storage and processing technology.

References:

[1] Gorchon, J., Hehn, M., Malinowski, G., & Mangin, S. (2022). Electronic transport induced ultrafast magnetization switching. Journal of Magnetism and Magnetic Materials, 563, 169919.                                                                                                                                                 

[2] Popova, E., Magdenko, L., Niedoba, H., Deb, M., Dagens, B., Berini, B., ... & Keller, N. (2012). Magnetic properties of the magnetophotonic crystal based on bismuth iron garnet. Journal of Applied Physics, 112(9).

[3] Magdenko, L., Popova, E., Vanwolleghem, M., Pang, C., Fortuna, F., Maroutian, T., ... & Dagens, B. (2010). Wafer-scale fabrication of magneto-photonic structures in Bismuth Iron Garnet thin film. Microelectronic Engineering, 87(11), 2437-2442.

The authors acknowledge the financial support from the French ANR project ULTRAMAG.

Rapid and accurate clinical biosensing represents a critical field of research; however, the conventional diagnostic methods (PCR, ELISA, CLEIA…etc.) are limited by complicated, time-consuming, label-dependent, and high operational costs. To address these limitations, optical biosensors such as SPR (Surface Plasmon Resonance) and SERS (Surface-Enhanced Raman Spectroscopy) are advantageous owing to their label-free, real-time and compact analytical capability.

SPR underpins various high-sensitivity biosensors due to its rapid and sensitive response to the local refractive index fluctuations, thereby improving sensitivity and shortening detection time. Nevertheless, in complex biological environments such as physiological fluids, limited selectivity represents a significant constraint of SPR. To address this issue, SERS is introduced owing to its inherent fingerprint spectroscopy, which effectively compensates for the selectivity constraint of SPR.

In this work, we proposed a dual-functional biosensor based on gold/aluminum oxide (Au/Al₂O₃/Au) MIM grating (period = 750 nm, duty cycle = 0.5, height = 110 nm) that integrates SPR for quantitative and SERS for qualitative analysis. The SPR response is characterized by tracking the shift of the reflection dip under the white-light spectrum, enabling determination of analyte concentration. In parallel, Raman signals are enhanced via plasmonic “hot spots” formed at the grating edges to identify the specific molecular species. Subsequently, COMSOL simulation is used to validate experimental results, which indicates R dip and hotspot localization for SERS and SPR, respectively. By jointly analyzing the dual-mode spectral responses, precise quantitative and qualitative data of the target analytes are obtained, demonstrating the capability of the platform for analyzing complex samples.

The proposed sensor exhibits an SPR sensitivity of 173 nm/RIU and strong SERS enhancement (EF = 10⁶) when evaluated using model analyte methylene blue (MB) and small-molecule compounds (4-ATP, 4-MBA, and glucose), achieving a limit of detection (LOD) as low as 10^-11M. Furthermore, the platform demonstrates superior performance in detecting the Alzheimer’s disease biomarker amyloid-β 42 (Aβ-42). Ultimately, the proposed dual-functional sensing platform is desirable and promising for clinical applications, offering high accuracy, time-saving, and easy-to-use.

Monolithic integration of optical isolators remains one of the main technological challenges for the development of photonic integrated circuits. Optical isolators require non-reciprocal (NR) transmission, which implies a propagation medium that simultaneously breaks time-reversal symmetry and spatial symmetry. The most efficient NR transmission in planar waveguides [1] is based on the Transverse Magneto-Optical Kerr Effect (TMOKE) at the interface between a magneto-optical (MO) material layer and the waveguide. However, the MO effect often remains perturbative and insufficient. Several hybrid integration approaches in photonic platforms aim at enhancing the non-reciprocal MO properties [2]. A particularly promising device based on magnetoplasmonics exploits TMOKE enhanced by both surface plasmon polaritons and a coupled-mode system in a slot waveguide [3]. TMOKE induces an asymmetrization of the coupled mode profiles, which depends on the propagation di rection: the optical energy carried by these modes does not follow the same path in the forward and backward directions. This property is used to realize non-reciprocal optical transmission.

The main objective of this work is to experimentally observe the asymmetrization of the modes during propagation and their non-reciprocal behavior using a Scanning Near-Field Optical Microscope (SNOM). The confinement of the optical mode at interfaces enables tracking of the evanescent field of the propagating mode along the waveguide edges using the atomic force microscopy (AFM) tip of the SNOM. We optimized the SNOM setup to enable the detection of guided modes when the magneto plasmonic waveguide is immersed in an external magnetic field. Numerical simulations were performed to design a device compatible with the SNOM geometry, including the grating coupler design with specific incidence angles and the waveguide length, as well as the fabrication of grating coupled structures.

Acknowledgements

This project has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement No101129645 (project CIRCULIGHT, www.circulight.eu)

References

[1] D. Jalas et al. What is-and what is not-an optical isolator. Nature Photonics, 7:579–582, 2013.

[2] B. J. H. Stadler and T. Mizumoto. Integrated magneto-optical materials and isolators: A review. IEEE Photonics Journal, 6, 2014.

[3] Sevag Abadian et al. Broad-band plasmonic isolator compatible with low-gyrotropy magneto-optical material. Optics Express, 29(3):4091–4104, 2021.

With the rapid growth of autonomous vehicle technologies, the demand for high-sensitivity infrared sensors, which play a critical role in vehicle safety and automation systems, is rapidly increasing in the automotive industry. In commercial photodetectors, Ge and InGaAs are mainly used in telecom band (1260 nm ~ 1625 nm) detection. Its drawback is the complex and costly epitaxial process and severe lattice mismatch with silicon substrates, which complicates integration with readout integrated circuits (ROIC). In contrast, 2D transition metal dichalcogenides (TMDs) offer dangling-bond-free surfaces, allowing for monolithic integration with Si-CMOS electronics and flexible substrates without lattice matching constraints. However, Due to their atomically thin thickness, 2D TMDs exhibit extremely high optical transmittance, resulting in intrinsically low absorption efficiency. Here we report first high-sensitive Metasurface-2D hybrid photodiode operating in the telecom band. To demonstrate a high sensitivity Metasurface-2D photodiode, we compare with a MoS2/MoTe2 heterostructure, which can be directly related to optical properties depending on the presence or absence of Metasurface. This novel structure effectively traps the light, leading to a significant increasing in photocurrent and consequently improving responsivity and detectivity. Therefore, it achieves a high sensitivity. We propose that our newly designed structure addresses the synergy of both 2D TMDs materials and Metasurface, and we anticipate that this approach will enable the development of devices capable of competing with sensors currently used in industry.

Halide perovskite materials excel in broad optoelectronic applications, and there is an urgent demand to develop perovskite-based integrated optoelectronic devices. However, the limitations posed by the incompatibility of perovskite thin film with wet lithography greatly hinder its potential in many important applications, including ultrahigh-density displays, high-resolution image sensors, high-density memristors, and integrated photonic circuitry. To tackle this bottleneck problem, we develop the self-aligned close-spaced sublimation growth of perovskite quantum wires and demonstrate 0.18-micrometer feature size perovskite patterns, meanwhile achieving a pixel density of 63,500 pixels per inch, the highest reported for perovskite. We showcase pixelation of perovskite quantum wires with color conversion films, addressing the need for full-color microdisplays. In addition, we demonstrate these films on curved substrates, holding promise for near-eye microdisplays. Processes shown here can also apply to other perovskite devices such as high-resolution displays, image sensing, and memristor arrays.

The unique electronic properties of CsGeX₃ perovskites (X = Cl, Br, I) make them promising candidates for nonlinear optical applications. Understanding charge localization is needed to fully understand their physical and electronic behavior. Here, we perform a theoretical investigation of electron and hole polaron formation, and self-trapped exciton binding in CsGeX₃ using hybrid density functional theory. We find that polaron stability decreases from Cl to I. In particular, single-electron polarons form highly favorably in CsGeCl₃ and CsGeBr₃, whereas single-hole polarons can only be formed in CsGeCl₃ . Double electron polarons are energetically favorable across the series. In addition, CsGeCl₃ and CsGeBr₃ exhibit stable self-trapped exciton configurations. These findings constitute a basis for understanding polaronic effects on the electronic properties of CsGeX₃ perovskites and open up access to their optimization in nonlinear optical applications.

Silicon oxide materials have an important place in microelectronics due to their chemical, physical, optical, and dielectric properties. They are widely used in silicon devices fabrication for different steps like isolation in STI (shallow trench isolation) trench on Front End Of Line (FEOL) integration, as inter level dielectric (ILD) layer for contact stack and for isolation between each metallic line in Back End Of Line (BEOL). As microelectronic market is more and more challenging, the integration of dedicated material is nowadays mandatory (gapfill, low temperature deposition, low stress …). Depending on Oxide deposition technique and precursors, it can be more or less gapfill, it can be doped and thus more adapted to a specific application. Then its flatness is a key parameter for the fabrication of sub-sequent levels. It is well known that chemical mechanical polishing (CMP) is the only way to achieve planarization. The requirements and the performance for oxide flatness and Material Removal Rate (MRR) have been constantly studied by scientists.The scope of this paper is to highlight Oxide material properties and their impact on MRR depending on silica slurry composition and pad properties (groove, porosity, subpad).In this study, different oxide materials are studied using different deposition techniques. These materials were all characterized: density, roughness, stress into the oxide film.

Then these oxides blanket wafers have been used to evaluate MRR using different kind of slurries and pads. The goal is to highlight material properties impact on MRR performance depending on slurry properties. In this paper, we used two different standard silica-based commercially available slurries. We compared MRR with one acidic slurry with lower solid particles percentage and an alkaline with high solid particles percentage one. Then, the impact of two pads is compared depending also on sub-pad type. The scope of this paper is to understand and highlight the material properties which drive MRR and define which process parameter can enhanced this behaviour (pad properties, pH and or slurry composition).

Then, in this work, we fix polishing recipe conditions and we focus on the MRR obtained with one slurry. There is almost 44% MRR difference between different kind of oxides. Therefore, MRR is correlated with material density for different combination of pad/slurry. The denser the material is, the lower the MRR. 

Thus, this paper illustrates a smart methodology based on the understanding of oxide material behaviour. SiO2 polishing rates is directly linked to material intrinsic properties and it can be enhanced by slurries (particles, pH) and pad properties (roughness, hardness). The benefit is to allow to select either an optimal oxide for a targeted CMP consumables set or the best pad/slurry combination regarding the oxide material. To go further, we will open discussion on planarization for advanced node technologies using this approach.

We present a graphene-molecular aggregate hybrid phototransistor based on the merocyanine dye HB238, an organic semiconductor whose optoelectronic properties are highly sensitive to molecular aggregation. The aggregation state of HB238 can be tuned via thermal evaporation parameters and post-depositon annealing, leading to pronounced changes in the structure of thin films of HB238 and their optical and electrical properties.

To leverage this tunability, we engineer a hybrid phototransistor platform that allows systematic separation of the effects of molecular aggregation, organic layer thickness, and optical excitation on charge transport at the graphene-organic interface. Precise control over the HB238 aggregation state enables access to well-defined stages of molecular order within an otherwise unchanged device architecture, allowing intrinsic aggregation effects to be isolated. 

Our device architecture also allows direct, on-chip comparison of the hybrid graphene/HB238 phototransistors with pristine graphene and pristine HB238 control devices fabricated on the same substrate. This ensures identical fabrication, processing and measurement conditions across all device types, enabling unambiguous identification of photocurrent generation and amplification mechanisms with exceptional comparability. We show that the hybrid devices exhibit a photocurrent enhancement of 10⁵ relative to pristine HB238 devices, highlighting the decisive role of graphene in the photoconductive gain of the hybrid device.

By probing the same hybrid device at different aggregation states, we directly demonstrate that molecular aggregation governs both the magnitude and gate-voltage dependence of the photoresponse. Systematic variation of the HB238 layer thickness reveals a thickness dependent modulation of gate-dependent photoresponse, indicating thickness controlled interfacial doping of graphene. Furthermore, spectrally resolved photocurrent measurements indicate distinct charge transfer efficiencies between monomeric and aggregated phases of the dye.

From a device fabrication standpoint, we demonstrate an encapsulation protocol that enables stable operation of the hybrid phototransistors under ambient conditions. While graphene transistors are typically highly susceptible to environmental doping under ambient conditions, our encapsulated devices exhibit optoelectronic characteristics indistinguishable from measurements performed under vacuum.

Our device demonstrates a multimodally tunable graphene-organic hybrid phototransistor in which molecular aggregation, layer thickness and optical excitation act as controlling parameters for the photoresponse. We believe that beyond device performance, the device acts as a versatile testbed for uncovering fundamental charge transport mechanisms at the interface between 2D materials and aggregating organic semiconductors, providing a stepping stone towards enhancements in device-relevant organic optoelectronics. 

Advanced photonic systems that exploit optical nonlinearities of graphene enable ultrafast signal processing and broadband on-chip functionalities. However, the high-temperature requirement (~1050 °C) of the CVD-based ACS process remains a critical barrier, as it surpasses the thermal budget of Si, introducing defect formation and surface deterioration, thereby limiting scalability for next-generation PIC integration.

In this study, we demonstrate low-temperature direct growth of graphene using the atomic carbon spraying (ACS) method without compromising its nonlinear optical response. This approach allows for the metal-free, direct growth of graphene on target substrates while ensuring the structural integrity of the underlying optical platform. Furthermore, we experimentally verify that low-temperature ACS method induces no observable thermal damage or defects on the Si surface. Subsequently, the characteristics of the synthesized graphene were analyzed using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Selected Area Electron Diffraction (SAED). The analyses confirmed that the graphene consists of randomly oriented 2D nanograins with high uniformity, preserving its intrinsic material quality.

To evaluate the retained nonlinearity for device applications, graphene was directly synthesized onto the end facet of an optical fiber and employed as a saturable absorber in a fiber ring laser cavity. The resulting device successfully generated ultrashort mode-locked pulses. The laser output exhibited a central wavelength of 1567.45 nm, a 3-dB bandwidth of 1.32 nm, a pulse duration of 3.26 ps, and a repetition rate of 1.31 MHz. Our work demonstrates that preservation of the nonlinear optical properties of graphene at low synthesis temperatures makes direct ACS synthesis a promising route for monolithic integration into next-generation photonic systems.

CsPbBr₃ is a promising perovskite solar-cell absorber due to its high stability under illumination and resistance to moisture, combined with favorable charge-transport properties. To maximize device efficiency, an electron transport layer (ETL) with suitable band alignment and high conductivity is required to enable efficient electron extraction and suppress charge recombination. SnO₂ is a widely used ETL candidate because it combines high electron mobility with excellent stability under ambient conditions. However, recombination losses associated with interfacial structure and surface chemistry at the CsPbBr₃/SnO₂ junction remain a key challenge. This study investigates the CsPbBr₃/SnO₂ interface at the atomistic and electronic scales using first-principles density functional theory (DFT) calculations and molecular dynamics (MD) simulations.
First-principles DFT calculations on CsPbBr₃/SnO₂ interface models are used as reference data for training a machine-learning interatomic potential using the Neuroevolution Potential (NEP) approach. The trained NEP enables large-scale, low-cost MD simulations of supercells, allowing temperature-dependent structural behavior to be studied across varying distances from the interface. In particular, we analyse octahedral tilting in CsPbBr₃ as a function of temperature and proximity to the interface and assess its impact on the electronic structure.

"AI for Science" has accelerated advancements in machine learning potentials (MLPs). These innovations are reshaping the molecular dynamics (MD) research paradigm by balancing accuracy and computational efficiency. GPUMD1, a world-leading MD tool developed in China, seamlessly integrates machine learning potentials (NEP models) into heterogeneous GPU architectures. This integration allows it to achieve first-principles accuracy at the computational cost of classical force fields, overcoming the bottleneck in simulating complex materials. Building on the GPUMD+NEP framework, the authors have made significant contributions, including the development of NEP892, a universal MLP that can predict the properties of both organic and inorganic materials, with the ability to fine-tune for enhanced accuracy of potential functions. Additionally, specialized potential functions, such as NEP-MB-pol3 and NEP-SiNWs4, enable workflows tailored to specific systems. NEP-MB-pol was the first to predict the transport coefficients of liquid water across all temperatures, and when combined with nuclear quantum corrections, it demonstrated consistency with experimental structures. Meanwhile, NEP-SiNWs explored the phonon hydrodynamic effects in one-dimensional nanowires. The authors have also employed machine learning to establish relationships between material properties and structures. This breakthrough in GPUMD, supported by national scientific research funding, has found applications across various disciplines. Looking forward, GPUMD is set to drive innovations in cross-scale simulations for energy and materials science through multiscale and multiphysics integration. Its open-source ecosystem and algorithmic advancements will continue to lead computational materials science into the era of "artificial intelligence for science."

The component materials used in solid oxide electrochemical cells (SOECs) play a crucial and multifaceted role in device development. However, the in-situ observation of material behavior under high-temperature operating conditions remains challenging, posing significant obstacles to understanding the fundamental mechanisms governing electrochemical reactions. To overcome this limitation, recent research has increasingly employed computational materials science approaches for the analysis and performance prediction of novel materials. In particular, atomistic-level investigations have proven effective in guiding chemical design and offering deep insights into material behavior. This study presents a comprehensive evaluation of state-of-the-art materials in terms of thermodynamic stability, ionic diffusion, and catalytic activity using density functional theory (DFT) and first-principles molecular dynamics (FPMD) simulations. Additionally, atomistic simulation techniques are introduced as complementary tools to experimental methods for probing intrinsic material properties. Finally, a machine learning-assisted computational framework is proposed to accelerate the discovery and development of high-performance materials for SOEC applications.

This project investigates machine learning approaches for predicting polymer glass transition temperature (Tg) to accelerate material design in applications such as packaging, automotive components, and medical devices. Using the Glass Transition Temperature Database1 of over 200 polymers, multiple molecular featurization strategies (e.g., Morgan fingerprints, Mordred descriptors, and MACCS fingerprints) are compared to identify effective numerical representations of polymer structure. Four regression models (Random Forest, XGBoost, Support Vector Regression, and Feedforward Neural Networks) are developed and evaluated through 5-fold cross-validation. Model interpretability is enhanced using SHAP values to reveal chemically meaningful structure–property relationships. The study aims to achieve Tg prediction performance comparable to published benchmarks (R² ≥ 0.75) and to provide a reproducible, scalable workflow for polymer property prediction, ultimately enabling more efficient polymer screening and informed molecular design.

The quest for novel materials to advance clean energy technologies has intensified the need for efficient, sustainable, cost-effective, and readily available catalysts. In this context, the catalytic dehydrogenation of formic acid offers a promising route for hydrogen storage and release, yet it often relies on expensive and rare noble metals. However, discovering new catalysts through direct synthesis in the lab is a slow and costly process due to the vast number of possible compositions. To overcome this challenge, recent advances in high-performance computing (HPC) have enabled high-throughput computational screening, significantly accelerating the discovery of alternative, less costly materials.
Here, we introduce an industrial-scale demonstrator for a high-throughput workflow designed to identify potential metal catalysts for formic acid dehydrogenation. By conducting large-scale DFT calculations on thousands of candidate materials and systematically refining the selection through increasingly stringent criteria, our approach efficiently narrows the search space to a handful of promising contenders.
We illustrate how this integrated methodology streamlines the pipeline from large-scale computation to industrial application, showcasing its power to target new alloys with favorable activity and stability. Moreover, we emphasize the exascale readiness of our approach, highlighting its scalability for future high-throughput campaigns. This platform not only accelerates discovery in the formic acid system but also offers a blueprint for broader materials screening, supporting sustainable energy initiatives and reducing the environmental and financial costs associated with traditional trial-and-error experimentation.

Nonlinear optical (NLO) materials capable of efficient second harmonic generation (SHG) are foundational components for modern laser systems, enabling applications in precision manufacturing, biomedical imaging, and optical communications. The discovery of new high-performance materials, however, is severely hindered by the slow pace of traditional methods. Experimental exploration is resource-intensive and serendipitous, while accurate computational screening using first-principles density functional theory (DFT) is prohibitively expensive for large-scale virtual searches. To overcome this bottleneck, we present a high-throughput deep learning framework for the rapid and reliable prediction of SHG efficiency. Our approach utilizes an ensemble of Atomistic Line Graph Neural Network (ALIGNN) models, trained from scratch on a comprehensive dataset of inorganic crystalline structures. The models directly predict the established Kurtz-Perry coefficient—a critical metric for initial experimental benchmarking—from only the material's stoichiometry and atomic coordinates. This ensemble strategy significantly enhances predictive stability and generalizability compared to single-model architectures. Our optimized model demonstrates strong performance, achieving 82.5% prediction accuracy within a tolerance threshold defined by an absolute error of ≤ 1 pm/V and a relative error of ≤ 0.5. This high accuracy validates the model's ability to capture the complex structure-property relationships governing nonlinear optical responses. By providing instantaneous, low-cost estimates of SHG activity, this work establishes a powerful and practical tool for the computational materials' community. It enables the rapid prioritization of the most promising candidate materials from vast chemical spaces and databases for subsequent focused theoretical or experimental investigation, thereby accelerating the development cycle for next-generation laser technologies.

Naturally occurring stochastic phenomena can generate unique random structures that are valuable for security and anticounterfeiting applications, analogous to the individuality of human fingerprint patterns. Here, we demonstrate a physically unclonable tag platform based on three-dimensional (3D) random morphology of poly(3,4-ethylenedioxythiophene) (PEDOT) films formed via stochastic crystal growth on hydrophobic MoS₂ substrates without external patterning sources. The resulting PEDOT films exhibit highly irregular micro-/nano-scale crystallite distributions, providing intrinsic randomness suitable for security key generation.

To quantitatively digitize the morphological uniqueness, high-speed confocal laser microscopy was employed to acquire 3D surface profiles, which were subsequently converted into informative binary key maps through mathematical processing. The extracted binary keys from multiple independent tags were evaluated using Hamming distance analysis and statistical metrics to verify inter-tag uniqueness and resistance to collisions. The results indicate that the intrinsic random orientation and deposition behavior of PEDOT crystallites on hydrophobic MoS₂ effectively yields reproducible-yet-unclonable morphological signatures.

Furthermore, we demonstrate an additional security modality enabled by the PEDOT/MoS₂ system, where the tags can be captured by infrared (IR) cameras, suggesting feasibility for practical authentication in future machine-vision and IoT-integrated security systems. This work highlights a materials-driven strategy for constructing anticounterfeiting tags by leveraging intrinsically stochastic crystallization of conductive polymers without lithographic patterning.

Active learning and Bayesian optimisation can dramatically reduce the number of experiments needed to optimise a material or a process, yet their practical adoption is often limited by the need to write and maintain custom code. We present MADGUI (Multi‑Application Design Graphical User Interface), a user‑friendly software that makes data analysis, surrogate modelling, and Bayesian optimisation accessible to researchers with no programming background.

MADGUI is implemented in Python with a Streamlit front‑end and accepts standard CSV/XLSX datasets. The workflow is organised into three connected pages. (i) The Main page performs rapid dataset inspection and descriptive statistics, and offers visualisation of feature-target relationships to support experimental intuition and data quality control. (ii) The Prediction page trains and evaluates predictive models (ElasticNet, Random‑Forest, or XGBoost regressors) with cross‑validation (leave‑one‑out or k‑fold), and reports prediction plots, residual diagnostics, feature importance and partial dependence to help users identify the most influential variables; predicted values can be exported for reporting or downstream automation. (iii) The Bayesian page converts the experimental design space into an explicit domain by letting users define bounds, step sizes, and/or allowed discrete values for each feature, and it supports user‑defined constraints between features (e.g., stoichiometry). Based on this space, MADGUI runs Bayesian optimisation (Gaussian‑process surrogate with expected‑improvement acquisition) to propose between 1 and 20 new experimental conditions per iteration, matched to laboratory throughput; suggested conditions are downloadable as CSV to directly plan the next batch of experiments. An optional mode initialises the optimiser with model‑generated candidates to reduce sampling bias when the predictive model is reliable. On a standard laptop, a dataset of ~100 samples can be processed end‑to‑end and yield new suggestions in ~10 minutes. This poster will provide a hands‑on demonstration of end‑to‑end closed‑loop optimisation and practical guidance on data formatting, constraint specification, and multi‑target optimisation (up to three objectives with user‑defined weights). MADGUI is freely accessible online and distributed as standalone executables (Windows/Mac), and the source code and demonstration datasets are available via a public GitHub repository, enabling both immediate use and advanced customisation.

Global population growth is increasing energy demand and intensifying the need for scalable energy storage. While lithium-ion batteries (LIBs) dominate current markets, their mass production is constrained by the limited lithium availability. In this light, sodium-ion batteries (SIBs) have emerged as a promising alternative, especially for grid-scale energy storage. However, their large-scale production requires overcoming several technical challenges, particularly those related to anode materials. Hard carbon (HC) is considered a leading anode candidate due to its high ion storage capacity, electrochemical and thermal stability, and low synthesis cost. Despite these advantages, HC-based anodes still suffer from sluggish Na diffusion, limited long-term stability, and an incomplete understanding of sodium-storage mechanisms. To elucidate ion-diffusion mechanisms, numerous experimental and computational studies have been conducted in the field. However, experimental approaches face limitations in resolving atomic-scale details, while density functional theory (DFT)-based simulations are computationally demanding and impractical for a comprehensive exploration of highly complex HC-based structures. With the emergence of data-driven methodologies, it becomes evident that machine learning interatomic potentials (MLIPs) enable near-DFT accuracy in structure-energy predictions at a significantly reduced computational cost. Motivated by this, herein, we present a workflow to set up and fine-tuning an MLIP based on the MACE architecture from foundational models to construct solid-state models and systematically investigate sodium storage mechanism in hard carbon. The framework  begins with the analysis of pretrained foundational models to identify gaps in describing energies and forces for C/Na-based systems, while comparing against C/Li systems. Once poorly represented regions are identified, additional DFT-generated structures are used to refine the potential. In parallel, unsupervised clustering is employed to analyze and classify structures based on their similarity, enabling more efficient and effective frame selection avoiding oversampling of the chemical space. The goal of this framework is to obtain a refined potential capable of constructing realistic hard carbon models and accurately simulating Na- and Li-diffusion for storage process at near-DFT accuracy, thereby identifying dominant storage mechanisms and structural features that govern it.

 Acknowledgment: The work is funded by NCBR (#WPC3/2022/50/KEYTECH/2024) and PLGRID support (PLL/2024/07/017633 and PLG/2025/018614).

Metal halide perovskites are promising materials for sustainable-energy and optoelectronic applications, but their long-term stability is often limited by defect-mediated ion motion due to their soft lattice. Ion migration can contribute to hysteresis, phase/structure evolution, and accelerated degradation under operating conditions, which is why it is now widely studied both computationally and experimentally. However, modelling ion transport in these materials remains challenging because migration barriers can be sensitive to DFT choices, and realistic diffusion is a finite-temperature, defect-driven process that requires long time and large length scales.

In this work, we combine first-principles benchmarking with a data-driven workflow to connect migration energetics to finite-temperature diffusion. We first benchmark halide migration pathways in a CsPbX33​ framework using nudged elastic band (NEB) calculations, and systematically test the sensitivity of representative barriers to key DFT choices, including pathway selection, charge treatment, spin–orbit coupling, exchange–correlation functional (e.g., PBE, vdW-DF-cx, r2SCAN+rVV10, and the hybrid functional PBE0), and halide species. This benchmarking identifies which diffusion trends are robust and provides a consistent reference for comparing compositional mixing in systems such as Csxx​Rb1−x1−x​PbBryy​I1−y1−y​.

Using these point-defect-containing configurations (including vacancies on both the X site and A site), we then train a machine-learned interatomic potential that captures the local chemistry governing defect-assisted ion hopping. The potential is validated against the DFT/NEB reference and enables molecular dynamics simulations at time and length scales beyond what is accessible with first-principles methods. Ion mobility is quantified from mean-square displacement (MSD) and temperature-dependent diffusion coefficients for both X-site and A-site ions. The phase transition temperature during heating is also evaluated to study the orthorhombic–tetragonal–cubic transition.

Overall, this study bridges DFT-level defect energetics and diffusion dynamics accessible at scale with machine-learned simulations. The workflow supports more reliable, data-driven screening of defect-driven transport trends in complex perovskite chemistries and provides guidance for strategies aimed at suppressing ion migration.

Meeting the rising demand for low-carbon energy requires the development of advanced fusion technologies. The United Kingdom has committed to constructing the world’s first fusion power plant, the Spherical Tokamak for Energy Production (STEP), by 2040. A key materials challenge for STEP is the oxidation of the tungsten-based first wall, which may occur during loss-of-coolant accidents or during remote maintenance operations.

To address this issue, increasing attention has turned to “SMART” alloys—self-passivating, oxidation-resistant materials designed for next-generation tokamak environments. Among these, the ternary alloy W‑11.4Cr‑0.6Y has emerged as a promising candidate due to its favourable oxidation behaviour and ability to form protective oxide layers. However, the industrial upscaling of SMART alloy production has introduced new challenges which must be properly understood.

To advance this understanding, a new machine‑learning interatomic potential (MLIP) within the neuroevolution potential (NEP) framework has been developed. This potential is designed to enable large-scale molecular dynamics simulations of tungsten-based SMART alloys. We present our current progress on the development and validation of this MLIP, demonstrating its capability to reproduce spinodal decomposition in W–Cr systems and showing strong agreement with density functional theory (DFT) calculations.

Machine learning interatomic potentials (MLIPs) have become a fundamental tool in computational materials science by enabling large-scale atomistic simulations with near ab initio accuracy at a fraction of the computational cost of electronic structure methods. . Despite these advances, constructing MLIPs that are both reliable and transferable is still a demanding task, as it requires extensive sampling of energies and forces from first principles calculations. This process is often repetitive, time consuming, and difficult to reproduce, highlighting the importance of automation with workflows. In our work, we present an end-to-end workflow for MLIP development built on AiiDA, an open source, Python based high throughput infrastructure designed for reproducible workflows with data provenance. The workflow will cover the full MLIP lifecycle, including the automated generation of ab initio datasets, optimisation of model parameters, validation, and iterative refinement via active learning.

The workflow will further be integrated into the broader DIAMOND platform, which serves as a demonstrator of artificial intelligence driven materials modeling. A central component of this effort is the development of an open-access repository of MLIPs, hosted on the TGCC cloud infrastructure and accessible through the DIAMOND portal. This repository will allow users to retrieve existing MLIPs, submit new models, and directly interface the potentials with standard simulation engines such as LAMMPS, thereby promoting reuse and community contribution.

As a proof of concept, we apply the workflow to the construction of both a Behler Parrinello neural network potential using the n2p2 package and an equivariant message passing neural network model using the MACE package for aluminum, with the goal of reproducing reference results reported in the literature by Noel Jakse et al[1]. 

References:

[1] Jakse, Noel, et al. "Machine learning interatomic potentials for aluminium: application to solidification phenomena." Journal of Physics: Condensed Matter 35.3 (2022): 035402.

High-entropy alloys (HEAs) have proven to be promising candidates for electrocatalysis due to their compositional flexibility and tunable surface properties. However, the vast configuration space of these materials hinders their systematic exploration using conventional experimental or numerical approaches. This study presents a novel multiscale methodology integrating advanced synthesis, characterization of the chemical structure and electrocatalytic properties, atomistic modeling, and deep learning to accelerate the discovery of active HEAs, shifting from a traditional structure-property paradigm to an inverse design approach, from property to material. This work is part of the French national PEPR DIADEM program, which aims to sustainably transform materials discovery methods through the integration of data science, atomistic simulation, and high-throughput characterization.

The research framework relies on the synergy between two complementary neural network models: REACT2COMPO and ATOMOD. REACT2COMPO serves as the primary predictive engine for inverse design. It uses target catalytic properties, derived from experimental operando voltammograms, to generate the optimal nanocatalyst configuration in terms of composition, size, and morphology. Its encoder-decoder architecture produces 3D atomic presence probability maps for each chemical species, capturing surface segregation effects and internal structural gradients essential for catalytic activity. Training this model requires high-fidelity 3D structural annotations provided by the ATOMOD model. ATOMOD fuses multimodal data from transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS/EXAFS) to reconstruct the spatial atomic distribution and local coordination environment within the nanoparticle.

The training of the ATOMOD model relies on a large database of TEM images and simulated XAS spectra from in silico-generated nanoparticles, using a protocol that combines classical molecular dynamics, Monte Carlo algorithms, and density functional theory. A hybrid "Sim-to-Real" strategy, based on the SIMEXP style-transfer model, is applied to simulated data to incorporate environmental complexities and measurement device characteristics that are often inaccessible to purely ab initio simulations.

In this work, as a first step toward inverse design, we focus on the complete processing chain of the ATOMOD model, from the in silico generation of nanoparticles to their use in extracting their structure and composition from TEM images and XAS spectra. Each step is illustrated by the initial results obtained. We will show that training the model using only TEM images allows for the statistically well-resolved determination of the atom positions within the nanoparticle, and we will examine the integration conditions of XAS spectra during training for determining the chemical nature of the atoms.

A computing solution combining the GNU Guix functional package manager with the Apptainer container system is presented. This approach provides fully declarative and reproducible software environments suitable for computational materials science. Its versatility and performance enable the construction of complete frameworks integrating workflow managers such as AiiDA, and Ewoks that can be deployed on HPC infrastructures. The efficiency of the solution is illustrated through several examples: (i) AiiDA workflows for automated dataset construction and analysis as well as path-integral molecular dynamics based on \textit{ab initio} calculations; (ii) workflows for the training of machine-learning interatomic potentials; and (iii) an Ewoks workflow for the automated analysis of coherent X-ray diffraction data in large-scale synchrotron facilities. These examples demonstrate that the proposed environment provides a reliable and reproducible basis for computational and data-driven research in materials science.

Eutectoid and near-eutectoid steels belong to a special class of high-strength, wear-resistant steels used for several applications. The composite structure of soft ferrite and hard cementite phases gives a good combination of strength and ductility. The mechanical properties of pearlitic steel depends on the interlamellar spacing of pearlite. In the present work, a two-step modelling framework is proposed to predict the interlamellar spacing of pearlite. In the first step, an artificial neural network model is developed to correlate the Gibbs free energy of isothermal pearlite transformation with the alloy composition and transformation temperature. In the second step, interlamellar spacing of pearlite is predicted using three different models with varying architectures. Among these, the first two models incorporate the predicted Gibbs free energy as an input parameter, whereas the third model predicts the interlamellar spacing directly from the alloy composition and transformation temperature. The results shows the impact of several parameters that are beneficial in the design of high-strength steels. 

The discovery and design of new materials increasingly rely on computational methods to explore large chemical spaces while reducing experimental cost and time. Density Functional Theory (DFT) is widely used to evaluate the electronic and structural properties of materials; however, its high computational cost limits its use in high-throughput materials exploration. In this context, machine learning (ML) provides an efficient alternative for predicting key materials properties.

In this work, supervised machine learning models are employed to predict the formation energy of binary AB compounds composed exclusively of transition metals. The models use as input only elemental and crystallographic descriptors derived from the periodic table, including atomic number, valence electron count, electronegativity, electrical conductivity, magnetic character, atomic radius, and space group information.

Two regression models, Random Forest Regressor and Gradient Boosting Regressor, were trained to predict the formation energy per atom. The Gradient Boosting model showed superior performance, achieving a coefficient of determination above 0.93 and a low mean squared error, indicating its capability to capture non-linear relationships between chemical descriptors and formation energy.

These results demonstrate that machine learning models can accurately estimate formation energies while significantly reducing computational cost compared to first-principles calculations. This data-driven approach supports the efficient exploration of chemical space and the accelerated identification of stable transition metal compounds for advanced materials applications.

Two-dimensional (2D) materials are an emerging technology in enabling the next generation of electronic, spintronic, and optoelectronic devices due to exceptional electronic and mechanical properties. These include high carrier mobility, long spin relaxation time, and ability to form heterostructures. Exploration of 2D materials has coincided with the advent of data-driven material discovery. Extensive databases, such as Alexandria 2D, C2DB, and 2DMatPedia, have emerged from ab initio material discovery, however these methods are computationally expensive and lack thorough benchmarking against experimental measurement. To accelerate the development of 2D material-based technologies, machine learning (ML) models are crucial for predicting electronic properties accurately and with low computational overhead. Such ML surrogate models can be leveraged for more traditional inverted-pyramid computational workflows, as well as adapter modules for conditioning material generators, such as GNoME and MatterGen, on desirable properties.

In this work, a fully-explainable gradient-boosted decision tree (GBDT) architecture is used to predict the bandgap of 2D materials. Chemically-relevant features are generated using elemental and compositional descriptors, such as atomic number, electronegativity, and element ratios. Structural features are not leveraged due to sparsity in the experimental data corpus. A gradient-boosted feature selection (GBFS) workflow is used to rank and prune the features based on their predictive power, as well as identifying non-linear feature interactions and accommodating feature sparsity. These properties allowing the GBFS model to avoid overfitting and enhance its generalizability. By training an ML workflow on data from these databases, with a focus on methodical feature selection, both the interpretability and accuracy of these models are improved.

The computational dataset includes 9,000 2D materials within 0.05 eVatom^-1 of the convex hull of stability and 477 feature descriptors are initially generated. Using GBFS and recursive feature elimination to reduce the feature set to 54 features, followed by Bayesian hyperparameter optimization of the GBDT, we can predict the direct electronic bandgap of 2D materials using a lightweight and fully-explainable ML model. The model demonstrates a mean-absolute error (MAE) of 0.35 eV and root-mean squared error (RMSE) of 0.52 eV of on an unseen test set. A separate set of 177 confirmed experimental bandgap values of bandgap for 2D materials is extracted from the literature corpus to benchmark the GBFS model, achieving MAE of 0.75 eV and RMSE of 0.97 eV. This approach is extensible to other properties of interest, such as carrier mobility, density of states at the Fermi level, and magnetic characteristics, demonstrating the broader applicability of the GBFS strategy in material prediction for 2D materials.

The toxicity and poor stability of lead-based perovskite solar cells (PSCs) have prompted an intensive search for sustainable and lead-free alternatives. Among the most promising candidates, tin-based perovskites such as methylammonium tin iodide (MASnI₃) and formamidinium tin iodide (FASnI₃) exhibit favorable optoelectronic properties and reduced environmental impact. In this study, a comprehensive photovoltaic and thermal stability analysis of MASnI₃ and FASnI₃ solar cells is conducted using the SCAPS-1D simulator combined with deep learning-assisted performance prediction. Device architectures are optimized through systematic variation of electron transport layers (ETLs) and hole transport layers (HTLs) to maximize power conversion efficiency (PCE) and thermal stability. The deep learning model enables efficient feature extraction and prediction of performance trends under varying operational and environmental conditions. Simulation results reveal that FASnI₃-based devices demonstrate enhanced carrier mobility, reduced recombination rates, and improved thermal robustness compared to their MASnI₃ counterparts. The optimized FTO/SnO₂/FASnI₃/Spiro-OMeTAD/Au configuration achieves a peak efficiency exceeding 25%, maintaining superior performance under elevated temperature stress. Furthermore, the study highlights the critical role of defect density and interfacial engineering in improving both photovoltaic and thermal stability of tin-based perovskites. These findings provide valuable insights into the design of efficient, eco-friendly, and thermally durable lead-free perovskite solar cells for next-generation photovoltaic technologies.

This work introduces a hybrid numerical–machine learning framework to analyze the impact of design parameters on the performance of graphene-based double-gate field-effect transistors (Graphene DG FETs) for nanoscale digital applications. Quantum transport is modeled using the non-equilibrium Green’s function (NEGF) formalism to accurately capture electrostatic control and carrier transport in graphene channels under variations in gate length, graphene thickness, gate oxide thickness, dielectric permittivity, and gate work function. Supervised machine learning is applied to NEGF-generated data to identify the most influential parameters through feature importance analysis. The extracted device characteristics are incorporated into circuit-level simulations by implementing graphene-based inverter gates in the Cadence environment, enabling evaluation of switching behavior, delay, and power consumption. The results highlight the dominant role of electrostatic design parameters and demonstrate the effectiveness of the proposed framework as a predictive tool for analaysing and optimizing Graphene DG FETs in low-power nanoscale digital circuits.

We present an integrated experimental–computational framework to accelerate synthesis optimization of the high-energy layered cathode LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) by coupling hydrothermal processing with Bayesian optimization (BO) to maximize the initial discharge capacity at 0.1C. A Random Forest surrogate model paired with an expected improvement (EI) acquisition function in the BO framework is iteratively updated using batch experimental outcomes and used to recommend process conditions within bounded continuous domains (hydrothermal temperature and time; multi-step calcination temperatures and times) alongside discrete precursor selections. Over early BO-guided cycles, the search progressively shifted from a baseline regime near ~160 mAh g^-1 toward higher-performing regions, yielding an initial best discharge capacity of approximately 190 mAh g^-1. To enhance model robustness, we screened the training data for suspected non-reproducible high-capacity data points, removed these outliers, and retrained the BO model using the original dataset augmented with all accumulated batch results from experiments. Subsequent validation showed a modest initial iteration outcome (~160 mAh g^-1), followed by a rapid improvement to ~180 mAh g^-1 in the next BO iteration, indicating more reliable navigation of the synthesis space after mitigating the outliers. Feature importance analysis consistently identifies the first calcination time and hydrothermal temperature as primary performance drivers for optimization, while precursor identity becomes increasingly influential under suboptimal conditions; notably, Ni/Co acetates combined with Mn sulfate appear favorable only within tightly controlled hydrothermal and sintering windows. Materials characterization further supports these structure–process–property relationships, with XRD indicating that low-capacity samples correlate with impurity phases. Overall, this study demonstrates a practical, data-efficient route for experiment-in-the-loop optimization of NCM811 hydrothermal synthesis.

The revolutionary development of machine learning (ML) and data science and analytics, coupled with its application in material science stands as a significant milestone of the scientific community over the last decade. Investigating active, stable, and cost-efficient catalysts is crucial for oxygen evolution reaction owing to significance in a range of electrochemical energy conversion processes. In this work, we have demonstrated an efficient approach of high-throughput screening to find stable transition metal oxides under acid condition for high-performance oxy-gen evolution reaction (OER) catalysts through density functional theory (DFT) calculation and a machine learning algorithm. A methodology utilizing both the Materials Project database and DFT calculations were introduced to assess the acid stability under specific reaction conditions. Building upon this, OER catalytic activities of acid-stable materials were examined, highlighting potential OER catalysts that meet the required properties. We identified IrO2, Fe(SbO3)2, Co(SbO3)2, Ni(SbO3)2, FeSbO4, Fe(SbO3)4, MoWO6, TiSnO4, CoSbO4 and Ti(WO4)2 as promising catalysts, several of which have already been experimentally discovered for their robust OER performance, while others are novel for experimental exploration, thereby broadening the chemical scope for efficient OER electro-catalysts. Descriptors of the bond length of TM-O and the first ionization energy were used to unveil the OER activity origin. From the calculated results, guidance has been derived to effectively execute advanced high-throughput screenings for the discovery of catalysts with favorable properties. Furthermore, the intrinsic correlation between catalytic performance and various atomic and structural factors was elucidated using the ML algorithm. Through these approaches, we not only streamline the choice of the promising electro-catalysts but also offer insights for the design of varied catalyst models and the discovery of superior catalysts.

Atomistic modeling based on density functional theory (DFT) provides first-principles accuracy but scales poorly with system size and time scales. At the same time, empirical potentials are fast but lack predictive power for complex chemistries. Machine learning interatomic potentials (MLIPs) fill this gap by learning high-dimensional potential energy surfaces (PESs) from DFT data and enabling large-scale simulations that retain near ab initio accuracy at orders-of-magnitude reduced cost [1]. Among these, universal (or foundational) MLIPs are particularly valuable for rapid screening and simulations of complex materials [2]. However, the ability of MLIPs to accurately predict the properties of a particular material is not guaranteed, and therefore they must be thoroughly validated [3, 4].

In this study, we demonstrate the use of uMLIPs [5, 6] for simulating structural relaxation in high-entropy oxides, i.e., multicomponent compounds containing at least four distinct chemical elements. The results of uMLIPs-based simulations are compared with structural information (partial distribution functions and mean square displacements) obtained experimentally using multi-edge X-ray absorption spectroscopy combined with reverse Monte Carlo simultions [7].  

This study was supported by the Latvian Council of Science project No. LZP-2022/1-0608.

[1] R. Jacobs, D. Morgan, S. Attarian et al., Curr. Opin. Solid State Mater. Sci. 35 (2025) 101214.

[2] J. Riebesell, R.E.A. Goodall, P. Benner et al., Nat. Mach. Intell. 7 (2025) 836.

[3] A. V. Shapeev, D. Bocharov, A. Kuzmin, Comput. Mater. Sci. 210 (2022) 111028.

[4] P. Žguns, I. Pudza, A. Kuzmin, J. Chem. Theory Comput. 21 (2025) 8142.

[5] B. Deng, P. Zhong, K. Jun, J. Riebesell, K. Han, C.J. Bartel, G. Ceder, Nat. Mach. Intell. 5 (2023) 1031.

[6] I. Batatia, P. Benner, Y. Chiang et al., J. Chem. Phys. 163 (2025) 184110.

[7] A. Kuzmin, J. Timoshenko, A. Kalinko, I. Jonane, A. Anspoks, Rad. Phys. Chem. 175 (2020) 108112.

In industrial sugar production, ash content is an important parameter for monitoring process performance and product quality. Gravimetric methods are commonly used for ash determination due to their accuracy; however, they require long analysis times and are not suitable for rapid process control. Conductometric measurements provide faster results but only reflect the soluble inorganic fraction, which limits their direct use.

In this study, thin juice, thick juice, and molasses samples taken from an industrial sugar processing line were analyzed using both gravimetric and conductometric methods. The experimental results were compared in order to examine the relationship between conductivity values and total ash content. A clear correlation was observed between the two methods for all sample types.

Based on the obtained data, simple correlation models were established to estimate gravimetric ash values from conductometric measurements. The proposed approach allows faster analysis while maintaining acceptable accuracy and can be used as a practical tool for routine process monitoring in sugar production. This study demonstrates the potential of data-based analytical correlations for improving efficiency in industrial materials processing.

Keywords:
Conductometric analysis, gravimetric ash, data-based correlation, process monitoring, sugar production

Entropy-Engineered Multi-Metallic MOFs Unlock High-Performance Ammonium-Ion Storage

Palani Barathi and Martin Pumera*

Advanced Nanorobots and Multiscale Robotics Laboratory, Faculty of Electrical Engineering and Computer Science, VSB - Technical University of Ostrava

17. listopadu 2172/15, Ostrava 708 00, Czech Republic

E-mail: martin.pumera@vsb.cz

Abstract

Aqueous ammonium ion batteries (AAIBs) are an emerging sustainable energy technology owing to their high ionic conductivity, safety, low cost, and non-metallic charge carrier. However, their practical applicability is restricted by low energy density, a narrower potential window, and poor cycling stability. An entropy-engineered amino-functionalized metal-organic framework (EnMOF-NH2) is reported as a promising cathode for high-performance AAIBs. EnMOF-NH2 consists of five metal nodes (Co, Ni, Fe, Mn, Mo) and an amino-functionalized benzene dicarboxylic acid linker (BDC-NH2), which provides multiple redox centers, enhanced structural stability, and abundant hydrogen bonding sites for efficient NH4+ storage. The incorporation of Mo metal nodes into the multi-metallic MOF can strengthen the metal-ligand interaction and suppress the metal dissolution, while amino functionalized BDC provides polarity to the framework and enables fast NH4+ storage through hydrogen bonding. EnMOF-NH₂ achieves a high reversible capacity of 130.8 mAh g⁻¹ at 0.3 A g⁻¹ in 1.0 M (NH₄)₂SO₄, outperforming the non-amino-functionalized EnMOF-BDC. It exhibits excellent rate capability, and capacity increases to 162% after 2500 cycles, indicating strong structural stability. A fuel cell coupled with an EnMOF-NH₂ cathode and perylene tetracarboxylic dianhydride (PTCDA) anode shows a wide voltage window of 0.01-1.8 V, a specific capacity of 59.1 mAh g⁻¹ at 0.5 A g⁻¹, and retains 83% capacity over 1000 cycles.
Keywords: Aqueous batteries, amino-functionalized MOF, Entropy engineering, Ammonium ion storage.

In the context of CO₂ capture and conversion technologies, developing industrially feasible catalysts with low environmental impact has become a priority. Herein, we present a novel lattice engineering strategy: the Thermal Stimulated Polarization (TSP) treatment. TSP consists of exposing the samples to an electrostatic force (i.e., constant voltage application) at a high temperature; causing a refinement of the crystal lattice showing a priority direction (i.e., polarization). In this sense, the specific new ordination, with customized photo-, electro- and thermal- properties, is maintained after the TSP treatment without the need to apply any external stimuli. Hence, the material presenting a new meta-stable state is referred as “permanently polarized”.

TSP has shown successful results when applied to hydroxyapatite (HAp, Ca₅(PO₄)₃OH) an abundant and biocompatible ceramic. More specifically, the TSP induces controlled: 1) OH- vacancies, 2) specific re-orientation and alignment of the remaining OH^- (acting as quantum pathways), and 3) new calcium phosphate co-existing phases. As a result, permanently polarized HAp (2P-HAp) transitions from a passive support to an active catalytic material with: 1) enhanced conductivity (from >500 MΩ·cm^-2 to 10 MΩ·cm^-2), 2) enhanced photo-absorption response (presence of trap states E_g = 2.85 eV, while the band gap of HAp is 5.11 eV; confirmed by DFT calculations and UV-Vis spectra); and 3) superior CO₂ and radical adsorption (presence of OH- vacancies and co-existing phases leads to the presence multiple acid/basic binding sites; as seen by NAP-XPS and DFT calculations). It is worth highlighting that each structural modification can be controlled by the TSP experimental conditions (i.e., atmosphere, voltage and temperature).

Overall, TSP unveils the possibility to carry out CO₂-valorization reactions to produce by design C1 (formic acid), C2 (ethanol), C3 (acetone) and even C4 (1,4-dioxane) products; selectively. All reactions are carried out under mild conditions: < 150 ºC, < 6 bars of CO₂ pressure or continuous flow conditions, H₂O as proton source and presence/absence of UV-light irradiation. Although we focus on the selectivity of the catalyst, 2P-HAp shows high conversion efficiencies for C_1-2 products (34.69±1.52 mmol·g_cat·h^-1).

A part from the results obtained for 2P-HAp, herein we aim to present the potential of a generalized lattice-engineering strategy for the development of a new generation of abundant catalysts. Currently we propose (from a theoretical point of view) the extension of the TSP towards other materials, highlighting the different polarization mechanisms which depend on the “starting” lattice structure. So far, we have been able to validate such hypotheses for amorphous SiO₂, showing catalytic activity for CO₂-to-C_1-2 reactions. Certainly, TSP proposes re-visiting already existing materials to improve their properties, rather than relying on the development of rare or exotic systems.

The capture and mineralization of CO₂ into thermodynamically stable solid phases is widely recognized as a promising route for long-term carbon stabilization, particularly under ambient conditions without external energy input. The spontaneous carbonation of certain bismuth-based oxides under ambient conditions has been reported, leading to the formation of stable bismuth subcarbonates (Bi₂O₂CO₃) through solid–gas or solid–solution interactions. However, the underlying mechanisms governing these carbonation processes remain insufficiently understood. Establishing a mechanistic understanding is therefore essential for advancing CO₂ mineralization under low-energy conditions.

In the present work, α-Bi₂O₃, BiOCl, and Bi₁₂O₁₇Cl₂ were selected as representative bismuth-based oxides with distinct structural motifs to examine structure-dependent carbonation behavior. Experimental results demonstrate that crystal structure decisively governs the accessible carbonation pathways of Bi-based oxides under ambient conditions. Under alkaline carbonate solutions and CO₂-containing environments, α-Bi₂O₃ showed limited carbonation in carbonate solutions but underwent direct carbonation under near-neutral CO₂ conditions, whereas BiOCl remained inert toward CO₂ and readily transformed into Bi₂O₂CO₃ via carbonate-driven ion exchange while preserving its layered framework. Bi₁₂O₁₇Cl₂ exhibited carbonation along both pathways, consistent with its intermediate structure.

To elucidate the atomic-level mechanisms, density functional theory (DFT) calculations were conducted. The results indicate that the carbonation pathways of bismuth-based oxides are governed by the electronic structure of Bi³⁺ centers and their local Bi–O coordination. Electron localization function (ELF) analysis shows that in Bi₂O₂-based layered structures, symmetric coordination renders Bi³⁺ lone pairs stereochemically inactive, suppressing structural reconstruction and enabling topochemical conversion between BiOCl and Bi₂O₂CO₃ driven by concentration gradients. In contrast, the surface of α-Bi₂O₃ exhibits stereochemically active lone pairs, generating Lewis acidic sites that promote surface reactions and subsequent carbonation upon CO₂ exposure. As a result, the carbonation of α-Bi₂O₃ proceeds predominantly through a surface-mediated pathway rather than a topochemical transformation. This mechanistic insight provides guidance for the rational design of low-temperature CO₂ capture materials with potential relevance to carbon management.

Separation of light hydrocarbons (olefins and alkynes) from paraffin gases is essential in petrochemical refining but remains highly energy intensive due to reliance on cryogenic distillation, which contributes significantly to global energy consumption. In this study, we demonstrate a green, low-energy mechanochemical separation strategy employing ball milling of hexagonal boron nitride (h-BN) powders under mixed hydrocarbon atmospheres. The mechanochemical process selectively adsorbs alkyne and olefin molecules onto in-situ formed BN nanosheets while minimizing paraffin uptake, enabling effective purification of paraffin gas streams and recovery of the adsorbed species via mild thermal treatment .

Quantitatively, the BN nanosheets generated through mechanochemical activation achieved exceptional uptake capacities, with ~708 cm³/g for acetylene (C₂H₂) and ~1048 cm³/g for ethylene (C₂H₄), surpassing previously reported materials under similar conditions . Advanced chemical analysis reveals that olefin and alkyne adsorption proceeds through quasi-chemical interactions involving C–N bond formation at defect sites on BN nanosheets, whereas paraffin adsorption is limited to weaker physisorption on BN particles. This mechanochemical route operates at room temperature and ambient pressures, significantly reducing energy demand compared to conventional methods and offering scalability for industrial separation applications .

The results highlight the potential of mechanochemistry-activated BN nanosheets as a transformative platform for energy-efficient gas separation and storage, opening pathways for sustainable hydrocarbon processing and potentially informing broader mechanochemical design principles for separations relevant to energy and materials science.

Boron Nitride Nanosheets: Scalable Mechanochemical Synthesis and Emerging Applications in Energy, Separation, and Advanced Materials

Two-dimensional boron nitride nanosheets (BNNS) have emerged as a unique class of materials combining high thermal and chemical stability, wide bandgap insulation, mechanical robustness, and tunable surface chemistry. Unlike graphene, BNNS offer intrinsic electrical insulation while retaining excellent structural integrity, making them attractive for applications spanning energy storage, gas separation, electronics, and extreme-environment materials. However, scalable and sustainable synthesis routes, along with a fundamental understanding of structure–property relationships, remain key challenges.

In this work, we present a mechanochemical approach for the scalable production of defect-engineered boron nitride nanosheets under ambient conditions. Ball-milling-induced exfoliation enables controlled generation of few-layer BNNS with high surface area and abundant edge and basal-plane defect sites, without the need for solvents, high temperatures, or harsh chemical treatments. Structural and chemical characterization using electron microscopy, spectroscopy, and surface analysis confirms nanosheet formation, defect activation, and tunable surface functionality.

The resulting BNNS exhibit exceptional performance across multiple application domains. In gas storage and separation, defect-rich BNNS demonstrate selective adsorption of small molecules, enabling energy-efficient separation of industrially relevant gases. In energy and thermal management applications, BNNS enhance thermal conductivity and stability when incorporated into polymer and ceramic matrices. Additionally, their chemical inertness and radiation resistance make BNNS promising candidates for protective coatings and next-generation electronic and insulating components.

Overall, this study highlights mechanochemically synthesized BN nanosheets as a versatile, scalable, and sustainable materials platform, bridging fundamental nanomaterials science with practical applications in energy, sustainability, and advanced manufacturing. The insights gained provide design principles for tailoring BNNS properties through defect engineering, opening new pathways for their deployment in next-generation functional materials.

The development of energy-efficient gas storage and separation technologies is critical for addressing global challenges in clean energy, decarbonization, and industrial sustainability. Mechanochemistry has recently emerged as a powerful and scalable strategy to engineer solid-state materials with tailored surface chemistry, defect structures, and gas–solid interactions under ambient conditions. Unlike conventional thermochemical synthesis routes, mechanochemical processing enables direct activation of materials without solvents or high temperatures, offering unique advantages for gas adsorption and separation.

Here, we demonstrate how mechanochemically engineered nanomaterials enable selective storage and separation of industrially relevant gases and outline how these principles can be extended to solid-state hydrogen storage. Mechanochemical activation generates high-surface-area nanostructures with defect-rich interfaces that promote selective adsorption through a combination of physisorption and quasi-chemical interactions. For hydrocarbon gases, this approach enables preferential uptake of unsaturated molecules over paraffins, allowing energy-saving separations at room temperature. Importantly, the same defect-engineering strategy provides tunable binding sites for hydrogen, offering a pathway to enhance hydrogen adsorption capacity and reversibility under mild operating conditions.

By coupling in-situ pressure–temperature monitoring with advanced structural and spectroscopic characterization, we establish correlations between mechanochemical processing parameters, defect formation, and gas uptake behavior. These insights form a unified mechanochemical design framework for gas storage and separation, bridging hydrocarbon purification and hydrogen energy applications. The results position mechanochemistry as a versatile platform for developing next-generation solid-state hydrogen storage materials that are scalable, sustainable, and compatible with emerging hydrogen infrastructure.

The increasing environmental challenges associated with fossil fuel consumption have accelerated the global shift towards sustainable and carbon-neutral energy sources, with green hydrogen has gained attention as a clean fuel. Solar-driven water splitting offers a promising and sustainable pathway for hydrogen generation. In this context, perovskite-based photocatalysts have emerged as highly potential materials due to their tunable band structures, strong visible light absorption, and favorable charge transport properties. Among these, LaNiO₃ stands out as a promising photocatalyst due to its narrow bandgap and well-suited band edges that enable efficient visible light absorption. Strategic modifications with a minimal loading of 1 % noble metals (Rhodium, Ruthenium, Iridium) further elevate the photocatalytic performance. Utilizing the solution combustion method, catalysts are synthesized and extensively characterized through techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, diffuse reflectance spectroscopy (DRS), and ultraviolet photoelectron spectroscopy (UPS)., Photoluminescence, and Time-resolved photoluminescence. Photocatalytic hydrogen evolution studies are conducted under solar simulator irradiation. Notably, the addition of noble metals has shown a significant decrease in the recombination rate as observed from lifetime studies. The photocatalytic hydrogen generation increased from 1.37 mmol g^-1 h^-1 to 20.86 mmol g^-1 h^-1 while the apparent quantum efficiency varied from 2.58% to 39.42%. The turnover frequency (TOF) on the basis of the active sites varied from 214.44 h^-1 to 1685.24 h^-1. The catalysts demonstrate stable and consistent performance over a 12-hour duration. The photocatalytic hydrogen yield trend was found to be Rh/LaNiO₃ > Ru/LaNiO₃ > Ir/LaNiO₃ > LaNiO₃.

Two-dimensional molybdenum disulfide (MoS₂) has emerged as a promising material for gas sensing owing to its high specific surface area and rich surface chemistry, however, its room-temperature sensing performance is often limited by poor charge transport and low intrinsic sensitivity. In this work, MoS₂/WO₃ nanocomposites were synthesized via a two-step hydrothermal route and systematically investigated for room-temperature ethanol gas sensing.

Structural and morphological analyses using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) revealed the formation of MoS₂ nanospheres with diameters below 200 nm uniformly embedded within a network of WO₃ nanorods with diameters less than 100 nm. XRD confirmed the coexistence of hexagonal MoS₂ and hexagonal WO₃ phases, while TEM evidenced intimate interfacial contact between the two constituents, indicating the formation of well-defined nanoscale heterojunctions. Nitrogen adsorption–desorption measurements demonstrated an enhanced specific surface area of the nanocomposites, favouring efficient gas adsorption.

X-ray photoelectron spectroscopy (XPS) revealed interfacial charge transfer from MoS₂ to WO₃, resulting in favorable band alignment and enhanced charge separation. Consequently, the MoS₂/WO₃ nanocomposite sensor exhibited a dramatic enhancement in ethanol sensing performance compared to pristine MoS₂, achieving a maximum sensitivity of 0.37 ppm⁻¹ at room temperature—more than eighty times higher than that of bare MoS₂. The sensor also demonstrated fast response and recovery times of 23 s and 11 s, respectively, along with good operational stability, showing only 16% degradation in response over four weeks.

The enhanced sensing performance is attributed to the synergistic effects of increased surface area, nanoscale heterojunction formation, and interfacial charge redistribution, highlighting MoS₂/WO₃ nanocomposites as promising candidates for high-performance room-temperature ethanol gas sensing.

Although green hydrogen holds great potential as a replacement for fossil fuels, achieving the projected 2.3 Gt annual demand would necessitate over 20 billion m³ of water, roughly matching the yearly needs of a nation of 60 million people. Water electrolysis, powered by renewable electricity, is among the most promising clean hydrogen production technologies, as it generates hydrogen without carbon emissions. Since current industrial electrolysis processes depend mainly on purified freshwater, a limited resource, developing it for large-scale hydrogen production risks worsening global drinking water shortages. In contrast, seawater which is virtually inexhaustible, offers an attractive alternative feedstock for electrolysis. Yet, significant challenges remain, while considerable research has focused on suppressing undesired chloride oxidation at the anode, achieving notable advances. However, less emphasis has been placed on issues at the cathode, where salt deposition blocks active sites and accelerates corrosion. Although natural seawater is mildly alkaline (pH 7.5–8.4), the local pH near the cathode rises sharply during electrolysis, driving precipitation of cations such as Mg²⁺ and Ca²⁺ as hydroxides. Another hurdle is reaction kinetics: in neutral seawater, both the anodic oxygen evolution reaction (OER) and cathodic hydrogen evolution reaction (HER) proceed sluggishly, demanding higher overpotentials to achieve practical current densities and thus lowering overall efficiency. To overcome these challenges, an ammonia-treated transition metal phosphide catalyst that delivered outstanding activity, reaching 500 mA cm^-2 at an overpotential of 574 mV in natural seawater and 1000 mA cm^-2 at 416 mV in alkaline seawater, both exceeding the performance of commercial Pt/C by 2X. During natural seawater electrolysis, the catalyst surface promotes the formation of ammonium (NH₄⁺) ions, formation these NH₄⁺ groups form hydrogen bonds with hydroxyl (OH-) species generated during interfacial water dissociation, effectively suppressing hydroxide precipitation. Simultaneously, they enhance the hydrogen-bonding network within the electric double layer (EDL), reducing the hydrogen transfer barrier and boosting HER kinetics. Therefore, the catalyst achieves outstanding activity and robust durability, operating reliably for more than 500 hours as a cathode in seawater electrolysis. This study highlight a promising approach toward achieving durable and efficient cathodic reactions for hydrogen production in seawater.

Methane pyrolysis is its heat decomposition into solid carbon and hydrogen gas without emitting carbon dioxide. However, the temperatures necessary for a high conversion rate are too high for large-scale hydrogen production by catalyst-free methane pyrolysis. Therefore, finding catalysts that allow one to decrease the operating temperature and make the process economically and environmentally viable is an important goal.

We employ two theoretical approaches in our search for suitable catalysts.

First, we use density-functional theory to describe the adsorption of C and H atoms and intermediate methane-pyrolysis molecules (CH_n with n = 3, 2, 1) on single-element metal catalyst surfaces. The results show, e.g., that the adsorption gets stronger with decreasing periodic-table group number of the d-block catalysts. More detailed analysis based on the Sabatier principle and microkinetic modelling reveals that various operating temperatures and methane/hydrogen partial pressures require various optimum catalysts. Additionally, we examine the effect of alloying on the C, H, and CH_n local adsorption characteristics on various surfaces of Cu_1–xAg_x (x = 0.00, 0.25, 0.50, 0.75, 1.00) alloys.

Second, we use ab-initio molecular dynamics to observe CH₄ reactions with the Cu_1–xAg_x surfaces and evaluate the reaction rates and trajectories of CH₄ decomposition. Our simulations show that while the local adsorption energies on the alloy are largely given by those on the individual metals, the dependence of the dynamic behaviour of the molecule on the composition of the alloy surface is non-monotonic. Therefore, despite the generally higher catalytic activity of pure Cu as compared to pure Ag, the most effective catalysts in the Cu_1–xAg_x system are found at intermediate x. Furthermore, we define markers such as bond-length standard deviation which quantify the catalytic potential of the surface and identify optimum catalysts without observing the simulated dissociation event in itself.

Collectively, our results reveal the advantages of bimetal catalysts for CH₄ decomposition over elemental metals, identify the (approximate) optimum compositions in the Cu_1–xAg_x case, and constitute new methodological insights into modelling and simulation of catalysis-related processes. As such, they establish a foundation for large-scale studies of catalyst surfaces, alloy compositions, or material classes.

Sustainable hydrogen production is a key process for the transition towards environmentally friendly energy systems. Among the available renewable approaches, sunlight-driven photocatalytic hydrogen generation represents a green and cost-effective route, particularly when based on non-critical and earth-abundant materials¹. However, the efficiency of photocatalytic processes is still strongly limited by material design, charge carrier recombination, and inadequate control over nanostructure formation.

In this context, this work investigates the synthesis-driven engineering of non-critical CeO₂–10 wt.% WO₃ nanocomposites for hydrogen production via ethanol photoreforming. The novelty of this study lies in the systematic comparison of three different synthesis routes in order to establish direct correlations between synthesis conditions, material properties, and photocatalytic performance.

The first nanocomposite was synthesized via chemical precipitation assisted by hexamethylenetetramine (HMTA)², employed as a complexing and pH-controlling agent to regulate the WO3 nucleation and particle growth on CeO₂ interface. The second sample was obtained through hydrothermal synthesis, a well-established method that allows to promote enhanced crystallinity and improved interfacial contact between the CeO₂ and WO₃ phases. The third material was prepared using a microwave-assisted synthesis, which provides rapid volumetric heating, high homogeneity, and unique defect structures due to non-equilibrium reaction conditions.

A clear dependence of hydrogen evolution on the synthesis strategy was observed and correlated with the chemico-physical properties of the as-prepared composites, deeply examined by XRD, FT-IR, N₂ adsorption-desorption measurements, SEM-EDX, UV-DRS and PL spectroscopies Furthermore, the photocatalytic stability in long-time on irradiation tests was evaluated as well as the type of irradiation source (solar lamp, solar simulator, natural solar light), the organic scavenger (ethanol, glycerol, and other biomass-derived sustainable compounds), the influence of pH, and the type of sample (powder or film).

This study demonstrates that the synthesis engineering is a crucial parameter for optimizing oxide-based nanomaterials for sustainable hydrogen production proposing promising routes for the development of high-performance photocatalysts for energy and environmental applications.

References

¹M.T. Armeli Iapichino, R. Fiorenza, V. Patamia, G. Floresta, A. Gulino, M. Condorelli, G. Impellizzeri,G. Compagni, S. Scirè, Catalysis Communications 2024,187,106850

²R. Fiorenza, S. Balsamo, M. Condorelli, L. D’Urso, G. Compagnini, S. Scirè, Catalysis Today 2021,380 ,187-198

The authors fully acknowledge for funding the MASE PRIDE project (CUP: F57G25000320006)

Graphene-based nanohybrids decorated with noble metal nanoparticles are attracting increasing attention for electrochemical sensing due to their synergistic combination of high electrical conductivity, large active surface area, and outstanding catalytic activity. In this work, palladium–graphene (Pd–Gr) nanohybrids were synthesized via a one-step in situ electrochemical exfoliation of graphite in the presence of Pd(II) precursors with different concentrations, enabling simultaneous generation of few-layer graphene and controlled nucleation of Pd nanoparticles. Three materials, denoted 1Pd-Gr, 2Pd-Gr, and 3Pd-Gr, were obtained and thoroughly characterized by SEM, TEM, EDX, XRD, Raman, FTIR, and XPS, revealing well-dispersed crystalline Pd nanoparticles anchored on graphene sheets, with precursor concentration governing particle size, dispersion, defect density, and surface chemistry.

The nanohybrids were integrated onto microfabricated electrochemical platforms by drop-casting on screen-printed and silicon-based electrodes employing nanocrystalline graphite as the working electrode. Electrochemical evaluation by cyclic voltammetry and impedance spectroscopy demonstrated that the 1Pd-Gr material, synthesized using the lowest Pd precursor concentration, exhibited the highest electroactive surface area, lowest charge-transfer resistance, and fastest heterogeneous electron-transfer kinetics, attributed to optimal nanoparticle dispersion and minimized aggregation.

As a proof of concept for food quality monitoring, the optimized 1Pd-Gr electrode was applied to the direct electrochemical detection of acetic acid, a key marker of fermentation and spoilage. The sensor displayed a linear response from 1.0 × 10^-7 to 5.0 × 10^-5 M, a limit of detection of 1.6 nM, excellent selectivity against common food interferents, and good operational stability and reproducibility. The combination of precursor-controlled in situ nanozyme synthesis with silicon-compatible microfabrication provides a promising route toward miniaturized, low-cost, and highly sensitive electrochemical devices for on-site food quality assessment.

Funding

This work was funded from the project "National Platform for Semiconductor Technologies" Contract no. G 2024-85828/390008/27.11.2024, SMIS Code 351364, funded by the European Regional Development Fund under the Operational Program for Smart Growth, Digitization and Financial Instruments (POCIDIF), Priority 4 – Development of Strategic Technologies for Europe – STEP, and by a grant of the Ministry of Education and Research, CNCS - UEFISCDI, project numbers: PN-IV-P7-7.1-PED-2024-0558, ctr no 17PED/03.01.2025 and the core program: PN 2307 - µNanoEl, Contract No. 8N/03.01.2023, µNanoEl within PNCDI IV (2022-2027).

Ordered porous multicomponent nanomaterials with high surface areas, regular pore geometries, and diverse compositions are highly attractive for sustainability applications including catalysis and separations. Here we show that precise control of the ordered pore architecture and multicomponent composition enables high activity and stability in electrochemical hydrogen evolution (HER) and CO₂ capture using two complementary material platforms. In the first example, we report an one-pot nanocasting approach in which metal salt precursors are simultaneously co-infiltrated and co-reduced in a KIT-6 template, yielding 3D gyroidally ordered mesoporous PtCu-rich multimetallic alloys doped with Fe, Co, and Ni. The gyroidal alloy electrocatalysts exhibit excellent HER performance, delivering overpotentials of 25 mV and 85 mV at 10 and 100 mA cm⁻², respectively, and minimal activity loss after 100,000 accelerated durability cycles in 1 M KOH. In the second example, we form ordered hierarchically macro-mesoporous carbons via acid-triggered macroscopic spinodal decomposition and block copolymer mesophase self-assembly, followed by sulfonation and pyrolysis to generate a conductive carbon framework with structural hierarchy. The resulting hierarchically macro-mesoporous carbons enable CO₂ capture and serve as high-dispersion catalyst supports for Pt-based alloys, achieving an overpotential of 6.5 mV at 10 mA cm⁻² for HER in 1 M KOH. Collectively, these results highlight how ordered hierarchical transport pathways and multicomponent chemistry can be designed to deliver high-performance platforms for energy and separations.

Glycerol Conversion to Lactate over Pt/Ce–ZrO₂ Catalysts: Influence of Support Doping on Selectivity and Stability.

Macchindra G. Chandgude^a,b, Anil. H. Valekar^a†, Kyung-Ryul Oh^a,* and Young Kyu Hwang^a,b,*

^a Green Carbon Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Republic of Korea

^b Department of Advanced Materials and Chemical Engineering, University of Science and Technology (UST), Daejeon 34113, Republic of Korea

^†Anil H. Valekar: R&D Center, Wi-fine Tech Co., Ltd., Daejeon 34013, Korea

* Corresponding authors: Young Kyu Hwang, Kyung-Ryul Oh

Email: ykhwang@krict.re.kr, kroh@krict.re.kr

Keywords: Glycerol, Lactic acid, Platinum, Ce-doped ZrO₂­, Support effect

Abstract

Glycerol valorization offers a sustainable approach for producing high-value chemicals from biomass-derived waste. We report Pt catalysts supported on ZrO₂ and Ce-doped ZrO₂ for the catalytic dehydrogenation of glycerol to lactate (LA), which demonstrate pronounced support-dependent performance. Pt/5CeZrO₂ achieved the highest LA yield (89.5%) along with an exceptional turnover frequency (TOF) of 7577 h^-1 at 1 h, the highest reported for heterogeneous glycerol dehydrogenation. Structural and electronic characterization revealed that Ce doping generates abundant oxygen vacancies and Lewis acid sites and induces lattice strain, promoting ultrafine Pt nanoclusters (~1 nm) with a high density of metal–support interfaces. These features enabled efficient glycerol conversion and outstanding stability under harsh reaction conditions (200°C, 9M KOH). The system further demonstrated industrially relevant performance metrics, including a 75% glycerol feed concentration, 12.6 kgLA L^-1 day^-1 space-time yield, and hydrogen co-production at 5.8 mol H₂ L^-1 day^-1. Correlation of LA selectivity with lattice strain elucidated structure–activity relationships associated with defect and interface engineering. Multiple recycling tests confirmed catalyst robustness. These findings highlight support engineering as a powerful strategy for advancing metal–oxide catalysts for scalable biomass valorization.

Recent advances in implantable biodevices have increased the demand for flexible and bioresorbable microbatteries that can deliver reliable power while minimizing long-term biological impact. Such microbatteries are essential for next-generation medical implants, as they offer high biocompatibility, mechanical flexibility, and controlled degradation in the body. These features eliminate the need for surgical removal and improve patient outcomes.

In this study, we present a novel flexible Na-ion battery for bioresorbable devices design based on micropillar electrodes. This architecture enables the fabrication of a highly functional, flexible, and biocompatible energy storage device suitable for transient medical applications. The proposed design achieves high areal capacity while maintaining reversible mechanical flexibility. The device demonstrates strong electrochemical stability under mechanical deformation, retaining 60% of its capacity after 100 charge–discharge cycles. Fatigue testing further shows capacity retention above 70%, confirming excellent mechanical and electrochemical robustness.

By using eco-friendly and bioresorbable materials, the Na-ion battery provides efficient energy storage and undergoes safe dissolution within the body, thereby reducing the need for secondary surgical procedures. These results highlight the potential of this technology to support next-generation implantable systems and contribute to safer and more sustainable medical devices.

Monitoring heavy metal ions (HMIs) in aqueous systems is essential for environmental safety and water quality assessment. Among these, iron (Fe) is an essential element at trace levels but can become problematic when present in excess. In this context, a naturally derived fruit extract is investigated as a sustainable colorimetric sensor for selective Fe³⁺ ion detection in aqueous system. The extract is prepared through a simple aqueous extraction process and contains a mixture of naturally occurring pigments and phytochemical constituents that act as active sensing components. For intellectual property considerations, the specific identity of the fruit extract is not disclosed at this stage. Selectivity studies performed against ten other common heavy metal ions demonstrate that only Fe³⁺ induces a significant response: at a concentration of 10 mM, the characteristic color of the extract completely vanishes, whereas the other metal ions produce no detectable color or spectral change, highlighting the extreme selectivity of the system for Fe ions.

UV-visible spectroscopic analysis provides further insight into this selective behavior. The absorption spectrum of the extract exhibits two prominent bands centered around ~550 nm and ~270 nm. The visible band near 550 nm, associated with the dominant color-imparting pigment, shows complete attenuation only in the presence of Fe ions, consistent with the observed naked-eye response, but does not display reliable linearity for quantitative analysis. In contrast, the absorption feature around 270 nm exhibits a pronounced, concentration-dependent change upon Fe³⁺ interaction, providing a linear response suitable for quantitative sensing, which, to the best of our knowledge, has not been reported previously for similar systems. These results indicate that while Fe³⁺ uniquely disrupts the visible pigment responsible for color, quantitative detection arises from interactions with specific UV-active phytochemical constituents, demonstrating an effective, highly selective UV-visible sensing pathway for iron in aqueous systems. The simplicity, extreme selectivity, and sustainability of this system suggest that it could be further developed into portable sensing platforms for future on-site iron monitoring.

With the current trend toward renewable energy, hydrogen generation using water, sunlight, and photocatalysis is expected to be a clean, CO2-free method. Dye-sensitized solar-cell-based photocatalytic water electrolysis devices operate by absorbing visible light with an organic dye and oxidizing water on a highly active OER metal catalyst surface using the oxidative power of holes generated by electronic excitation. In this study, we focused on the hole transport layer, a key issue in these devices, and optimized the protective layer to improve long-term stability against water and light and photocurrent density upon light irradiation.

A porous TiO2 layer was fabricated by screen printing on a cleaned FTO glass substrate. After calcination, the substrate was immersed in a solution of a visible-light-sensitized dye  to adsorb the dye. A gold film was then deposited as a hole transport layer (HTL) by spin-coating a solution containing additives such as Spiro-OMeTAD and P3HT. Finally, an OER catalyst, such as an IrOx catalyst, was deposited on the anode to fabricate an electrode-type device. The anode was characterized by light irradiation and electrochemical measurements. The electrolyte solution was a 0.1 M Na2SO4 aqueous solution (0.1 M Pi buffer solution) with a pH of 7, and simulated solar light (AM1.5G, 100 mW cm-2) was irradiated using a xenon lamp as the light source.

In our previous work, we demonstrated that the addition of fluorinated alkylthiol molecules (PFDT) to the hole transport layer (HTL) increased the photocurrent density under light irradiation conditions using LSV measurements. PFDT is a molecule with a high electron density. Chronoamperometry measurements under light irradiation showed that the current density remained higher than that of the control sample, even after prolonged reaction. This is thought to be due to the hydrophobic structure of the alkyl chain and fluorine groups in the side chain, which allows PFDT to remain inside the HTL without dissolving. Because existing doping agents are highly leaching in water, in this study we investigated more hydrophobic hole transport layers, such as P3HT. We report these results together.

Climate change is an important global challenge, and human activity is one of the main responsible to the called global warming. For instance, the growing consumption of fossil fuels to meet modern energy demands has accelerated the search for technologies capable of identifying the emitted toxic gases. Therefore, it is necessary a continuous monitoring of atmosphere gases level, bringing the importance of gas sensor technologies. Gas sensors are devices whose some physical property change reversibly upon exposure to the target gas. The chosen materials for chemical sensors are semiconducting metal oxides (SMO), due to its ability to modulate the electrical resistance when the gas analyte is adsorved on material surface. In addition, the use of nanomaterials can become sensors more sensitive due to the high exposed surface to volume and quantum confinement of charge carriers when the particle size is about the Debye length of the material.

The use of SMO, based on tin oxide nanostructures, will be presented for monitoring the levels of important gases at atmosphere, mainly CO (as a consequence of incomplete combustion), and NO2 (arising from a combination of atmospheric N2 and O2 gases emitted by cars and industries under conditions of high temperatures and pressures). Besides the most known stannic oxide (SnO2), we were able to produce stannous oxide (SnO) and the less stable, mixed valence oxide, Sn3O4, and these phases can present better sensor response and selectivity to NO2 than SnO2.

In addition to the gas sensor study in pristine stannous oxide nanobelts, we further investigate the effect of surface functionalization with Pt and Pd nanoparticles. The sensor device responses to H2, CO and NO2 were measured in dry air baseline atmosphere as function of the analyte concentration (1–1000 ppm) and operating temperature (100-350 °C). Noble metal decorated SnO devices exhibited enhanced chemical sensitization, resulting in increased sensitivity upon exposure to reducing gases at different working temperatures. Catalyst decoration of SnO led to enhanced sensitivity to CO, but only at lower temperatures (below 150 °C) and high analyte concentration (> 200 ppm), attributed to chemical sensitization, facilitated by absorption and oxidation of gas molecule at nanoparticle catalytic sites. Interactions of the SnO surface with NO2 were inhibited in both Pt- and Pd-decorated materials, which were related to the generation of electron depletion layers and band bending at the SnO-metal nanoparticle interfaces. Differences in sensor response of Pd- and Pt-decorated SnO sensors were analyzed based on the energy diagram of the materials, showing that strong potential barriers form at Pt and PtOx - SnO interfaces due to respective work functions, while only Pd in its Pd2+ oxidized state promotes such barriers. Based on these findings, we propose a SnO-based sensor array capable of selectively detecting and discriminating between reducing and oxidizing gases.

Developing advanced electrocatalytic materials for artificial nitrogen fixation is critical to overcoming the energy-intensive limitations of the conventional Haber-Bosch process. However, designing non-metal catalysts with precise active sites for sustainable C-N coupling remains a significant materials engineering challenge.

Herein, we report the synthesis of Lewis acid and Lewis base dual-doped graphene as a highly efficient electrocatalyst for ambient urea synthesis. We employed a unique sonocavitation and nebulization synthesis (SNS) strategy, utilizing acoustic cavitation energy to effectively incorporate heteroatoms into the graphitic lattice while maintaining a hierarchical structure. This material design not only provides abundant active sites but also leverages the inherent hydrophobicity of the graphene scaffold to physically suppress the parasitic hydrogen evolution reaction (HER).

From a materials perspective, the dual-doping strategy induces a powerful synergistic effect via a cooperative "push-pull" electronic modulation. Notably, the formation of acid and base moieties within the graphene lattice plays a pivotal role. These sites enable a dual-binding mechanism that effectively stabilizes key intermediates, facilitating not only N₂ activation but also the CO₂ reduction reaction (CO₂RR). The Lewis acid sites function as electron acceptors to withdraw electron density, while the Lewis base sites concurrently inject electrons into the anti-bonding orbitals. This precise electronic tuning significantly destabilizes the chemically inert N≡N and C=O bonds, drastically lowering the activation energy barrier for C-N coupling.

The resulting catalyst exhibits excellent electrochemical performance, achieving high selectivity for ammonia and urea synthesis at low overpotentials. Isotope labeling experiments confirmed the product origins, demonstrating the efficacy of the SNS-derived non-metal catalyst design for sustainable energy applications.

The development of cost-effective, highly active, and durable electrocatalysts is a fundamental requirement for a wide range of electrochemical energy conversion and storage technologies, including fuel cells and water electrolysis systems. Commercial application of these technologies is strongly limited by sluggish reaction kinetics and insufficient long-term electrochemical stability under harsh operating conditions. Despite considerable progress in reducing noble-metal usage and improving catalytic activity through advanced material design, durability degradation remains a persistent challenge across various electrochemical reactions. As a representative example, proton exchange membrane fuel cells (PEMFC) are particularly difficult for the long-term durability of oxygen reduction reaction (ORR) catalysts, where electrochemical degradation of Pt-based alloy nanoparticles continues to limit long-term fuel cell operation. These challenges highlight the necessity of further improving catalyst stability and electrode-level performance to realize reliable and sustainable electrochemical energy technologies.

Recent advances in computational science, particularly AI-driven multiscale modeling, have enabled systematic investigation of electrocatalyst materials and their structural stability. By integrating density functional theory (DFT) calculations, machine-learning-based force fields, and experimental validation, catalytic systems, including both active nanoparticles and their interactions with support materials, can be analyzed across various length scales, ranging from atomic-scale interactions to larger-length-scale behavior. This integrated approach improves the understanding of degradation mechanisms and stability trends, thereby supporting the rational design of next-generation electrocatalysts.

In this presentation, AI-assisted multiscale modeling integrated with electrochemical experiments is employed to investigate the durability of Pt-based alloy nanoparticles for the ORR. PtCo and PtNi intermetallic nanoparticles are synthesized via a low-temperature reduction method followed by heat treatment, and their electrochemical and physicochemical properties are systematically evaluated using electrochemical techniques and materials characterization. DFT calculations and machine-learning-based force fields, supported by experimental characterization, are employed to investigate catalytic stability through multiscale modeling. This approach contributes to a better understanding of catalyst degradation and stability in Pt-based ORR catalysts. This work was supported by MOTIE, Korea (20019175, RS-2025-25463656, P0022331) and the NRF funded by the Ministry of Science and ICT (RS-2024-00409675).

One of the critical challenges in fuel cells and metal-air battery systems is the oxygen reduction reaction (ORR) at the cathode. Achieving a complete reduction of O2 to H2O via the 4-electron pathway is essential for optimal performance. While Pt-based electrocatalysts are known to accelerate this pathway, their high cost restricts large-scale commercial application. Molybdenum (Mo)-based catalysts, characterized by strong binding energies that facilitate O-O bond cleavage and promote the formation of *O species, present a viable alternative. However, following the Sabatier principle, excessively strong binding interactions impede the desorption of O and OH intermediates, thereby diminishing the ORR rate. Therefore, a downward shift of the d-band center is advantageous for Mo-based catalysts. This can be effectively achieved through the atomic dispersion of metals, which decreases the average electron density and enhances catalytic activity by facilitating the desorption of reaction intermediates.

Herein, we present a novel approach for synthesizing Mo single-atom catalysts (SACs) derived from craft lignin, a renewable carbon source. The lignin-derived matrix offers significant advantages, including enhanced metal ion chelation and abundant anchoring sites due to its rich functional groups, promoting the atomic-level dispersion of Mo SACs. Our findings reveal that increasing the relative amount of the nitrogen source reduces the size of Mo carbides, leading to the successful synthesis of Mo SACs at sufficiently high nitrogen ratios. The structural and electronic properties of the synthesized catalysts were thoroughly characterized via transmission electron microscopy (TEM), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS). These analyses confirmed the atomic-scale dispersion of Mo and the tunability of its atomic density. Moreover, modulating the atomic density of Mo effectively regulates the electronic properties and catalytic performance toward the ORR. The optimized catalyst demonstrated superior ORR performance with a half-wave potential of 0.95 V vs. RHE and an excellent Tafel slope of 21.7 mV dec-1, confirming the efficient 4-electron reaction pathway (n = 3.6). Density Functional Theory (DFT) calculations further demonstrated that the enhanced activity is attributed to a synergistic effect: the amplification of active site density through atomic dispersion and the intrinsic enhancement of catalytic performance resulting from the tailored electronic structure. Furthermore, utilizing lignin as a carbon precursor offers remarkable economic and environmental benefits, achieving a >90% cost reduction compared to conventional carbon sources while ensuring sustainability. This study demonstrates a highly effective strategy for designing advanced, atomically dispersed electrocatalysts for ORR, paving the way for practically viable energy conversion technologies.

Enhancing the practical performance and durability of anion exchange membrane water electrolysis (AEMWE) requires overcoming the sluggish kinetics of the hydrogen evolution reaction (HER) in alkaline media. Unlike in acidic environments, HER in alkaline conditions is sluggish due to an additional water dissociation step. Recent studies have particularly highlighted that HER electrocatalysts and cathodes exhibit higher overpotentials and more severe degradation than the anode at the single-cell level, underscoring the need for advanced HER electrocatalyst and cathode designs.

Among various electrocatalyst candidates, Pt remains the benchmark HER catalyst owing to its outstanding activity and durability in alkaline environments. However, its high cost continues to be a major barrier to the large-scale commercialization of AEMWE. To address this issue and enhance catalytic performance, two main strategies have been actively suggested: (1) reducing platinum group metal (PGM) utilization through the development of highly ordered intermetallic alloys and (2) site-specific single-atom catalysts that exhibit superior performance with cost-effectiveness.

In this work, we present our recent strategies for designing highly efficient and durable HER electrocatalysts, paving the way toward practical hydrogen production through AEMWE.

In addition, this work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. RS-2024-00467234) and funded by the Ministry of Trade, Industry, and Energy (MOTIE), Korea, under “Innovative Digital Manufacturing Platform" (No. P0022331) supervised by the Korea Institute for Advancement of Technology (KIAT).

The present research reports a high-performance Molybdenum Oxynitride (MoON) nanostructured material deposited directly over stainless-steel mesh (SSM) via reactive magnetron sputtering technique for flexible symmetric supercapacitor (FSSC) application. The MoON/SSM flexible electrode manifests remarkable Na⁺-ion pseudocapacitive kinetics, delivering exceptional ~881.83 F.g^-1 capacitance, thanks to the synergistically coupled interfaces and junctions between nanostructures of Mo₂N, MoO₂, and MoO₃ co-existing phases, resulting in enhanced specific surface area, increased electroactive sites, improved ionic and electronic conductivity. Employing 3D Bode plots, b-value, and Dunn’s analysis, a comprehensive insight into the charge-storage mechanism has been presented, revealing the superiority of surface-controlled capacitive and pseudocapacitive kinetics. Utilizing PVA-Na₂SO₄ gel electrolyte, the assembled all-solid-state FSSC (MoON/SSM||MoON/SSM) exhibits impressive cell capacitance of 30.7 mF.cm^-2 (438.59 F.g^-1) at 0.125 mA.cm^-2. Moreover, the FSSC device outputs superior energy density of 4.26 μWh.cm^-2 (60.92 Wh.kg^-1) and high power density of 2.5 mW.cm^-2 (35.71 kW.kg^-1). The device manifests remarkable flexibility and excellent electrochemical cyclability of ~91.94% over 10,000 continuous charge-discharge cycles. These intriguing pseudocapacitive performances combined with lightweight, cost-effective, industry-feasible, and environmentally sustainable attributes make the present MoON-based FSSC a potential candidate for energy-storage applications in flexible electronics.

References:
1. Ranjan, B. & Kaur, D. Pseudocapacitive Storage in Molybdenum Oxynitride Nanostructures Reactively Sputtered on Stainless‐Steel Mesh Towards an All‐Solid‐State Flexible Supercapacitor. Small 20, 2307723 (2024). 
2. Ranjan, B. & Kaur, D. Pseudocapacitive Kinetics in Synergistically Coupled MoS2–Mo2N Nanowires with Enhanced Interfaces toward All-Solid-State Flexible Supercapacitors. ACS Appl. Mater. Interfaces 16, 14890–14901 (2024). 
3. Ranjan, B. & Kaur, D. Pseudocapacitance Powered Nickel Molybdenum Nitride Nanocomposite Reactively Cosputtered on Stainless-Steel Mesh toward Advanced Flexible Supercapacitors. ACS Appl. Energy Mater. 7, 4513–4527 (2024). 
4. Ranjan, B. & Kaur, D. Achieving enhanced pseudocapacitance in MoS2 nanowires rationally sputtered over NiMnIn shape memory alloy for flexible Na-ion supercapacitor. J. Energy Storage 71, 108122 (2023). 
5. Ranjan, B., Sharma, G. K. & Kaur, D. Rationally synthesized Mo2N nanopyramids for high-performance flexible supercapacitive electrodes with deep insight into the Na-ion storage mechanism. Appl. Surf. Sci. 588, 152925 (2022). 
6. Ranjan, B., Sharma, G. K. & Kaur, D. Tuning growth of MoS2 nanowires over NiTiCu nanostructured array for flexible supercapacitive electrodes with enhanced Li-ion storage. Appl. Phys. Lett. 118, 223902 (2021). 

The escalating presence of pharmaceuticals, dyes, and emerging contaminants in water systems demands innovative, sustainable treatment strategies. Combining processes has been shown to be an effective way to boost efficiency and overcome the limitations of the processes when they are alone, especially when there is a synergistic effect. In this context, this work presents hybrid materials integrating photocatalysts with adsorbents and other materials that can create a synergistic effect with them, designed for simultaneous degradation and removal of contaminants under environmentally benign conditions. The photocatalysts were synthesized using different sustainable methods and then combined with other types of materials, such as polyaniline, to create the hybrid system. The results show a significant increase in the efficiency of the photocatalyst after it was combined with polyaniline, leading to the total degradation of many contaminants in various water treatment applications; this combination created a heterojunction between the band gaps of polyaniline and the catalysts, which enhanced the performance of both materials. Regeneration strategies employing sulfate radicals demonstrated the materials’ reusability and operational resilience. This work bridges fundamental material design with scalable water treatment solutions, emphasizing the value of green hybrid systems for sustainable environmental remediation and circular economy applications.

The development of CO₂ reduction offers a complementary strategy which allows renewable electricity to drive the conversion of CO₂ into value-added products that can provide feedstocks for existing industries. This technology provides a means of storing renewable energy while reducing atmospheric CO₂ levels.

Among the explored catalysts for CO₂ reduction, copper and copper-based materials are unique in their ability to produce molecules containing two or more carbon atoms, such as ethylene and ethanol. In particular, mixed valence states of Cu and their interfaces have been identified as key active sites. Thus, a key topic in the CO₂ reduction space has been to engineer copper-based materials which seek to maximise their unique catalytic ability.

My research seeks to address this challenge through the engineering of copper-based materials derived from metal-organic frameworks (MOFs). By systematically varying the electrochemical environment, we investigated how MOF materials transform under different conditions, resulting in nanostructured catalyst surfaces with controllable ratios of copper valence states. These exhibited significant increases in surface roughness owing to the formation of oblong nanostructure, simultaneously achieving 45% C₂H₄ faradaic efficiency (FE). These insights will support the advancement of carbon recycling technologies with a facile method of creating active Cu nanostructures, in line with global efforts toward carbon neutrality.  

Lead (Pb²⁺) contamination in water poses severe health risks, yet conventional adsorption methods often suffer from limited capacity, slow kinetics, and strong pH dependence. Here we present a novel composite adsorbent (AC–CTS–EDTA), integrating activated carbon (AC), chitosan (CTS), and ethylenediaminetetraacetic acid disodium salt (EDTA-2Na). The composite was synthesized via amidation to immobilize EDTA-2Na onto the AC–CTS scaffold, and characterized by XPS, BET, and SEM analyses.

The material demonstrated outstanding performance: nearly complete Pb²⁺ removal (~99%) at low concentrations, high adsorption capacity under elevated loads, stability across pH 4–10, and rapid equilibrium within 2 minutes. Thermodynamic analysis confirmed spontaneous adsorption with reduced enthalpy compared to unmodified AC, indicating synergistic physisorption–chemisorption. Kinetic studies showed excellent correlation with the pseudo-second-order model, highlighting the role of amino, hydroxyl, and carboxyl groups in chelation. Even in the presence of strong competing Na⁺ ions, removal efficiency remained above 82%.

This multifunctional composite offers fast, stable, and high-capacity Pb²⁺ removal, representing a promising candidate for next-generation water purification technologies.

Lead-free bismuth halide perovskite derivatives have emerged as promising materials for solar driven CO₂ reduction, yet controlled regulation of crystal dimensionality and its catalytic implications remain limited.  In the present work, cesium bismuth bromide (Cs₃Bi₂Br₉) nanomaterials with quantum dot and plate like morphologies were synthesised via a ligand assisted reprecipitation method by tuning the coordination environment of the solvents, namely dimethyl sulfoxide and γ butyrolactone.  Solvent coordination strength was shown to govern nucleation and growth behavior, enabling dimensional control without compositional modification or additional ligands.  The distinct morphologies exhibit different surface defect densities, charge separation efficiencies, and CO₂ adsorption behaviors, which collectively result in morphology dependent CO₂ reduction activity and product selectivity. This work elucidates the role of solvent coordination chemistry in directing the structural evolution of lead-free bismuth halide perovskites and provides a practical strategy for structure guided catalyst design.

Waste polyester bottles pose critical environmental challenges due to their non-biodegradability, contribution to landfill accumulation, and generation of microplastics. Developing pathways to repurpose this waste into functional materials can mitigate environmental burden while enabling high-value applications. In parallel, current high-efficiency face-mask filters, although effective against particulate matter pollution, often suffer from high pressure drop and lack active functionalities. In this work, we report a scalable approach to convert waste bottle-grade polyester into ultrafine nanofibres (<75 nm mean diameter) and engineer both neat and silver-nanodot-embedded PET nanofibrous webs for advanced air filtration. When sandwiched between spunbonded nonwovens, the filtration performance improves from ~10% to >99%, while maintaining a low pressure drop of 13 Pa at normal breathing rate. The PET–AgND membranes also exhibit self-charging triboelectric behavior, generating up to 187 mV under airflow, enabling charge-assisted filtration without external power. Durability testing across 28 filtration cycles demonstrates sustained high efficiency (99.69%–99.90%) and modest pressure drop (13–18 Pa). Embedded Ag nanodots (3.5 ± 0.9 nm) impart robust antibacterial activity against E. coli and S. aureus, enhancing protective performance. This study provides a simple, sustainable route for transforming waste polyester into high-efficiency, self-charging, antimicrobial filter media for air-pollution remediation and personal protection.

Keywords: recycling, ultrafine nanofibres, electrospinning, air filtration, triboelectric filtration, antibacterial nanomaterials

Magnesium possesses significant potential as a solid-state hydrogen storage material owing to its substantial volumetric and gravimetric capacities. This study investigates the effect of high-energy ball milling, titanium, and carbon nanotube catalysis additives on the hydrogen absorption properties of a selected commercially available magnesium alloy. A high-energy ball mill was used to process Mg alloy, both with and without additives. Phases, powder morphology, particle size, and surface area of Mg alloy and Mg composite samples were studied. The hydrogen absorption was analyzed using Sievert's apparatus. The results were analyzed and compared with the processing conditions and additives. The results reveal enhanced hydrogen absorption of the magnesium alloy through the use of high-energy ball milling and catalyzing using Ti and MWCNT. Acknowledgments The authors would like to acknowledge King Fahd University of Petroleum and Minerals for support under Grant No. ER221007

High-entropy alloys (HEAs) have emerged as a promising class of electrocatalysts for water splitting due to their multi-element synergy, high configurational entropy, and tunable electronic structure.^1,2 Pulsed laser treatment provides a rapid, non-equilibrium processing route for high-entropy alloy formation, enabling elemental homogenization, metastable phase stabilization, and nanoscale surface restructuring without the need for high-temperature bulk synthesis.³

High-entropy alloy electrocatalysts based on Co–Cu–Fe–Mo–Mn/W systems were synthesized via mechanical alloying (MA) followed by spark plasma sintering and subsequently transformed into nanostructured catalysts through pulsed laser ablation in water and ethanol. Structural, morphological, and surface chemical properties were systematically investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The electrocatalytic performance toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was evaluated in alkaline media. Among the investigated compositions, CoCuFeMoMn, CoCuFeMoW, and CoCuMoMnW exhibited pronounced solvent-dependent activity trends. Laser-ablated samples showed significantly improved OER performance, achieving overpotentials as low as ~220 mV at 10 mA cm^-2 for CoCuFeMoW ablated in water, while mechanically alloyed samples delivered superior HER activity with overpotentials down to ~200 mV. These results demonstrate that controlled laser ablation of HEAs enables efficient tuning of surface chemistry and electrocatalytic behavior, providing a scalable strategy for high-performance bifunctional water-splitting catalysts.

(1)          Li, H.; Lai, J.; Li, Z.; Wang, L. Multi-Sites Electrocatalysis in High-Entropy Alloys. Advanced Functional Materials 2021, 31 (47), 2106715. https://doi.org/10.1002/adfm.202106715.

(2)          Mahdavi, H.; Akcan, O. Ş.; Morova, Y.; Yağcı, M. B.; Ünal, U.; Jahangiri, H. Pulsed-Laser and Mechanical Reduction of Graphene Oxide Combined with NiCoFeMoW High-Entropy Alloys for Electrocatalytic Oxygen Evolution Reaction. ChemSusChem n/a (n/a), 2500466. https://doi.org/10.1002/cssc.202500466.

(3)          Mahdavi, H.; Alamdari, A. A.; Ünal, U.; Jahangiri, H. Open-Air Pulsed Laser-Deposited NiCoCuFeMoMnOx High-Entropy Oxide Thin Films for Efficient Electrocatalytic Oxygen Evolution Reaction. ACS Appl. Energy Mater. 2025. https://doi.org/10.1021/acsaem.5c00194.

Proton conductors are key materials that determine the performance of energy devices such as fuel cells. For practical implementation, proton conductivities of 10^-2 – 10^-1 S/cm over a wide temperature range are required. Although solid oxide proton conductors exhibit excellent thermal and chemical stability, conventional perovskite-type materials, including BaZrO^3- and BaCeO^3-based oxides, rely on acceptor doping to generate oxygen vacancies, followed by proton incorporation via hydration reactions. This transport mechanism inevitably leads to high activation energies in the low-temperature region, which remains a fundamental limitation.
In this study, we focus on HNb₃O₈ nanosheet stacked membranes as a proton-conducting material that does not rely on defect control in bulk crystals. In these membranes, interlayer nanochannels formed by nanosheet stacking function as the primary proton transport pathways. Nb₃O₈^- nanosheets possess a two-dimensional framework composed of edge-sharing NbO₆ octahedra, and their surfaces are known to exhibit high hydration. Furthermore, HNb₃O₈ nanosheets obtained via acid exchange contain a high density of OH groups. In particular, electronically unstable OH groups bridging two Nb atoms are present. These OH groups are considered to act as mobile proton sources within the interlayer nanochannels, thereby enabling efficient proton transport.
As a result, the in-plane proton conductivity of the HNb₃O₈ nanosheet membranes reaches 1.3 × 10^-1 S/cm at 60 °C. Nafion-comparable proton conductivities are maintained over a wide temperature range from 20 to 100 °C. In addition, bond valence–based energy (BVE) calculations based on the bulk KNb₃O₈ crystal structure reveal that the NbO₆ octahedral network in the Nb₃O₈ framework intrinsically possesses an extremely low energy barrier for proton migration of 0.082 eV. This result indirectly supports the fast proton transport observed in the interlayer nanochannels. Furthermore, power generation was successfully demonstrated in a dual-chamber solid oxide fuel cell employing the nanosheet membrane as the electrolyte, confirming its viability for fuel cell applications.

Synthesis of Nanocrystalline Tungsten Carbide and Influence of Stacking Faults in Electrocatalysis

C. I. Hiley,^1,2 D. Houghton,^1,2 J. C. Clayton,¹ R.J. Kashtiban,³ J. M. MacPherson,^1,2 P. R. Unwin,^1,2 R. I. Walton^1,2

¹Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK.

²Hartnoll Centre, University of Warwick, Coventry, CV4 7AL, UK.

³Department of Physics, University of Warwick, Coventry, CV4 7AL, UK.

To reduce dependence of fossil fuels on our energy production, renewable sources are increasingly exploited. However, renewable energy sources are intermittent, and so for deep decarbonisation, energy storage solutions must be found. Whilst batteries are useful for small-scale and short-term storage, hydrogen gas has emerged as a leading candidate for long-term and large-scale storage and transmission for a variety of reasons.¹

Tungsten carbide (WC) is a layered material that is widely used in cutting and machining thanks to its extreme hardness and temperature resistance. It is a metallic compound with reasonably high conductivity and is chemically inert. WC has been explored as for heterogeneous catalysis² and electrocatalysis of the hydrogen evolution reaction, where it exhibits catalytic behaviour comparable to Pt.^3,4 The challenges in using WC in electrocatalysis arise from the typical high temperature synthesis conditions under reactive gases (CH₄/H₂, for example) that tend to give low surface area materials.

In this presentation, we describe the synthesis of WC by a convenient precursor decomposition route from ammonium metatungstate under an atmosphere of nitrogen gas at moderate temperatures (900 °C). This provides control of nanocrystalline morphology, with well-shaped ~20 nm crystallites, and the degree of stacking faults, in samples that are largely free of amorphous carbon. We assess crystallographic features of the materials from X-ray diffraction and high-resolution TEM, and examine if these affect the electrocatalytic performance, with the hydrogen evolution reaction as a test case.

¹Kumar, N.; Lee, S.-Y.; Park, S.-J. Nano Today 2024, 56, 102302.

²Levy, R. B.; Boudart, M. Science 1973, 181, 547-549.

³Esposito, D. V.; Hunt, S. T.; Stottlemyer, A. L.; Dobson, K. D.; McCandless, B. E.; Birkmire, R. W.; Chen, J. G. Angew. Chem. Int. Ed. 2010, 49, 9859-9862.

⁴Xiao, P.; Ge, X.; Wang, H.; Liu, Z.; Fisher, A.; Wang, X. Adv. Funct. Mater. 2015, 25, 1520-1526.

Abstract

Poly(ethylene terephthalate) (PET) is widely used in packaging, textiles, and coatings, leading to significant plastic waste accumulation. Chemical recycling offers a sustainable route to convert PET waste into value-added materials. This study presents a zinc acetate–catalyzed aminolysis process for PET and, for the first time, employs a commercially available polyetheramine, Jeffamine 2000 (PPG 2000), as the aminolysis agent. The resulting depolymerization product was characterized by gel permeation chromatography (GPC) to determine its molecular weight for polyurea (PU) film design. Multifunctional PU-based smart coatings were developed by incorporating MXene (Mo₂Ti₂AlC₃) as a functional filler. SEM confirmed uniform MXene dispersion, while XRD showed a crystal orientation shift from (106) to (004) with increasing MXene content. Thermal, mechanical, and electrical analyses revealed that PU-MXene-0.1 exhibited optimal performance, including the highest electromagnetic shielding efficiency (SE), as evaluated by the Nicholson–Ross–Weir (NRW) method. Higher MXene loadings led to property deterioration due to filler agglomeration, indicating an optimal MXene concentration for enhanced composite performance.

Funding The funding for the mechanical characterizations and DMA analysis was supported by grants from the Ministry of Research, Innovation and Digitization, CNCS UEFISCDI, project number PN−IV-P2-2.1-TE-2023-0806, ctr. 55TE/ 2025 and project number PN−IV-P7-7.1-PTE-2024-0466, ctr. no. 2PTE/2025, within PNCDI IV.

Acknowledgements IMT team would like to acknowledge for financial support in part by the Romanian Ministry of Education and research through the Core Program within the National Research, Development and Innovation Plan 2022−2027, under Project 2307−μNanoEl, contract number 8N/ 03.01.2023, and the project “National Platform for Semiconductor Technologies”, contract no. G 2024-85828/ 390008/27.11.2024, SMIS code 304244, co-funded by the European Regional Development Fund under the Program for Intelligent Growth, Digitization, and Financial Instruments.

Organic photocatalysts offer tailored properties and unique processability, necessary to ensure a sustainable route to green hydrogen by harnessing solar energy. To maximize light harvesting and charge generation during photocatalytic processes, two complementary organic semiconductors (donor and acceptor) are physically mixed to form D:A heterojunction nanoparticle (NPs). Through material engineering, intermixed morphologies can be achieved and ensure excellent charge generation across the visible spectrum, with improved charge stability. These charges can then be involved in redox reactions at the nanoparticle surface to conduct photocatalytic Hydrogen Evolution Reaction (HER).¹ 

However, the physical nature of donor and acceptor interactions in blends promote phase segregation, morphological instability, and strong dependence on nanoparticle size.² In practice, while optimized properties might be achieved at first, extended photocatalytic experiments usually showcase a loss of photocatalytic efficiency, either linked to poor colloidal, photochemical or morphological stability. 

Here, we address these challenges by exploring the benefits of covalent interaction between donor and acceptor materials,³ yet unexplored in the field of photocatalysis or nanoparticle engineering. This covalent linkage constrains the nanoscale morphology, suppresses phase segregation, and maintains high intermixing to support efficient charge separation. As a result, hydrogen evolution reaction (HER) rates superior to 1200 mmol g^-1 h^-1 are achieved, spanning among the highest reported to date.⁴

More interestingly, the morphological resilience of our approach ensured outstanding operational stability, with more than 95% of their initial HER rate preserved after 96 hours of photocatalysis. In contrast, nanoparticles prepared from physically mixed donor and acceptor show lower activity and faster deactivation, consistent with morphology-driven losses in D–A blend systems. Ultimately, we showcased that ensuring a covalent linkage between donor and acceptor maintains high performance across a broad nanoparticle size range, improving reproducibility.

This work opens new avenues for the field of organic photocatalysis. The covalent linkage of donor and acceptor materials leads to a general strategy to unite high efficiency with exceptional stability in organic photocatalysts.

1 C. M. Aitchison and I. McCulloch, Chem. Mater., 2024, 36, 1781–1792.

2  A. Holmes, E. Deniau, C. Lartigau-Dagron, A. Bousquet, S. Chambon and N. P. Holmes, ACS Nano, 2021, 15, 3927–3959.

3  Y. Wu, J. Guo, W. Wang, Z. Chen, Z. Chen, R. Sun, Q. Wu, T. Wang, X. Hao, H. Zhu and J. Min, Joule, 2021, 5, 1800–1815.

4 A. Holmes, Q. Chen, R. B. Ribeiro, L. R. Franco, X. Bi, M. Bergami, M. M. Brette, M. R. do N. Varella, M. C. Araujo, E. Wang, under review.

SrTi0.5Mn0.5O3  (STM55) perovskite has been previously investigated experimentally and proven to be a favorable thermochemical water splitter. However, further attempts to optimize its performance in producing H2   require a robust defect model to guide the selection of the doping levels and the thermodynamic conditions. Herein we  build a computationally inexpensive defect model; on one hand utilizing a statistical mechanical formalism to account for defect-defect interactions and on the other hand invoking density functional theory with Hubbard term (DFT+U).  Our treatment of defect-defect interactions is based on a linear model in temperature and off-stoichiometry accounting for binary  and ternary interactions . Furthermore, the formation and interaction energies computed with DFT+U were conducted after careful and systematic choice of the U term for both Mn and Ti.  The final model is proven to be both  quantitively and qualitatively robust in predicting the oxide off-stoichiometry in the temperature range (600 ◦C to 1500 ◦C) and as such can be employed to simulate hydrogen production using STM55.  Subsequently, we examine the effect of various parameters that can influence H2  production and suggest optimal thermodynamic operating conditions. Additionally, we analyze the effect of Mn doping level and suggest doping strategies to improve hydrogen production. The systematic framework presented in this study can be extended to other dopants and other perovskites with the favorable attribute of being computationally efficient while maintaining robust predictive capability.

Conventional agricultural fertilization methods are often inefficient, causing nutrient loss and environmental pollution. New strategies taking advantage of engineered nanoparticles can be a solution to improve nutrient delivery to crops at any growth stage. In the case of phosphorus, a vital macronutrient, only a limited fraction of soil-applied phosphorus is taken up by crops during each growing season. Foliar application of engineered nanoparticles offers a strategy in agriculture to enhance nutrient use efficiency and mitigate environmental impact by providing foliar fertilizers when crops require them, thus avoiding nutrient losses to the environment through reduced soil application. Nanoparticle uptake efficiency and potentially targeted delivery can be enhanced by tuning, e.g., size and morphology. Nanohydroxyapatite (Ca₅(PO₄)₃(OH), nHAp) is a promising candidate for controlled phosphorus delivery due to its biocompatibility, chemical stability, and adjustable dissolution kinetics.

In this study, nHAp particles were synthesized by a controlled hydrothermal method, focusing on the relationships among nucleation, growth mechanisms, and phosphorus release. The growth of nHAp crystals was selectively directed by the addition of a surfactant to favor phosphorus-rich (001) planes, making the structure suitable for foliar phosphorus delivery. Characterizations confirmed that higher surfactant concentrations resulted in shorter, less aggregated nanorods with improved suspension stability, whereas particles made without surfactant exhibited agglomeration. Co-doping nHAp with rare-earth elements enabled tracer-based investigations. Dissolution tests in plant-relevant media revealed pH-dependent phosphorus release: faster release under mildly acidic conditions and greater stability at neutral pH, suitable for storage and foliar application. Foliar treatment of potato leaves showed comparable phosphorus uptake for both nanoparticle and ionic forms; importantly, nanoparticle formulations did not cause tissue damage, unlike the ionic forms. These findings demonstrate that precise control over nucleation and crystallographic growth provides a reliable strategy for designing hydroxyapatite nanomaterials with tunable physicochemical properties, which could be useful for sustainable foliar phosphorus delivery and related agricultural applications.

Crystal facet engineering of anatase TiO₂ nanocrystals: Correlating structural evolution with photocatalytic efficiency towards malachite green and bisphenol-A

Piyali Das and Rajakumar Ananthakrishnan*

Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur-721302, India

Email: raja@chem.iitkgp.ac.in

The rational design and synthesis of well faceted semiconductor materials are essential for enhancing efficiency in photocatalytic applications. Facet dependent selectivity arises from variations in atomic arrangement and surface energy, which strongly influence surface reactivity. In this work anatase TiO₂ with predominantly exposed {001} facets was synthesized by systematically varying experimental parameters such as solvents, pH and reaction temperature to optimize conditions for achieving the smallest particle size with maximum {001} facet exposure. Among all samples TF2, synthesized using an ethanolic solvent at pH 6 and the hydrothermal temperature maintained at 180 ºC for 24h, demonstrated the greatest exposure of {001} facets and an average particle 9 nm which has been verified by PXRD and FESEM analysis. The TF2 sample exhibited remarkable photocatalytic performance, achieving complete degradation of 80 ppm cationic dye Malachite Green (MG) and 92% degradation of 20 ppm bisphenol-A (BPA) in 90 minutes. The intermediate products formed during photodegradation of BPA were identified using LC-MS analysis. Controlled studies revealed that involvement of reactive oxygen species (ROS) like superoxide radicals (O₂^.-) was majorly responsible for photodegradation process.

Keywords: Facet engineering, Photodegradation, ROS

References:

H. G. Yang, C. H. Sun, S. Z. Qiao, Nature, 2008, 453, 638-642.

H. G. Yang, G. Liu, J. Am. Chem. Soc., 2009, 131, 4078–4083.

J. Pan, G. Liu, Angew Chem. Int. Ed., 2011, 50, 2133–2137.

J.Wu, S. Lu, RSC Adv., 2016, 6, 67502–67508.

K. Reza, H. Jiangyong, J. Chem. Eng., 2020, 384,123384.

Y. Wu, F. Gao, J. Phys. Chem. C, 2021, 125, 3988−4000.

Hydrogen energy is an important approach to tackle global warming while assessing an increase of renewable energy parts in the worldwide energy need. In light of the increased research and opportunities for hydrogen energy deployment, the development of sensors for hydrogen detection is highly encouraged [1]. Graphene-based materials, owing to their tunable electronic properties and high surface area, have become a key element in today's sensor development [2]. Such materials are widely implemented in various applications, including the development of efficient resistive sensors [3]. If processing graphene materials has been a challenge at the beginning, nowadays, several methods of surface modification (oxidation, functionalization, decoration) have been developed to improve their processability and large-scale production [4]. Among all graphene-based materials, graphene oxide (GO) is largely employed as starting material to cover various application areas [5]. Regarding resistive sensor fabrication, GO is often chemically reduced into reduced graphene oxide (rGO) that presents better conductivity and additional surface oxygenated groups for further functionalization.

The rGO is suitable for nanocomposites preparation since it can be functionalized or decorated with different functional moieties comprising molecular moieties, metal nanoparticles, functional oxides, etc. rGO-based nanocomposites are, for this reason, highly attractive for sensitivity enhancement since their functional moieties are specific adsorption sites for gaseous molecules and for targeting selectivity while their high surface area are essential for increasing surface adsorption.

In this prospection, we prepared nanocomposites made of rGO decorated with metallic nanoparticles (NPs) such as Platinum (Pt), Palladium (Pd), and a combination of bi-metallic nanoparticles. We implemented different methods of functionalization, which will be presented here. The functionalization or decoration by nanoparticles enables the elaboration of nanocomposites that enhance the sensitivity by catalytic effect. The rGO/NPs are prepared both chemically and physically and then optimized by annealing treatment. The nanocomposites are also characterized by XRD, IR, UV-Vis, Raman, SEM, and TEM. At the end, I will present the sensors' performance of the nanocomposite upon exposure to hydrogen gas with an emphasis on the role of the nanoparticle distribution and their size on the responses. The result will highlight the effect of rGO and NPs working in synergy to enhance the sensor response for developing reliable hydrogen sensors. 

References:

1. Dawood, F. et al.. International Journal of Hydrogen Energy 2020, 45, (7), 3847-3869.

2. Cruz-Martínez, H. et al. Sensors 2021, 21, (6), 1992.

3.  Avouris, P. et al. MRS Bulletin 2012, 37, (12), 1225-1234.

4.  Agarwal, V. et al.. Chemical Engineering Journal 2021, 405, 127018.

5.  Smith, A. T. et al. Nano Materials Science 2019, 1, (1), 31-47.

The low solubility of gases in water poses a significant challenge for liquid-phase electrochemical gas evolution reactions, such as alkaline water electrolysis (AWE). Gas accumulation and sluggish bubble detachment at the electrode–electrolyte interface increases local resistance and cause voltage losses, ultimately reducing system efficiency. In this work, we present an alternative strategy to address these limitations by using a novel class of aqueous porous liquids (PL) with enhanced gas sorption capabilities during AWE. The PL electrolyte promotes efficient gas removal and bubble detachment by increasing the porosity of the liquid medium. As a result, stable gas evolution is achieved with a 23.3% reduction in overpotential during OER (from 500.20 mV to 388.51 mV) and a 10.1% reduction during HER (from 326.68 to 293.72 mV), accompanied by consistently lower steady-state overpotentials and suppressed voltage fluctuations across low to high current densities, indicating effective suppression of bubble accumulation on the electrode surface. Notably, the performance enhancement scales with current density at comparable voltages at ~200 mA cm⁻² with PL, and reduced charge transfer resistance, confirming that the improvement arises from enhanced bubble management rather than intrinsic changes in reaction kinetics. In situ high-speed imaging provides direct visual evidence, revealing reduced surface coverage and significantly higher detachment frequencies for both HER and OER compared to baseline KOH. Overall, this work provides comprehensive electrochemical and visual evidence that microporous water as electrolyte effectively suppress bubble-induced efficiency losses in AWE, offering a promising pathway for improved hydrogen production systems.

[1] D. P. Erdosy et al., “Microporous water with high gas solubilities,” Nature, vol. 608, no. 7924, pp. 712–718, Aug. 2022, doi: https://doi.org/10.1038/s41586-022-05029-w.

[2] A. E. Thorarinsdottir, D. P. Erdosy, C. Costentin, J. A. Mason, and D. G. Nocera, “Enhanced activity for the oxygen reduction reaction in microporous water,” Nature Catalysis, vol. 6, no. 5, pp. 425–434, May 2023, doi: https://doi.org/10.1038/s41929-023-00958-9.

[3] S. Liu, Y. Zhao, S. Li, and Z. Zhao, “Design hydrophobic-internal and hydrophilic-external micropores for the preparation of microporous water,” Chinese Journal of Structural Chemistry, vol. 44, no. 11, p. 100701, Nov. 2025, doi: https://doi.org/10.1016/j.cjsc.2025.100701.

This study investigates the correlation between the photophysical and structural properties of poly(3-hexylthiophene) (P3HT) nanoparticles prepared from aged precursor solution and their impact on the photocatalytic activity of the nanoparticles. Aging of P3HT solution caused the formation of crystalline aggregates that result in P3HT nanoparticles with outstanding conformational planarity, reduced energy bandgap, and expanded crystalline domains. These features facilitate the visible-light driven photogeneration of charges and their transfer to the nanoparticle’s surface, where they interact with water molecules and produce highly reactive oxygen species (ROS), which are capable of inducing the photodegradation of water pollutants. The photocatalytic activity of the nanoparticles was tested in the degradation of an organic dye, finding that the nanoparticles prepared from moderate aged solution achieved the highest photocatalytic efficiency.

Vanadium dioxide (VO₂) and vanadium pentoxide (V₂O₅) are multifunctional transition metal oxides widely investigated for applications ranging from thermochromic smart windows to catalysis, electrochemical devices, and gas sensing. VO₂ is particularly attractive due to its reversible metal‑insulator transition near 68°C, accompanied by abrupt changes in electrical conductivity and optical transmittance, while V₂O₅ is valued for its high oxidation state, layered structure, and strong surface reactivity. However, achieving controlled, scalable, and low-temperature fabrication of these oxides remains challenging, as their functional properties critically depend on stoichiometry, crystalline structure, and morphology, in addition to conventionally requiring high-temperature processing (>450°C).

In this work, we compare vapor-based and solution-based approaches for the low-temperature fabrication of vanadium oxide thin films, highlighting how processing conditions – such as oxidation state, film morphology, and crystal structure – affect functional properties. Among vapor-phase techniques, plasma-enhanced chemical vapor deposition (PE-CVD) is shows a promising capability to finely tune the oxidation state of vanadium during film growth through plasma-assisted gas-phase reactions. Compared to conventional thermal CVD or atomic layer deposition, PE-CVD enables reduced precursor consumption, lower substrate temperatures, and scalability to large-area processing, while the reactive plasma environments allow controlled stoichiometry of the deposited oxide layers. Complementary to vapor-phase methods, solution-processes provide an alternative and cost-effective route to achieve uniform oxide coatings, enabling compositional control through precursor chemistry and solvent environment while operating at mild processing conditions.

To achieve crystallization without compromising substrate integrity, nanosecond pulsed laser annealing (ns-PLA) is employed as a localized, ultrafast approach to induce film crystallization. The ns laser pulses enable rapid heating and cooling cycles, triggering crystallization in the as-deposited amorphous films while keeping the underlying substrate at room temperature. This allows the realization of well-defined vanadium oxide phases at an overall low thermal budget.

Overall, this work demonstrates low-temperature and scalable fabrication routes of multiple vanadium oxide thin films, establishing a versatile framework for integrating functional vanadium oxides into thermochromic, sensing, and catalytic devices on temperature-sensitive platforms.

[1] Basso, M., et al. (2024) Ultrafast laser crystallization dynamics of thermochromic VO2 thin films by simple moisture-assisted sol-gel. Chem. Mater. 36, 11, 5508–5520.

Hydrogen peroxide (H₂O₂) is gaining attention as mild, sustainable oxidant for remediation, organic synthesis and liquid fuel. However, the main synthesis method by anthraquinone autoxidation is energy-intensive and environmentally costly. Thus, there is strong interest in more sustainable, cost-effective synthesis ^[1]. In this context, photocatalytic H₂O₂ production stands out, as it uses H₂O and O₂ as raw materials and solar light as energy input. Graphitic carbon nitride (g-C₃N₄) is a promising 2D-layered photocatalyst for energy and environmental applications, being visible light responsive, derived from earth-abundant elements via facile synthesis, and having high stability and suitable electronic structure for O₂ reduction ^[2]. Yet, its photocatalytic performance is limited by a low specific surface area (<10 m²g^-1), poor conductivity, and rapid electron-hole recombination. To overcome these issues, various strategies have been explored in literature. This work investigates and demonstrates the efficiency of P-modified g-C₃N₄ photocatalysts for H₂O₂ synthesis from H₂O and O₂ under solar light. The photocatalysts were obtained by thermal polymerisation of melamine at 550°C for 4 h (5°C/min heating rate) in the presence of sodium hypophosphite as phosphor source.
The effect of phosphorus content on the micro/nanostructure, as well as on the electronic and optical properties, is discussed, while time-resolved absorption spectroscopy is used to assess its influence on the lifetime of photogenerated charge carriers. The activity is assessed in terms of H₂O₂ yield, apparent kinetic constants for H₂O₂ formation and decomposition, as well as solar-to-chemical conversion. Controlled phosphor incorporation into the g-C₃N₄ structure strongly enhances photocatalytic performance, boosting the H₂O₂ formation rate by up to 4.5 times for an optimum phosphor content of 20 wt.%, while maintaining a low decomposition rate. H₂O₂ synthesis under visible light (λ>420nm) isolates the contribution of visible light to the overall solar activity. To understand better the reactional pathway, quenching experiments are conducted using AgNO₃ and p- benzoquinone as electron and O₂^{• ̄} scavengers, respectively, and pure water without the hole scavenger IPA.
References
[1] P. García-Muñoz, L. Valenzuela, D. Wegstein (...) H. Remita, J. Bloh, N. Keller, Top. Curr. Chem. 381 (2023) 15.
[2] W-J Ong, L-L Tan, Y. H. Ng, S-T Yong, S-P Chai, Chem. Rev., 116 (12) (2016) 7159.
Acknowledgements
This research was funded by the Interdisciplinary Institute HiFunMat, as part of the ITI 2021-2028 program of the University of Strasbourg, CNRS and Inserm, supported by IdEx Unistra (ANR-10-IDEX-0002) and SFRI (STRAT’US project, ANR-20-SFRI-0012). We acknowledge funding from the Initiative d’Excellence (IdEx) of the University of Strasbourg under LocalCat4Water project. This work was funded by the French National Research Agency in the frame of the project MULTICAT (ANR-23-CE07-0038).

Covalent organic frameworks (COFs) are powerful materials for selective separation and charge-storage applications for effective metal-ion recovery. They typically consist of two or three bifunctional building blocks that undergo polycondensation to form highly ordered, crystalline structures. The unique chemistry of COFs imparts excellent physicochemical stability, well-defined nanochannels, and favourable electrical properties. Current research on COF development focuses on synthesis strategies, linkage chemistry, knot selection, and post-synthetic modifications to introduce ion-exchange functionality.

In this study, imide-, imine-, and amide-functionalized COFs with ion-exchange activity were designed and synthesised using solvothermal, hydrothermal, and microwave-assisted routes. The tailored COF architectures are proposed as ultra-selective sorbents for the recovery of transition-metal ions from battery waste under an externally applied electrical field, demonstrating their potential for practical environmental remediation and resource recovery. The selected metal recovery process is hybrid capacitive deionisation (HCDI).

HCDI is a dual-operation system comprising adsorption and desorption stages, driven by an external electrical source operating under either constant-voltage or constant-current regimes. A typical HCDI stack consists of parallel electrodes: a cathode fabricated from an active material capable of selective cation capture and an anode composed of activated carbon coated with an anion-exchange membrane. In the present work, the cathode was constructed from COF materials, allowing the selective separation of transition-metal ions, including cobalt, nickel, and manganese.

The COFs were synthesised from phthalaldehydes and their derivatives and diamines functionalised with sulfonic, carboxylic, phosphine, and hydroxyl groups, using a 1:1.25 molar ratio. Hydrothermal, solvothermal, and microwave-assisted synthesis methods were employed. The resulting materials were characterised using SEM, FTIR, Raman, PL, TGA.

Experimental results show that the COF materials exhibited high sorption capacity for Ni and Co ions, with a significant enhancement in Co ion-exchange capacity. Notably, Co²⁺ recovery increased from 3.8% to over 50% for materials synthesised via the solvothermal method. The Co/Li separation factor reached 4.1, compared with 1.1 for Co/Ni, indicating that incorporating ion-exchange functionalities into the COF framework substantially improves ion selectivity. Electrochemical analyses, including CV and EIS, further confirmed the preferential behaviour of the COF electrodes toward cobalt and nickel ions. These findings underscore the role of synthesis parameters in tuning the performance of ion-exchange COF materials and highlight their strong potential for advanced selective metal recovery technologies.

Acknowledgements: This research was funded as a whole by the National Science Centre, Poland, Sonata 2022/47/D/ST5/00298.

Advanced structural and optical characterization was used to investigate InAs quantum dot (QD) bilayers incorporating GaAs and GaAsSb spacer layers, grown by molecular beam epitaxy (MBE). Atomic force microscopy reveals the preservation of the QD density in the QD layers. Simultaneously, high-resolution STEM-HAADF imaging confirms the formation of well-defined QD pairs. It emphasizes the role of Sb incorporation in suppressing QD decomposition in the seed layer during overgrowth. This leads to increased size symmetry between vertically coupled dots.

Temperature- and power-dependent photoluminescence spectroscopy provides detailed insight into interlayer coupling and carrier recombination mechanisms. Spacer composition is shown to strongly influence the energetic ordering of emissions, with GaAsSb spacers inducing a reversal in the origin of the ground-state emission and a marked enhancement in photoluminescence intensity. Thermal activation analysis further distinguishes carrier escape pathways associated with different QD layers.

These results demonstrate how correlated nanoscale imaging and spectroscopic techniques enable precise structure–property relationships in complex QD nanostructures, supporting their optimization for advanced thin-film applications.

Keywords: Quantum dot nanostructures, microscopy characterization, Molecular beam epitaxy (MBE), Photoluminescence spectroscopy

Carbon-based materials with tailored nano-/mesoporous architectures are highly demanded across many application fields, particularly as nanoscale host matrices for functional nanoparticles. In this study, magnetron discharge plasma was employed to synthesize nano-/mesoporous CNₓ thin films using methane and nitrogen as gas precursors. Nitrogen incorporation into the carbon network, combined with post-deposition vacuum annealing, enabled template-free formation of nanoscale porous morphologies that can be tuned from sponge-like networks to vertically aligned nanorods. The resulting CNₓ layers grown on Si substrates were successfully applied as host matrices for the growth of Pt nanoparticles homogeneously distributed over porous layer. CNₓ:Pt composite films exhibited high electrocatalytic activity toward the hydrogen evolution reaction (HER) during water electrolysis. As a further step toward practical implementation, the deposition and activation protocol was successfully transferred to commercially relevant electrolyzer components, namely gas diffusion layers (GDLs) based on carbon fiber paper. CNₓ:Pt coatings formed on commercial GDL substrates showed superior electrocatalytic performance at Pt loadings as low as 0.02–0.03 mg cm⁻². To enable compatibility with polymer-containing GDL structures, the conventional high-temperature annealing step was further replaced by laser annealing, minimizing thermal damage to polymer component of the microporous layer. Optimal laser treatment conditions were identified, demonstrating a viable route toward scalable fabrication of highly efficient, low-platinum electrocatalytic cathodes.

Acknowledgement. This project has received funding from the European Union’s Horizon Europe research and innovation program under Grant Agreement No 101119286 and UKRI under Grant Agreement No 10090645 and No 10101683

Photocatalytic hydrogen production over semiconductor materials is a promising route to directly convert solar light into hydrogen, minimizing environmental impact and carbon emissions. Titanium dioxide (TiO₂) is one of the most widely studied photocatalysts and commonly combined with Pt as co-catalyst for enhanced photocatalytic activity. Due to the wide band gap of TiO₂, the TiO₂-Pt system is highly active in UV light but does not utilize photons in the visible light range. Therefore, the introduction of plasmonic nanoparticles is suggested to improve solar light absorption, enhancing the catalytic activity through local field enhancement and the transfer of hot charge carriers.
Finite-difference time-domain (FDTD) simulations are employed to systematically explore the influence of plasmonic nanosheres size, density, and spatial arrangement on local field enhancement and light-particle interaction at the TiO₂ interface. These insights guide the experimental fabrication of photocatalyst configurations using high-throughput deposition and characterization methods. To this end, photodeposition is utilized as a scalable and materials-efficient synthesis technique, enabling selective decoration of catalytically active sites and precise control over plasmonic nanoparticle size and loading.
By tuning the photocatalyst thickness, the co-catalyst loading, and the plasmonic nanoparticle size and density, we aim to maximize visible light utilization and establish structure-property relationships for the design of plasmon-enhanced photocatalysts. The presented framework intends to support the development of plasmonic photocatalysts compatible with scalable reactor designs for solar hydrogen production.

One of the emerging challenges in advanced societies is related to the reduction of pollution in water and air. In particular, the supply of safe and clean water will be one of the major issues in the coming decades, even in places where the water problem has had a limited impact. Policies that prioritise human society's sustainable growth while preserving the fragile natural balance are now a priority. Consequently, the development of new, inexpensive, environmentally friendly materials and methodologies for wastewater remediation is highly desired.

In previous works, we investigated the synthesis and properties of Au nanoparticles (NPs) and how they influence the formation of TiO2 nanowires (NWs) produced by a seed-assisted thermal oxidation process [1-5]. We find that NWs can be produced by annealing a thin layer of Au deposited on metallic Ti at high temperatures (T> 700 °C). The obtained NWs have Au NPs on top, a height of 1-2 um and a lateral size of 50–100 nm. The obtained materials were thoroughly characterised in terms of their morphology, optical properties, structure, and electrochemistry [3,4,5]. Additionally, they showed exceptional photocatalytic activity in the removal of water contaminants, making it profitable for application in environmental remediation [1,2,3].

            In the present work, we propose a two-step procedure to synthesise and decorate TiO2 NWs with noble metal Au NPs. We correlated the thickness of the Au deposited layer with the size and the distance between NPs synthesised on the side of the nanowires. We also performed a morphological, structural, optical and photoelectrochemical characterisation. Degradation of cationic and anionic contaminants was performed in standard conditions. In order to improve the photoactivity of the NWs, we performed the decoration in a reductive atmosphere (i.e., forming gas), and we observed not only the formation of Au NPs but also the formation of small, elongated nanostructures on the side of the nanowires. This could be used for the realisation of branched nanowire structures, where secondary nanowires emerge from a primary backbone. Moreover, considerations about the nanowire formation mechanism are provided. 

References

[1] E. Arcadipane, et al.  RSC Adv. 6, 55490 (2016)

[2] M. Zimbone, et al.  Molecules, 26, 3636 (2021)

[3] F. Giuffrida et al.  Thin Solid Films 771, 139783 (2023)

[4] M. Zimbone et al. J Mater Sci 59, 17831 (2024)

[5] M.Zimbone et al. Electrochemistry Communications, 180, 108021 (2025)  

Nanostructured tungsten trioxide (WO₃) is a n-type semiconducting metal oxide (SMOX) that exhibits polymorphic characteristics, which enables the formation of distinct crystalline phases (e.g. monoclinic, hexagonal, and orthorhombic). It is well established that beyond surface interactions, the crystal structure has been considered a key factor among the various physicochemical parameters that govern gas sensor performance. Despite the potential of WO₃ as toxic gas sensing layer, the majority of studies have focused on its thermodynamically stable monoclinic phase. Simultaneously, light stimulation has emerged as an efficient  strategy to enable sensor operation at milder temperature. Here, we report an investigation of the relationship between crystalline structure and UV light-assisted ozone gas sensing performance of WO₃ nanostructures operating at room temperature. XRD and Raman analyses revealed the formation of the following single phases: hexagonal, orthorhombic, and monoclinic. Electronic microscopy and surface area analyses revealed distinct morphologies and surface areas depending on the crystalline structure, i.e., monoclinic (cube-shaped, 20.9 m²/g), orthorhombic (wool-ball-shaped, 9.8 m²/g), and hexagonal (needle-shaped, 45.3 m²/g). Electrical measurements demonstrate the sensibility of the samples to sub-ppm ozone levels (10 ppb to 300 ppb) with complete  desorption, for all samples evaluated. Notably, the ozone sensing performance exhibited a strong dependence on the crystalline structure, following the order: monoclinic > orthorhombic > hexagonal. These results demonstrate that sensing performance is dictated by the intrinsic electronic properties of each crystalline phase rather than being solely dependent on surface area. Such findings offer fundamental insights into how the crystal lattice governs ozone detection in WO₃ nanostructures.

Polymer surface functionalization of mesoporous silica materials is a promising approach for a wide range of applications including (micro)pollutant sorption, catalysis or drug vectorization owing to their biocompatibility and high specific surface area. Derived from sol-gel chemistry, the MesoPIC process introduces a one-pot synthesis of mesoporous silica materials densely functionalized with polymer chains. It relies on the use of polyion complex (PIC) micelles acting as both templating and functionalization agents. Micelle assembly is driven by electrostatic complexation of a double hydrophilic block copolymer (DHBC) composed of a neutral block and a charged block with a micellization partner of opposite charge. The cooperative assembly of the PIC micelles and the inorganic precursors results in the formation of ordered mesostructured materials where the charged blocks of the DHBC are present as pendant functional chain in the mesopores.

The MesoPIC process has been extensively studied using DHBCs comprising a polyacid block, enabling dense and homogeneous polyanionic functionalization of mesopores with a range of tuneable morphologies (2D hexagonal, 3D cubic, lamellar) and pore sizes. The accessibility and high density of the functional groups withing the mesopores was demonstrated for polyacrylic acid and polysulfonic acid-functionalized materials developed for sorption and proton conduction applications. Notably, these materials allow the reversible sorption of active cationic entities, as needed for dye remediation and drug delivery. With the aim of broadening the scope of pore functionalization towards more diverse environmental applications, we report here the development of a new primary amine-based polybase-b-neutral block copolymer that (i) is able to form reversible micelle assemblies in water by complexation with polyions and (ii) can serve as both a templating and functionalizing agent of mesoporous silica with tuneable morphologies. Dense and homogeneous functionalization of mesopores with primary amine groups is of particular interest for the selective sorption of anionic micropollutants and for CO₂ capture. The reversible addition-fragmentation chain-transfer (RAFT) polymerization of this new block copolymer is therefore presented. A dynamic light scattering (DLS) study elucidates the formation of micelle assemblies in water with this new DHBC. The use of these assemblies as efficient templates of mesoporous hybrid materials is then explored across a range of physicochemical parameters and analysed through nitrogen sorption, transmission electronic microscopy (TEM) and small-angle X-ray scattering (SAXS) analyses. Finally, the properties toward pollutant adsorption together with CO₂ capture are presented.

Abstract

Transition metal dichalcogenides (TMDs) are key materials for energy storage and catalysis, but their performance is often limited by low conductivity and surface area. In this work, we present a simple, scalable electrodeposition method to synthesize mesoporous metal telluride films (MTe₂, where M = Co, Ag, Au, and Pd). Using a micelle-assisted soft-templating approach, we successfully grew uniform mesoporous structures directly on conductive substrates. Structural analysis via SEM, TEM, and XRD confirms a well-ordered network with an average pore size of approximately 20 nm. Compared to non-porous films, this architecture significantly increases the electrochemically active surface area (ECSA) and allows for faster electrolyte diffusion. We are currently applying these materials to the hydrogen evolution reaction (HER). Preliminary results indicate that combining the conductive telluride framework with this porous structure effectively improves reaction kinetics. This study demonstrates a practical route for designing high-efficiency electrodes for next-generation energy devices.

Keywords: Metal Tellurides, Mesoporous Materials, Soft-templating, Thin Films.

Nickel–molybdenum catalysts have emerged as promising systems for the dry reforming of methane (DRM), yet the structural role of Mo and its interaction with Ni remain strongly dependent on synthesis conditions. In this work, we investigate how different preparation strategies influence Ni-Mo interactions, phase evolution, and catalytic performance. Catalysts were prepared using one-pot and post-modification approaches while systematically varying the Ni/Mo ratio. Structural characterization reveals that the one-pot route favors intimate Ni–Mo interactions and alloy-like nanoparticles under appropriate reduction conditions, whereas post-modification leads to the segregation and crystallization of MoO₃ at higher Mo loadings. These structural differences strongly affect DRM behavior, with alloy-rich catalysts exhibiting enhanced activity, while excessive MoO_x phases obstruct active sites. An optimal Ni:Mo ratio of approximately 10:1 was identified, balancing alloy formation and Mo stabilization effects. Overall, this study highlights the critical role of synthesis strategy in governing metal–metal interactions and phase stability in Ni-Mo DRM catalysts.

Entropy-stabilized single-phase oxides represent a promising class of multifunctional catalysts, where entropy-driven stability and oxygen vacancy-induced lattice distortion synergistically enhance electronic structure and electroactivity. In this work, a Cu-Mn-Zn-Cr-O (CMZCO) medium entropy oxide (MEO) was synthesized via a facile solvothermal method. CuMn₂O₄ was prepared as a structural analogue, sharing the same spinel framework. Strategic substitution of Zn²⁺ for Cu²⁺ and Cr³⁺ for Mn³⁺ was hypothesized to minimize lattice distortion due to comparable ionic radii and stable oxidation states, thereby improving CMZCO’s structural and electrochemical properties. The CMZCO MEO exhibited a high specific capacity of 188 C/g (417.7 F/g) in 2 M KOH at 2 A/g. Integrated into a hybrid supercapacitor (HSC), it delivered power and energy densities of 600 W/kg and 33.33 Wh/kg, with ~84% capacitance retention over 10,000 cycles. Electrocatalytic performance showed low overpotentials of 130 mV (OER) and 116 mV (HER) in 1 M KOH, with extended stability. In alkaline seawater, overpotentials further decreased to 53 mV and 100 mV. Density Functional Theory (DFT) simulations validated the atomic level insights into electronic structure, reaction activity and stability, aligning with experimental results. Overall water splitting required 1.7 V at 10 mA/cm2, remaining stable at 1.9 V for 48 h. Sustainable applicability was demonstrated using a photovoltaic module for seawater splitting and HSC charging.

Abstract

In this study, adsorbents derived from dwarf palm (Chamaerops humilis) leaves were produced via pyrolysis and evaluated for dye removal from aqueous solutions. Carbonization was performed under three different conditions: (i) chemical-free pyrolysis at 800 °C, (ii) H₃PO₄-assisted chemical activation at 450 °C, and (iii) K₂CO₃-assisted chemical activation at 800 °C. The resulting adsorbents were systematically compared with dye (metyhlene blue) removal efficiency.

The results revealed that both the activation agent and pyrolysis temperature significantly affected the adsorption performance. The chemically unmodified adsorbent produced at 800 °C exhibited high dye removal efficiencies (95.8–97%), indicating that high-temperature pyrolysis alone was sufficient to generate effective adsorption sites. Among the chemically activated samples, K₂CO₃-activated carbon showed the highest performance, achieving up to 99.3% dye removal and a minimum residual dye concentration of 0.07 mg L⁻¹. In contrast, H₃PO₄ activation at lower pyrolysis temperature resulted in comparatively lower removal efficiencies (89.8–94.1), likely due to differences in pore development and surface chemistry.

The superior performance of K₂CO₃-activated adsorbents is attributed to enhanced pore formation and improved accessibility of adsorption sites, as supported by FTIR analysis. Overall, this study demonstrates that dwarf palm leaves are a promising, sustainable precursor for producing high-performance adsorbents for dye-contaminated wastewater, particularly when combined with alkaline activation and high-temperature pyrolysis.

Key words: dwarf-palm leaves, bio-based adsorbent, adsorption, dye removal, chemical activation”

Mn-Zn ferrite nanoparticles with tunable Curie temperature (T_C) and attractive magnetic response represent a critical component for Spinheat manufacturing technology. This innovative technology utilizes the heat generated by these nanoparticles under AC magnetic fields to achieve precise, on-demand heating and temperature fail-safe mechanisms in polymer processing. A key performance indicator for these materials is the specific absorption rate (SAR). A suite of Mn_xZn_1-xFe₂O₄ (x=0.0, 0.1, 0.2, …, 1.0) nanoparticles was synthesized via co-precipitation, achieving controlled particle size (10-15 nm) and tunable T_C (70-334 °C). This library enabled a detailed investigation into the complex interplay between composition, structure, magnetic properties, and SAR of these nanoparticles. A strong correlation was observed between composition, morphology, saturation magnetization (M_s), coercivity (H_c), and SAR. Notably, Mn_0.9Zn_0.1Fe₂O₄ exhibited a peak SAR of 11 W/g (400 kHz, 140 Oe) due to its optimal cation distribution, magnetic properties, and morphology. A Batchwise Bayesian Optimization (BBO) framework was applied to accelerate the discovery of materials with enhanced SAR. This materials informatics approach was instrumental in optimizing synthesis conditions to produce Mn_0.9Zn_0.1Fe₂O₄ nanoparticles with improved SAR values. Furthermore, an explainable automated regression workflow (XARW) was developed and trained to elucidate the non-linear relationships between physical properties and SAR. The optimized nanoparticles were embedded into epoxy and polydimethylsiloxane (PDMS) matrices to demonstrate in situ Spinheat-based controlled curing. This research exemplifies a closed-loop materials development strategy, leveraging a machine learning (ML)-driven experimental workflow for the rational design of high SAR nanoparticles. This approach paves the way for next-generation, energy-efficient Spinheat composite manufacturing. This research is supported by the National Research Foundation, Singapore, under its 29th Competitive Research Programme (CRP) Call (Award ID NRF-CRP29-2022-0002).

Water electrolysis is a key route toward green hydrogen and low-carbon energy systems, yet the oxygen evolution reaction (OER) in acidic media remains kinetically sluggish and strongly limits overall efficiency. RuO₂ is among the most active acidic OER catalysts, but its scarcity and operational degradation hinder large-scale deployment due to the surface reconstruction and Ru dissolution. Binary oxide alloys provide a promising pathway to simultaneously tune activity, stability, and cost. However, the vast compositional space makes purely experimental trial-and-error screening inefficient.

Here, we present a density functional theory (DFT)-driven screening framework to accelerate the discovery of Ru-based binary oxides, focusing on Ru_0.75X_0.25O₂ (X = transition metals) as practical candidates. The workflow combines the vacancy formation energies for oxygen and RuO4, considering lattice-oxygen mediated mechanism and metal dissolution for stability and OER Gibbs energy for activity.

Across the screened set, Ru_0.75Sc_0.25O₂ emerges as the most promising candidate, exhibiting a favorable adsorption energy balance for oxygenated intermediates while stabilizing surfaces in a manner that suppresses oxygen vacancy and Ru dissolution tendencies.

Beyond ranking candidates, the calculations provide mechanistic insight into how substituents reshape surface bonding and reaction energetics, thereby rationalizing activity-stability trade-offs in Ru-based catalysts. This work highlights a simple but systematic theoretical route for narrowing down experimentally viable binary oxide compositions and offers design principles for developing durable, low-Ru-content acidic OER electrocatalysts.

Many chemical reactions that are considered essential for building a carbon-neutral society are endothermic processes with positive enthalpy changes. Representative examples include reforming reactions for the effective utilization of methane contained in natural gas, ammonia decomposition reactions for green hydrogen storage, transportation, and utilization, and the reverse water–gas shift reaction for converting carbon dioxide into the key feedstock carbon monoxide. In these endothermic reaction systems, the supplied energy is stored as chemical bond energy, and such processes can therefore be described as energy-conversion-type chemical reactions.

The most common method of energy input in chemical reactions is heat. In conventional processes, thermal energy is supplied through heat transfer, which inevitably results in energy losses due to sensible heat accumulation and heat dissipation in regions not directly involved in chemical reactions. In this context, microwave heating has emerged as a promising alternative. Microwaves can deliver thermal energy directly and selectively to reaction-active sites in solid catalysts, enabling significantly higher energy efficiency compared with conventional heating methods.

To achieve efficient conversion of microwave energy into chemical energy, precise design of catalyst structures is critically important. A typical catalyst architecture consists of active metal nanoparticles immobilized on ceramic supports. In this presentation, we introduce our laboratory’s research on the development of innovative catalysts for microwave energy conversion, focusing on hydrogen production via dry reforming of methane and carbon dioxide, as well as hydrogen production via ammonia decomposition. A key design concept is the precise engineering of partially reduced sites formed at the interfaces between metal nanoparticles and ceramic supports.

Building on these studies, we have recently initiated research on the direct reduction of carbon dioxide to carbon monoxide without the use of hydrogen. Such reactions conventionally require extremely high temperatures of approximately 1500 °C, making the selection of suitable reactor materials highly challenging. In contrast, microwave heating enables the generation of localized states corresponding to temperatures of around 1500 °C exclusively at atomic-scale reaction-active sites. This unique feature allows highly demanding reactions to proceed while maintaining the overall reaction system at relatively low temperatures.

In the upcoming presentation, we will unveil a significant breakthrough in the field of rechargeable battery technology, focusing on the novel application of initiated chemical vapor deposition (iCVD) for crafting artificial polymer electrode interphases. This cutting-edge technique allows for the creation of finely tuned, uniform coatings that dramatically improve the stability and performance of batteries. By leveraging the unique properties of these polymer layers, this presentation has tackled some of the most persistent challenges in battery design, including enhancing cycle life, managing volume expansion, and preventing the degradation of battery materials over time.

The presentation will delve into the specifics of how iCVD technology enables the precise manipulation of polymer layer properties, such as thickness, hydrophobicity, and elasticity, to meet the rigorous demands of various battery applications. This approach not only extends the operational life of batteries but also opens new pathways for increasing energy density and efficiency, particularly in high sulfur cathodes and nickel-rich electrodes. By addressing these critical issues, the research paves the way for more sustainable, high-capacity, and durable energy storage solutions, which are crucial for the widespread adoption of electric vehicles and the advancement of renewable energy systems.

This study explores the development of a sensitive and selective sensing nanocomposite for detecting a widely used organophosphate pesticide called dimethoate. It poses significant environmental and health risks due to its high toxicity and persistence in agricultural products. To address these concerns, we developed a novel MoS₂ QDs/PANI nanocomposite and employed a photoluminescence technique to detect dimethoate. The MoS₂ QDs/PANI nanocomposite was synthesized in a single-step process and characterized using XRD, UV–visible, photoluminescence (PL), TEM, and FTIR techniques. The nanocomposite demonstrated selective detection of dimethoate which is one among other pesticides. Utilizing the PL approach, the sensing nanocomposite achieved a detection limit (LOD) of 1 nM and a linear range (LR) of 1–30 nM. The relative standard deviation (RSD) for metal ion interference was 3 % and 5 % for actual raw samples, indicating that, the nanocomposite has high specificity and stability. Additionally, the sensing nanocomposite exhibited a 5 % RSD for repeatability, confirming its reliability. The sensing parameters of the MoS₂/PANI nanocomposite were compared with existing literature, highlighting its superior performance. This novel nanocomposite offers a promising solution for effective and reliable dimethoate detection, contributing to improved food safety and environmental protection.

Atomically ordered Pt-based intermetallic catalysts offer exceptional structural robustness in acidic environments relevant to proton exchange membrane fuel cells (PEMFCs); however, their rigid atomic configurations fundamentally limit local electronic tunability and adaptive surface reconstruction under operating conditions. Here, we present an inter-sublattice random (ISR) alloy strategy that integrates atomic-level compositional disorder into a structurally ordered Pt–M framework, thereby decoupling crystallographic order from chemical complexity in Pt-based oxygen reduction catalysts. Through a sequential heteroepitaxial growth process, atomic-scale compositional randomness is introduced into the transition-metal sublattice of a pre-ordered PtCo intermetallic scaffold via selective Ni incorporation while preserving long-range crystallographic order, giving rise to a unique dual order-disorder motif. This inter-sublattice randomization enables precise modulation of Pt electronic states and stabilizes an electronically optimized Pt-rich surface, leading to favorable oxygen adsorption energetics and sustained catalytic performance under acidic operating conditions. Combined experimental and theoretical analyses reveal that sublattice disorder cooperates with Pt-skin formation to suppress structural degradation during electrochemical operation. More broadly, this work establishes sublattice-level disorder engineering as a general and transferable design principle for overcoming the intrinsic trade-off between activity and stability in ordered intermetallic catalysts.

Two-dimensional (2D) borophene has emerged as a promising member of the Xene family owing to its metallic conductivity, high mechanical strength, anisotropic electronic structure, and rich polymorphism. Despite these advantages, the practical application of borophene in nano-energy devices has been limited by the lack of scalable, low-cost, and environmentally benign synthesis routes. In this work, we report a green and efficient two-step sonochemical liquid-phase exfoliation strategy for the synthesis of few-layer borophene nanosheets directly from bulk boron powder using low-boiling solvents. The exfoliation behavior was systematically investigated in acetone solvent. The formation of stable borophene dispersions was confirmed by the Tyndall effect, UV–visible spectroscopy, and dynamic light scattering analysis. Structural, morphological, and chemical characteristics were comprehensively studied using SEM, TEM, HRTEM, Raman spectroscopy, FTIR, and XPS, confirming few-layer morphology dominated by B–B bonding with limited surface oxidation. The synthesized borophene nanosheets were subsequently integrated with graphene into a polydimethylsiloxane (PDMS) matrix to fabricate a flexible triboelectric nanogenerator (TENG) via a spin-coating process. The 2D fillers increased the surface charge density, dielectric polarization, and interfacial charge trapping, which made the borophene–graphene-doped PDMS TENG have a much higher open-circuit voltage of about 25–30 V and a short-circuit current of about 0.01 mA. This was better than devices filled with pure PDMS, bulk boron powder, or graphite powder. The device exhibited excellent mechanical durability, stable electrical output, efficient capacitor charging, and the ability to harvest biomechanical energy from various human motions. This work demonstrates a sustainable pathway for borophene synthesis and highlights its strong potential for next-generation nano-energy harvesting and self-powered wearable electronics.

Ammonia decomposition presents a critical pathway for hydrogen production and storage by enabling ammonia as a carbon-free hydrogen carrier. However, catalyst deactivation and inefficient nitrogen activation remain key challenges. Herein we report, a defect-engineered ceria-supported ruthenium catalyst, developed by integrating atomic-scale dispersion of Ru with controlled lattice modification. Ruthenium is stabilised as isolated atoms and sub-nanometre clusters on a praseodymium–cobalt co-doped ceria matrix synthesised via an optimised sol–gel route, maximising accessible active sites while suppressing sintering. Incorporation of aliovalent co-dopants into ceria matrix leads to a significant increase in oxygen vacancy concentration and modification of the electronic structure, which results in strengthened metal–support interactions and enhanced redox capability. These materials-level modifications facilitate N–H bond activation, leading to near-complete ammonia conversion under the investigated conditions. The optimised RC-Pr_0.3Co_0.2O_x catalyst outperforms undoped ceria and benchmark 1 wt% Ru–CeO₂ in both activity and long-term stability. This highlight defect-mediated metal–support synergy as an interdisciplinary materials design strategy for advancing ammonia cracking catalysts toward integration in solid oxide fuel cell–based, carbon-neutral energy systems.

In this work, a nanostructured electrolyte architecture was developed based on vertically oriented nanochannels (VONs), engineered to address the performance limitations inherent to conventional intermediate-temperature solid oxide fuel cells (IT-SOFCs). Traditional electrolyte configurations rely on mechanically robust, yet relatively thick ceramic layers, which ensure gas tightness but concurrently introduce high ionic resistance, thereby constraining overall power output. To overcome this issue, a template-assisted fabrication strategy was employed to achieve structural integrity and enhanced ion transport.

Anodized aluminum oxide (AAO) was synthesized as a mechanically stable and geometrically ordered template. The AAO templates were synthesized via controlled electrochemical anodization, producing uniform VONs. These one-dimensional VONs serve as confinement sites for the subsequent deposition of an ion-conducting phase. Gadolinium-doped ceria (GDC) was infiltrated into the AAO channels using electrodeposition. The resulting composite, consisting of GDC embedded within the alumina scaffolds, maintained a continuous and spatially confined ionic conduction network.

This VON minimized transport tortuosity and suppressed microstructural degradation mechanisms such as grain coarsening during cell heating. Electrochemical impedance spectroscopy (EIS) conducted across a range of temperatures revealed a marked enhancement in total conductivity compared to bulk GDC films.

Importantly, this approach enabled substantial reductions in the quantity of active ceramic material required, thereby offering a resource-efficient pathway for SOFC fabrication. The scalable nature of the AAO template, combined with the elimination of conventional sintering constraints, highlights the potential of this method for next-generation energy conversion systems, where material utilization, structural durability, and ionic performance must be optimized simultaneously.

Flash sintering has emerged as a promising non-conventional processing route for tailoring the defect chemistry and functional properties of oxide ceramics. In this work, the role of flash sintering in enhancing the photocatalytic efficiency of TiO₂ is systematically investigated through the co-doping of Fe and Cu. Fe-Cu co-doped TiO₂ photocatalysts were synthesized via flash sintering and compared with conventionally sintered counterparts to elucidate the influence of processing on structural, electronic, and photocatalytic properties. The synthesized materials were comprehensively characterized using XRD, TEM, SEM, BET, XPS, FT-IR, and UV–visible spectroscopy. XRD and TEM analyses confirmed successful incorporation of Fe and Cu into the TiO₂ lattice without the formation of secondary phases, indicating effective co-doping under flash sintering conditions. XPS revealed a significantly higher concentration of Ti³⁺ species and oxygen vacancies in flash-sintered samples, highlighting the critical role of flash sintering in defect generation. UV–visible spectroscopy demonstrated band gap narrowing in co-doped TiO₂, resulting in enhanced visible-light absorption. These defect-induced electronic modifications led to improved charge carrier separation by increasing the trapping efficiency of photogenerated electrons and holes. Consequently, flash-sintered Fe-Cu co-doped TiO₂ exhibited superior photocatalytic performance toward the degradation of methylene blue under visible-range white LED illumination. The results clearly establish flash sintering as an effective strategy for defect engineering in TiO₂, thereby significantly improving its visible-light photocatalytic activity.

Keywords:

Flash Sintering, Co-doping, Photocatalysis, Wastewater treatment

The development of high-performance and stable electrocatalysts for seawater electrolysis is key to sustainable hydrogen production. Herein, we demonstrate a self-supported, commercially favorable electrocatalyst composed of copper–iron layered double hydroxide anchored on nickel foam (CuFe-LDH/NF). We exclusively demonstrated the microwave (MW) synthesis of CuFe-LDH/NF for the first time and compared its performance with conventional hydrothermal (HT) method. The optimized bifunctional MW-CuFe-LDH/NF catalyst exhibits dual potential to perform long-lasting oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Explicitly, it requires an overpotential of 300 mV (vs RHE) for OER and -190 mV (vs RHE) for HER to drive 10 mA cm⁻² current density in alkaline electrolyte. A conductive and mechanically strong polypyrrole (PPy) coating was applied to enhance the electrochemical stability of CuFe-LDH/NF within seawater media. The PPy capping inhibits the chloride ions (Cl^-) attack, catalyst fouling by Ca⁺² and Mg⁺² ions, and mechanical pitting. The successful inhibition of Cl^- ions attack in long-term seawater electrolysis leads to a benchmark HER stability of >1000 h for MW-CuFe-LDH/NF@PPy-based devices. The present work emphasizes the fabrication of self-supported MW-CuFe-LDH/NF electrodes and the synergistic effect of PPy capping in amplifying conductivity and durability to attain commercial-scale H₂ production from seawater electrolysis.

Keywords: CuFe-LDH; Polypyrrole (PPy) capping; Self-supported microwave growth; Kilo-hour stability; seawater HER;

Real and alkaline seawater electrolysis is a promising route for sustainable hydrogen production but is severely limited by chloride-induced corrosion and poor long-term stability of oxygen evolution reaction (OER) catalysts. Herein, we report for the first time a fluoride-stabilised, self-healing NiFe-LDH catalyst with oxygen vacancies and azo-dye surface modification for alkaline and real seawater OER. Fluoride incorporation induces dynamic surface reconstruction and in situ self-healing behavior under corrosive conditions, while Zn-assisted cation vacancy engineering enhances electronic conductivity and OER selectivity. Three low-toxicity azo dyes, i.e., calmagite, acid red 27, and sunset yellow are employed to construct functional organic-inorganic interfaces that balance surface protection and mass transport. Using a microwave-assisted hydrothermal method, ultrathin and uniform NiFe-LDH layers are rapidly grown on Ni foam. Notably, the fluoride-stabilized NiFe-LDH maintains stable operation for over 1000 h at 1.0 A cm⁻² in simulated alkaline seawater, while all catalysts, regardless of further optimization, exhibit durability exceeding 950 h (marked on 2026-01-11) at 1 A cm⁻² in real alkaline seawater. The optimized F-NiFeZnvac-LDHMW@ADs/NF catalyst delivers an overpotential of 295 mV at 500 mA cm⁻², demonstrating a balanced combination of activity, durability, and scalability for industrial alkaline seawater electrolysis. This report is a singificant step forward towards the commercialisation aspect of real-time seawater electrolysis via structurally stable NiFe-LDH anodes (a possible substitute for Raney Ni catalyst).

The increasing application of nanoparticles in agriculture raises important questions about their effects on plant growth and development. This study investigates the influence of silica nanoparticles (SiO2 NPs) of varying sizes (10 nm to 150 nm) and concentrations on the growth, transpiration, and overall health of the plant Salvia hispanica (chia).

We conducted a series of controlled experiments to assess the impact of these nanoparticles on seed germination, root and shoot development, and transpiration rates. Our results demonstrate that smaller SiO2 NPs (10 nm) significantly hinder germination and growth, resulting in delayed radicle emergence and reduced lateral root formation. This is attributed to a gel-like barrier formed by interactions between the nanoparticles and seed mucilage, which impedes water uptake. In contrast, larger SiO2 NPs (50 nm) at moderate concentrations (200 mg L⁻¹) were found to enhance plant health, promoting improved growth metrics and transpiration rates.

Additionally, we observed the uptake and transportation of SiO2 NPs within chia plants, highlighting the potential for environmental exposure and contamination through transpiration. These findings underscore the critical role of nanoparticle size and concentration in mediating plant interactions and suggest that careful consideration is necessary when utilizing nanoparticles in agricultural practices.

This presentation aims to provide insights into the complex dynamics between nanoparticles and plant physiology, offering valuable information for the development of sustainable agricultural practices that leverage nanotechnology while minimizing ecological risks.

Noble metal-free, cost-effective cocatalyst aluminum (Al)-modified acid-treated g-C₃N₄ (O-pgCN) was explored for photocatalytic H₂ production in a slurry photoreactor. The surface and band engineering of acid treatment, resulting from oxygen functionalization, were also explored. The functionalized porous g-C₃N₄ anchored with 1 wt.% Al cocatalyst O-pgCN@Al generated 845 μmol g⁻¹ H₂ under UV-visible irradiation from 5 vol% of methanol-water solution and was 8.04 times higher than pristine O-pgCN. The wt.% loading of Al onto O-pgCN was explored, where 1 wt.% Al provided sufficient active sites for the reduction reaction. The efficient photocatalytic production of H₂ was due to the extended visible light activity of O-pgCN, effective charge and reactant migration on the 2D porous O-pgCN, as well as the efficient separation and transfer of charges to the Al cocatalyst for reduced recombination, and provision of Al metal sites for increased reduction reaction. 100 mg catalyst loading was the optimum, above which turbidity caused activity decline. The composite showed good photostability and was capable of generating H₂ from various sacrificial agents, including ethanol, glycerol, ethylene glycol, and TEOA. Thus, when combined with inexpensive, earth-available, and non-noble metal Al, O-pgCN@Al shows excellent promise as a morphology-driven and cocatalyst-supported composite for large-scale, efficient, and sustainable H₂ production.

Vacuum-free liquid-metal printing offers a scalable and ambient-compatible route [1,2] for producing ultrathin semiconducting oxides for transparent electronics and optoelectronics. In this work, we report the rapid exfoliation and printing of ~2 nm-thick two-dimensional (2D) tin oxide and indium oxide nanosheets directly from liquid metal surfaces, followed by thermal annealing in air. The effect of annealing on the stoichiometry, morphology, and crystal structure of the printed oxides is systematically investigated. Annealing promotes nanocrystalline and phase transformations, leading to a dominant tin dioxide (SnO₂) or indium oxide (In₂O₃) phase while preserving excellent optical transparency exceeding 99% across the visible spectrum. Thin-film transistors based on the annealed 2D oxides exhibit stable n-channel behaviour with field-effect mobilities of ~7.5 cm² V⁻¹ s⁻¹ for SnO₂ and up to ~96 cm² V⁻¹ s⁻¹ for In₂O₃, outperforming their as-printed counterparts. In addition, ultraviolet photodetectors fabricated from annealed nanosheets demonstrate orders-of-magnitude enhancement in photoresponsivity, reaching 10³–10⁴ A W⁻¹. Structural and in situ annealing studies reveal that annealing-induced nanostructural evolution within the oxide layers underpins the observed performance improvements. This study highlights liquid-metal-derived 2D oxides as high-quality, vacuum-free semiconductors for large-area, transparent electronic and optoelectronic applications.

References

[1]         A. Zavabeti, J. Z. Ou, B. J. Carey, N. Syed, R. Orrell-Trigg, E. L. Mayes, C. Xu, O. Kavehei, A. P. O’Mullane, R. B. Kaner, K. Kalantar-Zadeh, T. Daeneke, Science 2017, 358, 332.

[2]         P. Aukarasereenont, A. Goff, C. K. Nguyen, C. F. McConville, A. Elbourne, A. Zavabeti, T. Daeneke, Chemical Society Reviews 2022, 51, 1253.

There has been a growing demand for organic semiconductor devices due to their potential in flexible electronics, photodetection, and low-cost large-area applications [1]. Among conjugated donor-acceptor(DA)polymers,poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) has emerged as a promising material owing to its favorable energy levels, strong intermolecular interactions, and good film-forming properties [2], [3]. However, achieving high charge carrier mobility and stable device performance remains a critical challenge, largely governed by the thin-film deposition method [4]. In this study, TQ1-based organic field-effect transistors (OFETs) were fabricated using two different deposition approaches: the conventional spin-coating method and the Floating Film Transfer Method (FTM). Optical analysis revealed distinct differences between the films prepared by the two techniques. The UV–Vis absorption spectra of spin-coated TQ1 thin films before and after annealing demonstrated improved absorption features upon thermal treatment. For FTM-casted TQ1 films, polarized UV–Vis spectra confirmed enhanced chain alignment and anisotropy, resulting in a high dichroic ratio (DR) of ~5.6. Furthermore, the transfer characteristics of the fabricated OFETs (Fig. 1c) showed that the FTM-based device exhibited a mobility of 5.0 × 10⁻³ cm²/V·s and an on/off current ratio of ~10⁶, in contrast to the spin-coated device with a mobility of 4.3 × 10⁻⁴ cm²/V·s and an on/off ratio of ~10⁵. These results clearly indicate that the FTM deposition method provides improved optical ordering and significantly enhances charge transport compared to conventional spin coating. The findings highlight the crucial role of deposition technique in optimizing TQ1 polymer OFETs for high-performance, solution-processable organic electronics suitable for flexible sensors and low-power optoelectronic applications.

The detection of nitrogen dioxide (NO₂), a highly toxic air pollutant, is essential for safeguarding public health and understanding atmospheric chemistry. However, designing sensors with high selectivity and sensitivity remains challenging due to the coexistence of multiple interfering gases in real-world environments. While SnO₂-based chemiresistive sensors offer advantages such as high sensitivity, compactness, and cost-effectiveness, they suffer from poor selectivity due to non-specific adsorption and interference from humidity. Traditional catalytic filters improve selectivity but are hindered by signal crosstalk, increased system complexity, and high power consumption.

To address these challenges, we present a novel smart sensing system based on a porous alumina membrane (PAM)-based nanotube array gas sensor with a vertical top-bottom electrode structure and an integrated ZnO nanosheet catalytic filter. The PAM template enables precise fabrication of vertical channels, effectively insulating of the sensing layer from filter-induced signal interference. The sensing element, composed of Pd/SnO₂ nanotube arrays fabricated via atomic layer deposition (ALD), providing exceptional sensing performance. Complementing this, the ZnO nanosheet catalytic filter, grown in-situ via a mild solution method, provides high catalytic activity, selectively oxidizing interfering gases while allowing accurate NO₂ detection. This innovative sensor design achieves exceptional selectivity for NO₂, with negligible responses to ethanol, formaldehyde, toluene, CO, NH₃, and NO. Additionally, the ZnO filter effectively suppresses humidity interference, enhancing reliability in real-world conditions.

The sensor demonstrates remarkable performance, with a sensitivity of 815% at 1 ppm NO₂ and a theoretical detection limit of 1.86 ppb in dry air at 250 °C. Compared to commercial electrochemical NO₂ sensors, the proposed system exhibits comparable accuracy while offering significant advantages in miniaturization and integration. A scalable photolithography process enables the sensor to be fabricated at sizes as small as 10 µm, highlighting its potential for mass production and seamless integration into Internet of Things (IoT) platforms. This work showcases the potential of engineered nanomaterials, such as PAM-based ZnO nanosheets and Pd/SnO₂ nanotubes, for developing advanced sensors to monitor environmental pollutants. These technologies present a sustainable path toward improving air quality monitoring and protecting public health.

Cobalt-based single-atom catalysts (Co SACs) are considered promising materials for promoting the two-electron oxygen reduction reaction (2e⁻ ORR) to efficiently produce H₂O₂. However, general strategies for systematically tuning their electronic structures remain scarce. In this work, we show that both in-plane and axial heteroatom coordination can effectively regulate the electronic states of Co centers, thereby dictating their 2e⁻ ORR activity and selectivity. By linking atom-induced charge redistribution with H₂O₂ generation performance, we propose a universal design principle for achieving tunable SACs.

Introducing electron-withdrawing O or electron-donating N atoms forms asymmetric Co–N_xO_y–O–C coordination environments, among which the Co–N₅–O–C configuration exhibits the optimal performance. Its electron-rich Co center, stabilized in a distorted pentacoordinate geometry, significantly enhances the 2e⁻ ORR, yielding 90% H₂O₂ selectivity and a mass activity of 89.5 A g⁻¹ at 0.65 V vs. RHE. These values surpass those of symmetric Co–N₄–O–C and electron-deficient Co–N₂O₂–O–C structures.

Density functional theory calculations reveal that the electron-donating N atoms in Co–N₅ broaden the Co dz² orbital near the Fermi level, weakening *OOH adsorption to favor the 2e⁻ pathway. Conversely, the in-plane O atoms in Co–N₂O₂ withdraw electrons from the Co center, creating additional empty d-states and strengthening *OOH binding, which suppresses H₂O₂ selectivity.

Under flow-cell operation, Co–N₅–O–C delivers 15.88 mol gcat⁻¹ h⁻¹ of H₂O₂ at 300 mA cm⁻² with >88% Faradaic efficiency over 50 hours. It also enables complete degradation of 50 ppm organic pollutants within 10 minutes, demonstrating strong potential for practical wastewater treatment applications.

The downsizing of platinum electrocatalysts to the single-atom limit is frequently proposed as a route to maximize atomic utilization in the hydrogen evolution reaction. However, in many reported platinum single-atom catalysts, strong interactions with heteroatom-containing supports modify the electronic structure of the metal center, complicating the interpretation of intrinsic HER reactivity and reaction mechanisms. Here, we investigate the intrinsic hydrogen evolution behavior of platinum single atoms by systematically controlling the platinum nuclearity from isolated atoms to nanoparticles (3–5 nm) using an electrochemical deposition approach. This method enables the preparation of structurally well-defined platinum single atoms on carbon supports while minimizing electronic perturbations arising from metal–support interactions. Transmission electron microscopy and X-ray absorption spectroscopy confirm the absence of nanocluster contributions and the atomic dispersion of platinum. Under acidic conditions, the platinum single-atom catalyst exhibits hydrogen evolution activity approaching the intrinsic limit, with an overpotential of 15.5 mV at 10 mA cm^-2and a mass activity of 289.9 A mg_Pt^-1 at 50 mV. Density functional theory calculations, together with CO stripping experiments, establish a direct relationship between the local atomic coordination of platinum and its hydrogen evolution reactivity, and reveal reaction pathways that differ fundamentally from those of platinum ensembles. These results clarify ambiguities in the interpretation of platinum single-atom catalysis for hydrogen evolution and provide a mechanistic basis for defining intrinsic activity in atomically dispersed electrocatalysts.

Ammonia (NH₃) is a widely used industrial chemical and agricultural fertilizer that poses harmful environmental and public health effects. Elevated NH₃ concentrations degrade air quality and pose associated health risks by contributing to the formation of particulates [1]. Moreover, NH₃ emissions play a key role in ecosystem acidification and affect the soil and aquatic environments [2]. Therefore, the detection of NH₃ with high precision is critical for environmental monitoring, industrial safety, and public health.

The development of sensitive, reliable, compact, user-friendly, cost-efficient, and room-temperature-operable detection systems is crucial to sensor technology. In recent years, surface acoustic wave (SAW) devices have been one of the best candidates for this purpose [3]. The sensing mechanism of SAW devices is based on detecting minor deviations in the velocity of the SAW. These deviations are measured by the shift in the device's working frequency. On the other hand, tungsten trioxide (WO₃) is particularly promising for NH₃ detection due to its high surface reactivity and intense interactions with reducing gases [4]. Therefore, WO₃-based SAW sensors offer a powerful approach for highly sensitive, low-power NH₃ detection at room temperature.

In this study, SAW sensor devices were designed and fabricated by MEMs techniques. Then, WO₃ thin films were deposited onto SAW sensor devices with RF magnetron sputtering. To characterize the crystallographic, morphological, and structural properties of the fabricated patterns, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy were performed to evaluate the sensing film quality. A WO₃-based SAW sensor was dynamically measured for NH₃ over the concentration range of 1.16 ppb (particles per billion) to 11.6 ppm (particles per million) at room temperature. The frequency shifts of the sensors were recorded to determine various sensor characteristics, including sensitivity, response time, recovery time, and reproducibility. The sensor exhibited a precise and reproducible signal response to NH₃ at room temperature, indicating strong interactions between the target analyte and sensing layer, and high sensing performance. Room-temperature operation offers low power consumption and improved stability compared to conventional sensors. The results demonstrate that the fabricated sensors are promising candidates for real-time room-temperature NH₃ detection in environmental monitoring, industrial safety, and public health.

Acknowledgements: This study is financially supported by the Scientific Research Project Committee of Gebze Technical University (YÖK-ADEP 2024-A-113-19).

References:

[1] Behera S. N., et al., Sci. Total Environ., 2010, 408 (17), 3569-3575.

[2] Wang J., et al., Sci. Total Environ., 2020, 747, 141340.

[3] Kılıç A., et al., IEEE Sens. J., 2025, 25 (13), 42629-42637.

[4] Kılıç A., et al., Semicon. Sci. Technol., 2023, 38 (3), 035008.

Enzymes are highly efficient catalysts with growing relevance in energy and environmental technologies, including CO2 capture. However, their development is often constrained by limited stability, loss of activity under harsh operating conditions, and limited reusability. Realizing practical enzyme-enabled CO2 capture therefore requires host materials that stabilize biocatalysts while preserving substrate access and long-term function [1]. Metal–organic frameworks (MOFs) offer an attractive platform for enzyme immobilization due to their exceptional tunable chemistry, morphology, porosity, and thermal stability, as well as compatibility with mild synthetic routes that can preserve enzyme integrity [2].

Here, we investigated the entrapment of Persephonella marina carbonic anhydrase (PmCA) within leaf-shaped zeolitic imidazolate frameworks (ZIF-L), a two-dimensional MOF, to determine how host-guest interactions govern both enzyme activity and framework structure. Using a mild, enzyme-compatible synthesis condition, PmCA was successfully entrapped in ZIF-L while retaining its catalytic function for CO2 hydration after encapsulation.

Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) confirm enzyme incorporation and the characteristic leaf-like morphology. Powder X-ray diffraction (PXRD) shows that the ZIF-L crystallinity is preserved upon enzyme entrapment. Low-dose scanning transmission electron microscopy (STEM) provided nanoscale insight into host–guest organization, revealing enzyme-sized nanocavities (~5 nm) distributed throughout the ZIF-L nanosheet. Energy-dispersive X-ray spectroscopy (STEM-EDS) further corroborated the presence of immobilized PmCA within the ZIF-L crystal.

The emergence of nanocavities that closely match the molecular dimensions of PmCA indicates a local, enzyme-directed structural adaptation of ZIF-L during crystallization. Rather than passively occupying pre-formed voids or adhering to external surfaces, the enzyme appears to template the formation of confined, accessible sites within the growing framework. Functional assays confirm that encapsulated PmCA remains catalytically active toward CO2 hydration, demonstrating that the enzyme-compatible synthesis yields PmCA@ZIF-L composites with preserved activity [3].

Our findings provide mechanistic insight into enzyme immobilization in MOFs, specifically how biomolecules can reshape host architectures at the nanoscale, and inform the rational design of MOF-based biocatalysts for carbon management and broader energy–environmental applications. By coupling advanced electron microscopy with spectroscopy and functional testing, we highlight an interdisciplinary pathway to bio-inspired, hybrid materials that combine structural adaptivity with catalytic performance.

1 Wang, X. et al. ACS Cent Sci 6 (9), 1497–1506 (2020)

2 Feng, Y. et al. Coord Chem Rev, 431, 213677 (2021)

3 Talebi Deylamani, S., Bognar, Z. et al. Nano Lett 25, 49, 17122 (2025)

Volatile Organic Compounds (VOCs) represent a critical threat to both air quality and public health. Indeed, even at trace-level concentrations, prolonged exposure to these compounds can cause "Sick Building Syndrome," chronic respiratory illnesses, and severe carcinogenic risks. Standard VOC remediation processes, such as filtration and physical adsorption, merely transfer pollutants from the gaseous phase to a solid substrate without chemical neutralization, thereby creating secondary waste. Conversely, conventional thermal catalytic oxidation, although effective, requires high activation temperatures, often exceeding 400°C, for complete VOC mineralization. Moreover, it produces CO₂, the primary cause of anthropogenic climate change. Carbon Capture and Utilization (CCU) technologies have emerged to valorize this gas. This study addresses this dual challenge by developing advanced sepiolite-supported photothermal catalysts designed for the mitigation of VOCs and the subsequent valorization of CO₂ into high value-added products. Sepiolite, a natural fibrous clay mineral with a tunnel-like microstructure, high specific surface area (>300 m²/g), and thermal stability below ~300 °C, provides an excellent platform for dispersing active catalytic phases. Its use as a support for catalytic and photocatalytic processes has been widely demonstrated, including in our previous works involving supported nanoparticles of TiO₂, ZnO and other metal-oxide semiconductors [1]. After a tailored thermal pretreatment to optimize the sepiolite surface silanol groups and porosity, the mineral was coated with manganese and cerium oxides. These oxides create a powerful redox cycle that, under solar light irradiation, utilizes photothermal effects to generate localized high temperatures, allowing the total oxidation of VOCs into H₂O and CO₂ at lower temperatures (160°C) compared to bare thermocatalytic tests (210°C). Furthermore, sepiolite assembled with Ni and Ce oxide nanoparticles enables the photothermal reduction of CO₂ into CH₄ and CO, driven by Ni‑mediated CO₂ activation and further enhanced by Ce [2]. This synergistic approach demonstrates a sustainable and energy-efficient pathway for air pollution remediation by replacing thermal heating with a localized solar photothermal process, significantly reducing the carbon footprint of air purification and highlighting the potential of clay-based composites as low-cost and high-performance materials for green chemistry and the circular economy. Finally, the integration of natural minerals and nanostructured oxides can overcome the thermodynamic barriers of traditional catalysis while providing a comprehensive solution to air pollution and CO₂ remediation.

[1] M. Akkari et al. J. Hazard. Mater. 340 (2017) 281–290.

[2] G. Dativo et al. J. CO2 Util. 82 (2024) 102765.

Cobalt phosphates are promising low-cost electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), offering an attractive alternative to noble metal-based systems. Our group has previously employed various strategies to enhance the catalytic performance of cobalt phosphate materials, including heterometallic doping and the use of different catalytic supports.^1-3  However, strategies to introduce controlled porosity into cobalt phosphate frameworks remain limited in the literature, despite the critical role of porosity in enhancing catalytic activity. Herein, we report synthesis of porous cobalt phosphate using monoalkyl phosphate based cobalt complexes as single-source precursor. The reaction of a cobalt(II) salt with monoalkyl phosphates leads to the formation of layered coordination polymers with the general formula [(RO)PO₃Co(H₂O)]_n, where R represents an alkyl group. These complexes adopt layered architectures in which alkyl groups are confined between inorganic metal phosphate layers.⁴ By exploiting the intrinsic thermal instability of the alkyl chains in these complexes and their controlled removal, a porous cobalt phosphate framework is synthesized.

Nitrogen adsorption studies of material obtained after controlled removal of alkyl chains reveal a high BET surface area of 384 m² g^-1, confirming the formation of a porous structure. Furthermore, structural and morphological characterization using FT-IR, XPS, ICP-OES, powder XRD, and SEM confirms the formation of an amorphous CoPO_x phase. Electrochemical studies demonstrate that CoPO_x exhibits enhanced catalytic activity for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), delivering an overpotential of 240 mV for OER and 116 mV for HER at a current density of 10 mA cm^-2 in 1 M aqueous KOH solution. This improved performance is attributed to the increased surface area and the greater availability of active sites afforded by the porous architecture. Overall, this work presents a scalable materials chemistry strategy for porosity engineering in metal phosphates, highlighting the potential of single-source precursor approaches for energy-related electrocatalytic applications.

References:

(1) Chaudhary, S.; Murugavel, R. Chem. Mater. 2024, 36 (13), 6475.

(2) Chaudhary, S.; Murugavel, R. Chem. Asian J. 2025, 20 (5), e202401177.

(3) Saha, J.; Verma, S.; Ball, R.; Subramaniam, C.; Murugavel, R. Small 2020, 16 (12), 1903334.

(4) Arya, H.; Murugavel, R. Dalton Trans. 2025, 54 (29), 11232.

Heterostructures of two-dimensional (2D) materials are promising for gas sensing. Yet, as illustrated by MoS₂/MoO₃ systems, most studies still rely on powder-based routes with low mobility and limited sensitivity, and thus the underlying mechanisms and tunability remain unclear. In this work, mechanical exfoliation was combined with optimized remote plasma oxidation to rapidly build a 2D MoS₂/MoO₃ heterostructure device platform, and polarity inversion in the sensing response as a function of MoS₂ dimensions was observed. MoS₂ devices were fabricated with two thicknesses of 6 layers (6L) and ~20 layers (20L), and lateral dimensions of 5 × 10 μm² and 1 × 10 μm². The pristine 6L n-type MoS₂ exhibited a −28% response to NH₃ (5 ppm) and an 80% response to NO₂ (5 ppm). Subsequently, only the top 2–3 layers were converted into a flat amorphous MoO₃ overlayer to form a MoO₃/MoS₂ heterostructure (Type III). Then, the 6L device showed an enhanced NH₃ response (−60%) while the NO₂ response decreased to 17%. In contrast, for 20L devices, the NH₃ response remained nearly unchanged, whereas the NO₂ response was reversed to −30%. This illustrates an unconventional polarity transition in the sensor response as a function of MoS₂ thickness, also observed upon varying the in-plane dimensions, indicating tunable response in 2D heterostructure gas sensors.

The overall response is considered to be governed by perturbations at the heterointerface, as conductance is dominated by the high-carrier density near the interface. Molecular dynamics simulations indicate that oxidation of MoS₂ is limited to its surface, confining heterostructure formation to the topmost region and introducing a strong built-in electric field that amplifies adsorption, accounting for the pronounced NH₃ enhancement. Adsorption-energy calculations further reveal strong NH₃ binding on the MoO₃ surface (0.6 eV on average and up to 1.3 eV at oxygen vacancies), substantially stronger than binding on MoS₂ edges, consistent with the weak thickness dependence. By contrast, NO₂ adsorption on amorphous MoO₃ (−0.31 eV on average and −0.4 to −0.5 eV at oxygen vacancies) is slightly weaker than adsorption on S-terminated MoS₂ regions, whose adsorption energy is −0.5 eV. As the number of S-terminated edge sites increases with MoS₂ thickness, edge adsorption becomes dominant. Since the heterointerface separates opposite carrier types, adsorption at distinct sites modulates the interfacial carrier density in opposite directions, leading to polarity inversion in the NO₂ response. Response tuning is therefore attributed to spatial asymmetry across the heterointerface and competitive dominance between adsorption sites on the MoO₃ surface and MoS₂ edges. Finally, transport characterization was performed to further elucidate the sensing and transition mechanisms. This work provides a physical basis for tunable 2D heterostructure sensing platforms.

Buried junction dye-sensitized photoelectrochemical cells (DSPECs) have emerged as a promising photosystem for sustainable chemical transformation. However, high-photovoltage photoanodes are still essential to minimize external bias and maximize high solar-to-chemical conversion efficiency. To develop these photoanode, we establish a rational photosensitizer design strategy that induces molecular torsion near the TiO2 interface to lead ideal charge transfer pathway. We developed four indenothiophene-based photosensitizers featuring various spacers (thiophene or phenyl) and methyl substituent on the cyanoacetic acid acceptor. Intensity-modulated photovoltage spectroscopy (IMVS) reveals that inducing molecular torsion near the TiO2 interface efficiently suppresses charge recombination by an interfacial passivation effect. Consequently, the most tilted photosensitizer exhibited a remarkable open-circuit voltage of 0.90 V and a power conversion efficiency 11.04%. Furthermore, the corresponding buried junction DSPEC demonstrated high performance in glycerol oxidation to formic acid, achieving 90% faradaic efficiency and a production rate of 270 mmmol m−2 h−1. These findings provide a strategic guideline for controlling interfacial ideal charge transfer pathway in high-performance DSPECs.

Implementation of stringent pollution regulations and advances in engine technology are placing additional demands on the development of advanced materials for emission control catalysts. Following the ‘precursor’ approach, well-defined model catalysts are prepared by anchoring atomically defined noble metal clusters and monodisperse nanoparticles (NPs) on metal oxide supports. Herein, we address the influence of the Pt NP size, the elemental composition of bimetallic PdPt NPs, and the oxidation state of the catalysts on the CO oxidation reaction. In addition, we show the impact of the surface properties of structured CeO₂ NPs on the stability and activity of Pt₁₇(PPh₃)₈(CO)₁₂ⁿ⁺-based catalysts.

Atom-precise clusters (e.g., Pt₁₇(PPh₃)₈(CO)₁₂ⁿ⁺) and monodisperse mono- and bimetallic PdPt NPs ranging in size from 1 to 8 nm were obtained by polyol reduction. These syntheses were carried out using batch and continuous flow procedures. In particular, we used a modular, multistage platform based on continuous stirred tank reactors (CSTR) in a cascade to synthesize the atom-precise Pt clusters in the quantities required for catalyst testing and application. CeO₂ nanocubes and nanorods were obtained by microwave-assisted hydrothermal synthesis, leading to reduced reaction times and costs. For catalyst preparation, the Pt clusters or NPs were supported on the CeO₂ particles to obtain a 1%-wt loading by incipient wetness impregnation of the colloidal dispersion. All catalysts were then calcined in air to remove any residues from the NP or cluster synthesis. NPs, supports and catalysts were analyzed, i.e. by electron microscopy (STEM-HAADF) with energy-dispersive X-ray analysis, electron spray ionization mass spectrometry (ESI-MS), optical emission spectroscopy with inductively coupled plasma (ICP-OES) and Raman spectroscopy. The catalytic performance was tested in the oxidation of CO (reaction conditions for a WHSV of 60.000 L / g_Pt h: total flow 1 L / min, 8 % O₂ / 1000 ppm CO in N₂).

The performance of Pt-CeO₂ catalysts in the oxidation of CO was influenced by the size and oxidation state of the Pt species, as well as the support morphology. Pt NPs with an average size of 3.5 nm exhibited the lowest temperature of 50% CO conversion (T₅₀) when the catalyst was oxidized (100 °C). The introduction of a reductive catalyst treatment step (5%H₂/N₂) after three test cycles decreased the T₅₀ for all catalysts, with Pt₁₇ clusters showing the lowest T₅₀ of 50 °C. The sample containing Pt₁₇ clusters exhibited the lowest T₅₀ at 50 °C. The morphology of the CeO₂ support and the surface noble metal loading further influenced the stability of the Pt clusters and the catalytic performance. A low surface noble metal concentration enhanced their stability, resulting in a lower T₅₀ (53 °C for CeO₂ nanocubes and 91 °C for CeO₂ nanorods) than a higher surface concentration.

The hydrogen evolution reaction (HER) is one of the most widely studied reactions in electrochemistry, electrocatalysis and/or photoelectrocatalysis [1]. For electrochemical devices, electrode materials containing nickel and copper are the most attractive in the transition metal series [2], due to their accessibility and their electronic and chemical properties.

Given our expertise in the synthesis of metal nanoparticles (NPs) by the organometallic approach [3], we have investigated NiCu NPs synthesized by this approach as cathode material for anion exchange membrane water electrolysis application. Optimizing the synthesis conditions allowed us to achieve alloy-type NiCu NPs with an average size of ca. 4.2±0.5 nm as indicated by TEM analysis (figure 1). Other state-of-the-art techniques (ICP, IR-FT, HRTEM-EDX, XPS, XRD, XANES, EXAFS) permitted to have a precise overview of the other structural properties of these NiCu NPs. Then, they were deposited onto a carbon support (Ketjentblack) for evaluation in the electroproduction of hydrogen by a range of electrochemical methods. This novel NiCu electrocatalyst exhibits a good catalytic activity in alkaline environment, displaying an overpotential of 273 mV at the current density of -10 mA cm–2 and a good stability within 24 h as well.

References

[1] J. Zhu, L. S. Hu, P. X. Zhao, L. Y. S. Lee, K. Y. Wong, Chem. Rev. 2020, 120, 851– 918.

[2] C. Wei, Y. Sun, G. G. Scherer, A. C. Fisher, M. Sherburne, J. W. Ager, Z. J. Xu. J. Am. Chem. Soc. 2020, 142, 7765– 7775.

[3] C. Amiens, D. Ciuculescu-Pradines, K. Philippot, Coord. Chem. Rev., 2016, 308, 409–432.

[4] T. Straistari, N. Romero, J. Esvan, M. Gil-Sepulcre, C. Amiens, O. Rüdiger, S. DeBeer, D. Jones, J. Rozière, S. Cavaliere, K. Philippot, Nanoscale 2025, 17(30), 17592-17603.

The impact of nanoscale materials for highly efficient electrodes, catalysts, etc. is often limited by the ability to produce those materials at a meaningful scale and competitive cost. Nanoporous metals and alloys can now be made through a wide range of methods, but electrochemical dealloying is the most popular as it is versatile and well controlled. Dealloying is limited in sample size and production scale by the precursor synthesis step(s) and the chemical etching required to produce the nanoscale pores. An alternative approach to produce nanoscale porosity has now been demonstrated using a commercially viable, environmentally friendly method of low-temperature oxide reduction in powder metal samples. This method requires no wet chemistry, and the only byproduct of synthesis is water vapor. Being that the precursor is a powder metal, the process is immediately scalable. This method can also be combined with dealloying to create hierarchical porosity for smaller features in less time using more dilute acid solutions. This technique may be applied to a diverse range of metals and alloys, and the example of hierarchical nanoporous silver will be highlighted to demonstrate the ability to produce superior nanoscale features with less time, energy, cost, and chemicals.

Mixed ionic-electronic conducting oxides are key materials in electrochemistry and catalysis, often adopting perovskite or Ruddlesden-Popper structures. Here, we study Sr₂₋ₓLaₓFeO₄₋_δ, examining how lanthanum substitution and oxygen vacancies influence the electronic structure using DFT (PBE+U, U_eff = 4 eV for Fe). Both types of defects reduce the average Fe oxidation state from 4+, but in markedly different ways.

In oxygen-deficient Sr₂FeO₄₋_δ, localized Fe³⁺ states form small polarons, reflected in magnetic moments and Fe–O bond distortions [1]. In contrast, La-doped Sr₂₋ₓLaₓFeO₄ shows delocalized electrons spreading across multiple Fe sites. This difference arises because oxygen vacancies disrupt the Fe–O network, causing stronger local lattice distortions that favour localization.

These variations in electronic structure have direct implications for proton incorporation [2]. The higher covalency in Fe–O bonds, compared to Zr–O in Ba(Zr,Y)O₃, results in less favourable hydration thermodynamics. Consequently, the degree of electron localization in these oxides likely influences their ability to uptake protons.

[1] Y. A. Mastrikov, D. Gryaznov, A. Chesnokov, G. Zvejnieks, M. Sokolov, M. M. Kuklja, R. Merkle, E. Kotomin, Phys. Rev. Mater. 9 (2025) 105801

[2] R. Merkle, M. F. Hoedl, G. Raimondi, R. Zohourian, J. Maier, Ann. Rev. Mater. Res. 51 (2021) 461

Towards contributing to global climate action, the electrochemical conversion of carbon dioxide into value-added multi-carbon products or fuels is one of the most important technological challenges of this century, which can provide the possibility of large-scale chemical production and carbon neutrality. Especially, Cu-single atom catalysts have attracted the most research interest due to its metal utilization efficiency and C₂ selectivity via C-C coupling. However, the electrochemical production efficiency of Cu-SACs catalysts is impractically low because of limited selectivity and long-term stability. Also mechanistic study of C₂ production on single atom site is still unclear. Herein, we synthesized copper–nitrogen-carbon moieties (Cu–N–Cs) with altered coordination environment such as Cu-N-S, Cu-N-O and found that coexistence of these coordination at certain ratio was crucial for catalyzing electrochemical CO₂ reduction into various C2 products due to its diverse chemical properties and enhanced stability. We anchored copper single atom to modified graphitic carbon structure via low–temperature microwave hydrothermal methods. At low Cu ratio, Cu atom preferentially anchored with the phenol group out of the graphitic structure forming CuN₂O₂ moieties. By increasing Cu loading amounts to 7wt% as confirmed with TEM-EDS and ICP-MS analysis, Cu ion anchors at the edge carbon structure and formed Cu-N2 coordination. The final structure of catalyst has CuN₂O₂ & CuN₂ mixing coordination which exhibited boosted FEs of EtOH (30%) at 100mA/cm2. Also In-situ XANES & EXAFS results demonstrated that mixed coordination environment has synergistic effect when the current applied at 100mA/cm². Around 20% FEs of ethanol at 200mA/cm² with 20h stability also shows that Cu-SACs with modified coordination structure has potential for industrial application. In addition, DFT calculations revealed that the ethanol intermediate, OCCHO*, is favored on the mixed coordination sites (Cu-N₂ & CuN₂O₂) and this was further confirmed experimentally by in-situ IR measurements showing the presence of this key intermediate.

Increasing concerns over perfluorooctanoic acid (PFOA), a representative per- and polyfluoroalkyl substance (PFAS) often referred to as “forever chemicals”, underscore the urgent need for simple, rapid, and sensitive detection strategies for water monitoring. Nanozymes, nanomaterial-based artificial enzymes, have emerged as powerful tools for chemical and biological sensing due to their high stability, low cost, and superior peroxidase-like catalytic activity. In this study, we developed a nanozyme composite consisting of Fe₃O₄ nanoparticles immobilized on multi-walled carbon nanotubes (Fe₃O₄@MWCNTs) and applied it to the rapid and sensitive colorimetric detection of PFOA in water. UV-vis absorbance analysis confirmed that the nanozyme composite can effectively catalyze the oxidation of chromogenic substrates, such as 3,3,5,5-Tetramethylbenzidine (TMB), exhibiting a blue color in the presence of hydrogen peroxide (H₂O₂). Upon exposure to PFOA, electrostatic and hydrophobic interactions blocked the catalytic sites of nanocomposites, suppressing TMB oxidation and resulting in a clear “Turn-Off” optical response. This sensing platform enabled quantitative detection of PFOA within the low concentration range of 10 to 1,000 ng/L PFOA, with a limit of detection (LOD) of 2.35 ng/L, demonstrating a promising, low-cost, and practical strategy for monitoring environmentally relevant PFOA concentrations in water.

Water electrolysis is a key route toward green hydrogen and low-carbon energy systems, yet the oxygen evolution reaction (OER) in acidic media remains kinetically sluggish and strongly limits overall efficiency. RuO₂ is among the most active acidic OER catalysts, but its scarcity and operational degradation hinder large-scale deployment due to the surface reconstruction and Ru dissolution. Binary oxide alloys provide a promising pathway to simultaneously tune activity, stability, and cost. However, the vast compositional space makes purely experimental trial-and-error screening inefficient.

Here, we present a density functional theory (DFT)-driven screening framework to accelerate the discovery of Ru-based binary oxides, focusing on Ru_0.75X_0.25O₂ (X = transition metals) as practical candidates. The workflow combines the vacancy formation energies for oxygen and RuO₄, considering lattice-oxygen mediated mechanism and metal dissolution for stability and OER Gibbs energy for activity.

Across the screened set, Ru_0.75Sc_0.25O₂ emerges as the most promising candidate, exhibiting a favorable adsorption energy balance for oxygenated intermediates while stabilizing surfaces in a manner that suppresses oxygen vacancy and Ru dissolution tendencies.

Beyond ranking candidates, the calculations provide mechanistic insight into how substituents reshape surface bonding and reaction energetics, thereby rationalizing activity-stability trade-offs in Ru-based catalysts. This work highlights a simple but systematic theoretical route for narrowing down experimentally viable binary oxide compositions and offers design principles for developing durable, low-Ru-content acidic OER electrocatalysts.

Flow electrode capacitive deionization (FCDI) is a newly developed water treatment technique that differs from the original capacitive deionization (CDI) by eliminating the need for discharging process, thus achieving higher desalination capacity and continuous desalination operation. However, traditional carbon materials in FCDI offer little in terms of selective recovery of precious ions in multi-ion electrolyte mixtures, which is a highly valuable criteria in water treatment technology. The characteristics of electrodes and ion exchange membranes play a crucial role in controlling the selectivity of ions in flow electrode system. In this study, we tried to realize the selective and continuous ion recovery using the combination of redox-active Prussian blue as electrode material and modified membranes in FCDI configuration. Prussian selectively absorbs monovalent Na⁺ ions from Na⁺/Ca²⁺ mixtures through intercalation reaction, in which the smaller hydrated size of Na⁺ ion is more favored to fit in the crystal lattice. Additional selectivity is achieved through modifying the cation-exchange membrane (CEM) with polymer multilayers. A layer-by-layer method were used to deposit (PAH) and (PSS) on the CEM. It showed that the coating changed the CEM from divalent to monovalent ion-affinity due to the different ion sizes and charge density. The combination of Prussian blue and the modified CEM raised the selectivity for sodium 17 times, from 0.2 of pristine CEM to 3.35. Furthermore, multi-chambered desalination system utilizing functionalized CEM, AEM and the addition of EDTA achieved simultaneous separation and recovery of up to 3 ions: Li, Ni and Co. for We believe that our approach can provide the insight into the selective recovery of valuable materials using FCDI system.

KEYWORDS: selective ion recovery, flow electrode deionization, redox-active Prussian blue, polymer multilayers, layer-by-layer deposition, desalination.

To address the limited ion adsorption capacity of carbon-based capacitive deionization (CDI), which primarily relies on double-layer mechanism, recent efforts have focused on the rational design and development of efficient Faradaic materials for CDI applications. The development of a transition metal-based electrode has attracted much attention for emerging electrochemical applications due to its unique electrochemical properties. In this study, we synthesized and applied Co- and Mn-doped transition metal compounds (Cu₂O@MCF) as the electrodes for asymmetric CDI using a simple hydrothermal method. The synthesized electrodes were analyzed using various characterization techniques to confirm successful doping and structural integrity. Electrochemical performance assessments revealed significant improvements in ion-capture capacity and overall desalination efficiency. Specifically, the optimized asymmetric CDI cell configuration, consisting of Cu₂O@MCF(Cl) as an anode and Cu₂O@MCF(Na) as a cathode, led to a significant increase in salt adsorption capacity (27.42 mg/g) over conventional symmetric carbon electrode (11.22 mg/g). Furthermore, the synthesized electrodes demonstrated effective phosphate ion removal, highlighting their potential applicability in wastewater treatment. To further enhance the application of transition metal compounds in CDI electrodes, we have also investigated the crystalline metal-organic framework (MOF)-based NiCu-FA. The newly developed NiCu-FA by simple hydrothermal method demonstrated high salt adsorption capacity, high salt adsorption rate, and outstanding CDI cycle stability, emphasizing the importance of high surface area with salt-activated transition metal. The high adsorption capacity of 10.55 mg/g could be achieved, which is over 76% increase compared to that of pristine AC electrode (5.98 mg/g). These findings suggest that transition metal compounds significantly enhance electrode performance by synergistically combining electric double-layer capacitance and pseudocapacitance effects, due to their unique morphological and electrochemical properties. The results contribute to sustainable water treatment and resource recovery efforts, showcasing the effectiveness of the materials in improving CDI performance and opening new avenues for their application in environmental cleanup and resource management.

The development of cost-effective, high-efficiency, and durable electrocatalysts is crucial for advancing renewable energy conversion technologies, particularly in water splitting. However, optimizing the adsorption strength of oxygen intermediates to overcome the competitive trade-off between reaction kinetics and long-term stability remains a significant challenge. Inspired by recent theoretical understanding of the electronic characteristics of rare-earth intermetallic compounds, particularly the role of 4f-associated electronic effects and rare-earth-induced valence perturbation. By introducing a third rare-earth element (RE) into CoFe-based catalysts to generate asymmetric RE-CoFe units, which can regulate orbital coupling CoFe 3d - Nd 4f and the electronic structure, offering a viable strategy to enhance oxygen evolution reaction (OER) activity. Herein, we propose a neodymium (Nd) induced valence electronic perturbation strategy to regulate the electronic structure of active sites in CoFe-based catalysts for OER. To strengthen the interaction between Nd and the CoFe-Prussian blue analogue-derived pyrolysis approach was employed to construct uniformly dispersed Nd-doped CoFe species anchored on a nitrogen-doped carbon substrate. The resulting catalyst delivers an overpotential of 255 mV at a current density of 10 mA cm^–2 in alkaline electrolyte. In addition to high OER activity, the catalyst shows excellent operational stability, sustaining 10 mA cm^–2 for more than 2000 hours with negligible performance loss. Furthermore, to evaluate its practical robustness, a comprehensive durability test was conducted for 1000 hours under fluctuating conditions, including constant potential, on-off cycles, and light fluctuations, showing minimal performance degradation. These results indicate that Nd doping modulates the electronic configuration of CoFe dual active sites and simultaneously reinforces the structural integrity of the catalyst under dynamic electrochemical environments. This work offers a general design strategy for rare-earth modified transition metal electrocatalysts aimed at long-life oxygen evolution reaction in alkaline water electrolysis.

Waste valorization of CO₂ through thermocatalytic hydrogenation represents a promising pathway for the clean and renewable production of value-added chemicals such as light olefins. This approach has attracted significant scientific interest, with numerous metal oxides investigated as composite catalysts supported on alkaline materials to facilitate the modified Fischer-Tropsch synthesis route. In this study, LaFeO₃ perovskite (LFO) and its potassium-promoted derivatives (K/LFO) are synthesized using a novel mechanochemical method. For comparative evaluation, the same materials are also prepared via conventional sol-gel and hydrothermal synthesis routes. The as prepared samples were systematically characterized to determine their phase composition, surface chemistry, morphology, and oxidation state distribution of the iron active sites. Structural and spectroscopic analyses revealed that the mechanochemical route produced a defect-rich perovskite with sites of multiple Fe cation oxidation states and oxygen vacancies, whereas the sol-gel and hydrothermal routes yielded more stoichiometric, less reducible lattices. Upon K incorporation, extensive structural reconstruction occurred, leading to the emergence of Fe₃O₄ and FeC_x phases. Catalytic evaluation studies at 20 bar demonstrated a strong dependence on both synthesis and promotion. The mechanochemical K/LFO-m catalyst exhibited the highest CO₂ conversion (50%) and light-olefin selectivity (17%), outperforming the sol-gel and hydrothermal counterpart. This superior activity was attributed to sustained oxygen-vacancy density, multiple Fe cation states, and homogeneous K dispersion, which facilitated CO₂ activation and C-C coupling. Moreover, the effect of reaction temperature demonstrated that CO₂ conversion increases with an increase in temperature, while C₂-C₄⁼ selectivity reaches a plateau over 370^oC, while temperature increase hinders paraffin formation. Overall, the findings highlight the critical interplay between defect chemistry and alkali promotion in tuning perovskite-derived Fe active sites for efficient CO₂-to-olefin conversion.

In recent decades, there has been a notable surge in demand for energy storage, driven by widespread adoption of electric vehicles, portable electronics, and the global shift towards energy generation from renewable sources. While lithium-ion batteries (LIBs) dominate the current energy storage market, alternatives to state-of-the-art LIBs are being sought as LIBs are expensive, rely on non-abundant materials, and offer a limited energy density of approximately 250 Wh/kg. Lithium-sulfur (Li-S) batteries present a promising alternative with a theoretical capacity ten times higher than that of LIBs (1675 mAh g−1) and a theoretical energy density of 2500 Wh/kg. However, sulfur cathodes face challenges such as low cycle life, poor rate capability, polysulfide shuttling, and incompatibility with carbonate electrolytes. Various approaches have been explored to mitigate the phenomena of polysulfide formation and shuttling which includes nanoconfinement of sulfur, attaching sulfur to an organic backbone. In addition to these methods, recent studies indicate that the monoclinic phase of sulfur enables a single-step reaction from S8 to Li2S during cycling, avoiding intermediate polysulfides and resulting in stable cycling for over 1000 cycles. In this work, we report the loading of monoclinic sulfur onto electrospun polyacrylonitrile (PAN)-derived carbon fiber (CF) mats for use as cathodes in Li-S batteries. We demonstrate that KOH activation of these CF mats significantly enhances the loading of monoclinic sulfur, achieving a nearly four-fold increase. Consequently, Li-S cells fabricated with these activated and sulfur-loaded CF mats, paired with a low-cost carbonate electrolyte and lithium metal anode, achieved a specific capacity of 970 mAh g-1 at 1C (areal capacity of 1 mAh cm-2). The cells retained 91% of their initial capacity after 1000 charge-discharge cycles without the need for sulfur confinement. Additionally, the cells delivered a specific capacity of 400 mAh g-1 at a C-rate as high as 40C. These findings suggest that activated CFs with non-confined monoclinic sulfur have significant potential for the commercialization of Li-S batteries using cost-effective carbonate electrolytes.

Ag NWs-based transparent heaters show strong potential as transparent conductive films with excellent optical and electrical characteristics. Their performance is highly dependent on the dimensions of the NWs, which control charge transfer and network connectivity. In this work, Ag NWs were synthesized via a solvothermal route (in Teflon-lined autoclave at 170 °C for 2.5 h) using ethylene glycol (EG), poly(vinyl pyrrolidone) (PVP), silver nitrate (AgNO₃), sodium chloride (NaCl), and potassium bromide (KBr) as the reducing agent, capping agent, metal precursor, and growth promoters, respectively.Different batches of Ag NWs with controlled diameters ranging from ~40 to 100 nm were synthesized by systematically varying the Br⁻/Cl⁻ molar ratio and keeping all other parameters constant. A printable ink of Ag NWs was formulated by using hydroxypropyl methylcellulose (HPMC) as a binder in deionized water. Ag NW films were made by Meyer rod coating on polyethylene terephthalate (PET) substrates, which were further laminated with glass and polyvinyl butyral (PVB). The impact of NW size on electrical, optical, and electrothermal performance was studied. Ag NWs networks with higher aspect ratios have better percolation, which results in more continuous electrical paths across the film. These optimized films have immense potential for transparent heating applications.

Photocatalysis is widely recognized as an eco-friendly and energy-efficient advanced oxidation process for water treatment; however, its large-scale application is often hindered by poor catalyst recovery, particle agglomeration, and limited light utilization in slurry systems. In this work, we report the development of a bio-based floating photocatalytic material designed for the efficient removal of emerging contaminants, including per- and polyfluoroalkyl substances (PFAS) and commonly detected antibiotics. The floating photocatalyst was fabricated using chitosan as a sustainable biopolymer support and TiO₂ nanoparticles as the active photocatalytic phase. A freeze-casting and freeze-drying strategy was employed to generate a lightweight, highly porous aerogel-like structure with interconnected macropores, enabling enhanced mass transfer and efficient exposure of catalytic sites. To impart water repellence and long-term buoyancy, the composite was surface-modified using stearic acid, resulting in a hydrophobic outer layer that prevents water infiltration while preserving internal porosity. The resulting chitosan–TiO₂–stearic acid composite exhibited stable flotation, low density, and mechanical integrity under aqueous conditions. Photocatalytic experiments demonstrated excellent removal efficiencies for representative antibiotics and fluorinated model compounds under both UV–visible and sunlight irradiation, attributed to the synergistic effects of adsorption on the bio-based matrix and photocatalytic degradation by TiO₂. The hydrophobic surface further promoted the preferential interaction of organic contaminants with the floating catalyst, enhancing local pollutant concentration near active sites and improving degradation kinetics. In contrast to conventional suspended photocatalysts, the floating architecture enabled efficient light harvesting at the air–water interface and facilitated simple recovery and reuse without secondary separation steps.

Importantly, the proposed materials fabrication route relies on low-cost, renewable, and environmentally benign components, offering a scalable and green alternative to petroleum-based polymer foams and immobilized catalyst systems. This bio-based floating photocatalytic platform represents a promising strategy for sustainable water treatment, combining buoyancy, reusability, and high catalytic performance for the remediation of emerging pollutants. The approach provides a viable pathway toward energy-efficient, low-impact advanced oxidation technologies aligned with circular economy and environmental sustainability goals.

Reducing CO₂ emissions into atmosphere is a major issue to mitigate the current climate change. Moreover, being able to photo-convert CO₂ into more valuable species and form clean solar fuels and molecules would be a step forward to the industry decarbonation. Among the photocatalysts investigated to photoreduce CO₂, Bi-based materials have demonstrated their interest to selectively form CO, a molecular building block which can further be used to obtain methanol, acetic acid, aldehyde and even fuels... Among them, Bismuth oxyhalides show an interesting capacity to separate photogenerated charges, thanks to an internal electric field induced by their layered structure, leading to promising photocatalytic properties. However, only few studied are dedicated to Bismuth oxyfluoride materials.

At ICCF, we explore these Bismuth oxyfluoride compounds family on various forms. Indeed, we are able to synthesize by classical chemical routes powders with different stoechiometries (Bi₇O₅F₁₁, BiO_0.5F₂, BiOF), while we can also obtain the same compounds in thin films by reactive magnetron sputtering of a pure Bi target in Ar/O₂/CF4 atmosphere. In both cases, we demonstrated an enhanced photocatalytic activity of these materials by adding metallic Bismuth nanoparticles thanks to potential plasmonic effect. From one hand, these nanoparticles obtained by hydrothermal synthesis can be simply added to powder. More original route is to exsolve them from BiO_xF_y grains using hydrazine as a reducing agent. BiO_xF_y/Bi heterojunctions can also be obtained in one pot in thin film by reducing the reactive gases used during reactive sputtering.

We investigate the influence of this Bi nanoparticles (size, amount, synthesis route) on these systems. The composition, structure and morphology of these materials were studied by XRD, Raman spectroscopy, XPS, TEM and SEM. Their optical properties were determined from UV-visible spectroscopy and ellipsometry.

Experiments of CO₂ photoconversion show that an optimal metallic amount has to be found to enhance the photocatalytic activity. The BiO_xF_y/Bi thin films presents an efficiency significantly higher than the pure compound in powder and reach a value close to the one of TiO₂ P25, but with a high selectivity to form CO and a higher stability over time. To go further, we are now working on nanostructuration of these materials using an original method: the reactive sputtering onto liquid. If this technique was already investigated to form dispersion of metallic nanoparticles into liquid, we suceeded for the first time to use it in reactive mode to obtain dispersion of sperical, well-crystallized metallic or oxyfluoride nanoparticles with a mean size ranging from 6 to 8 nm and presenting a photocatalytic response. Dispersed on porous support, they show an increased photocatalytic activity (tested by photodegradation of methyl-orange into water), paving the way of high surface specific aera system for CO₂ photoreduction.

Manganese-based Prussian blue analogues (Mn-PBAs) are promising sodium-ion battery (SIB) cathodes due to their high operating voltage and low material cost. However, their practical deployment is hindered by severe structural degradation, including Jahn–Teller distortion, Mn dissolution, and an irreversible cubic-to-tetragonal phase transition during deep desodiation, which collectively drive rapid capacity fade and poor durability.

Here, we introduce a molecular-level hydrogen-bond anchoring strategy to reinforce the structural stability of manganese hexacyanoferrate (MnHCF). By incorporating tetrahedral ammonium (NH₄^⁺) ions into A-site cavities, strong N–H···N hydrogen-bond interactions are established with cyanide ligands, modulating the local coordination environment and suppressing Jahn–Teller distortion. This strategy effectively prevents irreversible phase transformation and mitigates particle cracking, thereby preserving structural reversibility during long-term cycling.

The hydrogen-bond anchored MnHCF (A-MnHCF) exhibits excellent cycling durability, retaining ~88% capacity after 1000 cycles at 1 C. In-situ XRD measurements directly confirm suppression of the cubic-to-tetragonal transition, while spectroscopic analyses (FT-IR and XPS) verify the persistence of NH4⁺ ions and the stability of hydrogen-bond interactions throughout electrochemical cycling.

This work establishes hydrogen-bond anchoring as a viable strategy to stabilize Mn-based PBAs at the molecular level,  revealing a generalizable design concept for extending the lifetime of low-cost SIB cathodes. These insights provide new opportunities for developing durable cathode materials for grid-scale energy storage applications.

Cesium niobate (Cs₂Nb₄O₁₁) is a known antiferroelectric material, which also exhibits photocatalytic properties. Considering this material is lead-free, intuitively it would be expected there would be a large body of research exploring the aforementioned properties that are intrinsic to this material. However, this is not the case. Rather, studies of cesium niobates -- especially Cs₂Nb₄O₁₁ -- are seldomly reported. It is surmised that the lack of extensive reported work for Cs₂Nb₄O₁₁ is influenced by the inherent challenges in the synthesis of alkali-niobates; which are well established. For brevity we elaborate the latter as encompassing the volatility of alkali salts, sluggish reactivity of crystalline Nb₂O₅, and the moisture sensitivity or metal-organic precursors. In particular, while metal-organic precursors are a viable alternative to circumventing the slow reactivity of Nb₂O₅, it carries the burden of working in controlled atmospheres (glovebox etc.) which is a formidable obstacle for early-career researchers, whom may only have access to limited resources. 

We have sought to establish a robust and reproducible means of synthesising Cs₂Nb₄O₁₁, to provide a viable means of exploring the (anti)ferroelectric and electrocatalytic properties of this material. This was motivated by our previous work which elucidated the synthesis of the lead-free piezoceramic, sodium potassium niobate (Na_0.5K_0.5NbO₃, KNN), via a single-component precursor.

Herein we report how Cs₂Nb₄O₁₁ can be made similarly -- via a single-component precursor -- by utilising the niobium metal oxyanion cluster hexaniobate [(Nb₆O^₁₉)^_-8]. We characterise Cs₂Nb₄O₁₁ using PXRD, Raman spectroscopy, and in situ TEM with heating, to demonstrate transformation of the amorphous Cs₂Nb₄O₁₁ precursor, to crystalline Cs₂Nb₄O₁₁. We also report our investigations from ferroelectric characterisation and electrochemical studies, to characterise ferroelectric behaviour, as well as the propensity to support charge intercalation and electrocatalysis, respectively.    

Energetic metal–organic frameworks (EMOFs) have emerged as tunable energetic materials for solid rocket motors (SRMs); however, their influence on aluminum oxidation and alumina particulate formation at the exhaust plume level has not been systematically investigated. Conventional aluminized SRMs remain indispensable for defense and space propulsion, yet indigenous high-performance formulations continue to exhibit combustion inefficiencies, including incomplete aluminum oxidation, large alumina particulates, and visible exhaust smoke, which are undesirable from both tactical and environmental perspectives. In this work, nickel–cobalt–based EMOFs are evaluated as functional micro-additives for regulating aluminum combustion behavior and reducing smoke and alumina particulate emissions in aluminized solid propellants. Baseline formulations employed micron-sized aluminum particles (18 µm; specific surface area ≈ 0.1 m² g⁻¹; calorific value 29.103 MJ kg⁻¹) with ammonium perchlorate as oxidizer and hydroxyl-terminated polybutadiene as binder. Exhaust particulates were collected using a rotating probe with adhesive copper substrates positioned at multiple axial locations downstream of the nozzle, and particle size distributions were quantified by optical microscopy across chamber pressures of 1–5 MPa. A scalable and cost-effective synthesis route was developed for Ni–Co-based EMOFs exhibiting mesoporosity (BET surface area 2.5 m² g⁻¹; average pore diameter 19.7 nm) and a calorific value of 18.947 MJ kg⁻¹. Baseline tests produced predominantly spherical alumina particles (1–60 µm), with over 50% smaller than the parent aluminum particles, indicating partial fragmentation and oxidation accompanied by visible smoke. EMOF additives act as distributed energetic catalysts by accelerating oxidizer decomposition, modifying thermal and chemical gradients around aluminum particles, suppressing molten aluminum coalescence, and promoting finer alumina particulates. These results establish a direct link between aluminum–EMOF chemistry, exhaust plume particle size distribution, and combustion behavior, positioning EMOFs as functional energetic materials for advanced solid propellant systems.

Improving catalytic selectivity remains a central challenge in chemical synthesis. Achieving high levels of chemo-, site-, and stereoselectivity fundamentally depends on the rational design and implementation of suitable catalysts and ligand environments. In this context, the development of modular and tunable catalyst platforms enables selective access to a single isomer or product among multiple thermodynamically or kinetically accessible species. To illustrate these concepts, I will discuss two distinct catalytic strategies that leverage the structural and electronic tunability of molecular complexes involved in sustainable chemical transformations.

Iron-based complexes serve as an ideal platform for such studies due to the earth-abundance of iron and its diverse reactivity. These systems offer rich redox chemistry and allow fine-tuning of key catalyst parameters, including oxidation state, spin state, and charge distribution, both at the metal center and the ligand framework. In particular, I will focus on the selective electrochemical reduction of CO₂ to CO in aqueous media using porphyrin and phthalocyanine complexes of iron and cobalt. Rational functionalization of these macrocyclic ligands has enabled control over the composition of CO/H₂ syngas mixtures; however, catalytic activity often remains suboptimal. To address this, immobilization of the functionalized metal complexes onto high-surface-area conductive supports is a promising strategy to enhance both activity and stability. I will present mechanistic insights obtained through computational and spectroscopic approaches that inform the rational design of next-generation Fe- and Co-based molecular electrocatalysts for CO₂ conversion.

In a second example, I will highlight recent advances in metallaphotoredox catalysis, an emerging field that merges transition metal catalysis with visible-light photoredox processes to access reactive organometallic intermediates under mild conditions. Notably, the nickel-catalyzed photoredox allylation of aldehydes with allyl acetates serves as a model system for the generation of nucleophilic organonickel species via light-driven pathways. Building upon this framework, I will describe the development of an enantioselective photocatalytic transformation in which steric and electronic factors play a decisive role in determining the outcome of product selectivity. This section will include a mechanistically guided strategy for selecting geometric and electronic descriptors to enable accurate prediction of enantioselectivity in asymmetric catalysis.

Sonication- Induced Scission for Precise Geometric Control during MoS₂ Exfoliation.

Jack Doran¹, Anthony Dawson¹, Weimiao Wang¹, Seán Fulham¹, Finn Huonder¹,  Cian Gabbett¹, and Jonathan N. Coleman¹

¹School of Physics, CRANN & AMBER Research Centres, Trinity College Dublin, Dublin 2,

Ireland

                                                            doranj4@tcd.ie

Electrochemically exfoliated (EE) MoS₂ nanosheets show promise in low-cost printed electronic devices. [1] Understanding how critical nanosheet properties such as mean lateral size ⟨L⟩ aspect ratio (AR) and average nanosheet thickness, ⟨t⟩ affect the electronic performance of 2D nanosheet networks is essential to optimizing charge transport. Liquid-cascade centrifugation (LCC) is an established  method to select nanosheet sizes from dispersions, however, LCC is unable to decouple ⟨L⟩ and ⟨t⟩, and therefore the AR is constrained. [2] Sonication-induced scission presents an alternative for controlling ⟨L⟩ and AR in solution-inks without varying ⟨t⟩, allowing access to nanosheet geometries which are unreachable through LCC. Using atomic force microscopy (AFM), optical spectroscopy, and other analytical methods, we show how these properties can be steered by varying the scission time on MoS₂ inks. Nanosheet networks were subsequently fabricated using spray coating. The conductivity of these networks exhibits strong dependence on the AR as predicted by theoretical modelling. [3] These results provide crucial insights into the parameters which dictate electrical performance of 2D nanosheet networks, and how sonication-induced scission techniques enable targeted nanosheet selection.

[1] Torrisi, F. & Carey, T. Graphene, related two-dimensional crystals and hybrid systems for printed and wearable electronics. Nano Today 23, 73-96 (2018).

[2] Backes, C., et al. Production of Highly Monolayer Enriched Dispersions of Liquid-Exfoliated Nanosheets by Liquid Cascade Centrifugation. ACS Nano 10, 1589-1601 (2016).

[3] Gabbett, C., et al, Understanding how junction resistances impact the conduction mechanism in nano-networks. Nat Commun 15, 4517 (2024).

Low specific capacity and limited cycle life are the two most common challenges in sodium-ion battery (SIB) research, which stem from a lack of understanding of the sodium storage mechanism in carbon materials. Here, we report how physical morphology, microstructure, and the presence of nitrogen affect the sodium storage properties of carbon materials derived from (a) lignin and (b) lignin blended with polyacrylonitrile (PAN). This is carried out by preparing (i) carbon particles (powder form in bulk) from pure lignin and (ii) electrospun carbon fibers from lignin + PAN at 900°C and 1200°C in each case. We test these materials in a half-cell configuration with sodium metal and evaluate their electrochemical performances, mainly capacity and cycling stability. Carbon fibers exhibit a higher specific capacity (418.74 mAh/g) than carbon powder (170.63 mAh/g) at a rate of C/4 when prepared at 900°C. At a higher carbonization temperature of 1200°C, the performance of the two morphologies is reversed, i.e., carbon powder outperforms carbon fibers with a capacity of 334.33 mAh/g compared to 124.28 mAh/g at C/4. We discuss these results and propose a plausible sodium storage mechanism based on pore-filling, intercalation into expanded interlayer spacing, and the presence of nitrogen in carbon.

The global energy landscape requires the development of sustainable energy production sources capable of replacing finite fossil fuels and reducing environmental problems. Renewable energies are currently in use; however, their intermittency makes it necessary to convert them into energy vectors suitable for long-term storage. The production of hydrogen from water using sustainable processes, such as photocatalysis or electrocatalysis powered by an external source of renewable electricity, is believed to be a promising solution. Unfortunately, most active catalysts capable of carrying out these transformations are based on expensive precious metals. Therefore, the design of highly active, stable, and precious metal-free photocatalysts and electrocatalysts is of utmost importance for the energy transition.

In this regard, molybdenum sulfide-based materials have emerged as potential precious metal-free candidates towards hydrogen evolution reaction (HER). Bulk molybdenum disulfide (MoS₂) shows low activity in HER because its activity originates mainly at the edge sites, while the basal planes are catalytically inert. Generally, most strategies used to improve the activity of MoS₂-derived catalysts have focused on the nanostructuring of these materials to maximize the exposure of active edge sites. Nevertheless, the most convenient approach to achieve this goal should involve the activation of basal planes by defect engineering.

Recently, we have established an innovative bottom-up synthetic strategy that uses Mo₃S_4-7 molecular cluster complexes as precursors to engineer defective molybdenum sulfide nanomaterials (called {Mo₃S₄₋₇}_n) with a greater number of defects in both the edge positions and the basal planes and, therefore, with higher activity. Remarkably, the unique structural configuration of these subunits has made it possible to obtain advanced heterogeneous catalysts for hydrogenation and dehydrogenation reactions in fine chemical synthesis.^[1,2,3] In this communication, it will be shown how, thanks to the extended molecular nature of the {Mo₃S₄₋₇}_n nanomaterials and their processability in the form of heterojunctions with conductive carbon supports and inorganic semiconductors, highly active HER electrocatalysts and photocatalysts have been obtained, respectively.^[4] Furthermore, the ability to adjust the composition of the molecular cluster precursor allows the derived materials to be precisely tuned and, therefore, the nature of the HER active sites to be deciphered.

References

[1] Rodenes, M; Gonell, F.; Martín, S.; Corma, A. Sorribes, I. JACS Au. 2022, 2, 601-612.

[2] Rodenes, M.; Dhaeyere, F.; Martín, S.; Concepción, p.; Corma, A. Sorribes, I. ACS Sustainable Chem. Eng. 2023, 11, 12265-12279.

[3] Rodenes, M.; Oštrić, D.; Martín, S.; Concepción, P.; Corma, A.; Sorribes, I. ChemSusChem 2025, 18, e202500343.

[4] Gonell, F.; Rodenes, M.; Martín, S.; Boronat, M.; Sorribes, I. Corma, A. Chem Mater. 2023, 35, 8483-8493.

The development of low-cost, high-performance electrocatalysts for the oxygen evolution reaction (OER) is critical for sustainable hydrogen production via water splitting. Here, we present a scalable, open-air fabrication route combining atmospheric-pressure spatial atomic layer deposition (AP-SALD) and Ag nanowire (AgNW) networks to engineer Cu₂O/AgNW nanocomposites with exceptional OER activity.

AP-SALD enables the conformal, thickness-controlled deposition of Cu₂O thin films at 220 °C, leveraging its advantages of high deposition rates, atmospheric operation, and compatibility with roll-to-roll processing. AgNWs, synthesized via a simple spray-coating method, provide a highly conductive, porous backbone that enhances electron transport and mass diffusion. By optimizing the Cu₂O thickness, we achieved a record-low overpotential (η₁₀ = 409 mV), Tafel slope (47 mV dec⁻¹), and turnover frequency (4.2 s⁻¹ at 350 mV) in 1 M KOH, surpassing most Cu-based OER catalysts reported to date. The 50 nm-thick Cu₂O coating on AgNWs exhibited the highest performance, attributed to its maximized active surface area, uniform conformality, and synergistic electronic effects between the AgNW network and Cu₂O layer.

Structural and morphological analyses (XRD, SEM, EDX) confirmed the homogeneous distribution of Cu₂O on AgNWs, while electrochemical impedance spectroscopy (EIS) revealed enhanced charge transfer kinetics. Stability tests demonstrated durability over 25 hours, highlighting the potential for long-term operation. This work underscores the versatility of AP-SALD for depositing functional oxides on nanostructured supports, offering a cost-effective, scalable pathway to engineer advanced nanomaterials for clean energy conversion and environmental remediation.

Alkaline water electrolysis (AWE) is a key technology for sustainable hydrogen production using earth-abundant materials; however, its efficiency is limited by sluggish kinetics of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) on conventional transition-metal catalysts. NiFe-based electrocatalysts are among the most promising low-cost alternatives, particularly for OER, yet their HER performance is often compromised by strong hydroxyl adsorption that weakens hydrogen adsorption and leads to a bifunctionality gap. Incorporation of a third metal, such as molybdenum (Mo), has emerged as an effective strategy to overcome these limitations by tuning the electronic structure and surface chemistry [1,2].

Here, a series of engineered NiFeMo nanostructured electrocatalysts with varying metal ratios were synthesized hydrothermally on Ni felt substrates and systematically investigated to establish a correlation between physicochemical properties and electrocatalysts performance. Electrochemical measurements reveal that an optimized NiFeMo composition (1:1:1) exhibits enhanced bifunctional activity under alkaline conditions. Atomic force microscopy (AFM) shows that Mo incorporation increases the average grain size from ~50 nm to over 100 nm and surface roughness from ~20 nm to ~60 nm, contributing to an increased electrochemically active surface area.

Kelvin probe force microscopy (KPFM) was employed to probe nanoscale electronic properties and correlate them with morphological features. While the average surface work function remains nearly constant at ~5.1 eV across all samples, Mo-containing catalysts exhibit pronounced electronic heterogeneity at grain boundaries. Local contact potential difference measurements reveal potential barriers of approximately ~50 mV at grain boundaries in NiFeMo catalysts, in contrast to Mo-free NiFe samples. These grain-boundary electronic modulations indicate altered charge distribution and may facilitate the formation of catalytically active sites, thereby enhancing reaction kinetics.

This work demonstrates that Mo incorporation not only modifies the nanostructure and surface morphology of NiFe-based electrocatalysts but also reconfigures their nanoscale electronic landscape. The combined AFM/KPFM approach provides critical insight into how grain-boundary electronic effects govern macroscopic electrocatalytic performance, offering design guidelines for advanced nanomaterials for energy conversion applications.

[1] F. Qin et al. ACS Energy Lett. (2018), 3, 546–554

[2] Z. Wang Applied Surface Science (2023), 607, 154803-154810

Acknowledgments: The research was supported by the Moving2Neutrality (M2N) project (reference nº C644927397-00000038), co-funded by Component C5-Capitalization and Business Innovation under the Portuguese Resilience and Recovery Plan, through the Next Generation EU Fund.

The development of efficient catalysts for sustainable chemical processes plays a crucial role in the global transition toward low-carbon energy systems. Among the pathways for CO₂ valorization, methanol synthesis from CO₂-derived syngas has attracted significant interest due to its potential to enable carbon-neutral fuel and chemical production. Industrial methanol catalysts are typically based on ternary Cu/ZnO/Al₂O₃ systems, where catalytic performance is strongly governed by the nature of the metal–oxide interfaces. However, conventional formulations rely on high metal loadings, resulting in inefficient utilization of the active phase.

Developing Cu/ZnO/Al₂O₃ catalysts with significantly reduced metal content while maintaining high catalytic efficiency therefore remains a key challenge. In this work, we investigate the use of atomic layer deposition (ALD) as strategy to engineer atomically controlled ZnO layers on high-surface-area porous Al₂O₃ supports, combined with conventional impregnation methods for copper incorporation. This approach enables systematic tuning of metal loadings and precise control over the Cu–ZnO interfacial structure.

N₂ physisorption measurements and scanning electron microscopy imaging reveal that ALD-deposited ZnO modifies the textural and morphological properties of the support while preserving high surface area. Temperature-programmed experiments and in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) provide deeper insight into the behavior of Cu–ZnO interfaces under reaction conditions, allowing identification of key surface intermediates involved in methanol synthesis from syngas.

This study highlights the critical role of atomically engineered metal–oxide interfaces in enhancing catalytic efficiency at reduced metal loadings. The results demonstrate the potential of atomic layer deposition as a powerful tool for the rational design of advanced nanocatalysts for sustainable CO₂ valorization.

The conversion of carbon dioxide into value-added chemicals represents a key challenge for achieving carbon neutrality and sustainable energy systems. In this contribution, we investigate nanostructured catalytic materials specifically designed for efficient CO₂ reduction, combining experimental characterization with multiscale modeling to elucidate structure–activity relationships.

The proposed catalysts are based on engineered nanoscale architectures with tailored surface chemistry and controlled interfaces, enabling enhanced adsorption, activation, and electron transfer during CO₂ conversion. Experimental studies involving electrochemical and photocatalytic measurements demonstrate improved selectivity and stability toward targeted reduction pathways. These results are supported by computational modeling, which provides insight into reaction mechanisms, active sites, and energy barriers governing CO₂ activation at the nanoscale.

By correlating experimental performance with theoretical predictions, this work identifies key design principles for optimizing catalytic efficiency while maintaining material scalability and environmental compatibility. The findings contribute to the rational development of low-cost and sustainable nanomaterials for CO₂ mitigation and valorization, addressing critical challenges in clean energy conversion and environmental remediation.

Key words: Nanostructured catalysts, CO₂ reduction, Engineered nanomaterials, Sustainable energy, Multiscale modeling.

This study presents a sustainable MnCO3/MWCNT composite engineered composite derived from sugarcane biomass for dual applications in coin-cell symmetric supercapacitor and visible-light-driven photocatalytic degradation of the environmentally toxic chlorpyrifos (CPF) insecticide. X- ray Diffraction (XRD) analysis confirmed the rhombohedral phase purity and the successful incorporation of the MWCNT network. The composite was further characterized using Field Emission Scanning Electron Microscopy (FESEM), High Resolution Tunneling Electron Microscopy (HRTEM) and X-ray Photoelectron Spectroscopy (XPS) revealing conductive MWCNTs net wrapped onto MnCO3 Sphere. Brunauer–Emmett–Teller analysis indicates a high surface area of 133 m2/g, providing abundant active sites to facilitate electrochemical and catalytic activity. In a three-electrode system, MnCO3/MWCNT composite exhibits a specific capacitance of 555 F/g at 1 A/g and a reversible capacity of 100 F/g at 10 A/g current density preserving 99% retention and coulombic efficiency over 2000 cycles. A coin-cell symmetric supercapacitor assembled employing MnCO3/MWCNT composite exhibits impressive specific capacitance of 110 F/g at 0.5 A/g along with excellent cycling stability (99% retention after 10,000 cycles) achieving an energy density of 51.2 Wh/kg and a power density of 3230 W/kg energy. Charge storage kinetics reveals a dominant diffusion-assisted mechanism with a minor capacitive contribution. Simultaneously, the MnCO3/MWCNT composite demonstrates outstanding photocatalytic activity, achieving 81.3% degradation of CPF under visible-light irradiation. Radical scavenging experiments identify photogenerated holes (h+) and superoxide radicals (•O2 -) as the primary active species, confirming efficient charge separation at MnCO3/MWCNT heterointerface. Overall, the synergistic integration of biomass-derived MnCO3 spheres with conductive MWCNTs highlights the composite’s potential as a low-cost, sustainable and multifunctional material for advanced energy storage and environmental remediation.

High-entropy oxides have recently emerged as a promising class of electrocatalysts due to their tunable electronic structures, high defect densities, and compositional flexibility [1]. In this work, multicomponent HEOs composed of Ni, Co, Fe, W, and a fifth transition metal were successfully integrated into electrospun polyacrylonitrile nanofibers to fabricate porous, nitrogen-doped carbon membranes for the alkaline oxygen evolution reaction. A gas-assisted electrospinning strategy was employed to achieve homogeneous dispersion of HEO precursor species within the polymer matrix while simultaneously enhancing fiber porosity and surface area [2]. Subsequent stabilization and calcination at 800 °C resulted in mechanically robust, electrically conductive carbon nanofiber membranes embedding crystalline HEO nanoparticles[3]. Comprehensive structural and physicochemical characterizations, including X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy (SEM/TEM), energy-dispersive X-ray spectroscopy mapping, X-ray photoelectron spectroscopy, and surface area analysis, confirmed the preservation of single-phase HEO structures, uniform elemental distribution, catalytic graphitization of the carbon framework, and strong interfacial coupling between the HEO nanoparticles and the N-doped carbon matrix. Electrochemical performance was systematically evaluated using linear sweep voltammetry, Tafel slope analysis, electrochemical impedance spectroscopy, double-layer capacitance measurements, and long-term stability tests in alkaline media.Among the investigated compositions, the Mo-containing HEO@NC membrane exhibited superior OER activity, delivering a low overpotential of approximately 240 mV at 10 mA cm⁻², along with the smallest charge-transfer resistance (~653 Ω) and favorable reaction kinetics. The enhanced performance is attributed to Mo-induced electronic modulation, increased oxygen-vacancy concentration, improved electrical conductivity, and accelerated charge transport across the HEO–carbon interface. In contrast, Cu- and Mn-based HEO systems showed comparatively higher overpotentials and slower kinetics, highlighting the critical role of compositional entropy engineering.

This study demonstrates that the synergistic integration of high-entropy oxides with electrospun, nitrogen-doped carbon nanofibers provides a scalable and versatile platform for designing efficient, earth-abundant OER electrocatalysts. By avoiding noble metals and employing scalable fabrication techniques, this approach directly addresses key challenges in sustainable energy conversion and green hydrogen production. The findings underscore the potential of entropy-driven materials and electrospinning technologies in advancing next-generation electrocatalysts for renewable energy systems and water-splitting applications.

In this study, Co-based non-precious group metal (PGM) oxide electrocatalysts were synthesized for the oxygen evolution reaction (OER) using co-precipitation, electro-deposition method, and so on. These catalysts were subsequently applied as anode electrodes in an anion exchange membrane water electrolyzer (AEMWE). We easily and creatively developed nano-sized Co-based oxide catalysts with abundant oxygen vacancies, large electrochemical surface area, morphology control, and electronic modification by using several synthesis methods. As a result, the catalyst demonstrated superior catalytic activity and long-term stability in half-cell tests. Recent reports have mainly focused on the catalytic activity of electrocatalysts in half-cell tests. However, it is crucial for electrocatalysts to exhibit excellent performance in full cells to achieve commercial viability. The AEMWE cell's performance surpassed that of any previously reported AEMWE cells, even when compared to those using IrO2 as an anode catalyst.

This study presents a novel approach for synthesizing Zirconium Carbide-Nickel (ZrC-Ni) cemented carbides with enhanced mechanical properties. A low-cost solution-based route was used to coat ZrC powders with well-distributed metallic nickel dots. Varying compositions with loadings of 2, 4, 6 and 10 vol% Ni were consolidated using spark plasma sintering (SPS) at 1900 ◦C under 50 MPa of uniaxial pressure giving relative densities of 96 ± 1 %. The sintered ZrC-Ni cemented carbides had an even distribution of the Ni binder phase in all compositions, with retained ultrafine ZrC grain sizes of 10 ± 1 μm from the starting powder. The enhanced sinterability of the coated powders allowed for consolidation to near theoretical densities, with a binder content as low as 2 vol%. This is attributed to the uniform distribution of nickel and an extensive Ni-ZrC interface existing prior to sintering. The small size of the Ni dots likely also contributed to the solid-state sintering process. The mechanical performance of the resulting cemented carbides was evaluated by measuring the hardness at high temperatures and estimating toughness at room temperature using Vickers indentations. These results demonstrated that the mechanical properties of the ZrC-Ni cemented carbides synthesized by our method were comparable to those of conventionally prepared cemented carbides with similar grain sizes and binder contents, and superior to conventionally prepared cemented carbides. Therefore, ZrC-Ni cemented carbides processed by this novel approach are a promising alternative to conventional cemented carbides for a wide range of applications.

In the framework of clean hydrogen production as means for renewable energy storage, hematite photoanodes (α-Fe₂O₃) have received renewed interest because of its abundance, cheapness and ability to efficiently absorb sun light for solar water splitting applications^1,2. Nevertheless, pure hematite suffers from poor photo-electrochemical activity due to short holes mean free path (few nm) and slow water oxidation kinetics. Efficient strategies can help tackle these issues such as doping^1,3,4 or using co-catalysts to improve charge transfer efficiency during oxygen evolution reaction⁵. 

We report here on the study of the photoelectrochemical efficiency of hematite based photoanodes modified by electrodeposited NiO_xH_y co-catalyst. Photocurrent and cyclic voltammetry measurements show an important effect of the co-catalyst in the absence of the light (onset potential decreasing, as expected), while a strong oxidation of the photoanode in the presence of the light prevent us from keeping the benefit of this effect, the stable values of the photocurrent decreasing drastically. The correlation between photoelectrochemical measurements, electrochemical impedance spectroscopy, on one hand, and Raman spectroscopy and synchrotron X-rays spectromicroscopy (STXM, X-PEEM) on the other, allowed us to unveil the chemical and electronic structure at the interface with the electrolyte and thus to explain the macroscopic photoelectrochemical behavior.  We will discuss the effect of the light on the charge transfer at the hematite photoanode – electrolyte interface when the hematite surface is activated by NiO_xH_y catalyst.

(1)           Stanescu, D.; Piriyev, M.; Villard, V.; Mocuta, C.; Besson, A.; Ihiawakrim, D.; Ersen, O.; Leroy, J.; Chiuzbaian, S. G.; Hitchcock, A. P.; Stanescu, S. J. Mater. Chem. A 2020, 8 (39), 20513–20530. https://doi.org/10.1039/D0TA06524B   

(2)           Iandolo, B.; Wickman, B.; Zorić, I.; Hellman, A. J. Mater. Chem. A 2015, 3 (33), 16896–16912, https://doi.org/10.1039/C5TA03362D  

(3)           Rioult, M.; Magnan, H.; Stanescu, D.; Barbier, A. J. Phys. Chem. C 2014, 118 (6), 3007–3014, https://doi.org/10.1021/jp500290j

(4)           Stanescu, S.; Alun, T.; Dappe, Y. J.; Ihiawakrim, D.; Ersen, O.; Stanescu, D. ACS Appl. Mater. Interfaces 2023, 15 (22), 26593–26605, https://doi.org/10.1021/acsami.3c02131

(5)           Fabbri, E.; Habereder, A.; Waltar, K.; Kötz, R.; Schmidt, T. J. Catal. Sci. Technol. 2014, 4 (11), 3800–3821, https://doi.org/10.1039/C4CY00669K

Surface texturing of crystalline silicon (c-Si) remains essential for enhancing optical absorption through light trapping in industrial solar cell production. Wet chemical texturing dominates industrial fabrication, but its use of hazardous chemicals and environmentally dangerous waste conflicts with sustainability goals, and material removal increases cost and limits ultra-thin wafers. Laser ablation-based texturing methods have also been explored, but they often induce deep damage that degrades electrical properties, limiting their use in high-efficiency cells. Laser-Induced Periodic Surface Structuring (LIPSS) offers a dry alternative that modifies only a shallow surface layer, reducing reflectance while minimizing subsurface damage. We demonstrate a single-step, maskless Si texturing process based on LIPSS, enabling large-area periodic nano-structures without chemical etching.

Using a femtosecond laser at 1030 nm, periodic reliefs with ~830 nm period and depths of a few hundred nanometers were formed. LIPSS parameters, including scan speed, power, and pulse overlap, were optimized via optical response, identifying conditions that minimized reflection over 350–1100 nm. Full-size M2 PERC solar cells were fabricated on optimized surfaces and characterized through IV measurements. After soft chemical smoothing and final parameter refinement, 85–90% absorption was obtained, yielding efficiencies up to 17.35% and Voc of 0.63 V. A throughput of 20 cm² min⁻¹ was demonstrated, and the process scales with repetition rate and beam multiplexing toward industrial speeds.

Although this efficiency represents the highest reported for LIPSS-textured samples, it remains below state-of-the-art PERC cells. To identify performance limits, textured wafers were etched to controlled depths while measuring minority-carrier lifetime. Lifetime analysis revealed that damage extends well below the surface, indicating that 1030 nm pulses penetrate deeply into Si and generate subsurface defects. To mitigate this, the wafer was heated during processing up to 400 °C. Numerical calculations showed that Si absorption at 1030 nm increases strongly at elevated temperature, reducing optical penetration depth. Experimentally, heating reduced the LIPSS formation threshold power and increased minority-carrier lifetime.

To conclude, we demonstrated 17.35% efficiency for a full M2 PERC cell fabricated on a LIPSS-textured Si surface at 20 cm² min⁻¹ throughput. Further analysis revealed that improving Si absorption at the processing wavelength is critical to prevent subsurface damage, which was accomplished by heating the wafer to increase its absorption coefficient. The performance of PERC cells fabricated on temperature-optimized LIPSS-textured Si will be reported. We believe that LIPSS-based dry texturing provides a realistic pathway to replacing conventional wet chemical texturing in crystalline Si solar cell production.

In previous studies, trace amount of promoters on the catalyst surface significantly improved its catalytic performance in Fishcer-Tropsch synthesis. One of the techniques used to incorporate trace amount of promoter on the surface of catalysts is atomic layer deposition (ALD). In ALD, an increase in precursor exposure time in each cycle of deposition proves to be beneficial in increasing the amount of promoter on the mesoporous surface. However, the significance of controlling the amount of promoter in the catalyst through ALD on the catalytic performance has not been established previously. In this research, TiO₂ was deposited on mesoporous Al₂O₃ through ALD and subsequently impregnated with 17.5 wt.% cobalt. The ALD process was optimized and the characteristics of the resulting materials was related to the conversion and selectivity of the FTS reaction. TiO₂/Al₂O₃ was characterized through N₂-physisorption, TEM, and ICP, while Co/TiO₂/Al₂O₃ was additionaly characterized through XPS, CO DRFITS, H₂-TPR, and CO Chemisorption. Based on the results, extremely low loadings of TiO₂ (0.05-0.1% Ti) on the Co-based catalyst supported on Al₂O₃ exhibited higher C₅₊ selectivity and CO conversion than the non-TiO₂-deposited catalyst. This behavior could be attributed to the creation of TiO₂ overlayer on the surface of cobalt, whose nature was induced and controlled through ALD. For the catalysts with a higher ALD exposure time and 0.11 wt.% of Ti, the TiO₂ overlayer was evidenced by the smaller crystallite size of cobalt (12 nm), shifting to lower binding energy of Co³⁺ (779.9 eV) in XPS spectra, and lower wavenumber of linear CO-Co (2056 cm^-1) in CO chemisorption. Interestingly, this catalyst also had the highest TOF (0.18 s^-1) and C₅₊ selectivity (94.9%). Thus, controlling the ALD process parameters consequently tunes the catalytic performance of the resulting catalyst.

This study investigates a lattice engineering strategy in single phase CaMo_1-xW_xO₄: Er³⁺, Eu³⁺ (x = 0, 0.25, 0.5, 0.75, 1) solid solutions to modulate the charge transfer quenching gate for high sensitivity dual mode thermometry. By systematically substituting Molybdenum with Tungsten, the host electronic environment is tuned to regulate the thermal stability of both upconversion and downconversion pathways across an expansive thermal range from 10 K to 673 K. Under 980 nm NIR excitation, the material exhibits characteristic Er³⁺ green and Eu³⁺ red upconversion emissions, a mode specifically suitable for biological applications due to its ability to operate within the first biological transparency window, minimizing autofluorescence and enabling deep tissue penetration. Simultaneously, 378 nm near UV excitation triggers Eu³⁺ red emission and a stable NIR-II channel at approximately 1541 nm, further extending the utility of material for high scatter sensing environments.

Cryogenic analysis conducted at 10 K identifies intrinsic energy transfer efficiencies and negative thermal quenching effects associated with phonon assisted thermalization. By correlating structural lattice evolution, determined via Rietveld refinement, with the onset of luminescence quenching, this work defines the optimum compositional windows for precision sensing. This established material based blueprint for tailoring energy migration in scheelite structured materials provides a framework for multi-environment sensing, transitioning from industrial energy systems to advanced biomedical monitoring.

Photocatalysis and adsorption represent attractive technologies for removing organic pollutants from water, which stimulate the development of low cost and high–surface-area materials capable of solar-light driven advanced oxidation processes and/or efficient contaminant capture. While photocatalysts can degrade the pollutants to less harmful side-products, adsorption requires regeneration processes, to extend the lifetime of adsorbent materials. Traditional regeneration procedures often require energy-intensive or chemically demanding steps, reducing the overall viability and sustainability of the approach. For this reason, current research is moving toward “smart” adsorbent systems in which high adsorption capacity is coupled to in situ regeneration through heterogeneous photocatalysis. In this scenario, in this work nano-sized photocatalysts based on CeO_₂-x nanoparticles, synthesized by sustainable approach in aqueous media, along with widely used conventional TiO₂ photocatalysts, are tested in light-driven decolouration of different dyes, used as model molecules, exploiting UV and solar simulating irradiation sources. Hyper-crosslinked bio-based cellulose-based resin, characterized by high specific surface area and carboxycellulose films are investigated as adsorbents and adsorption process monitored by adsorption isotherms and kinetic studies. Thanks to complementary investigations, including spectroscopic characterization and thermogravimetric analysis, the efficiency of the photocatalytic and adsorption process and the condition to achieve high decolouration yield and adsorbent regeneration have been assessed.

Keywords:  Adsorption, hyper cross-linked resins, photocatalysts, water remediation, dyes

Acknowledgements: The authors thank the European Union for funding the project “Photocatalytically-regenerable hierarchically porous adsorbents for efficient water treatment” PHOTOPAD, P2022FP2W4, 2023-2025CUP B53D23027540001through Next Generation EU, Mission 4 Component 1 and MUR within PRIN call 2022 PNRR.

The transition to a circular economy requires catalysts that are not only highly active and selective but also intrinsically stable. This study presents a robust strategy for the structural engineering of Metal-Organic Frameworks (MOFs) applied to biomass conversion and alternative energy. Rather than relying on post-synthetic modification, we focus on pre-designing starting materials to control structural defects and create coordination unsaturated sites (CUSs), eliminating the need for extrinsic active species.

To unravel the structure-property relationships, we utilized synchrotron-based X-ray absorption spectroscopy (XAS). We report two key findings: First, defect-engineered Zr-based MOFs demonstrated exceptional reactivity in converting mono- and disaccharides to lactic acid. Characterization via extended X-ray absorption fine structure (EXAFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed that intrinsic structural defects were the primary drivers of this activity. Second, the incorporation of pre-designed titanium-oxo-carboxylate clusters into MIL-125-(Ti)-NH2 frameworks induced abundant defects at Ti centers, which served as superior active sites for photocatalytic hydrogen generation. This work illustrates that precise defect engineering is a powerful tool for developing next-generation catalysts for sustainable chemical and energy processes.

 The intensification of human activities has severely deteriorated water and air quality through the release of organic pollutants, including emerging organic compounds (EOCs), persistent organic pollutants (POPs), microplastics, greenhouse gases (GHGs) and volatile organic compounds (VOCs). These contaminants pose major risks to human health and contribute to cultural heritage degradation, particularly in indoor environments. Current remediation technologies often exhibit limited efficiency or poor sustainability, as conventional adsorbents typically require energy-intensive regeneration or are disposed of after single use.

Adsorption represents a sustainable remediation strategy due to its spontaneous nature, absence of secondary pollution, and ability to concentrate contaminants onto regenerable porous solids. Micropores provide molecular-level interactions essential for high adsorption sensitivity, while meso- and macropores promote efficient mass transport. Hierarchically porous materials (HPMs), featuring interconnected porosity across multiple length scales, therefore offer unique opportunities to combine high uptake capacity with enhanced diffusion. However, a systematic understanding of how pore morphology and network topology affect adsorption/desorption performance is still lacking.

Within this framework, the HIPAD project aims to advance beyond the state of the art by developing safe, efficient, and sustainable HPMs with tailored adsorption properties. The proposed adsorbents are derived from renewable resources, by-products, and post-consumer wastes, enabling their upcycling through low-impact processes. HPMs with micro- to macroporous architectures are designed to maximize pollutant capture and regenerability. By investigating the relationship between pore morphology, topology and adsorption/desorption behavior, the project will enable the rational design of high-performance materials capable of selectively capturing target pollutants under mild conditions, paving the way for next-generation, low-impact filtration technologies.

Keywords:  environmental pollution, materials engineering, hierarchically porous materials, nanomaterials, upcycling

Acknowledgements: The authors acknowledge financial support under the Italian Science Fund (FIS 2 Call) funded by the Italian Ministry of University and Research (MUR) for the project “HIerarchically Porous materials with tailored ADsorption proper-ties to face environmental pollution” (HIPAD, Proposal code FIS-2023-01686, CUP B53C24009520001, Grant Assignment Decree No. n. 23314 adopted on 11/12/2024 by the Italian MUR).

Per- and polyfluoroalkyl substances (PFAS) are a large group of synthetic organofluorines widely used in industrial and consumer applications due to their thermal stability, chemical resistance, and surfactant properties. The same properties cause environmental persistence and create compliance risks with the EU Drinking Water Directive limits that became mandatory since 2026 (0.1 µg/L sum of 20 PFAS or 0.5 µg/L PFAS total) (1).

While anionic PFAS such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are widely studied, zwitterionic precursors such as 6:2 fluorotelomer sulfonamidopropyl betaine (6:2 FTAB), a major component in modern firefighting foams such as Capstone®/Forafac® 1157 (Product B), pose a unique threat. These compounds act as persistent precursor reservoirs and have recently been detected in drinking water sources in Europe, Canada, and the UK (2). 

The state-of-the-art technology relies on adsorption by activated carbon (AC) in fixed-bed columns; however, AC production has a high carbon footprint (8.6–18.3 kg CO₂-eq/kg AC) and lacks efficient on-site regeneration options. Electrosorption, the field-driven and reversible uptake of ions at polarized electrodes, has been applied for conventional anionic PFAS such as PFOA and PFOS, but its application to zwitterionic PFAS remains unclear due to their dual ionic character (3).

In this study, electrosorption of 6:2 FTAB using Ti₃C₂Tₓ MXenes was investigated. MXenes are attractive for environmental applications due to their conductivity, tunable chemistry, and their layered structure.

Two stable and homogeneous MXene electrodes were developed, including a binder-free electrode and one using a non-fluorinated binder. Electrochemical characterization showed a specific capacitance of ~90 F/g in 1 M Na₂SO₄ at 3 mV/s. Electrosorption of 6:2 FTAB (C₀=100 µg/L) was strongly potential dependent, with adsorption enhanced at negative potentials due to favorable electrostatic attraction with the positive headgroup. Distribution coefficients (K_d) of up to 10⁵ L/kg were achieved at -800 mV vs Ag/AgCl, which is two orders of magnitude higher than the K_d obtained at positive potential of +800 mV in 10 mM Na₂SO₄.

The approach was further validated using real firefighting-foam samples containing 6:2 FTAB and co-occurring organic PFAS and the performance was maintained, achieving selective electrosorption of 6:2 FTAB with Kd of 1.3 × 10⁵ L/kg. DFT and complementary XRD and XPS analyses confirmed adsorption mechanisms and electrode stability across the applied potential range.

1. https://environment.ec.europa.eu/topics/water/drinking-water_en.

2. Teymoorian, Termeh, Gabriel Munoz, and Sébastien Sauvé. "PFAS contamination in tap water: Target and suspect screening of zwitterionic, cationic, and anionic species across Canada and beyond." 

3. Saeidi, Navid, et al. "Electrosorption of organic compounds: State of the art, challenges, performance, and   perspectives."

Traditionally, rare-earth ion-doped silicate glass has been the cornerstone of commercial fiber lasers and amplifiers due to their established performance. However, rare earth materials have limited resources and these systems are limited by predetermined emission wavelengths corresponding to specific 4f-4f transitions and limited natural resources. Our research aims to introduce a more versatile and tunable  alternative by harnessing the unique optical properties of carbon dots.
In this work, Red emitting CDs with near unity Quantum Yeild is developed and integrated in optical fibers. Initial experiments have demonstrated promising signs of signal amplification within these CD-doped fibers under various pumping conditions, fiber diameter and concentration. Maximum gain obtained so far is 9.7 dB with 100nm   3 dB bandwidth in the region 600-700 nm. 

Metallic nanowire (MNW) networks have emerged as highly promising transparent and flexible electrodes owing to their excellent electrical conductivity, high optical transparency, and mechanical compliance. These properties make them particularly attractive for next-generation sustainable energy devices, notably solar cells, as well as for smart windows and low-emissivity coatings. However, the widespread deployment of MNW-based electrodes is currently limited by their insufficient thermal, electrical, and chemical stability.

In this contribution, we present an overview of oxide-stabilized MNW networks as advanced nanocomposite materials designed to address these limitations while meeting sustainability requirements. The deposition of ultrathin oxide layers (e.g., ZnO, SnO₂, Al₂O₃, MgO, or ZrO₂) onto randomly oriented MNW networks leads to a drastic enhancement of stability, while simultaneously enabling the tuning of optical, electrical, and emissive properties. Particular attention is devoted to eco-friendly fabrication routes and to silver-free alternatives, such as Cu-based core@shell nanowire architectures, which offer clear advantages in terms of resource availability and environmental impact.

Beyond applicative considerations, recent fundamental insights into MNW networks are discussed, including the identification of optical percolation phenomena and generalized Hagen–Rubens behavior in dense networks. These findings establish universal design rules linking network density, sheet resistance, and infrared emissivity, independent of nanowire diameter. Such concepts open new pathways for engineering transparent electrodes and low-emissivity coatings optimized for solar energy harvesting and thermal management.

Overall, this presentation highlights how oxide-coated MNW nanocomposites constitute a versatile and scalable materials platform for sustainable energy technologies, while also addressing current challenges and future opportunities at the interface of nanomaterials science, environmental responsibility, and device engineering.

Few recent references associated to the abstract (for which Prof. Daniel Bellet was the last author):

[1] Nguyen et al., Small 2022, 2106006; [2] Papanastasiou at al., Adv. Funct. Mater. 2020, 30, 1910225; [3] Bardet et al., ACS Appl. Nano Mater. 2023, 6, 15234; [4] Papanastasiou et al., Adv. Materials Technologies 2023, 8, 2200563; [5] Sekkat et al., Adv. Materials Technologies 2023, 8, 2301143; [6] Bardet et al., Nanoscale 2024, 16, 564; [7] Chernukha et al., ACS Omega 2025, 10, 2573818; [8] Bardet et al., Nanoscale 2024, 16, 564 ; [9] Khan et al., ACS Appl. Mater. Interfaces 2024, 16, 10439.

The increased production and use of plastics in the last decades have led to a major environmental issue, and pollution by microplastics and nanoplastics is a big concern in today’s society. Even though both micro- and nanoplastics pose threats to the environment and to human health, nanoplastics are of additional concern due to their smaller size making them harder to remove and detect in the environment. Thus, it is important to develop new tools to efficiently remove both micro- and nanoplastics.

Nanomaterials have gained a lot of attention for environmental applications and iron oxide nanomaterials, in particular, can be quite interesting for pollutant removal, as their magnetic character makes them easy to recover and they are also easy to functionalize. Most approaches with iron oxide nanoparticles consist in functionalizing them to enhance the pollutant capture, but some works have demonstrated that bare iron oxide nanoparticles can also be promising adsorbents for plastic particles.

So, we have designed iron oxide nanostructures (IONSs) of two different particle sizes (~130 nm or ~320 nm) by optimizing solvothermal polyol routes and studied their interactions with polystyrene particles. The interest of IONSs is that they consist of oriented aggregates of nanograins, leading to superparamagnetic behavior and high saturation magnetization, making them easy to recover after adsorption. The synthesized IONSs were studied in the capture of plastic particles of different size in water, to evaluate in the effect of both IONSs and plastic size in this process. Polystyrene (PS) was chosen as the target plastic, and two PS sizes were studied: 150 nm (nanoplastic range) and 982 nm (close to microplastic range). PS particles were mixed with IONSs in water and after a certain contact time, magnetic separation allowed to remove the IONSs with captured PS. The remaining PS in suspension was then quantified. We tested different quantification methods (TOC, GC-pyrolysis and UV-Vis spectroscopy) and demonstrated that UV-Vis was a simple and reliable technique. For micro-PS, the removal efficiency (RE) was similar for both IONSs, reaching ~90% in <5 min. For nano-PS, the 130 nm IONSs showed a better performance, reaching close to 100% RE in only 10 min, while the 320 nm IONSs needed 30 min to reach this value. Kinetic and isotherm studies were performed, with nano-PS following pseudo 1st order and Langmuir, while micro-PS followed Freundlich. SEM of the IONSs with PS also hinted at different mechanisms for 150 and 982 nm PS.

All this work showed the great potential of the IONSs in the adsorption of micro- and nanoplastics. Next steps will aim to find solutions for the final fate of PS particles and IONSs recyclability. Preliminary desorption tests showed that nano-PS are much harder to desorb from the IONSs then micro-PS, with further work needed. Other strategies to degrade the PS using thermal or enzymatic approaches are being tested in early stages.

Synthetic dyes released into water constitute a significant environmental challenge because of their persistence and adverse ecological and health effects. The development of sustainable materials capable of combining efficient adsorption with pollutant degradation is therefore highly desirable. In this contribution, multifunctional bio-based materials were designed starting from lignocellulosic precursors transformed into hyper-crosslinked polymer networks through a green synthetic approach based on mild conditions and environmentally friendly solvent. The obtained resins exhibit a highly developed porous architecture, with Langmuir specific surface areas reaching about 1500 m²/g, making them particularly effective for the capture of dye molecules from water.

To extend their functionality beyond adsorption, photoactive nanoparticles were immobilized within the porous framework, providing photocatalytic activity under solar irradiation. The resulting nanocomposites were then integrated into transparent, cellulose-derived films with high water absorption capacity, enabling easy handling and potential application in water treatment systems. A comprehensive characterization of the materials was carried out to elucidate their structural, morphological and textural features. Their performance was assessed through adsorption experiments with different dyes, supported by the analysis of adsorption isotherms and kinetic behaviour. The stability and practical applicability of the materials were further evaluated by repeated adsorption and regeneration cycles, highlighting their promise as renewable, reusable and multifunctional systems for the remediation of dye-contaminated waters.

Acknowledgements: The authors acknowledge financial support under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, Call for tender No. 1409 published on 14.09.2022 by the Italian Ministry of University and Research (MUR), funded by the European Union – NextGenerationEU– Project Title “Photocatalytically-regenerable hierarchically porous adsorbents for efficient water treatment” (PHOTOPAD, code P2022FP2W4, 2023-2025), CUP B53D23027540001, Grant Assignment Decree No. 1389 adopted on 01.09.2023 by the Italian MUR.

The authors also acknowledge financial support under the Italian Science Fund (FIS 2 Call) funded by the Italian Ministry of University and Research (MUR) for the project “HIerarchically Porous materials with tailored ADsorption properties to face environmental pollution” (HIPAD, Proposal code FIS-2023-01686, CUP B53C24009520001, Grant Assignment Decree No. n. 23314 adopted on 11/12/2024 by the Italian MUR).

A significant demand exists for a high-strength material exhibiting specified mechanical properties at cryogenic temperatures for the effective design of particular structural components of the fusion reactor, such as coils and jackets. The target properties of yield strength of (YS) > 1500 MPa and fracture toughness of (KIC) > 130 MPa.m^1/2 are hardly attainable with conventionally used steels like 316LN, JK2LB, Incoloy 908, and JJ1. XM-19 (Nitronic50), a non-magnetic, corrosion-resistant austenitic stainless steel, provides excellent strength and toughness at cryogenic temperatures; however, some drawbacks must be addressed before this material can be considered as the best option for the design of fusion reactor compartments. The study focuses on the characterization of the properties of conventional Nitronic50 and modified Nitronic50, referred to as N50H, which was produced by modified chemical composition and controlled casting, forging, and heat treatment routes during manufacturing process. Mechanical testing including tensile testing, fracture toughness evaluation, and fatigue assessment performed at cryogenic temperatures. Moreover, optical and electron microscopy are used to correlate material response with deformation modes, microstructural features, and precipitates stability.

Metallophthalocyanines constitute an extended family of organic molecular materials exhibiting specific optical, electrical, chemical and adsorption properties due to their high aromaticity, the extended delocalization of p-electrons and the class of grafting peripheral groups on macrocycles [1]. These properties can be modulated consecutively to gas adsorption according to the chemical characteristics of gases (reducing or oxidizing power, aromatic character, or radicals) making metallophthalocyanine as the most renowned sensing material for gas micro-sensor development [2]. Coated onto a great diversity of substrates by a large panel of deposition methods (thermal evaporation, drop-casting, spin-coating, langmuir-blodgett…), thin films exhibit electronic conductivity, acoustic impedance and optical index significantly modified by gases even for very low concentrations, that confer to micro-sensors their high sensitivity, low limit of detection and high resolution [3].

This lecture highlights the key role of transducer on gas sensor response. Based on physical and chemical properties of phthalocyanine and gas/material interactions involved, the selection of conductometric, acoustic or plasmonic as transducing mode greatly affects the sensitivity and mainly the selectivity of gas microsensors involving metallophthalocyanines as sensing materials. On the one hand, the high selectivity of conductometric phthalocyanine sensors towards nitrogen dioxide NO2 in ppb-range, attributed to the high density of delocalized p-electrons, is established. On the other hand, the aromatic character of phthalocyanines make acoustic microsensors highly selective to aromatic hydrocarbons as toluene and xylenes due to the p-stacking interaction involved. Finally, sensors developed on plasmonic transducers exploit the dielectric character of phthalocyanine thin film (low intrinsic conductivity) and exhibit higher sensitivity to reducing gases, mainly to ammonia. Application fields will be discussed.

[1] Hamad, Othman Abdulrahman, Rebaz Obaid Kareem, and Peshang Khdir Omer. "Properties, characterization, and application of phthalocyanine and metal phthalocyanine." J. Chem. Rev 6.1 (2024): 39.

[2] Mukherjee, Debdyuti, et al. "Phthalocyanines as sensitive materials for chemical sensors." Materials for Chemical Sensing (2016): 165-226.

[3] Su, Heng C., et al. "Chemiresistive sensor arrays for detection of air pollutants based on carbon nanotubes functionalized with porphyrin and phthalocyanine derivatives." Sensors and Actuators Reports 2.1 (2020): 100011.

Transition metal oxides (TMOs) are materials whose properties can be tuned through their structure and composition, which makes them of particular interest for the development of energy applications such as the fabrication of electrodes for lithium- or even sodium-ion batteries [1] or as active material for catalysis processes [2]. Although, niobium (Nb) and titanium (Ti) metals are considered as critical raw materials for the EU, the superior lifetime, stability and safety of these Ti-Nb oxides make it worth studying their properties and developing techniques to process small quantities of these materials. In this sense, to reduce the requirements of primary raw material, we will focus our studies on the formation of active layers of the TMOs, in order to reduce as much as possible the material needed.

On the other hand, the production of Ti-Nb oxides requires typically high temperature treatments over long periods of time, in order to allow the diffusion of Ti into the characteristic niobium oxide Wadsley-Roth structure. Combined with this, the oxygen deficit plays a major role in enhancing both electrical and optical properties of the oxide, as well as in the creation of additional active sites for redox reactions to be used in the applications above mentioned [3]. The most widespread technique for generating oxygen deficiency is annealing the material in a reductive atmosphere, as H₂ or low-mid vacuum, among others. However, this approach suffers from poor controllability and scalability and low energetic efficiency (high temperatures are required). The main strategy of this work is to overcome the complexity to control oxygen-vacancies concentration and crystal structure changes in Ti-Nb oxides compounds (titanium niobates or TNOs) by employing ultrafast laser irradiation. Recently, we optimized an ultrafast-laser powder bed processing technique to produce uniform and compact sintered layers of a monoclinic oxygen-deficient Nb₂O₅ phase [4], where the microstructure and oxygen-deficiency determined the electrical properties of the layers (much more conductive than pure Nb₂O₅).

In this work, we have followed a similar but new approach, irradiating a mixture of high purity powders of TiO₂ and Nb₂O₅, in order to produce TNO layers. As a result of the optimization of laser processing parameters, we have been able to produce continuous layers of TNO on fused silica. The morphology, structure, niobium and titanium distribution in the layer and optical and electrical properties of the so produced material will be described as well as its potential use in applications like those previously mentioned, discussing the possibilities of integration into lithium-ion batteries or photocatalytic devices.

[1] S. Boyd et al., Inorg. Chem. Front. 5 (2018) 999.

[2] S. Martha et al., RSC Adv. 5 (2015) 61535.

[3] T.F. Yi et al., Nano Energy 85 (2021) 105955.

[4] B. Sotillo et al., Mater. Des. 224 (2022) 111346.

Elucidating crystal-facet behaviors of Cerium dioxide for Pd/CeO2-x catalyst on selective hydrogenation of alkynols

He Jiaxin 1[0000-0001-6157-8525], Zhang Jian 1*[0000-0002-0912-1197] 

1 State Key Laboratory of Solidification Processing School of Materials Science and Engineering, Northwestern Polytechnical University Xi’an, 710072, P. R. China

Abstract:

2-methyl-3-buten-2-ol (MBE) is one of important raw materials and intermediates in fine chemicals and widely used in the production of vitamins (A, B6, and E), high-value-added polyols and perfumes. Selective hydrogenation 2-methyl-3-butyn-2-ol (MBY) to MBE has emerged wide-spread attention over the past decades. Selective hydrogenation procedure proceeds over noble metal-based catalysts under mild conditions (e.g., Pd, Pt, and Au). Unfortunately, Over-hydrogenation from MBY to 2-methyl-3-butanol (MBA) remains a persistent issue, particularly focus on over-dissociation of hydrogen in conventional Pd or Pt catalysts. Single-atom catalyst (SAC) demonstrates fully surface-exposed, atomically dispersed active sites and high selectivity in a variety of industrially important reactions. These remarkable catalytic merits substantially reduce the metal loadings required in current commercial catalysts, positioning SACs as highly promising candidates for next-generation industrial catalysis. Cerium dioxide (CeO2) is attributed to an ideal support for SAC due to its rich oxygen vacancies and unique surface properties. Nevertheless, the polycrystalline facet structure of CeO2 inevitably generates different morphology of active sites (e.g., SAC, nanocluster or nanoparticle), and thus leading the uncontrollable selective distribution during the reaction. Highlight in this work, we tailored the morphology of CeO2 (rods, cubes, and octahedra) to expose specific crystal facets for modulating atomic-level dispersed Pd species. Cube CeO2 (C-CeO2-x) exposes (100) facets with abundant oxygen vacancies, effectively captures Pd precursors and yields a Pd SAC (Pd1/C-CeO2-x). Based on the design of CeO2 crystal facet engineering, isolated Pd single-atom sites weakens the adsorption of alkene bond and impels the hydrogen heterolysis, thereby optimizing the product selectivity of MBE. Pd1/C-CeO2-x achieves a remarkably high MBE selectivity of 95.7% without toxic metallic and quinoline inhibitors, significantly outperforming Pd1/R-CeO2-x (51.5%) and Pdn/O-CeO2-x (4.4%). This study not only elucidates the critical role of support crystal facets in governing selectivity but also paves a promising avenue for the targeted synthesis to fine chemicals.

The increasing deployment of lithium (Li)-ion batteries (LIBs) in electric vehicles and large-scale energy storage systems has led to a growing accumulation of end-of-life batteries, raising concerns regarding resource sustainability and environmental impact. Conventional recycling routes based on pyrometallurgical or hydrometallurgical processes enable material recovery; however, these approaches are often energy-intensive, multistep, and environmentally burdensome. Recently, solution-based relithiation methods, in which degraded cathodes are immersed in Li-containing regeneration solutions, have been proposed as a direct regeneration strategy to restore key cathode functionalities, including electrochemical capacity and crystallographic integrity. By bypassing high-temperature treatments and aggressive chemical processing, this approach offers a potential alternative to conventional metallurgical recycling. Despite its promise, the effectiveness of relithiation remains highly dependent on the properties of the regeneration solution, and the governing role of solvent characteristics has not yet been systematically elucidated.

In this work, we investigate how intrinsic solvent properties in regeneration solutions regulate chemical-potential-driven relithiation of spent cathodes. Effective regeneration requires the simultaneous fulfillment of multiple conditions, including appropriate electrochemical potential alignment to thermodynamically favor Li insertion, sufficient Li-ion mobility to enable efficient relithiation, and suppression of undesirable side reactions that impede interfacial charge-transfer kinetics. Rather than focusing on specific chemical formulations, we propose a general conceptual framework that links solution-level solvent properties to the feasibility and kinetics of cathode relithiation. The structural and electrochemical recovery of regenerated cathodes is examined through X-ray diffraction, electrochemical impedance spectroscopy, and X-ray absorption near-edge structure analyses, revealing partial restoration of crystallographic order, reduced interfacial resistance, and changes in transition-metal oxidation states consistent with Li reinsertion. The regenerated cathodes are further evaluated in Li metal battery configurations, demonstrating improved reversible capacity and cycling stability relative to the spent state. These results highlight the practical relevance of solvent-guided relithiation principles and provide insights toward the rational design of regeneration solutions for end-of-life cathodes.

Hydrogen energy is gaining attention as an alternative energy source that can replace conventional fossil fuels, and water splitting technology is spotlighted because it can produce hydrogen without the involvement of carbon-based materials. However, time-consuming and complicated catalyst synthetic processes pose significant challenges for commercialization. In this study, we synthesized three-dimensional porous graphene by irradiating a polyimide with an infrared-range light, and metal elements were decorated on the graphene surface, resulting in a hierarchically structured metal-graphene hybrid electrocatalyst. Surface analyses confirmed that a porous graphene-like carbon structure was formed by initial irradiation, and the structure was maintained even after loading metal elements. Structure characterizations also clearly showed the transformation from polyimide to graphene, and XPS characterizations revealed that metal elements were generally well-synthesized on the graphene surface. Electrochemical measurements revealed that water splitting reactions were available for the synthesized catalysts, and the final product exhibited better electrocatalytic performance compared to commercial catalysts. Based on these results, it is expected that we can greatly reduce the time and cost by changing the catalyst synthesis process while improving the catalytic activity and durability. Ultimately, it is also expected that applying this catalyst to water splitting technology can contribute to the improvement and commercialization of hydrogen production.

Acidic water electrolysis is a compelling route to green hydrogen, yet it still depends largely on scarce noble-metal catalysts1,2 because few Earth-abundant systems combine activity, durability, and selectivity at low pH. Here we report a vanadium polyoxometalate (POM)–carbon nanotube (CNT) hybrid in which catalytic function is not altered by changing composition, but instead programmed by controlling supramolecular assembly and the resulting local electrochemical microenvironment. 3

The molecular platform is a decavanadate-based compound incorporating non-innocent Na⁺ and TRIS-derived organic counter-cations, whose accessibility depends on the POM–CNT interfacial architecture. When the material is used as a simple physical mixture with CNT (1/CNT), it delivers strong oxygen evolution reaction (OER) performance in 1 M H₂SO₄, reaching an overpotential of 0.34 V at 10 mA cm⁻² with 80% Faradaic efficiency, outperforming IrO₂ under identical conditions. In contrast, when the same building blocks are assembled in a directed manner on CNT surfaces (1@CNT), the TRIS⁺ functionality becomes exposed and the hybrid switches to hydrogen evolution reaction (HER) catalysis, exhibiting an onset potential of −0.07 V and 94% Faradaic efficiency, approaching Pt/C benchmarks.

Mechanistic insights supported by in-operando confocal microscopy and theoretical analysis indicate that crystal-interaction control and microenvironment engineering govern the selectivity switch. In this framework, OER is associated with an alcohol-oxidation-reaction-mediated pathway, whereas HER is promoted when TRIS⁺ acts as a proton-sponge that enriches protons near the POM surface. Overall, these results establish assembly control as a general strategy to create switchable, bifunctional molecular electrocatalysts for robust water splitting under strongly acidic conditions.

This work has received financial support from the Ministry of Science and Innovation of Spain (Projects PID2021-127341OB-I00, PID2024-162420OB-I00) and  Xunta de Galicia (for the Oportunius Research Professor Program.

References: 1-Aygün, Mehtap et al. ChemSusChem 2021,14,4973; 2-Herreros-Lucas, Carlos et al. Adv. Sci. 2025,12, 05104; 3-Quiros-Diez, E. P. et al. Adv. Mater. 2025, e12902. DOI:10.1002/adma.202512902.

Morphology Engineered Moss-like Cerium Molybdate for High-performance Symmetric Supercapacitor

Joel Skaria Joseph a,b,  Subramanian Sakthinathan a,b, ,Te-Wei Chiu a,b*

a Department of Materials and Mineral Resources Engineering, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan.

b Institute of Materials Science and Engineering, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan.

Correspondence:      tewei@ntut.edu.tw (Te-Wei Chiu)

aBSTRACT

The synthesis of distinctive porous moss-like cerium molybdate morphology with a moss-like morphology, a high-performance supercapacitor electrode, utilizing simple hydrothermal method is the main emphasis of this work. XRD structural analysis verifies the composite's effective formation of cubic crystal with space group Fm3m. The isotropic growth of nanoballs forming a moss like morphology is affirmed by FESEM and HRTEM analysis. Additional research on electrochemical part demonstrates their higher cycle performance, increased electron conductivity, improved surface area, and structural durability. With 100% capacity retention and coulombic efficiency, the idiosyncratic structure produced a high specific capacitance of 450 F/g at 1 A/g in a three-electrode system after 3000 long cycles. A significant pseudocapacitive contribution of 65% at 100 mV/s over diffusion-controlled reaction is found when charge storage kinetics is examined using Dunn's technique. A symmetric coin-cell constructed using a moss-shaped cerium molybdate achieves an energy density of 17.8 Wh/kg and a power density of 2754 W/kg energy with a remarkable specific capacitance of 106 F/g at 0.5 A/g and spectacular cycling resilience and coulombic efficiency (99% retention after 20,000 cycles). This provides unique morphological dominance of electrode material, offering prospects to develop various high-performance energy storage materials by tuning morphology and crystal structure.

Keywords: moss-like morphology, hydrothermal, pseudocapacitive, capacity retention, structural durability.

Reference:

Manthiram, A.; Gopalakrishnan, J.  J. Less-Common Met., 1984, 99, 107–111.

Goodenough, J. B. Energy Environ. Sci. 7 (2014), 14-18.

Joseph, J.S; Palraj, J; Sakthinathan, S; Annal Therese, H; Chiu, T.W.  J. Phys. Chem. Lett. 2025, 16, 9722-9728.

2D Metal Phosphorous Trichalcogenides (MPCh3) for Photothermal Conversion and Solar Desalination

Honglei Wang,1 Dong Wang,2 Peter Schaaf,2 Paolo Samorì1

1University of Strasbourg, CNRS, ISIS UMR 7006, 8 Allée Gaspard Monge, Strasbourg F-67000, France

2Chair Materials for Electrical Engineering and Electronics, Institute of Materials Science and Engineering and Institute of Micro and Nanotechnologies MacroNano, TU Ilmenau, Gustav-Kirchhoff-Str. 5, Ilmenau 98693, Germany

Email: honglei.wang@unistra.fr

Abstract:

Metal phosphorous trichalcogenides (MPCh3, M = Fe, Ni, Sn etc.) have recently emerged as an important class of two-dimensional (2D) materials, owing to their unique physicochemical features, including adjustable energy bandgap, significant specific surface area and versatile surface properties. A narrow bandgap as low as 1.2 eV endows these materials with great potential for photothermal conversion and solar desalination. However, MPCh₃ materials generally suffer from poor stability under aqueous and oxidative conditions, resulting in very limited reports on their application in this field. Herein, polyvinyl alcohol (PVA) was deposited at the edges of NiPS₃ nanosheets to enhance their environmental stability, enabling efficient photothermal conversion and solar desalination. Furthermore, carbon nanodots (CNDs) were anchored onto the surface of FePS₃ nanosheets to construct a 2D/0D nanoheterostructure, which exhibited a high water evaporation rate of up to 1.68 kg m⁻² h⁻¹ after 300 s of irradiation under one-sun illumination. The structure-property relationship and the underlying mechanism were investigated and will be discussed here, which provides valuable understanding and strategic guidance for the design of efficient 2D photothermal materials.

References:

1. Wang, H.; Bo, Y.; Wang, H.; Klingenhof, M.; Tao, Z.; Wang, D.; Wu, B.; Tamayo, A.; Han, B.; Cheng, P.; van Aken, P. A.; Sofer, Z.; Chen, R.; Strasser, P.; Schaaf, P.; Guldi, D. M.; Samori, P., Enhanced Photothermal Conversion through 2D/0D Nano-Heterojunction Engineering for Highly Efficient Solar Desalination. J. Am. Chem. Soc., 2025, 147, 25750-25760.

2. Wang, H.; Cheng, P.; Wu, B.; Yan, Y.; Schaaf, P.; Sofer, Z.; Wang, D., Two-Dimensional Metal Phosphorous Trichalcogenides (MPCh3) for Sustainable Energy Storage and Conversion: Nanoarchitectonics and Advanced Applications. Invited review paper, Adv. Func. Mater., 2024, 34, 2407432.

Achieving precise control over the layer number and structural uniformity of two-dimensional polymers remains a critical challenge, limiting their practical implementation in sustainable energy and environmental applications. Two-dimensional covalent organic frameworks (2D COFs), featuring ordered porosity, tunable surface chemistry, and high chemical stability, are particularly attractive for membrane-based separation, ion transport, and energy conversion processes. However, scalable strategies enabling well-defined thickness control are still scarce.

Herein, we report an adsorption layer–confined growth strategy for the ambient and gram-scale synthesis of 2D COF nanosheets (2D CONs) at solid–liquid interfaces. By confining polymerization within the nano-adsorption layer on layered double hydroxide (LDH) substrates, the growth kinetics and anisotropic extension of COFs are effectively regulated. This approach enables precise control over the nanosheet thickness from 0.8 nm (bilayer) to 10.1 nm (29 layers), while maintaining high crystallinity and lateral sizes of approximately 2.0 µm within 6 hours. After acid-assisted removal of the inorganic template, the resulting 2D CONs exhibit excellent dispersibility in various solvents, with concentrations up to 0.028 g L⁻¹.

Benefiting from their well-defined thickness, accessible nanochannels, and tunable surface charge, the 2D CONs can be processed into ultrathin membranes (0.5–3.0 µm) displaying high anion selectivity and long-term stability. When applied to osmotic energy harvesting, these membranes deliver an output power density of 78.5 W m⁻² under a 50-fold NaCl concentration gradient, outperforming commercial benchmarks and most previously reported COF- or 2D-nanosheet-based membranes of comparable thickness.

Moreover, this adsorption layer–confined strategy is readily extendable to different monomer systems and inorganic substrates, providing a versatile platform for the rational design of advanced COF-based nanomaterials. This work highlights the importance of confinement-controlled synthesis in tailoring nanostructures for efficient, low-cost, and environmentally friendly materials, offering new opportunities for sustainable energy conversion.

High Throughput Continuous Degradation of Imidacloprid using an immobilised Titanium dioxide platform

Abhijnan Maitra, Raka Mondal

The escalating ecological consciousness and increasingly rigorous environmental regulations are propelling worldwide initiatives to eliminate persistent pesticides from aquatic systems. Among these, a widely applied neonicotinoid insecticide, Imidacloprid, has caused substantial aqueous contamination owing to its overuse. The key innovation of this study lies in the development of a robust, optimised, high-throughput continuous degradation of Imidacloprid using visible-light-activated TiO₂ photocatalyst. This shift broadens the scope for sustainable, Visible light-driven remediation processes integrated with a high-volume recirculating photoreactor (2.5L), designed to accelerate degradation kinetics and overcome the shortcomings of conventional UV-driven and batch-mode systems. At the same time, the study evaluated multiple key parameters such as the amount of catalyst added, the initial concentration of imidacloprid (1-10 mg/L) being broken down, the light intensity incident on the reaction system, temperature, and pH of the aqueous phase or reaction medium in the degradation of imidacloprid and optimised how these parameters could be adjusted. The result shows that the degradation efficiency of the Recirculated mode is 50-70% higher than the Batch mode, along with an overall stable reaction environment, which enables the industrial-scale application. Although Suspended TiO₂ provides higher efficiency, due to a greater accessible surface area than the immobilised one, the immobilised configuration has superior operational stability and ease of separation after the degradation.  As expected, the degradation efficiency will increase by increasing light intensity from 125 W to 450 W. The time to reach C/C₀ to 0.1 is almost 2.5 hrs shorter for 450W than for 125W. Similarly, increasing the Catalyst concentration from 30 mg/L to 100 mg/L nearly doubled the degradation rate. Optimal performance is attained at mildly acidic pH, moderate catalyst loadings, and elevated temperatures. Complete degradation is assured through TOC and HPLC analysis. The kinetic behaviour of the degradation process follows pseudo-first-order reaction kinetics, with rate constants decreasing at higher IMC concentrations due to surface saturation and reduced photon penetration. Therefore, this research demonstrates the potential for the use of visible-light titanium dioxide in the development of continuous flow photochemistry used for the remediation of neonicotinoid-imprinted wastewater. Furthermore, this research provides a basis for developing larger-scale, optimised aqueous-phase titanium dioxide photocatalysis to create effective means for cleaning agricultural chemicals from surface and sediment waters.

The global transition toward a hydrogen-based energy economy is driven by the urgent need to decarbonize energy systems and reduce environmental impacts associated with fossil fuel consumption. Aqueous Phase Reforming (APR) of biomass-derived oxygenates represents a promising route for sustainable hydrogen production under moderate reaction conditions, provided that efficient and robust nanostructured catalysts are developed.

In this work, morphology-engineered Pt/CeO₂ nanocatalysts were synthesized and systematically evaluated for hydrogen production from methanol–water mixtures via APR. Platinum (0.5 wt%) was supported on cerium oxide with controlled nanostructures, including nanoparticles, nanoporous frameworks, and nanorods, enabling a detailed investigation of structure–property–performance relationships. Catalytic experiments were carried out in a 300 mL stainless-steel batch autoclave using methanol–water feed ratios of 1:3 and 1:1, catalyst loading of 10 g L⁻¹, reaction temperatures ranging from 180 to 240 °C, initial pressures of 4–20 bar, and reaction times of 1–2 h. The influence of catalyst pre-reduction using 5 vol% H₂/Ar was also examined.

The results demonstrate that nanostructural engineering and surface reduction significantly enhance hydrogen productivity. Nanorod and nanoporous Pt/CeO₂ catalysts outperformed nanoparticle-based systems due to improved platinum dispersion, higher oxygen vacancy concentrations, and strengthened metal–support interactions. The optimized catalyst exhibited hydrogen production rates comparable to reported low-temperature APR benchmarks, underscoring the potential of engineered nanomaterials for sustainable hydrogen production and clean energy applications.

Tungsten trioxide (WO₃) is an n-type semiconducting metal oxide (SMOx) widely applied as resistive gas sensor due to its chemical stability, good sensitivity and selectivity. It has been investigated as an ozone (O₃) sensing layer, since O₃ is a toxic gas that can cause respiratory diseases at high concentrations (above 50 ppb). Despite the potential, WO₃ based sensors typically require relatively high operating temperatures (~ 300 °C) to achieve optimal performance, which may compromise sensing-material stability, safety concerns in the detection of flammable gases, and increased manufacturing complexity. To overcome these challenges, the photo-stimulation has been used as an efficient strategy to obtain gas sensors operating at room temperature. However, the fast recombination of charge carriers in pristine SMOx impairs their sensing performance. Thus, the formation of heterostructures with other SMOx may induce the formation of interfaces, hinder the charge recombination process and consequently enhance the sensing performance. Based on these considerations, in this study we propose a strategy for obtaining WO₃/SnO₂ heterostructures exhibiting good sensitivity to sub-ppm O₃ levels at room-temperature under UV illumination. Pristine WO₃ and SnO₂ compounds were synthesized via the polymeric precursor method, and then hydrothermal treatment was performed to obtain WO₃/SnO₂ heterostructures with varying mass ratios. The obtained materials were characterized by XRD, FESEM, TEM, and XPS to evaluate their structural, morphological, and surface properties. XRD analyses confirmed the presence of both WO₃ and SnO₂ phases, without the presence of spurious phases. Regarding room temperature gas-sensing performance, we observed that all heterostructures were sensitive to all O₃ levels tested (10–300 ppb) under continuous UV stimulation. The W5S5 (50 mg WO₃ : 50 mg SnO₂) and W2S8 (20 mg WO₃ : 80 mg SnO₂) samples exhibited a significantly superior sensing response compared to pristine WO₃ . This enhancement was attributed to the formation of a potential barrier at the WO₃/SnO₂ interface, which creates a depletion region that effectively hinders charge carrier recombination, thereby maximizing the availability of photogenerated carriers for surface interactions. The results demonstrate that the heterostructure strategy is highly efficient for enhancing resistive O₃ sensing performance at room temperature.

Thermoelectric generators (TEGs) are highly attractive for powering wearable sensors and devices. In this work, we demonstrate a facile, low-cost route to manufacture flexible, wearable and eco-friendly paper-based thermoelectric generators. For this purpose, we have prepared bespoke water-based inks of CuO nanoparticles + poly(3,4 ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The CuO nanoparticles of size ~ 50 nm used in the formulation of inks were prepared by co-precipitation. The prepared inks were dip-coated on paper substrates. The ink composition was optimized by varying the content of CuO nanoparticles in the ink matrix. The power factor of the optimized composition was found to be 403 µW/mK2, which is reported for the first time for CuO-based flexible, wearable thermoelectric generators. This low-cost ink composition is a promising candidate for p-type thermoelectric materials for the fabrication of devices.

The increasing occurrence of emerging organic contaminants in aquatic environments poses a significant threat to ecosystems and human health, emphasizing the need for advanced and sustainable wastewater treatment technologies. Photocatalysis represents a promising solution due to its ability to degrade persistent pollutants under mild operating conditions. However, the development of efficient photocatalysts remains challenging in terms of cost, sustainability and environmental safety. In this context, the valorization of iron-rich industrial residues offers an attractive pathway for the design of functional materials within a circular economy framework.

This work focuses on the development of zeolite-based photocatalysts synthesized using ash and iron-rich mining and industrial wastes as alternative sources of metal cations. These residues, characterized by high iron content and reactive metal oxide phases, were exploited to generate zeolitic nanocomposites integrating nanoscale spinel ferrites and semiconductor phases, enabling combined adsorption, photocatalytic and magnetic functionalities. Waste valorization and urban mining strategies were employed to transform secondary raw materials into functional photocatalysts while mitigating environmental risks associated with waste disposal.

The structural, morphological and compositional properties of the materials were investigated using XRD, XPS, Raman, FT-IR, XRF, SEM, TEM, PL spectroscopy and BET surface area analysis. The high adsorption capacity of the developed materials is attributed to the incorporation of iron species on the external surface and within the zeolite's structural channels, increasing the density of accessible active sites and enhancing interaction with target pollutants.

The resulting materials exhibit enhanced photocatalytic activity under visible light irradiation, benefiting from high surface area, improved charge separation and synergistic interactions between the zeolitic support and the active nanophases. Photocatalytic performance was evaluated through the degradation of emerging organic micropollutants in wastewater, including pharmaceuticals (amoxicillin, penicillin), pesticides (imidacloprid) and microplastics (polystyrene). Advanced analytical techniques such as HPLC, ion chromatography, TOC/TN, chemical oxygen demand measurements and atomic absorption spectroscopy were employed to assess pollutant removal efficiency, mineralization degree and potential metal leaching. The regeneration and reuse potential of the developed photocatalysts was investigated, supporting circular bioeconomy principles.

This study demonstrates that the controlled valorization of iron-rich industrial residues can yield efficient and environmentally safe zeolite-based photocatalysts for the remediation of emerging pollutants, contributing to sustainable materials development and environmental protection.

Growing demand for plastics, driven by changing patterns of human activity, is intensifying pressure on climate targets because today’s plastics value chain remains heavily dependent on fossil feedstocks and fossil energy. Achieving net zero therefore requires a shift from a petroleum-based linear model to sustainable, closed-loop production routes. In this context, electrocatalytic upgrading of biomass-derived molecules in aqueous media offers a compelling pathway to generate plastic precursors using renewable electricity. Among candidate routes, the electro-oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) has attracted increasing attention, since FDCA is a promising renewable alternative to terephthalic acid for polyesters and thermoset resins.

Despite rapid progress, practical implementation of HMF electro-oxidation remains fundamentally constrained by intrinsic limitations, including: (i) weak HMF adsorption and sluggish interfacial activation at the anode; (ii) catalyst deactivation and poor durability induced by competitive adsorption of reaction intermediates; and (iii) difficulty in maintaining high FDCA selectivity at elevated current densities and product concentrations. Here, we address these bottlenecks by engineering a “electron-bridge” motif on layered double hydroxide (LDH) catalysts. Density functional theory combined with in situ product analysis elucidates preferred adsorption sites and an optimised reaction pathway enabled by the electron-bridge motif.

Importantly, the same electron-bridge framework also promotes HER by accelerating sluggish H₂O dissociation kinetics and optimising hydrogen adsorption–desorption thermodynamics. Integrated into a coupled HER‖HMFOR electrolyser, the bifunctional electron-bridge motif delivers simultaneous green hydrogen production and biomass upgrading at a low cell voltage of 1.55 V to reach 100 mA cm⁻², achieving ~99% FDCA selectivity together with excellent cycling stability. The strategy is scalable and can be extended to other electro-refinery reactions, including CO₂ reduction and electrochemical nitrogen-to-ammonia synthesis.

Interface Engineering of CoPi/PANI@NiCoP Composite for Efficient Alkaline Hydrogen Evolution

Karthika T. T., Sarika Sasidharan, Sheik Muhammmadhu Aboobakar Shibli and Anuj A Vargeese

(a) Department of Chemistry, National Institute of Technology, Calicut, Kozhikode, 673601, India; (b) Centre for Renewable Energy and Materials & (c) Department of Chemistry, University of Kerala, Kariavattom Campus, Thiruvananthapuram 695581, India

The rational design of advanced electrocatalysts through interface engineering and electronic structure regulation is crucial for enhancing the efficiency of sustainable hydrogen evolution reaction (HER) in alkaline water electrolysis. Slow reaction kinetics and inefficient charge transport continue to limit the performance of the catalyst. Herein, we report a hybrid heterostructured electrocatalyst prepared by integrating chemically synthesized cobalt phosphate (CoPi) and polyaniline (PANI) onto a nickel–cobalt phosphide (NiCoP) matrix to enhance alkaline HER activity and durability. The CoPi–PANI@NiCoP heterostructure synergistically combines the advantages of metal phosphides, redox-active cobalt phosphate species, and a conductive polymer network. X-ray photoelectron spectroscopy studies confirm strong interfacial interactions, including the formation of Co–N coordination and a significant increase in the Co²⁺/Co³⁺ ratio from 0.46 to 0.76 upon PANI incorporation. These electronic modifications promote efficient charge redistribution and accelerated electron transfer across the engineered interfaces. The PANI network provides abundant nitrogen functionalities and continuous conductive pathways, leading to reduced charge-transfer resistance and enhanced kinetics. Electrochemical impedance spectroscopy further confirms improved interfacial charge transport due to the synergistic interaction between CoPi, PANI, and the NiCoP support. After HER, in O 1s spectra, the relative intensity of the oxygen-deficient surface sites increased, and the lattice oxygen decreased, implying surface reconstruction and the formation of active hydroxylated sites, which confirms the occurrence of surface activation during electrocatalysis.  As a result, the optimized CoPi/PANI-3@NiCoP catalyst achieves a low overpotential of 115 mV at 10 mA cm^-2 and a Tafel slope of 123.8 mV dec^-1 in 1.0 M NaOH, following a Volmer–Heyrovsky mechanism. In addition to delivering enhanced HER activity, the catalyst maintains excellent stability during prolonged alkaline operation, confirming its resilience under realistic electrolysis conditions. This behaviour reflects the effectiveness of polymer-assisted interface modulation in creating a robust heterostructure with stable active sites. The performance improvement is attributed to the synergistic interplay between interfacial electronic coupling and redox-active Co centers, which facilitate charge redistribution and accelerate electron transfer.

Rechargeable zinc-air batteries (ZABs) are widely regarded as promising candidates for sustainable energy storage; however, their practical viability is hindered by the sluggish kinetics of oxygen reduction and evolution reactions (ORR/OER) at the air cathode. High-entropy oxides (HEOs), particularly high-entropy spinel oxides, offer tunable electronic structures and high catalytic activity, yet their performance is often limited by insufficient active site accessibility and mass transport issues. In this study, we propose a facile and scalable glycine-assisted sol-gel strategy to overcome these microstructural bottlenecks. We successfully synthesized a five-component high-entropy spinel oxide, (FeCrCoMnZn)₃O₄, and systematically engineered its pore architecture by controlling calcination temperatures at 500°C, 600°C, and 700°C. The glycine acts as a dual-function agent, facilitating the formation of a homogeneous gel and subsequently generating a porous network through gas release during thermal treatment. Structural characterization revealed that temperature regulation is critical; while lower temperatures yielded smaller, less effective pores, and higher temperatures caused pore collapse due to sintering, the intermediate temperature of 600 ºC (GLY600) produced an optimal, interconnected coral-like network with large average pore sizes. Crucially, our investigation highlights that this optimized porosity operates synergistically with surface chemistry. X-ray photoelectron spectroscopy (XPS) analysis indicated that the GLY600 sample possessed a significantly higher concentration of oxygen vacancies compared to the other samples. This abundance of defects, combined with the enhanced diffusion channels provided by the porous network, resulted in superior bifunctional electrocatalytic activity. The optimized catalyst exhibited a low OER overpotential of 447 mV and a favorable Tafel slope of 77.58 mV dec⁻¹, indicating rapid reaction kinetics. The practical impact of this material design was validated in a rechargeable ZAB configuration. The device utilizing the optimized porous cathode achieved a peak power density of 80 mW cm⁻² and a substantial discharge capacity. Most remarkably, the battery demonstrated unprecedented durability, maintaining a stable voltage gap over 1000 hours of continuous charge-discharge cycling. This exceptional stability is attributed to the tailored pore structure, which effectively mitigates the accumulation of reaction products and maintains oxygen diffusion pathways over long operational periods. These findings provide a compelling blueprint for designing advanced, porous high-entropy electrocatalysts for next-generation energy storage systems.

Rechargeable metal-air batteries are increasingly recognized as viable candidates for grid-level energy storage; however, their efficiency is often constrained by the sluggish kinetics of the oxygen evolution and reduction reactions (OER/ORR). High entropy oxides (HEOs) offer a platform for tailoring electrocatalytic properties through their multicomponent nature, yet current research has largely focused on the role of oxygen vacancies, leaving the effects of cation synergy and non-stoichiometry less defined. This study investigates the impact of varying Co and Fe ratios in non-stoichiometric spinel-structured (Co,Fe,Cr,Mn,Zn)3O4 HEOs synthesized via a modified sol-gel Pechini method.

Structural and morphological characterization was conducted using X-ray diffraction (XRD), High Resolution Transmission Electron Microscopy – Selected Area Diffraction (HRTEM - SAED), Scanning Electron Microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). XRD, HRTEM - SAED analysis confirmed that all compositions, regardless of stoichiometric deviation, retained a single-phase cubic spinel structure (space group Fd-3m). Furthermore, SEM imaging and EDS mapping verified the formation of chemically homogeneous particles with uniform elemental distribution, indicating that the non-stoichiometric synthesis did not lead to phase segregation or impurities.

To understand the electronic origins of the catalytic activity, the materials were analyzed using Ultraviolet Photoelectron Spectroscopy (UPS) and X-ray Photoelectron Spectroscopy (XPS). The analyses revealed a non-linear correlation between the cation composition, work function, and metal-oxygen (M-O) bond length. Specifically, Co-rich compositions exhibited a contraction in M-O bond lengths and a corresponding reduction in the work function. These electronic modifications facilitated favorable charge transfer kinetics at the catalyst interface.

Electrochemical evaluation indicated that the Co-rich composition (Co0.3Fe0.175Cr0.175Mn0.175Zn0.175)3O4 (Co0.3) provided improved bifunctional performance compared to the stoichiometric and Fe-rich counterparts. The Co0.3 catalyst exhibited an OER overpotential of 428 mV at 10 mA cm-2 and a bifunctional index (BI) of 0.95 V. When employed as the air cathode in an aqueous zinc-air battery, the device achieved a discharge capacity of 457.66 mAh and maintained operational stability for over 600 hours. These findings suggest that tuning the Co-Fe redox synergy and optimizing the work function through non-stoichiometry is an effective strategy for enhancing the catalytic activity of high entropy spinels.

High-entropy perovskite oxides (HEPOs) combine the compositional flexibility of perovskite oxides with the structural stability of high-entropy oxides, which enables tunable physicochemical properties and robust electronic structures. These attributes make HEPOs particularly attractive as bifunctional air cathode catalysts for alkaline rechargeable zinc–air batteries (ZABs). In this study, we report a systematic A-site doping strategy to engineer the electronic structure and defect density of HEPOs, specifically synthesizing (LaX)(FeCoCrMnZn)O₃ (X = Sr, Nd, Ca) via a modified Pechini sol-gel route. Structural characterization via X-ray diffraction (XRD) and Rietveld refinement confirmed that the LaSr and LaNd variants crystallized into single-phase perovskite structures, whereas the LaCa sample exhibited secondary oxide impurities. X-ray photoelectron spectroscopy (XPS) revealed critical variations in the surface electronic environment; specifically, the LaNd catalyst displayed the lowest work function (2.7 eV) and the highest concentration of surface oxygen vacancies compared to LaSr (3.85 eV) and LaCa (4.0 eV). These electronic descriptors directly correlated with electrochemical performance: LaNd exhibited superior OER activity with the lowest overpotential and the fastest reaction kinetics. Conversely, LaSr demonstrated the highest intrinsic ORR activity, characterized by a half-wave potential of 0.71 V, suggesting a trade-off between OER and ORR optimization depending on the A-site dopant. The practical impact of this electronic tuning was validated in rechargeable ZABs. Devices utilizing the LaNd air cathode achieved an unprecedented cyclic durability. While LaSr and LaCa-based batteries began to degrade after 300 and 350 hours respectively, the LaNd-based ZAB maintained stability for over 450 hours with only a 5.67% increase in the voltage gap. Post-cycling characterization confirmed the structural integrity of the LaNd catalyst, attributing its longevity to the optimized work function and vacancy-rich lattice. These findings establish A-site cation tuning as a critical pathway for manipulating the work function and defect chemistry of HEPOs to design highly durable bifunctional electrocatalysts.

This study establishes a definitive correlation between engineered point defects and the VOC-sensing performance of Gd-Doped CeO2 (GDC). We strategically modulate the oxygen vacancy landscape via aliovalent Gd3+ substitution (0–25 mol%) in the material, and the structure is confirmed by XRD, Raman, and HR-TEM analyses. Advanced spectroscopic techniques (UV-Vis, PL, XPS, EPR) quantitatively track the subsequent evolution of the electronic structure, revealing a systematic reduction in the band gap and the formation of vacancy-derived mid-gap states that enhance carrier mobility. The sensing results demonstrate a pronounced volcanic trend, with 15GDC emerging as the apex performer. It delivers the highest response to acetone, the fastest response and recovery kinetics, and exceptional pellet-to-pellet reproducibility. Importantly, this research moves beyond phenomenological observation to uncover the underlying kinetic mechanisms. A detailed Arrhenius analysis indicates that the optimally doped 15GDC exhibits the highest activation energy for the rate-limiting surface reaction. This counterintuitive finding is significant; its specific vacancy profile, neither too sparse nor too clustered, yields a highly reactive and catalytically optimal surface. Our work thus demonstrates that peak sensing performance is achieved not solely by maximizing vacancy concentration, but by engineering a defect architecture that optimally aligns charge transport with surface reaction energetics, thus providing a clear design principle for next-generation metal-oxide sensors. To theoretically understand the modulation of the electronic structure in doped CeO₂, density functional theory (DFT) calculations were performed to investigate the electronic band structure of GDC, along with the corresponding projected density of states (PDOS).

Magnesium hydride (MgH₂) is a promising hydrogen storage material due to its high theoretical hydrogen storage capacity (7.6 wt%), abundance and low cost, reversible hydrogen absorption and desorption, high volumetric density, and chemical stability, making it an ideal candidate for energy storage applications. One of the major challenges are the dehydrogenation rates, which are relatively slow. It has been proposed that catalytic doping can improve its kinetics. In this contribution, we will present two different strategies for improving it.

Firstly, first-principles calculations of MgH₂/G-SACs (graphene-based single-atom catalysts) heterojunction models reveal that the Ti decoration of G-SACs induces elongation of Mg–H bonds. This is caused by reducing the effective charge of H atoms at the interface, suggesting the Mg–H bonds tend to weaken. As for dehydrogenation thermodynamics, it was found that Ti-decorated G-SACs reduce the hydrogen desorption energies of MgH₂.  Out of several models for Ti incorporation into the graphene, the scenario with N-decorated graphene with single vacancy forming a complex with Ti adatom was found to be most stable and induce greatest enhancement of the hydrogen diffusion, as revealed by ab initio molecular dynamics simulations.

In the second case study, we employed machine learning potential molecular dynamics simulations (MLP-MD) to provide atomistic insights into the dehydrogenation kinetics of MgH₂. Our simulations revealed a novel H₂ formation mechanism characterised by H₂ nucleation followed by diffusion to the surface for desorption, highlighting the critical role of subsurface processes beyond conventional surface-driven reactions. Comprehensive screening of 22 doping elements identified Ni as the most effective dopant. These optimal dopants serve a dual function: acting as thermodynamic sinks for H capture, while maintaining a balanced interaction strength to facilitate H–H coupling and H₂ release. This atomistic-level insight provides a strong theoretical support for the experimentally observed 'hydrogen pump' effect.

Heterostructure engineering of nanomaterials is an effective strategy to overcome the limitations of single component photocatalysts by enhancing light absorption, facilitating charge separation, and suppressing electron-hole recombination. In particular, two-dimensional (2D) materials offer large interfacial contact areas, short charge transport pathways, and tunable electronic structures, making them highly advantageous for photocatalytic applications. In this study, a heterostructure comprising of 2D MoS2 and nano TiO2 in 1:18 molar ratio has been synthesized and evaluated for photocatalytic hydrogen evolution. The heterostructure exhibits a dramatic enhancement in H2 generation compared to pristine MoS2 and TiO2. The hydrogen evolution rates for MoS2 and TiO2 have been found to be ~0.27 and 2.74 µmol g-1 h-1, respectively, whereas the MoS2@TiO2 heterostructure has achieved a significantly higher rate of ~134 µmol g-1 h-1. Based on the band gap energies and band edge positions determined from UV-visible spectroscopy and electrochemical studies of the individual components, an S-scheme charge transfer mechanism has been proposed here for the said heterostructure, which enables efficient charge separation with strong redox ability and accounts for the significantly improved photocatalytic performance observed.

To effectively treat wastewater, decontamination techniques and advanced oxidation processes requires materials with high catalytic and/or absorption performance, as well as high stability and recyclability. Photocatalysis and adsorption appear to be suitable methods for these applications. In this context, magnetic ferrites have emerged as promising candidates due to their robust chemical stability and the practical advantage of magnetic recovery. This work focuses on the adsorptive performance of cobalt ferrite nanopowders Co_xFe_3-xO₄ (x=1 et x=1.5), synthesized via hydrothermal method. The adsorption phenomenon is a preliminary step to the catalytic process, but depending on the circumstances, it can, on tis own, decontaminate a polluted solution.

The physical-chemical properties of the synthesized nanoparticles were characterized using a multi-technique approach. X-rays and electron diffraction results confirmed the formation of spinel structure with well-defined crystalline nano-octahedrons with average sizes between 8 nm and 9 nm. Nitrogen sorption (BET) measurements revealed a mesoporous structure with high specific surface areas, reaching 102 m².g^-1 for x=1 and 107 m².g^-1 for x=1.5. Complementary analyses, including Infrared spectroscopie, confirmed the characteristic vibration modes of the coordination polyhedra of spinel structures, while Diffuse Reflectance Spectroscopy (DRS) highlighted a bandgap energy varied according to the composition, ranging from 2.1 to 2.3 eV.

Adsorption tests were conducted using Methyl Orange (MO) as a model dye to evaluate the influence of key operational parameters. The results demonstrate that solution pH is the most influential factor, with a maximum efficiency achieved at pH 4 due to strong electrostatic attraction. A comparative analysis reveals that the x=1 composition exhibits superior adsorption performance and faster kinetics than x=1.5. At an initial concentration of 40 ppm, both materials exhibited ultra-fast kinetics: CoFe₂O₄ (x=1) achieved 100% removal in just 2 minutes, while Co_1.5Fe_1.5O₄ (x=1.5) reached 99.5% in 2.5 minutes. When the concentration was increased to 60 ppm, the performance gap widened: x=1 maintained a high removal rate of 92.7% within 4 minutes compared to 73.5% for x=1.5. While CoFe₂O₄ typically forms an inverse spinel structure, the higher cobalt content in x=1.5 may induce cationic imbalance and local structural disorder, affecting the availability and reactivity of active surface sites.

In conclusion, the Co_xFe_3-xO₄ synthesized shows significant potential for rapid water treatment. Furthermore, the material’s magnetic properties ensure easy recovery via an external magnetic field. Its high stability also enables efficient recycling through mild chemical treatments such as solvent washing.

The development of efficient and sustainable photocatalysts for the removal of recalcitrant organic dyes from wastewater is a priority for environmental remediation. Among various materials, magnetic cobalt ferrites are highly attractive due to their narrow bandgap, chemical stability, and the advantage of magnetic separation. This study investigates the photocatalytic performance of hydrothermally synthesized nanoparticles and while the x = 1 phase is well-documented, the photocatalytic properties Co_1.5Fe_1.5O₄ phase under visible light have been very little explored to date.

This study explores the use of Co_xFe_3-xO₄ ferrites as photocatalyst for the degradation of a model pollutant (Rhodamine B). Two different compositions (x = 1 and 1.5) were synthesized using nitrates as precursors via a hydrothermal route. Structural studies showed that the powders consist of nanometric (8–9 nm) monocrystalline particles of octahedral shape. X-rays and electron diffraction results confirmed the cubic spinel structure. N-type semiconductor behavior was confirmed using Mott Schottky method and the direct band gap energies were obtained from diffuse reflectance spectroscopy (DRS): 2.32 eV and 2.18 eV for CoFe₂O₄ and Co_1.5Fe_1.5O₄ respectively. Due to its lower charge transfer resistance (2.8 kΩ.cm^-2), higher photocurrent density (1.18 µA.cm^-2), and longer photogenerated charge lifetime (5.2 ns), the x = 1.5 composition shows the greatest potential for this application. The response surface methodology (RSM) based on Box-Behnken design (BBD) was used to optimize the rhodamine B photodegradation process under simulated sunlight: RhB concentration, pH and catalyst mass. Under optimal conditions (at pH 9, with a catalyst dosage of 0.95 g.L^-1 and RhB concentration of 10 ppm), the dye was completely degraded within 180 min for x = 1.5 compared to 240 min for x = 1. Total organic carbon (TOC) analysis shows an advanced mineralization and achieves a higher removal rate of 96 % for x = 1.5 after 180 min. Hydroxyl radicals and photogenerated holes were detected as the dominant reactive species in radical scavenging experiments. An increase of the cobalt concentration in ferrite-based catalysts improves photocatalytic efficiency by reducing bandgap energy and improving charge photogeneration and transfer processes.

In conclusion, this research highlights the significant potential of cobalt ferrites as visible-light-driven photocatalysts for sustainable treatment of water. Integrating the RSM approach enables precise optimization of the decontamination process and reduces the number of experiments required.

Real-time monitoring of trace volatile organic compounds is often compromised by ambient humidity, which induces baseline drift and signal quenching through thermodynamic competition for surface active sites.This interference induces severe baseline drift and signal quenching, particularly in hydrophilic 2D Ti₃C₂T_x MXenes. To address this, a structural engineering strategy is introduced to mitigate humidity interference by constructing a hydrophobic, porous sensing interface capable of selective gas permeation. A hierarchical nanocomposite comprising Carbon Quantum Dots (CQDs) decorated on few-layer Ti₃C₂T_x  nanosheets was encapsulated within a Poly(methyl methacrylate) (PMMA) matrix. Through a morphological phase transition, the dense composite is transformed into a micro-cellular scaffold. Crucially, this topological reconfiguration establishes a stable hydrophobic state governed by the Cassie-Baxter wetting regime, where trapped air pockets within the micro-pores effectively repel water vapor clusters. Simultaneously, the inherent high gas permeability of the interconnected porous network acts as breathable diffusion channels, ensuring the rapid permeation of smaller formaldehyde molecules to the catalytically active CQD/MXene heterojunctions. The resulting sensor exhibits exceptional performance, featuring a high response toward 5–400 ppb formaldehyde and remarkable stability across a broad humidity range (40–90% RH). These findings demonstrate that such engineered hydrophobic scaffolds provide a robust, scalable solution for overcoming the persistent humidity bottleneck in environmental sensing.

An important feature of ZnO is the exceptionally high flexibility of defect engineering, which makes this material a unique platform for both fundamental and applied research. The concentration and type of intrinsic defects, such as oxygen and zinc vacancies, interstitial atoms, or complex defect states, can be effectively controlled by selecting the synthesis method, growth atmosphere and pressure, annealing temperature and duration, mechanical treatment, as well as plasma- or ion-beam-based techniques. This high degree of control over the defect structure provides a fundamental opportunity for the intentional formation of a ferromagnetic state in ZnO without the introduction of extrinsic magnetic impurities, which is important both in terms of material purity and potential spintronic applications.

It should be emphasized that the problem of so-called d⁰ ferromagnetism has a distinctly interdisciplinary nature and lies at the intersection of solid-state physics, materials science, and nanophysics. It is directly related to the fundamental question of whether magnetic ordering can emerge in systems that do not contain ions with partially filled d- or f-shells, which are traditionally considered a prerequisite for magnetism. In this context, ZnO serves as a convenient model system that enables investigation of the role of defects as sources of localized spin moments, as well as the mechanisms governing their collective interaction and exchange at the nanoscale.

Colloidal solutions of ZnO nanoparticles are widely used as building blocks for the fabrication of more complex hybrid and core–shell systems, particularly those incorporating plasmonic metals such as silver or gold. These nanocomposites, in turn, are actively employed in gas, chemical, and biosensor applications, where surface and interfacial effects play a dominant role. Notably, an unexpectedly sensitivity of the localized surface plasmon resonance peak position in ZnO/Ag nanocomposites to the duration of magnetic-field treatment has been detected. This behavior is most likely associated with defect-induced ferromagnetism, which has been intensively studied in ZnO nanostructures over the past two decades and opens new prospects for the development of multifunctional magneto-plasmonic sensing platforms.

The use of green hydrogen technology is becoming increasingly important due to the essential transition to zero carbon emissions. Making this technology more cost-effective presents a significant challenge. The use of precious metals such as platinum for green hydrogen electrolysis makes this technology expensive because of the non-sustainable supply of these materials. Replacing these critical materials with earth-abundant metals, such as transition metals, can help make green hydrogen technology more affordable and scalable. The lower intrinsic electrocatalytic activity of transition metals hinders their development as electrocatalysts for hydrogen electrolysis, but their activity can be enhanced through various methods. In this research, we focused on the synergistic effect between transition metals to modify their activity by altering their electronic configuration through creating solid solutions of Ni-Co with different chemical composition ratios. Atomic Layer Deposition (ALD) made this approach more feasible due to the sequential deposition of different metals at the atomic scale, allowing precise control over chemical composition and achieving a uniform distribution of elements in thin layers.

The chemical composition and electronic configuration evolution of the thin layer were studied using X-ray Photoelectron Spectroscopy (XPS) and Kelvin Probe Force Microscopy (KPFM). Furthermore, the atomic-scale distribution of Ni and Co was confirmed by Transmission Electron Microscopy (TEM), indicating a good mixture. The hydrogen evolution reaction (HER) performance of Ni-Co with different ratios was investigated in alkaline electrolyte (1 M KOH) by analyzing voltammetry behavior (cyclic voltammetry) and electrochemical impedance spectroscopy (EIS). Analysis of the electrochemical results revealed that mixing metals in an even ratio enhanced electrochemical activity. Specifically, fixing the sequence of pulses in the ALD process to achieve a 50:50 ratio of Ni to Co resulted in a reduction of the HER Tafel slope to 75.5 mV/dec, compared to 111.5 and 99.2 mV/dec for pure Ni and Co thin layers, respectively. Additionally, there was a significant improvement in charge transfer resistance for HER (260.8 Ω at -200 mV vs RHE). This notable enhancement in Ni:Co with an even ratio is attributed to increased structural stress, indicated by a higher full width at half maximum (FWHM) in XRD results. Furthermore, the work function of Ni-Co thin layer was lower than the pure films, indicating the cocktail effect in 50:50 chemical composition. According to the Equiatomic Mix Theory, this stress facilitates a balanced adsorption and desorption reaction during HER, which is crucial for efficiency. This balanced series of reactions aligns with the Sabatier Principle, optimizing catalytic activity for hydrogen evolution.

The rapid, sustainable synthesis of advanced nanomaterials is essential for meeting global energy, environmental, and catalytic challenges. Our work employs continuous flow, a unique supercritical fluid-based process utilized in less than 1% of reported hydrothermal methods, offering clean solvent alternatives, rapid kinetics, and molecular-level control. This approach enables scalable, cost-effective, and durable nanomaterials production across diverse applications. Our materials portfolio spans carbon nanostructures, from graphene derivatives to carbon quantum dots (CQDs) [1-5]. Nitrogen-doped CQDs demonstrate enhanced photoluminescence properties (QY up to 40%, lifetimes of 13 ns), excitation-independent emission, and exceptional sensing performance for heavy metals such as chromium (VI). Life-cycle assessment confirms continuous flow as a greener alternative to batch synthesis. Beyond carbon systems, we engineer functionalized 2D nanostructures with controlled crystallinity, homogeneous composition, and high conductivity, achieving flexible films with conductivities up to 4 × 10⁴ S cm⁻¹. Furthermore, strain-engineered nanocomposites reveal tunable band structures and work functions, enabling dual catalysis under visible light and mechanical activation. Coupled with density functional theory (DFT) modelling, our research advances a structure–property–performance framework, accelerating rational materials design. These findings establish continuous flow as a transformative technology, closing the loop between design, synthesis, and application, and supporting the vision of “making materials that matter.”

References

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Detection of toxic and flammable gases at room temperature with minimal power consumption is critical for environmental monitoring and safety. Two-dimensional (2D) van der Waals materials and their heterostructures offer unique opportunities for such applications due to their high surface sensitivity, atomically sharp interfaces, tunable band alignment, large surface-to-volume ratio and compatibility with low-power device architectures. Here, we report a one-step chemical vapor deposition route to synthesize native-oxide MoO₂-MoSe₂ heterostructure flakes and demonstrate their use as self-powered, highly selective gas sensors. Comprehensive structural and spectroscopic characterization, like Raman and PL spectroscopy, AFM, HRTEM, EDS, XPS and UPS, confirms a well-defined MoO₂-MoSe₂ interface and compositional gradation within individual flakes. Two distinct device types emerged from the same growth: S1 (MoO₂ dominant, metallic) and S2 (MoSe₂ and MoO₂, heterostructure). The heterostructure (S2) exhibits ultrabroadband photoresponse with external quantum efficiency ≈10⁴ %, fast ON-OFF kinetics <200 ms and a pronounced, reversible response towards NO₂ under visible-light illumination, reaching a limit of detection ≈10 ppm at room temperature. In contrast, the MoO₂-rich flakes (S1) show a selective response towards H₂ gas at room temperature. Crucially, S2 operates at zero or few-millivolt external bias, due to the photogenerated carriers separated by the built-in electric field at the MoO₂-MoSe₂ junction which produce the sensing current, enabling true self-powered operation. Moreover, light exposure not only amplifies sensitivity and shortens response/recovery dynamics but also improves the NO₂ limit of detection. Additionally, in the presence of humidity, the response is further enhanced, making the device robust in real-world conditions. The complementary selectivity (NO₂ for light-activated heterostructure, H₂ for metallic MoO₂) and the ability to operate with negligible external power highlight the potential of the native-oxide 2D heterostructure devices for low or self-powered, MEMS-compatible gas sensors and on-chip environmental monitors. This work demonstrates a scalable materials and device strategy to achieve selective, room-temperature, self-powered gas detection for practical sensing applications.

The synthesis of well-dispersed transition metal nanoparticles (NPs) on a stable, high-surface-area support is a fundamental challenge in material science, critical for catalysis, energy storage, and environmental remediation. Conventional methods like wet impregnation struggle with nanoparticle size control, distribution, and metal-support interaction strength, often leading to sintering. Creating intimately mixed bimetallic systems is even more complex. These issues drive the need for novel synthesis platforms that intrinsically combine tunable support with atomic-scale metal uniformity.

Calcium Silicate Hydrate (C-S-H), concrete's binding phase, is a uniquely promising yet underexplored material. Its inherent nanoporosity, high surface area (>100 m²/g), and ability to undergo isomorphic substitution of Ca²⁺ ions present a transformative opportunity. We hypothesize C-S-H can be an active precursor matrix, incorporating transition metals (Fe, Ni, Co, Cu, Zn) directly into its atomic lattice. A subsequent reductive thermal treatment can then segregate these metals in-situ into anchored nanoparticles with exceptional dispersion and stability. However, traditional C-S-H synthesis lacks the precise pH and ionic control required for reproducible, high-level multi-element doping.

Our core objective is to demonstrate this method reliably produces atomic-level homogeneous precursors. Under controlled reduction (He/H₂), these transform into a new nanocomposite: transition metal nanoalloy particles anchored on a calcium silicate matrix. We aim to establish clear synthesis-structure-property relationships, highlighting the universality, tunability, and enhanced catalytic potential of these materials.

We overcome prior limitations using a dynamic, computer-controlled titration system. For alloy NP formation, the filtered and dried product is treated at 600°C under flowing He/H₂ for 3 hours, reducing the ions and prompting their segregation into (alloy) nanoparticles. For monometallic doping, we synthesized single-doped C-S-H with each target metal. Post-treatment, Cu-doped samples formed Cu⁰ NPs, showing promising, highly selective activity in preliminary methanol reforming tests. For bimetallic systems like Co/Ni, we achieved tunable alloy nanoparticles.

In conclusion, we developed a novel, versatile, and scalable titration platform for a new nanocomposite class of materials. It enables precise fabrication of transition metal-doped C-S-H with atomic-level homogeneity, generating finely dispersed, anchored NPs in-situ upon reduction. This bridges the ubiquitous C-S-H phase with advanced nanocatalysis, transforming a common construction material into a sophisticated design platform. Future work includes optimizing titration parameters and conducting in-situ XRD/XAS studies to understand segregation dynamics.

The development of light-driven photo-converting devices hinges on the availability of affordable and environmentally friendly photoelectric materials. Bismuth vanadate (BiVO₄) stands out as a promising candidate; however, its relatively high band gap energy (2.4 eV) limits its efficiency under visible light. In this work, we aimed to reduce the band gap of BiVO₄ by inducing controlled oxygen deficiency, producing BiVO₄₋ₓ thin films via RF Magnetron Sputtering. Using a factorial experimental design, we systematically varied RF power, film thickness, pressure, and thermal treatment to obtain films with distinct compositions and properties. The band gap values, determined using the Tauc method, revealed a strong dependence on deposition parameters, with the band gap spanning from 3.03 eV to as low as 1.65 eV. Remarkably, the sample exhibiting the lowest band gap demonstrated an approximately 50-fold increase in photocurrent production compared to others. In addition, optimized BiVO₄₋ₓ films showed a dramatic decrease in optical transmittance, from 80% in non-optimized films to 10% in optimized ones, corresponding to an 87.5% reduction, indicating substantially improved visible light harvesting. Although the precise mechanism responsible for the band gap reduction remains to be fully clarified, the improvement is likely related to crystalline and electronic structure modifications induced by the deposition conditions, as evidenced by the observed crystalline and electronic structural changes. The multifactorial approach proved essential in pinpointing the optimal synthesis conditions. Overall, significant band gap reduction and enhanced photoactivity highlight the potential of BiVO₄₋ₓ films as highly efficient materials for solar energy conversion devices.

The rapid growth of the world’s population and the intensive development of industrial activities have led to an alarming increase in environmental pollution. The contamination of water resources now represents a major threat to human health and ecosystems [1]. Untreated industrial discharges, particularly from the textile, agricultural, and pharmaceutical industries, release a wide variety of toxic organic molecules. Although often present at trace levels, these substances exhibit high toxicity and can cause long-term adverse effects on fauna, flora, and human health. Simultaneously, the accurate detection of biomolecules of clinical interest has become essential for the diagnosis and monitoring of numerous diseases.

Surface-enhanced Raman spectroscopy (SERS) has led to significant advances in chemical detection and materials characterization [1,2]. Its superior performance arises from two main mechanisms: electromagnetic (EM) enhancement, due to surface plasmon resonance in metallic nanoparticles (NPs), and chemical (CM) enhancement, resulting from charge transfer between the probe molecule and the substrate.

Metallic nanoparticles (Au, Ag), although highly effective for EM enhancement, may suffer from agglomeration and instability, which can reduce performance over time. Two-dimensional (2D) materials and semiconducting metal oxides (MOs) offer a promising alternative, enabling improved SERS efficiency through enhanced charge transfer, increased active site density, and greater chemical and structural stability [2–5]. In this context, we are developing innovative hybrid materials, combining 3D metal oxides (e.g., VO₂(B)) with 2D materials (e.g., MoS₂) decorated with metallic nanoparticles, to serve as SERS substrates that leverage both EM and CM enhancement mechanisms. This approach aims to provide a versatile platform for ultrasensitive chemical and biomolecular detection.

[1] Sun et al., Journal of Environmental Sciences, 153, 251-263 (2025)

[2] Chen et al., TrAC Trends in Analytical Chemistry, 130, 115983 (2020)

[3] Tite, T et al., Appl Phys Lett, 104 (2014)

[4] Wu et al., Analyst, 142, 326 (2017)

[5] Chen et al., Nanomaterials, 14, 1654 (2024)

Nickel-iron layered double hydroxides (NiFe-LDH) are widely recognized as state-of-the-art non-noble electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. While the intrinsic structural advantages of NiFe-LDH are well established, the catalyst-electrolyte interface remains a critical variable governing reaction kinetics. Traditional optimization strategies often rely on "One-Factor-at-a-Time" approaches, which overlook the complex, non-linear interactions between operating parameters. In this study, we employed Response Surface Methodology (RSM) based on a Central Composite Design (CCD) to systematically quantify the individual and interactive effects of three key electrolyte parameters: alkali cation identity (Li+, Na+, K+), hydroxide concentration (0.2 – 1.0 M), and temperature (20 – 60 C). The study utilized NiFe-LDH nanosheets grown in situ on carbon paper via a hydrothermal method. The OER performance was evaluated based on two measured quantities : the overpotential at 10 mA·cm-2 and the Tafel slope. Analysis using quadratic polynomial models revealed distinct governing factors for thermodynamic and kinetic metrics. The overpotential is controlled by a significant concentration-temperature interaction (C × T), identifying a "saddle" topology where the thermal benefit is strictly dependent on the hydroxide concentration. In contrast, the Tafel slope was overwhelmingly governed by the cation nature , following the order K+ < Na+ < Li+, confirming that the intrinsic reaction barrier is modulated by the alkali metal type. Multi-objective optimization using a desirability function identified an optimal operating window at 1.0 M KOH and 49°C. Experimental  measurements under these conditions yielded an overpotential of 290 mV at 10 mA·cm-2 and a Tafel slope of 35.3 mV·dec-1. Electrochemical Impedance Spectroscopy (EIS) and chronopotentiometry further confirmed low charge-transfer (Rct= 2.1Ω) resistance and excellent operational stability. This work provides a statistically grounded, transferable framework for optimizing the electrolyte environment in alkaline water electrolysis, demonstrating that tuning the cation-concentration-temperature synergy is as critical as catalyst design itself. Crucially, the optimization resolved a kinetic-thermodynamic trade-off: while the Tafel slope decreased linearly with temperature, the overpotential exhibited a non-linear minimum near 50°C, requiring a precise thermal setpoint (49°C) to balance both metrics.

The sustainability of marine energy harvesting is severely challenged by biofouling and environmental weathering, which degrade the light transmission and efficiency of photovoltaic interfaces. Developing engineered nanomaterials that withstand these harsh conditions while maintaining optical transparency remains a critical bottleneck. Here, we introduce a plant cuticle-inspired solid slippery surface (PI-SSS) based on surface-grafted polymer brushes, which act as a stable molecular matrix to enhance the adhesion strength of lubricating copolymer and the substrate (~0.96 MPa) via strong ion-dipole interactions. The resultant PI-SSS demonstrates excellent optical transmittance (~91.3%) and liquid repellence, particularly against crude oil, alongside multifunctional anti-biofouling properties (e.g., proteins, chlorella, and mussels). The durability of the coating is validated under extreme conditions, such as prolonged acid and base solution exposure, repeated adhesion/peeling cycles, and seawater immersion, while maintaining its slippery behavior. These features significantly protect solar cells from harsh environments, ensuring a photoelectric conversion efficiency of 15.8% and a stable output voltage of approximately 2.0 V after continuous UV irradiation for a week, and 50 cycles of thermal tests between -15 °C and 100 °C, offering a promising approach for marine solar photovoltaic protection.

As global initiatives for marine nuclear energy and environmental remediation intensify, the real-time monitoring of radionuclides within the chemically extreme conditions of high-salinity and corrosive aquatic environments has emerged as a formidable challenge. Organic electrochemical transistors (OECTs) based on organic mixed ion-electron conductors (OMIECs) featuring electrochemical modulation and coupling of ion and electron species have emerged as promising platforms for radionuclide ion detection. However, OMIECs are typically linear polymers, which suffer from excessive structural swelling and morphological disorder during electrochemical doping, causing data distortion. Here, we report n-type two-dimensional covalent organic frameworks (2D COFs) as novel OMIECs (BTID-BFDO COF and BTDD-BFDO COF). The rigid π-conjugated lattice serves both as a charge transport pathway and an ion-electron coupling plane, while one-dimensional nanoconductors function as directional conduits for rapid ion transport and simplified loading platforms for specific recognition units. The 2D OMIEC exhibits favorable current modulation amplification and exceptional stability compared to linear polymers with the same structure. Furthermore, we elucidate the mechanisms of ion transport and doping within the rigid porous structure of 2D OMIECs. This study establishes a novel design paradigm for developing semiconductor materials capable of high-performance real-time monitoring of radionuclides in complex marine environments.

Proton exchange membrane water electrolysis (PEMWE) is a leading technology for high-purity hydrogen production, but the anodic oxygen evolution reaction (OER) remains a bottleneck due to sluggish kinetics and harsh operating conditions. Currently, iridium (Ir)-based oxides are the only viable OER catalysts for PEMWE anodes, yet their scarcity and high cost limit large-scale deployment. Enhancing activity and durability at low Ir loadings is crucial for PEMWE commercialization.Supporting Ir nanoparticles on conductive and corrosion-resistant substrates has been explored to increase catalyst utilization. While Sb-doped SnO₂ (ATO) has been commonly used, it suffers from severe Sb leaching and conductivity loss under high anodic potentials, leading to rapid degradation. In contrast, F-doped SnO₂ (FTO) offers superior chemical stability and acid resistance, making it a promising support for Ir-based OER catalysts.

Traditional solution-based synthesis methods for FTO, such as sol-gel and spray pyrolysis, face limitations in F doping efficiency and control over crystallinity and electrical conductivity. These methods often lead to impurity-rich regions and lack uniformity, which are detrimental under high-current OER conditions.To address these challenges, we employed a dielectric barrier discharge (DBD) plasma-assisted process to fabricate FTO supports. This method allows for efficient F incorporation into the SnO₂ lattice in a gas-phase environment, overcoming the limitations of solution chemistry. The plasma process provides a uniform modification of powder particle surfaces, resulting in enhanced electrical conductivity and durability.

Our DBD plasma-treated FTO supports exhibit exceptional structural integrity and conductivity retention under PEMWE conditions. Ir nanoparticles on FTO demonstrated significantly reduced dissolution and enhanced cycling stability compared to Ir/ATO catalysts. In-situ spectroscopy and density functional theory (DFT) analysis revealed that FTO stabilizes Ir oxidation states and mitigates over-oxidation.The practical viability of the Ir/FTO catalyst was confirmed in single-cell PEMWE testing, achieving over 2500 hours of stable operation at industrial current densities (>1 A cm^-2). These findings establish a rational design strategy for durable OER catalysts and support architectures in PEMWE systems, highlighting the role of FTO in enhancing performance and stability.

The performance of resistive gas sensors based on semiconducting metal oxide (SMOx) materials is influenced by their microstructural features, particularly particle size, morphology, and surface area [1]. Nanostructured materials typically exhibit enhanced sensing behaviour due to their high surface-to-volume ratio increases the number of active sites available for gas adsorption. These microstructural characteristics are directly dependent on the synthesis route and annealing conditions used to prepare the material. Among SMOXs, zinc oxide (ZnO) has been one of the most widely investigated as a gas sensing layer due to its stability, ease of synthesis and notable sensitivity to various toxic gases, including O₃, NO₂ and ​​​​​​NH₃ [1,2]. Moreover, ZnO has exhibited notable gas sensing performance at room temperature when stimulated by ultraviolet (UV) light, owing to the photogeneration of charge carriers that facilitate surface reactions [3]. In this work, we investigated how the annealing atmosphere influences the microstructure and light-assisted gas sensing performance of ZnO nanoparticles. The nanoparticles were synthesized using a modified polymeric precursor method. For crystallization, ZnO precursor powder was divided in two equal portions, and subjected to thermal treatments at 700 °C for 2 hours under different atmospheres. In the first treatment, annealing was carried out in air, and the resulting sample was designated Z-O₂. To hinder the particle growth process, the second portion was annealed in a reducing atmosphere (N₂), yielding a dark-grey powder, labeled Z-N₂. To eliminate residual organic species, this powder underwent an additional post-treatment in an oxygen-rich atmosphere at 400°C for 4 h, producing a light-grey powder referred to as Z-N₂O₂. XRD analyses confirmed all samples crystallized in the hexagonal ZnO phase without other phases. SEM images revealed that the Z-N₂O₂ sample exhibited a smaller average particle size (36 nm) compared with Z-O₂ (54 nm) consistent with the impact of the reducing atmosphere on hindering grain coarsening. Regarding O₃ sensing performance, electrical measurements showed that only Z-O₂ and Z-N₂O₂ were sensitive to sub-ppm levels of O₃ gas (10–300 ppb). The enhanced response of Z-N₂O₂ was attributed to its reduced particle size, which increases the surface-to-volume ratio and the number of active adsorption sites.  Overall, these results demonstrate an effective strategy to obtain ZnO nanoparticles through controlled annealing atmosphere, enabling the development of highly responsive,  light-activated-toxic-gas sensors capable of operating at room temperature.

Acknowledgements

FAPESP Grants 2023/09790-6

References

[1] A. Kumar et al., Coord. Chem. Rev. 541 (2025). https://doi.org/10.1016/j.ccr.2025.216836

[2] M.A. Franco et al., Sens. Actuators Rep. 4 (2022). https://doi.org/10.1016/j.snr.2022.100100

[3] P.P. Ortega et al., Chemosensors 13 (2025). https://doi.org/10.3390/chemosensors13040152

Photoelectrochemical (PEC) systems can couple solar-driven oxidation reactions at a photoanode with hydrogen evolution at a cathode, enabling simultaneous environmental conversion and renewable fuel production. Here we report a dual-functional PEC platform designed to oxidatively convert persistent organic polymer waste while producing hydrogen under illumination. The process is promoted in chloride-containing aqueous electrolytes, where reactive chlorine species assist oxidative bond cleavage and accelerate conversion. Conversion is monitored by changes in particle morphology and dissolved organic carbon, together with analysis of soluble oxidation products, while hydrogen generation is quantified by gas analysis. This study demonstrates a general strategy to integrate waste conversion with solar hydrogen production in a single PEC architecture, providing design insights for improved efficiency, stability, and future scale-up.

Solution casting has been used to create polymer nanocomposites (PNC) films based on HPMC/PVA/PVP-ZnO/Fe2O3. For loading of ZnO/Fe2O3 NPs, XRD determines the structural characteristics and demonstrates the notable fluctuation in the distinctive peaks associated with the semi-crystalline/amorphous phase of various HPMC/PVA/PVP ternary polymer ratios. FTIR analyses of pure film and ZnO/Fe2O3 doped HPMC/PVA/PVP polymer films demonstrated the vibrational alterations brought about by the dopant ZnO/Fe2O3 NPs in the polymer blend. The optical absorption edge and direct and indirect optical energy band gaps were identified using UV–visible absorption spectra. As the concentration of ZnO/Fe2O3 NPs increased, both optical band gaps shrank. The conductivity and dielectric characteristics in the frequency range of 0.1 Hz to 6MHz at room temperature are studied using the AC impedance spectroscopy technique. The conductivity was shown to rise as the concentration of NPs increased.  For all manufactured PNC films, the frequency dependence of AC conductivity with varying ZnO/Fe2O3 concentrations follows the Jonscher power law with frequency exponent n³1. Plots of the dielectric permittivity (ε′ & tanδ) with frequency at various concentrations and room temperature were presented. Ultimately, the findings demonstrate that the produced films' optical and electric characteristics may be readily adjusted to make them a viable option for high-performance energy storage devices.

The issue of the trap states formation in semiconducting nanoparticles is of great importance for developing quantum dots with the desired optical properties. Researchers have conducted great number of theoretical and experimental studies over last decades  to determine nature of formation of trap states in the band gap region but still there is no widely accepted point of view on this problem [1,2].

Our previous results [3,4] demonstrate that dipole moment plays significant role in formation of trap states. Recent results obtained by another theoretical study also demonstrate important role of dipole moment in trap states formation [5,6].

We have considered two types of CdS nanosized clusters stoichiometric (Cd-S bond in the center) and non-stoichiometric (Cd or S atom centered) ones. We have used  DFT method for small and medium size CdS nanosized clusters and DFTB method for large CdS clusters (number of atoms up to 1000) to show correlation between dipole moment and trap states formation.

We have considered all possible variations of location of single surface defect – removed SH group for small and medium size nanocrystals. Our results demonstrate correlation between dipole moment and trap states formation. Usually increase of dipole moment correlates with the decrease of energy of first electronic transition calculated through TD DFT. 

DFTB calculations for large clusters (300–1000 atoms) have also demonstrated that the location of surface defects play important role in formation of trap states. We have created surface defects by removing SH groups in directions along and against the dipole moment. The results show that probability of formation of trap states increases if the termination of SH group provided increase of dipole moment and vice versa.

Also effect of electrostatic field applied along the direction of dipole moment vector demonstrate that manipulation with dipole moment also affects the band gap size. Namely increase of dipole moment correlates with band gap decrease and vice versa.

References

[1] Houtepen, A., Hens Z., Owen J., Infante I. Chem. Mater. 2017, 29(2), 752–761.

[2] Giansante, C.; Infante, I; J. Phys. Chem. Lett. 2017, 8, 5209-5215

[3] Aldongarov A., Assilbekova A., Irgibaeva I., Barashkov N. in Chemical Modelling: Volume 15, ed. M. Springborg and J. Joswig, The Royal Society of Chemistry, 2019, vol. 15, pp. 173-188.

[4] Aldongarov A., Irgibaeva I., Hermansson K., Agren H. Molecular Physics 2014, 112(5–6), 674–682.

[5] Steenbock T., Drescher E., Dittmann T., Bester G. Chem. Mater. 2024, 36, 13, 6504–6514

[6] Steenbock T., Dittmann T., Kumar S., Bester G. J. Phys. Chem. Lett. 2023, 14, 39, 8859–8866

Metal semiconducting oxides (MOXs) are widely studied for their functional properties. Among various applications, they have been used as resistive gas sensors due to their sensitivity and fair stability. Tin dioxide (SnO₂), an n-type wide band-gap semiconductor, is commonly used as a sensing layer for detecting toxic gases such as NO₂, O₃, CO, NH₃, toluene, and benzene. While SnO₂ exhibits excellent sensing performance, it typically requires operating temperatures above 200^oC, which increases device power consumption. One promising way for room-temperature operation is the photo-stimulation of the sensing material. The presence of photocarriers generated by the irradiation of the MOXs favors the chemisorption processes.  Regarding the synthesis of MOXs, they have been synthesized by physical and/or chemical methods, however, most of them requires expensive precursors and/or special conditions (e.g. high vacuum, high temperatures, and so on.). To address this, alternative methods have been explored to lower synthesis temperature and time.

Here, we report the synthesis of Zn-doped SnO₂ nanoparticles via a microwave-assisted nonaqueous route at a relatively low temperature (160 °C) and short time (20 min). We also investigate the effects of Zn doping on the structural, electronic, and gas-sensing properties of SnO2 nanocrystals. XRD and HRTEM analyses confirmed a single-phase SnO₂ structure with ~ 7 nm particles. XPS spectra revealed the increase of oxygen deficiency as the Zn content increased. Electrical measurements showed that Zn-doped SnO₂ nanoparticles were highly sensitive to sub-ppm NO₂ levels (from 100 ppb) at room temperature under continuous light stimulation, presenting good recovery and stability. Also, the Zn-doped SnO₂ NPs revealed good stability of their NO₂ sensing performance even under ambient moisture. This enhanced performance stems from Zn ions creating additional surface oxygen vacancies that act as active sites for NO₂ adsorption. Overall, this study demonstrates that microwave-assisted synthesis offers a rapid, promising route to sensing materials for environmental monitoring applications. This research is supported by the brazilian funding agencies FAPESP and CNPq.

Balancing high water permeability with efficient removal of low-molecular-weight organic compounds (LMWOCs) remains a major obstacle in the development of layered two-dimensional membranes. Graphene oxide (GO) membranes are attractive due to their mechanical stability and ease of fabrication; however, uncontrolled sheet restacking often restricts nanochannel regulation and limits separation performance. Covalent organic frameworks (COFs) offer highly ordered microporous structures and tunable chemical functionality, yet their fragile nature and poor film-forming ability hinder their use as independent membranes. To address these challenges, we present a graphene oxide–covalent organic framework (GO–COF) hybrid membrane that combines the structural integrity of GO with the porosity and charge functionality of COFs. The membrane is constructed through vacuum-assisted assembly of sulfonated COF nanosheets within GO lamellar stacks. Introduction of ionic COF nanosheets effectively increases the interlayer spacing of GO from approximately 0.78 to 1.58 nm, while simultaneously imparting fixed negative charges and interconnected microporous transport channels. This engineered architecture delivers a high water permeance of up to 193.5 L·m⁻²·h⁻¹·bar⁻¹ and achieves greater than 99% rejection of methylene blue. Analysis of transport behavior indicates that separation arises from the synergistic interplay of molecular sieving, electrostatic exclusion, and dynamic adjustment of interlayer channels. Cationic solutes strongly interact with negatively charged COF regions, leading to temporary channel contraction that enhances size-based exclusion, whereas anionic solutes are repelled electrostatically and induce minimal structural change. The hybrid membrane further demonstrates strong resistance to fouling and sustained performance during repeated filtration cycles. These results highlight the effectiveness of integrating charged COF nanochannels into GO laminates as a practical strategy for designing high-performance membranes for advanced water treatment and environmental separation applications

The enhancement of effective photocatalytic materials for organic pollutant degradation has proven to be an important undertaking in the field of environmental materials. Graphitic carbon nitride (g-C3N4) is a photocatalyst of interest for water remediation, yet the effect of zinc oxide (ZnO) loading, particle size and accessible surface area of ZnO/g-C3N4 (ZCN) composite on Rhodamine B (RhB) dye degradation remains underexplored. In this study, bulk g-C3N4 is synthesized by single-step polymer condensation of thiourea precursor and subsequently size-reduced by controlled ball milling while assembling ZCN composites with 2.5 wt%, 5 wt%, 7.5 wt%, and 10 wt% of ZnO. The photocatalytic degradation of RhB dye is evaluated under a fixed UV source at room temperature. Time-resolved UV–vis spectroscopy, collected at 15-minute intervals, monitors the decay of the RhB absorption maximum and the evolution of intermediate features, enabling extraction of apparent first-order kinetics. The milled ZCN composite samples with xx wt% of ZnO show faster decoloration and higher rate constants than the pristine g-C3N4 and other ZCN composites, correlating with engineered surface-area and band gap of ZCN composite and shortened charge-transport lengths. These results establish a direct structure–property–performance relationship: particle-size engineering improves interfacial contact and band-gap engineering improves utilization of photogenerated carriers without altering the g-C3N4 lattice in ZCN composite. This work demonstrates a scalable strategy to enhance the efficiency of ZCN photocatalysts for the removal of hazardous dyes from the wastewater produced by the textile industry.

Biomass-derived hard carbon was synthesized and investigated as an anode material for sodium-ion batteries in a half-cell configuration. XRD patterns exhibited broad peaks, confirming an amorphous carbon structure, while Raman spectroscopy revealed D and G bands, indicating the coexistence of disordered and graphitic regions. SEM images showed a rough, porous morphology, and EDX analysis confirmed uniform carbon distribution with residual elements from the precursor. Electrochemical studies- including cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS), demonstrated stable and reversible sodium-ion storage. CV curves indicated reversible electrochemical behavior, GCD profiles revealed consistent charge-discharge characteristics for more than 200 cycles, and EIS suggested efficient ion transport and balanced charge-transfer processes. The material delivered a reversible capacity of > 300 mAhg^-1, highlighting its stable structure and promising electrochemical performance. These results position biomass-derived hard carbon as a sustainable and efficient candidate for sodium-ion battery applications.

Efficient Methylene Blue Photodegradation on TiO₂ Thin Films Fabricated by Pulsed Laser Deposition

_{E-G. Broască^1,2, G. Popescu-Pelin¹, F. Bilea1, C. Zagăr¹, L. I. Toderascu¹, I. Antohe¹, Simonescu Claudia-Maria² and G. Socol^1
 1National Institute for Laser, Plasma and Radiation Physics, 409 Atomistilor, 077125 Magurele, Romania}

 _{²National University of Science and Technology POLITECHNICA Bucharest, Faculty of Chemical Engineering and Biotechnology, Department of Analytical Chemistry and Environmental Engineering, Gheorghe Polizu 1-7, Bucharest, Romania,}

_{*e-mail: elisa.broasca@inflpr.ro}

Dyes are an essential part of modern life, appearing in a wide range of goods and industrial activities such as leather making, paper manufacturing, food production, cosmetics, and clothing. However, during the manufacturing and application processes, large quantities of synthetic dyes are spilled into the environment, particularly affecting water resources. ^[1,2] TiO₂ coatings were fabricated by Pulsed Laser Deposition (PLD) technique in different atmospheres (Ar, O₂, N₂, and He). This study aims to compare the photocatalytic efficiency of these coatings for degrading methylene blue (MB) in water under controlled UV irradiation using a Hg lamp (λ= 365nm). The changes in the concentration of MB solution were observed by UV-Vis measurements at regular intervals. The final dye concentrations were then determined using a calibration curve. The color of MB solution has become less intense (hypsochromic and hypochromic effect at the maximum absorption wavelength of 662 nm) due to the N-dealkylation reaction of the dye. 

High performance liquid chromatography with time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS) was employed to identify the phenothiazine derivatives formed during the photodegradation. The results reveal a difference in the photocatalytic activity, which is significantly influenced by the physicochemical properties of TiO₂ coatings. XRD and XPS analyses were used to identify the crystalline structure and chemical state of the TiO₂ coatings. Characterization via HRSEM revealed a direct correlation between the nature of deposition gas species and the resulting coatings morphology, which strongly influence the MB photocatalytic degradation performances due to their porosity and specific active surface.

[1] M.A. Rauf, S. Salman Ashraf, Fundamental principles and application of heterogeneous photocatalytic degradation of dyes in solution, Chemical Engineering Journal, 151 (1–3), 2009, 10-18, https://doi.org/10.1016/j.cej.2009.02.026

[2] A. Ayele, D. Getachew, K. Murugesan, A. Suresh, Phycoremediation of synthetic dyes: An effective and eco-friendly algal technology for the dye abatement, Journal of Chemistry, 2021, 2021, 9923643, https://doi.org/10.1155/2021/9923643

Acknowledgements: This work was supported by the Romanian Ministry of Education and Research through program NUCLEU - LAPLAS VII, contract 30N/2023.

Ammonia (NH₃) is a toxic reducing gas of significant concern for environmental monitoring, occupational safety, and air-quality control. Moreover, NH₃ has emerged as a potential biomarker for certain diseases when detected at low concentrations in exhaled breath. In this work, we report highly sensitive NH₃ detection using silicon nanowire (SiNW) arrays engineered with metal-oxide nanoparticles to enhance gas–surface interactions under realistic environmental conditions.

SiNWs were fabricated using a straightforward and scalable process, exploiting their high surface-to-volume ratio and favorable electrical properties for gas sensing applications. The pristine SiNW sensors exhibit a strong response to NH₃, with notably improved sensitivity in humid environments — a key challenge for practical gas sensors. To further engineer the sensing layer, tungsten trioxide (WO₃) and titanium dioxide (TiO₂) nanoparticles with varying concentrations were incorporated onto the SiNW surfaces. This nanostructured hybrid design leads to enhanced sensitivity and faster response times, with sensor performance strongly dependent on nanoparticle type and loading.

The sensing characteristics were systematically analyzed in terms of sensitivity, response and recovery times, selectivity, and humidity influence. Sensor response was evaluated for NH₃ concentrations ranging from 1 to 12 ppm, demonstrating reliable detection below 2 ppm, relevant for both environmental exposure limits and breath-analysis applications. The results highlight the role of engineered nanomaterial interfaces in improving gas-sensor performance and robustness.

These findings contribute to the development of efficient, low-cost, and environmentally relevant ammonia sensors based on engineered nanomaterials, with potential applications in air-quality monitoring, human safety, and medical diagnostics.

Cobalt phosphates are promising low-cost electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), offering an attractive alternative to noble metal-based systems. Our group has previously employed various strategies to enhance the catalytic performance of cobalt phosphate materials, including heterometallic doping and the use of different catalytic supports.^1-3  However, strategies to introduce controlled porosity into cobalt phosphate frameworks remain limited in the literature, despite the critical role of porosity in enhancing catalytic activity. Herein, we report synthesis of porous cobalt phosphate using monoalkyl phosphate based cobalt complexes as single-source precursor. The reaction of a cobalt(II) salt with monoalkyl phosphates leads to the formation of layered coordination polymers with the general formula [(RO)PO₃Co(H₂O)]_n, where R represents an alkyl group. These complexes adopt layered architectures in which alkyl groups are confined between inorganic metal phosphate layers.⁴ By exploiting the intrinsic thermal instability of the alkyl chains in these complexes and their controlled removal, a porous cobalt phosphate framework is synthesized.

Nitrogen adsorption studies of material obtained after controlled removal of alkyl chains reveal a high BET surface area of 384 m² g^-1, confirming the formation of a porous structure. Furthermore, structural and morphological characterization using FT-IR, XPS, ICP-OES, powder XRD, and SEM confirms the formation of an amorphous CoPO_x phase. Electrochemical studies demonstrate that CoPO_x exhibits enhanced catalytic activity for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), delivering an overpotential of 240 mV for OER and 116 mV for HER at a current density of 10 mA cm^-2 in 1 M aqueous KOH solution. This improved performance is attributed to the increased surface area and the greater availability of active sites afforded by the porous architecture. Overall, this work presents a scalable materials chemistry strategy for porosity engineering in metal phosphates, highlighting the potential of single-source precursor approaches for energy-related electrocatalytic applications.

References:

(1) Chaudhary, S.; Murugavel, R. Chem. Mater. 2024, 36 (13), 6475.

(2) Chaudhary, S.; Murugavel, R. Chem. Asian J. 2025, 20 (5), e202401177.

(3) Saha, J.; Verma, S.; Ball, R.; Subramaniam, C.; Murugavel, R. Small 2020, 16 (12), 1903334.

(4) Arya, H.; Murugavel, R. Dalton Trans. 2025, 54 (29), 11232.

Conventional two-dimensional thin-film-based smart energy-saving devices face limitations in controlling phase transition temperatures and in material selectivity. In contrast, three-dimensional (3D) devices offer better temperature tunability and broader material options for surface coatings. However, existing designs still face challenges like limited deformation and asymmetric structures, hindering adaptation to varying sunlight incidence and azimuth angles. This study proposes symmetric 3D devices incorporating a shape memory alloy actuator, black paint for solar absorption, and a polydimethylsiloxane (PDMS)/Al2O3 composite as an RC film, exhibiting the following characteristics: (i) reversible, continuously tunable 3D mechanical deformation between SH and RC modes via a temperature-responsive actuator; (ii) autonomous operation without external power or manual intervention, ensuring energy-saving functionality; and (iii) effective operation across diverse climates with durable, flexible, and adaptable design and adjustable transition temperatures for enhanced thermal responsiveness. Theoretical simulations confirm a maximum cooling power reduction of 6.8% in summer and a heating power reduction of 5.6% in winter. Performance evaluations under varying tilt angles and solar incidence conditions, along with climate simulations across 15 global climate zones, validate the effectiveness and adaptability of the device for real-world applications. These findings highlight its potential as a scalable, sustainable, versatile, and energy-efficient solution for future architectural and environmental applications.

Monitoring trace levels of heavy metal ions in aqueous systems is critical for environmental safety and human health. Copper (Cu²⁺), although an essential micronutrient involved in various biological processes, becomes toxic when present beyond permissible limits, necessitating its sensitive detection at low concentrations. However, many existing Cu²⁺ sensors rely on sophisticated instrumentation, synthetic aldehyde precursors, or multistep fabrication strategies, which limit their practicality, scalability, and sustainability. To address these challenges, we present a simple, water-soluble fluorescence sensor formed via an in situ Schiff base reaction between polyethylenimine (PEI) and bio-derived vanillin for selective Cu²⁺ detection in aqueous media. The resulting imine (–C=N–) linkages act as emissive centers, while the aromatic and phenolic functionalities of vanillin facilitate electron delocalization and strong metal coordination, enabling an efficient fluorescence response toward Cu²⁺.

Under solar simulator illumination using a 450 nm filter, the PEI-vanillin solution exhibits a bright greenish-yellow fluorescence, which progressively diminishes upon the addition of Cu²⁺, indicating efficient fluorescence quenching due to Cu²⁺- imine complexation. In contrast, under ambient light, the solution displays a distinct blue coloration after Cu²⁺ addition, enabling naked-eye detection. Fluorescence spectroscopy further confirms a concentration-dependent quenching response over a wide dynamic range, spanning from millimolar (10-2 mM) through micromolar (800-1μM) to nanomolar (1000-10 nM) concentrations, with high selectivity against competing 10 other metal ions such as Co²⁺, Ni²⁺, and Fe³⁺. Owing to its high sensitivity, the sensor enables trace-level Cu²⁺ detection with a limit of detection of ~290 nM in aqueous systems. Excellent photostability is observed with negligible fluorescence loss even after long-term storage (over 9 months) under ambient conditions. Unlike solid-phase Schiff base sensors that require surface pretreatment and synthetic precursors, this system forms spontaneously in water and has been successfully drop-cast onto Whatman filter paper, where it retains strong fluorescence and exhibits efficient Cu²⁺- induced quenching. This enables the fabrication of portable test strips, while future integration with mobile-based platforms can further extend its applicability for on-site environmental monitoring.

In this study, silver-decorated tungsten trioxide (Ag/WO₃) structures were synthesized, and their photocatalytic and antimicrobial efficiencies were systematically investigated. Ag/WO₃ photocatalysts containing 1%, 3%, and 5% Ag were prepared via a wet chemical reduction method and characterized using nitrogen porosimetry, XRD, XPS, SEM-EDS, TEM, and UV-Vis spectroscopy. The introduction of silver enhanced visible-light absorption and improved crystallinity through the surface plasmon resonance effect of Ag nanoparticles, while excessive silver loading (5%) led to particle agglomeration and reduced surface area. Photocatalytic tests using methylene blue (MB) and rhodamine B (RhB) in aqueous media demonstrated that 1% Ag/WO₃ exhibited the highest activity. Under solar irradiation, it achieved 95% removal of MB (10 mg/L) and 64% removal of RhB (10 mg/L) within 60 minutes, whereas under UV light, it enabled complete degradation of MB and 98% removal of RhB over the same duration. This superior performance is attributed to optimal Ag nanoparticle dispersion, which improves charge separation and visible-light harvesting without compromising porosity. Higher Ag loadings lead to diminished activity due to aggregation effects. Antimicrobial studies conducted against E. coli BL21 and S. aureus under both dark and light conditions revealed that 1% Ag/WO₃ also exhibited significantly enhanced bactericidal activity compared to bare WO₃. The improved antimicrobial performance is associated with synergistic effects between Ag nanoparticles and the WO₃ matrix, promoting reactive oxygen species formation and membrane disruption. Overall, these results demonstrate that low Ag loading, particularly 1%, provides an optimal balance between structural, optical, photocatalytic, and antimicrobial properties, making Ag/WO₃ structures a cost-effective and multifunctional material for dye-polluted wastewater treatment and microbial inactivation.

The development of high-performance Li–CO₂_Mars batteries is essential for future energy storage in CO₂-rich environments such as Mars. However, practical Li–CO₂ systems suffer from sluggish reaction kinetics, large overpotentials, poor reversibility, and electrolyte instability, severely limiting achievable capacity and cycling stability. Herein, a tailored solvent chemistry strategy is proposed to enhance Li–CO₂_Mars battery performance by integrating mixed-solvent electrolytes with a RuNi/CSC bimetallic nanoalloy catalyst. Binary electrolyte systems were formulated by mixing dimethyl sulfoxide (DMSO) with propylene carbonate (PC), N,N-dimethylformamide (DMF), 1,3-dioxolane (DOL), glutaronitrile (GLN), and dimethoxyethane (DME), enabling regulation of Li⁺ solvation structure, interfacial chemistry, and electrochemical reaction kinetics. The cosolvation of these solvent mixtures resulted in enhancements in physical properties, such as ionic conductivity and viscosity, compared to 1 M LiTFSI in DMSO, which has been widely used as the electrolyte for Li-CO_2Mars batteries. Benefiting from the optimized electrolyte and the catalytic activity of the RuNi/CSC nanoalloy, the Li–CO₂_Mars battery delivers an ultrahigh full discharge capacity of 28,804 mAh g⁻¹ at a current density of 200 mA g⁻¹ with a coulombic efficiency of 99.1%, demonstrating highly reversible electrochemical utilization of CO₂. Furthermore, the mixed-solvent system suppresses parasitic side reactions, promotes uniform discharge product formation, and mitigates electrode passivation, thereby improving stability and reaction reversibility. Post-cycling characterization confirms the reversible formation and decomposition of discharge products, verifying that CO₂ reduction and evolution reactions dominate the electrochemical process. This work highlights the critical role of solvent chemistry in governing Li–CO₂_Mars battery behavior and provides an effective electrolyte design strategy for advanced Li–CO₂_Mars batteries and future extraterrestrial energy storage applications.

Zinc-ion batteries are promising candidates for next-generation energy storage owing to their intrinsic safety, cost-effectiveness, and environmental compatibility, yet MnO₂ cathodes suffer from sluggish charge-transfer kinetics and progressive structural degradation driven by Jahn–Teller distortion and Mn dissolution during repeated Zn²⁺/H⁺ insertion and extraction. Here, we construct a CoO–Co_xB interfacial layer on MnO₂ through a facile room-temperature solution-phase redox reaction, yielding MnO₂@CoO–Co_xB in which nanorod-aggregated secondary particles are uniformly encapsulated by an amorphous layer of approximately 15 nm without altering the original morphology. XPS and Mn K-edge XANES and EXAFS analyses reveal an electron-enriched interfacial region and a stabilized MnO₆ environment at the MnO₂/ CoO–Co_xB interface, as evidenced by a slight decrease in the average Mn valence, a mitigated pre-edge feature associated with Jahn–Teller distortion, a modest expansion of the (211) lattice spacing, and a more ordered Mn–O and Mn–Mn framework. These results indicate that the CoO–Co_xB heterointerface plays a decisive role in reinforcing local coordination while enabling mixed ionic and electronic transport across the interface. Electrochemically, MnO₂@ CoO–Co_xB exhibits higher b-values and an enlarged capacitive contribution in cyclic voltammetry, together with reduced charge-transfer resistance in electrochemical impedance spectroscopy, evidencing accelerated interfacial kinetics and enhanced surface-dominated redox reactions. Consequently, the MnO₂@CoO–Co_xB cathode delivers higher reversible capacities and superior rate performance than bare MnO₂ and maintains a capacity that is approximately 90 mA h g⁻¹ higher than the uncoated electrode over 800 cycles at 1.0 A g⁻¹ in aqueous ZnSO₄-based electrolytes. These findings highlight room-temperature CoO–Co_xB interfacial engineering as an effective strategy to concurrently improve the structural stability and kinetic properties of Mn-based cathodes for durable aqueous zinc-ion batteries.

Atomically ordered Pt-based intermetallic catalysts offer high structural robustness in acidic environments relevant to proton exchange membrane fuel cells (PEMFCs), yet their rigid atomic configurations fundamentally limit chemical adaptability and electronic tunability under operating conditions. Here, we introduce an inter-sublattice random (ISR) alloy strategy that decouples crystallographic order from chemical complexity by integrating atomic-scale compositional disorder into an ordered Pt(Co,Ni) intermetallic framework. Through a sequential heteroepitaxial growth process, Ni atoms are selectively incorporated into the transition-metal sublattice of a pre-ordered PtCo scaffold, yielding a chemically randomized Co/Ni sublattice embedded within an ordered Pt framework. Atomic-resolution analyses reveal that ISR formation proceeds via a transient ordered-disordered core-shell intermediate followed by directional Co/Ni atomic exchange. This inter-sublattice randomization precisely modulates Pt electronic states and stabilizes a Pt-rich surface under electrochemical conditions, thereby optimizing oxygen adsorption energetics and suppressing structural degradation. Consequently, the ISR-Pt(Co,Ni) catalyst delivers sustained ORR activity and durability in acidic media and surpasses the U. S. DOE PEMFC targets in single-cell performance at low Pt loading. This work establishes sublattice-level disorder engineering as a general and transferable design principle for overcoming the activity-stability trade-off in ordered intermetallic electrocatalysts.

Nitrogen dioxide (NO₂) is a highly toxic air pollutant requiring sensitive and selective detection for environmental monitoring. Here, we report a morphology-engineered GaN-decorated SnO₂ nanopolygon (NPG) sensing platform that exhibits significantly enhanced NO₂ sensing performance. SnO₂ nanowires (NWs) were first synthesized via a vapor–liquid–solid growth mechanism and subsequently transformed into nanopolygons through high-temperature HCl etching, resulting in a substantial increase in specific surface area. GaN nanoparticles were then decorated onto the SnO₂ NPGs using a self-designed vertical hydride vapor-phase epitaxy (HVPE) process with precisely controlled deposition times.

The optimized GaN-decorated SnO₂ NPG sensor demonstrated a markedly improved response of 111.1 toward 10 ppm NO₂ at 300 °C, compared to 56.1 for pristine SnO₂ NWs. The sensor also exhibited excellent selectivity against interfering gases, good repeatability, and long-term stability. Furthermore, a low detection limit of ~18 ppb was achieved. The enhanced sensing performance is attributed to the synergistic effects of increased surface area (29.7 m²/g), abundant adsorption sites, and effective resistance modulation induced by n–n GaN/SnO₂ heterojunctions.

This study highlights morphological engineering combined with controlled GaN decoration as an effective strategy for designing high-performance NO₂ gas sensors, offering new opportunities for advanced semiconductor gas-sensing systems.

Detecting and controlling Berry curvature (BC) in two-dimensional transition metal dichalcogenides (TMDCs) is crucial for developing valley-current-based thermoelectric devices. This study presents the first experimental verification of the BC-driven valley Nernst effect (VNE) in a monolayer (ML) WSe₂ layer integrated into a Pt/YIG bilayer structure. To overcome the challenge of observing valley polarization, the time-reversal symmetry of the ML WSe₂ was broken by the magnetic proximity effect (MPE) from the YIG substrate under an external magnetic field. This induced a population imbalance between the K⁺ and K^- valleys, generating a transverse valley voltage (V_VNE) perpendicular to an applied temperature gradient. Experimental results show that ML WSe₂ exhibits a significantly higher V_VNE than 2 nm and 8 nm thick WSe₂ layers, confirming that the effect is most pronounced in the monolayer limit where inversion symmetry is broken. Furthermore, a comparison between ML WSe₂ and ML MoS₂ revealed that the magnitude of V_VNE is primarily determined by the strength of the BC, which is more pronounced in WSe₂ due to its stronger spin-orbit coupling. These findings establish the Pt/ML WSe₂/YIG structure as a viable platform for BC-driven thermoelectricity and offer a path toward utilizing momentum states of quasiparticles in next-generation devices.

The increasing severity of global warming has highlighted the need for renewable energy technologies, particularly those aimed at reducing dependence on fossil fuels. Electrochemical energy conversion systems, including fuel cells and water electrolysis, have been extensively investigated due to their high energy efficiency and relevance to green hydrogen production. In fuel cells, sluggish cathodic kinetics of the oxygen reduction reaction lead to significant overpotentials, which require platinum based catalysts. However, the high cost of platinum has driven efforts to reduce noble metal loading through the use of carbon support materials.

Graphene has emerged as a promising support material owing to its high electrical conductivity and large specific surface area. However, oxide-based synthesis approaches, such as the graphene oxide reduction route, inevitably introduce oxygen functional groups and structural defects, limiting electrical conductivity. In particular, reduced graphene oxide, typically produced via the Hummers method, exhibits a disrupted sp2 carbon network due to residual oxygen functionalities and lattice defects, which impede efficient electron transport.

Non-oxidized graphene (NOG) offers a compelling alternative by preserving the intrinsic graphitic structure of graphene. Synthesized through oxygen-free chemical exfoliation, NOG exhibits minimal structural defects, resulting in significantly enhanced electrical conductivity, large surface area, and excellent electrochemical stability compared to carbon black and rGO. These properties make NOG an attractive carbon platform for electrochemical energy systems.

In addition to fuel cell applications, NOG is applicable to electrolysis based hydrogen production. In alkaline and neutral electrolysis systems, non-precious metal oxide catalysts, including nickel, iron, and cobalt based materials, are widely used for the oxygen evolution reaction (OER) but exhibit limited electrical conductivity. Incorporating NOG as a conductive additive enables efficient electron transport, thereby improving material utilization and charge transfer characteristics. Consequently, NOG demonstrates potential as a conductive carbon component for cost effective electrolysis systems. This work was supported by MOTIE, Korea (20019175, RS-2025-25463656, P0022331) and the NRF funded by the Ministry of Science and ICT (RS-2024-00409675).

High-Performance Hard Carbon Anodes from Biomass Briquettes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have been widely investigated as an alternative to lithium-ion systems. Developing cost-effective and environmentally benign high-performance anode materials remains a key challenge for SIBs [1]. In this study, we optimized pyrolysis parameters to tailor the porous structure and reduce surface area, forming closed pores for efficient reversible sodium storage [2]. This research investigates hard carbon synthesized from biomass briquettes using two distinct thermochemical routes: Reactor and Autoclave methods. Reactor-based samples were pre-treated at 350°C under an Argon atmosphere, while the autoclave process involved pre-treatment at 180°C in air. All samples were carbonized at 1400°C for 3h. Chemical activation was evaluated using raw material to KOH ratios of 1:0, 1:1, and 1:4. Structural properties were characterized via XRD, XPS, SEM, Raman spectroscopy, and TEM. Electrochemical testing revealed that the reactor-based synthesis under an Argon atmosphere yielded superior performance. The 1:1 KOH ratio sample demonstrated an initial discharge capacity of 325 mAh/g and maintained over 90% capacity retention after 50 cycles, indicating strong structural integrity. Although the 1:4 ratio showed a slightly higher initial capacity of 326 mAh/g, it stabilized at a lower value of ~265 mAh/g. Comparative analysis with the 1:0 control sample confirmed that KOH activation is essential for enhancing porosity and sodium storage behavior. The results indicate that biomass-derived hard carbon produced via the reactor method with a 1:1 KOH ratio offers an optimal balance of capacity and cycling stability. This work highlights a sustainable pathway for developing high-performance anodes for next-generation sodium-ion energy storage.

Keywords: Sodium-ion batteries, Hard carbon, Biomass briquettes, KOH activation, Anode materials.

Acknowledgments.

This research was funded by the projects AP22783602 “Enhancement of the Initial Coulombic Efficiency of the Biowaste-derived Hard Carbon as an Anode for Sodiumion Batteries” from the Ministry of Science and Higher Education of the Republic of Kazakhstan.

References

[1] Mutiat, O. M., Alpysbayev, A., Abduakhitov, D., Kudaibergenov, K., Bakenov, Z., Myung, S. T., & Konarov, A. (2025). Effect of pre-treatment conditions on the electrochemical performance of hard carbon derived from bio-waste. RSC Advances, 15(2), 1105–1114. https://doi.org/10.1039/D4RA08029G

[2] Rakhymbay, L., Bazybek, N., Kudaibergenov, K., Myung, S. T., Bakenov, Z., & Konarov, A. (2024). Present development and future perspectives on biowaste-derived hard carbon anodes for room temperature sodium-ion batteries. Journal of Power Sources, 602, 234347. https://doi.org/10.1016/j.jpowsour.2024.234347

Designing high-performance electrode nanoarchitectures remains a key challenge in advancing next-generation supercapacitors. Layered double hydroxides (LDHs) are promising due to their tunable chemistry, yet their low intrinsic conductivity and sluggish ion transport limit their use as stand-alone electrodes. In this study, we introduce a rapid, environmentally friendly plasma surface-engineering strategy to overcome these bottlenecks. Sulfur and hydrogen plasma treatments were applied to ZnNi-LDH nanosheets, and their effects on structural, surface, and electrochemical properties were systematically evaluated. Plasma processing was found to enhance crystallinity, introduce beneficial defect sites, and generate functional surface groups, collectively improving ion diffusion and charge-transfer kinetics. The plasma-engineered ZnNi-LDH electrode exhibited a high specific capacitance of 856 F g⁻¹ at 1 A g⁻¹, excellent rate capability, and remarkable cycling stability. An asymmetric S-LDH//AC device demonstrated an energy density of 16 Wh kg⁻¹ and a power density of 572 W kg⁻¹ with stable performance over 5000 cycles. This sustainable plasma-based modification route provides a promising pathway for developing high-performance LDH electrodes for future energy-storage applications.

Recent efforts in proton exchange membrane fuel cell (PEMFC) research have increasingly focused on overcoming the limitations of high-cost platinum (Pt) catalysts for the oxygen reduction reaction (ORR). Among various alternatives, M–N₄-type non-precious metal catalysts have been extensively investigated, owing not only to their cost-effectiveness but also to their superior stability under acidic conditions.

In this study, Fe–N₄ catalysts were synthesized with carbon nanoribbons to improve the accessibility of active sites, thereby enhancing catalytic performance. Carbon nanoribbons possess a fine, elongated structure and abundant edge sites, which provide a unique platform for stabilizing single Fe atoms in a well-dispersed M–N₄ configuration.

During the experimental process, it was found that heat treatment significantly influenced the adsorption environments, inducing competitive adsorption between oxygen and nitrogen species. To enable fine-tuning, the heating rates were carefully optimized across two distinct conditions. The heat-up durations were 3 h and 30 min, corresponding to heating rates of approximately 4.9°C min^-1 and 29.3°C min^-1.

As a result, the catalyst prepared under a slow temperature ramp, with a heat-up duration of 3 h to reach 900 °C (corresponding to a heating rate of 4.9°C min-¹⁾, characterized by a gradual increase in temperature, exhibited the highest activity. Controlled temperature ramping effectively suppressed the formation of undesired byproducts such as Fe₂O₃, while promoting the incorporation of Fe-N₄ into carbon nanoribbons. Ultimately, the optimized heat treatment process enabled the highly selective formation of Fe-N₄ catalysts.

To maximize the formation of Fe-N₄ active sites, carbon nanoribbons with abundant edge sites were employed. Moreover, Fe-N₄_GNRO@CNT exhibited a higher half-wave potential than Fe-N₄_GNRO, indicating enhanced ORR kinetics. Based on these results, Fe-N₄_GNRO@CNT is expected to exhibit superior durability compared Fe-N₄_GNRO. In addition, a controlled temperature ramp was employed and optimized to suppress the formation of undesired byproducts, resulting in enhanced ORR activity.

This work was supported by MOTIE, Korea (20019175, RS-2025-25463656, P0022331) and the NRF funded by the Ministry of Science and ICT (RS-2024-00409675). 

The development of fuel cells is essential to solving energy problems. Solid oxide fuel cells (SOFCs) exhibit high power generation efficiency and, unlike proton-conducting fuel cells, can ignore the carrier concentration decrease due to dehydration and chemical expansion due to hydration. High oxide-ion conductivity is required for the electrolyte portion of SOFCs. Recently, yttria-stabilized zirconia is used as the electrolyte for SOFCs. However, the high operating temperature of 800°C raises concerns about cell degradation and increased costs due to the high temperature. Lowering the operating temperature requires lowering the activation energy for oxide-ion conductivity. Most previous research on oxide-ion conductors has focused on ceramic materials. The typical strategy for improving oxide-ion conductivity has been to increase the carrier concentration by controlling the amount of oxygen vacancies and interstitial oxygen through doping. In this study, we focused on nanosheet materials, which are prepared by exfoliating layered blocks from layered oxides. By stacking nanosheets, we can obtain free-standing membranes that are much thinner than conventional ceramic materials. A unique feature of nanosheet materials is their ability to undergo cation exchange (intercalation). The nanosheet dispersion was obtained from the layered oxide Dion-Jacobson, and a free-standing nanosheet membranes were made by suction filtration. By immersing the free-standing nanosheet membranes in a solution containing various cations, the original alkali metal layer was exchanged for other cations through intercalation. By exchanging potassium for strontium, the activation energy was successfully decreased, and a material exhibiting high oxide ion conductivity at low temperatures was discovered.

The increasing global consumption of fossil fuels has intensified greenhouse gas emissions and accelerated global warming. Hydrogen is regarded as a promising energy carrier due to its potential for renewable production and high energy density, motivating continued interest in efficient hydrogen to electricity conversion technologies. Polymer electrolyte membrane fuel cells (PEMFC) are considered a promising option due to their high-power density and low operating temperature; however, durability limitations remain a major barrier to practical application.

Carbon corrosion in the cathode catalyst layer remains a critical durability issue in PEMFCs. Carbon supports are vulnerable to oxidation under harsh operating conditions, including dynamic operating states and repeated startup and shutdown cycles. Under high overpotentials on cathode during operation, carbon oxidation is accelerated, resulting in platinum detachment, collapse of the pore structure, electrical disconnection, and severe mass transport limitations. These processes can weaken the structural stability of the catalyst layer and become detrimental under high voltage operation, where efficient oxygen transport is required.

In previous work, a fluorine doped graphene nanoribbon carbon nanotube composite (F-GNR@CNT) was synthesized and characterized, and was found to exhibit improved structural stability and electrical conductivity. Based on these results, this study systematically evaluates the influence of incorporating different wt.% of F-GNR@CNT into cathode. Catalyst layers containing various F-GNR@CNT loadings were fabricated and subjected to electrochemical characterization, accelerated stress testing (AST), and performance evaluation under conditions designed to real PEMFC operation.

The results show that increasing the F-GNR@CNT content enhances carbon corrosion resistance. Higher additive loadings might help preserve the catalyst-support interface and maintain electrical pathways during AST. Cathode electrode containing higher amounts additives of F-GNR@CNT demonstrated slower degradation rates, and stable operation during AST. Results indicate that optimized F-GNR@CNT incorporation can achieve a favorable balance between structural durability, mass transport behavior, and electrochemical performance

Overall, these findings highlight the practical utility of F-GNR@CNT as a cathode additive that enhances both durability and initial performance. The improved structural stability, carbon corrosion resistance, and water-management behavior demonstrate that fluorine-doped carbon composites can provide a scalable pathway to long-term, reliable PEMFC operation. This work suggests that engineered carbon materials can contribute to mitigating durability limitations and to the development of hydrogen energy systems.

This work was supported by MOTIE, Korea (20019175, RS-2025-25463656, P0022331) and the NRF funded by the Ministry of Science and ICT (RS-2024-00s409675).

Transition metal sulfides (TMS) have received increasing attention due to their applications in electrocatalysis, photoelectrochemical energy conversion, energy storage technologies and sensors. Among them, copper sulfide (CuS) is a promising material due to its high electronic conductivity, enabling its use in optoelectronics and electrochemical devices. Despite the wide range of synthetic strategies reported for copper sulfide (CuS) nanocrystals, including solvothermal, hot-injection, and colloidal approaches, achieving precise control over phase purity and nanocrystal morphology remains challenging. These limitations largely arise from the lack of mechanistic understanding of their synthetic pathways, including nucleation, growth and formation of intermediate phases. Hence, monitoring the synthesis insitu is crucial to understand  the reaction mechanism of the nanocrystal formation.

In this study, we employ insitu X-ray total scattering to directly monitor the synthesis of CuS nanoplatelets. The total scattering data was acquired at the beamline P21.1 at PETRA III at DESY with a temporal resolution of 1s at 101.38 keV using our insitu cell which enables insitu X-ray scattering experiments at elevated temperatures and under inert conditions [1]. The colloidal solvothermal synthesis route was conducted using a copper(II) precursor and a sulfur source dissolved in an organic solvent. Heating the reaction solution to 120°C with a heating rate of 10°C per minute yields the phase pure CuS. Analysis of the total scattering data via the pair distribution function (PDF) enables real-time tracking of the atomic-scale structural evolution during nanocrystal formation, providing access to both crystalline and amorphous species present during the reaction. Peaks in the PDF correspond to real interatomic distances, their shapes reveal local geometry and disorder. This makes the PDF especially powerful for studying systems where long-range order is weak or absent, like nanoparticles. This approach allows us to follow the reaction pathways during the solvothermal synthesis of CuS nanoplatelets, thereby uncovering the reaction mechanism, including the identification of key intermediates. 

[1] Sani Y. Harouna-Mayer et al. “Modular reactor for in situ X-ray scattering, spectroscopy and ATR-IR studies of solvothermal nanoparticle synthesis”. In: Journal of Synchrotron Radiation 33.1 (Jan. 2026), pp. 142–153. doi: 10.1107/S1600577525009634. url: https://doi.org/10.1107/S1600577525009634.

Graphitic carbon nitride (gCN) is an emerging metal-free visible-light photocatalyst with strong potential for advanced oxidation processes; however, its practical performance is limited by fast charge recombination and sub-optimal surface reactivity. Here, we present a comprehensive study on plasma-engineered gCN combining low-temperature air plasma functionalisation, surface-sensitive X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), scanning electron microscopy (SEM), and density functional theory (DFT) modelling to elucidate structure–activity relationships and photocatalytic optimisation.

Cold ambient air plasma introduces oxygen- and nitrogen-containing functionalities on gCN, including amide (–CONH₂), carboxyl (–COOH) groups, as evidenced by high-resolution XPS supported by DFT-calculated core-level shifts. DFT simulations identify energetically favourable adsorption sites for these groups on both melon-like and more condensed heptazine-based structure and reveal pronounced redistribution of surface charge density. Density of states (PDOS) analysis indicates the appearance of new surface-related electronic states close to the valence band edge and modification of frontier orbitals, consistent with experimentally observed shifts in valence band structure. UPS further confirm changes in the electronic structure induced by plasma functionalisation, indicating modification of the valence band position and work function, which implies more favourable energetics for hole transfer and interfacial redox reactions. SEM analysis demonstrates that plasma treatment does not induce morphological degradation or exfoliation of gCN flakes, confirming that the observed performance enhancement originates predominantly from chemical and electronic surface modification rather than from changes in texture or surface area.

The synergistic impact of plasma activation and photocatalysis is demonstrated through enhanced degradation of pharmaceutical contaminants, including in real wastewater matrices, where combined plasma–photocatalytic treatment frequently exceeds 80% removal efficiency while maintaining near-neutral pH. Beyond performance metrics, this work provides mechanistic insight into how plasma-induced functional groups govern interfacial charge transfer, oxidant activation and surface reaction pathways on gCN.

The results establish plasma engineering as a rational and scalable strategy for tailoring photocatalyst surface chemistry without metal doping or aggressive chemical modification. The plasma–gCN platform thus represents a robust materials concept for sustainable photocatalysis and next-generation advanced oxidation technologies.

Passive daytime radiative cooling (PDRC) is an emerging sustainable cooling strategy and is considered a highly promising approach to alleviate the rising global energy demand for space cooling.¹ This technique enables cooling without external energy input and can even achieve sub-ambient temperatures under intense solar irradiation. The fundamental principle of PDRC lies in maximizing thermal emission through the atmospheric transparency window (8–13 µm) while minimizing solar absorption in the wavelength range of 250 nm to 2.5 µm. Over the past decades, various PDRC systems, including super-white paints, highly porous materials, and multilayer photonic structures, have demonstrated effective daytime cooling performance. In particular, polymer-based materials with low solar absorption, high mid-infrared emissivity, and good processability have attracted increasing attention.² However, many state-of-the-art polymer PDRC devices rely heavily on fluorinated polymers, raising concerns regarding environmental persistence and sustainability. More importantly, most PDRC devices require sophisticated fabrication techniques, which hinder their scalability and practical deployment, especially in regions with limited infrastructure, thereby restricting their potential impact on reducing energy consumption and heat-related mortality.

In this work, we explore passive daytime cooling devices with promising cooling performance based entirely on universally accessible and environmentally benign materials.^3-5 First, a flexible PDRC foil is fabricated by upcycling discarded chip bags, which are typically considered non-recyclable plastic waste due to their multilayer structure. Second, a food-grade, paint-like cooling composite is developed using natural starch and finely ground eggshell powder. By reducing the eggshells to fine particles, efficient solar scattering exceeding 90% is achieved, leading to effective daytime cooling. Both approaches contribute to reduced cooling-related energy consumption while simultaneously mitigating the environmental impact of plastic waste. Most importantly, these designs provide a practical pathway for individuals and communities to fabricate their own passive cooling materials, even in regions with limited infrastructure, offering a scalable and inclusive solution to rising summer temperatures and heat-related health risks.

References

1. Yin, X.; Yang, R.; Tan, G.; Fan, S., Science 2020, 370, 786.

2. Wang, C.; Chen, H.; Wang, F., Prog. Mater. Sci. 2024, 144, 101276.

3. Song, Q.; Tran, T.; Herrmann, K.; Schmalz, H.; Retsch, M., Adv. Mater. Technol. 2023, 8, 2300444.

4. Song, Q.; Retsch, M., ACS Sustain. Chem. Eng. 2023, 11, 10631.

5. Song, Q. M.; Kubacki, E.; Berger, A.; Retsch, M., Adv. Funct. Mater. 2025, e13897.

Designing efficient electrocatalysts for the hydrogen evolution reaction (HER) is essential for achieving renewable and sustainable energy conversion. In particular, HER in alkaline media presents specific challenges due to the need to balance hydrogen adsorption (H_ad​), hydroxyl adsorption (OH_ad), and water dissociation steps. Consequently, the rational design of electrocatalysts that can effectively dissociate water while strongly binding hydrogen intermediates is a key approach to enhancing alkaline HER performance. Notably, significant advancements have been made in the development of transition metal phosphide nanocatalysts, which demonstrate high HER activity owing to phosphorus incorporation that lowers the energy barrier for proton adsorption. Although single-phase materials such as Ru₂P have shown promise, they often fall short in overcoming the sluggish reaction kinetics characteristic of HER under alkaline conditions.In this study, we present the in-situ formation of Ir₂P clusters on Ru₂P hollow nanotubes, which serve as highly efficient electrocatalysts for alkaline HER. Density functional theory (DFT) calculations reveal that the protruding Ir₂P clusters on the Ru₂P surface enhance reaction kinetics by facilitating a cascade mechanism: water dissociation on Ru₂P, followed by hydrogen spillover to Ir₂P, and subsequent H₂ evolution. This synergistic interfacial interaction is enabled by the geometric and electronic coupling at the Ru₂P/Ir₂P boundary. Our findings emphasize that the controlled synthesis of hybrid nanostructures offers a promising pathway for developing highly active and stable HER catalysts in alkaline environments.

In this period, the attention to multifunctional materials has grown significantly due to their intriguing applications. In particular, fluoride systems doped with rare earths ions represent emerging materials that find different fields of application: bioimaging, photocatalyst, optics and photovoltaics. In fact, it is noticed that these systems, placed inside a solar cell, can exploit a wider range of solar energy portion, improving the performance of the photovoltaic cell.

Overall, these materials are binary and ternary lanthanide-based fluorides, doped with rare-earth ions constituted by an inorganic fluoride matrix based on sodium, yttrium and/or gadolinium and by luminescent elements like europium.

The engineering of fluoride materials is significant also in other applications. Indeed, luminescent species-doped fluoride systems have been employed also as sensors for the detection of polluting compounds.

In this study, novel cesium-based metalorganic complexes with rare earth metals have been reported. We describe a one-pot synthesis of two novel bimetallic precursors based on cesium-yttrium or cesium-europium, using β-diketonate ligands to balance the charge of the cations, and polyethers to complete the coordination sphere of the central metals. The structure of Cs(I) metal-organic compounds is of the type “CsRE(hfa)4·2tetraglyme”, with RE = Y(III) or Eu(III), Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and tetraglyme = 2,5,8,11,14-pentaoxa-pentadecane.

The adducts show high volatility, good mass transport properties and high solubility in ethanol, thus they represent appropriate candidates for solution deposition processes of Cs-RE-fluoride layers.

In addition, cesium-europium film exhibits interesting features to be used as a sensor to detect the presence of nitro-compounds in water-based solutions, through luminescent measurements of the lanthanide specie.

C. B. thanks the University of Catania within the Erasmus+Study program.

Metal oxide semiconductor gas sensors play a crucial role in environmental monitoring and hydrogen safety. Vanadium dioxide (VO₂) and vanadium pentoxide (V₂O₅) are widely investigated metal oxides for gas sensing owing to their rich polymorphism, tunable electronic structure, and high chemical reactivity. In particular, monoclinic vanadium dioxide (VO₂ (M1)) exhibits a reversible metal–insulator transition (MIT) near 68°C, inducing abrupt changes in electrical conductivity and optical transmittance, which can be exploited for dual-mode hydrogen sensing. Combining crystalline VO₂ with amorphous V₂O₅ phases within tailored nanostructures represents an effective strategy to enhance hydrogen sensitivity while preserving operational stability.

Generally, the sensing performance of metal-oxide sensors is strongly dependent on film crystallinity, phase composition, and surface morphology. Conventional furnace annealing (FA) typically produces smooth, low-surface-area films and requires high temperatures and long processing times, limiting sensor performance and sustainability. Here, nanosecond pulsed laser annealing (ns-PLA) is employed as an ultrafast and energy-efficient approach to fabricate vanadium oxide thin films with controlled phase composition and nanostructure. VO₂ (M1) thin films and amorphous–crystalline a-V₂O₅/VO₂ heterostructures were prepared via environmentally friendly sol–gel routes and crystallized either by ns-PLA or FA. Ns-PLA enables localized heating that simultaneously promotes crystallization and spontaneous nanostructuring, while FA yields dense and smooth films.

Dual chemoresistive and optical H₂ sensing mode was achieved via film functionalization with Pt nanoparticles. Gas sensing measurements performed at moderate operating temperatures revealed n-type behavior with excellent baseline recovery, long-term stability, and detection limits in the ppm range. ns-PLA-processed VO₂ films exhibited enhanced optical modulation upon H₂ exposure compared to FA-treated samples.

In-operando structural and chemical analyses revealed that the hydrogen sensing mechanism is governed by the reversible formation of hydrogen bronzes in both crystalline VO₂ and amorphous V₂O₅ phases, accompanied by reversible changes in the vanadium oxidation state and MIT-assisted electronic modulation.

Overall, these results demonstrate that ns-PLA provides a powerful and sustainable route for the fabrication of dual-mode hydrogen sensors based on vanadium oxide thin films, enabling high sensitivity, stability, and functional tunability through precise control of phase composition and nanostructure.

[1 ] Paolucci, V., Basso, M., et al. (2025) Pulsed laser annealed amorphous/crystalline a-V2O5/VO2 heterostructure for selective NO2 and H2 sensing. Sensors and Actuators B: Chemical 428, 137235.

[2 ] Basso, M., et al. (2024) Sol-gel Pt-VO2 films as selective chemoresistive and optical H2 gas sensors. ACS Appl. Mater. Interfaces, 16, 42, 57558–57570.

Electrochemical water splitting is a promising carbon-free route to hydrogen production, yet its overall efficiency is limited by the sluggish kinetics of the oxygen evolution reaction (OER), particularly in acidic electrolytes. Ru-based catalysts are attractive for acidic OER due to their high intrinsic activity; however, they often undergo rapid dissolution and oxidation-driven degradation, limiting their durability for practical operation. To address these challenges, we develop IrRuO₂ nanocatalysts supported on Pd₃Pb multi-frame architectures, combining interfacial engineering with controlled dopant incorporation. The catalysts are synthesized via seed-mediated growth to construct the Pd₃Pb multi-frame support, followed by deposition of a Ru/Ir-containing shell and subsequent thermal oxidation to generate a conformal mixed-oxide phase. By systematically tuning the thermal oxidation temperature, we regulate Pd incorporation into IrRuO₂ through interfacial atomic diffusion, enabling precise control over the dopant level and local oxide environment. Notably, Pd incorporation suppresses detrimental overoxidation of the active oxide phase and mitigates catalyst dissolution under acidic conditions, thereby enhancing OER activity and markedly improving operational stability. Electrochemical analysis demonstrates that the supported IrRuO₂ catalysts deliver superior performance compared with undoped counterparts, while post-reaction structural and compositional characterization confirms the stabilized oxide framework on the Pd₃Pb multi-frame. This study provides a practical strategy for efficient dopant engineering in IrRuO₂-based catalysts and offers design guidelines for high-performance, acid-stable OER electrocatalysts via support-assisted diffusion and thermal activation.

Alloying of two-dimensional (2D) transition metal dichalcogenides is a promising strategy to expand their potential applications. In this work, first-principles calculations are employed to clarify hydrogen evolution reaction (HER) activity  in the composition-dependent in MoVNbSe₂ ternary and RuMoVNbSe₂ quaternary alloy nanosheets. First, the ternary alloy exhibits homogeneous atomic mixing, showing higher HER activity than its binary correspondents. The formation of Se vacancies facilitates a transition from the semiconducting 2H to the metallic 1T phase. Experimentally, the highest HER activity was observed at a Mo composition of x_Mo = 0.58, where surface oxidation is minimized. Our calculation shows that the 1T phases is always less stable than the 2H phase. On the one hand, it becomes more and more stable as x_V  or V_Se increases, implying higher  metallicity. Second, further incorporation of Ru into MoVNbSe₂ leads to RuMoVNbSe₂ quaternary alloys with superior HER performance. In addition, Ru incorporation brings about extra stabilization of the metallic 1T phase relative to the 2H phase. Again, Se vacancies stabilize the 1T phase, which is in consistency with our experimental results. The HER activity was evaluated using Gibbs free energy calculations for hydrogen adsorption (ΔG_H*). Hydrogen adsorption at Se vacancies near Ru atoms showed ΔG_H* values closest to zero , indicating that Ru acts as the most active catalytic site in the quaternary alloy. In addition, Ru enhances the metallic character, compensating for the surface oxidation issues associated with V and Nb in the ternary system. Experimentally, the nanosheet morphology was preserved across all compositions. Higher annealing temperatures caused partial transformation to the cubic phase. Atomic-resolution STEM confirmed uniform atomic mixing, and XPS showed increased metallicity with less surface oxidation. These results agree with computational predictions and explain the improved HER performance of the ternary and quaternary alloys.