This study investigates ZnO thin films incorporating copper nanoparticles (Cu NPs) as efficient photocatalysts for solar-driven wastewater treatment. The ZnO@Cu composite films were fabricated by in-situ integration of Cu NPs into the ZnO during atomic layer deposition (ALD) growth. Structural characterization by X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy confirmed the preservation of the wurtzite ZnO structure, with metallic Cu NPs of an average size of around 80 nm embedded into the semiconductor matrix. UV–vis spectroscopy demonstrated enhanced visible-light absorption by the ZnO@Cu films - which is attributed to the localized surface plasmon resonance in Cu nanoparticles, while Kelvin probe force microscopy revealed local variations in ZnO surface potential in the vicinity of Cu NPs, indicating electron transfer from ZnO to Cu and the formation of a Schottky-type barrier at ZnO/Cu interface. Photocatalytic degradation of methylene blue (MB), Rhodamine B (RhB), and caffeine under simulated solar irradiation demonstrated significantly enhanced photocatalytic performance of the ZnO@Cu films compared to pristine ZnO. The ZnO@Cu photocatalyst achieved degradation efficiencies of 78.2%, 89.6%, and 38.5% for MB, RhB, and caffeine, respectively, in contrast to pure ZnO, which showed degradation efficiencies of 44.4% (MB), 42.4% (RhB), and 14.2% (caffeine), confirming the effectiveness of the ZnO@Cu composite toward both dye and emerging organic pollutants. The improved photocatalytic performance is attributed to the injection of hot-electrons from Cu NPs into the ZnO conduction band, as revealed from our photoconductivity measurements, which show nearly two orders of magnitude larger photoinduced carrier generation in ZnO@Cu films under simulated sunlight illumination. These results demonstrate that Cu NPs effectively enhance charge-carrier generation and utilization in ZnO, leading to improved solar-driven photocatalytic activity.

In this study, we investigate the reduction mechanism and modifications of the electronic structure of anatase TiO2 thin films induced by low-energy H2+ ion bombardment at room temperature, focusing on hydrogen-induced changes in the oxidation states of Ti atoms, local chemical bonding of oxygen and the formation of defect states within the band gap. During the initial stages of bombardment, the energetic hydrogen reacts with lattice oxygen to form hydroxyl groups, followed by the reduction of Ti4+ to Ti3+. For the higher doses, the formation of H-O-H bridge bonds causes splitting of O-Ti bonds and formation of H2O gas molecules, accompanied by a reduction of Ti3+ and Ti4+ states to Ti2+. At the same time, the reduction of Ti4+ to lower oxidation states introduces some defect states within the band gap of TiO2, associated with Ti3+ defects or the formation of double-oxygen-vacancy clusters at Ti2+ sites.

Background/Objectives: Polymethyl methacrylate (PMMA) is widely used in medical and dental applications because of its favorable mechanical properties and ease of processing. However, its clinical performance is limited by low surface hardness, hydrophobicity, and susceptibility to microbial colonization and biofilm formation. This study aimed to investigate the effects of amorphous titanium dioxide (TiO2) nanolayers deposited by atomic layer deposition (ALD) on the surface morphology and antibacterial properties of PMMA-based materials. Methods: Amorphous TiO2 coatings were deposited on bone cement PMMA and dental PMMA substrates using ALD with TiCl4 and H2O precursors at 80 °C. The low deposition temperature enabled the conformal of thermally sensitive polymer substrates. Surface characterization was performed using atomic force microscopy (AFM) and scanning electron microscopy (SEM) to evaluate coating morphology and nanoscale topography. Antibacterial activity was assessed against S. aureus and P. aeruginosa through planktonic growth and biofilm formation assays, with additional evaluation of ultraviolet (UV) activation and surface polishing. Results: AFM analysis revealed that amorphous TiO2 coating on standardly laboratory practice-polished PMMA increased the arithmetical mean roughness (Ra) from 1.82 nm to 14.60 nm, and maximum height (Rmax) from 36.20 nm to 298.00 nm. Polishing before coating significantly increased surface roughness and height variation, resulting in complex micro- and nanotopography. Microbiological analyses demonstrated variable antibacterial effects depending on bacterial species and surface characteristics. Comparison of planktonic growth, biofilm formation and OD590 ratio showed that amorphous TiO2 coating on polished PMMA reduced biofilm formation and planktonic growth in P. aeruginosa with a decreased OD ratio, while S. aureus biofilm formation was reduced. S. aureus had a consistently higher OD590 than P. aeruginosa. UV treatment alone did not produce consistent antibacterial enhancement. Conclusions: The study findings suggest that the surface topography had a greater role than UV treatment in determining bacterial adhesion. Surface roughness was strongly associated with S. aureus adhesion., whereas P. aeruginosa showed minimal response to the tested surface modifications. These findings suggest that TiO2 coating after standard polishing alone may not provide consistent antibacterial activity under the tested conditions and point to the importance of nanoscale surface design in developing antimicrobial polymer biomaterials.

Developing efficient and low-Pt electrocatalysts is critical for the commercialization of direct ethanol fuel cells (DEFC). Herein, a novel bimetallic iron-nickel metal-organic framework, MIL-88B(Fe2/Ni)-NH2 ((Fe2/Ni)MOF), was synthesized using 2-aminoterephthalic acid as a linking ligand. Different loadings of reduced graphene oxide (rGO, 1-8wt%) were incorporated via solvothermal synthesis to enhance structural stability and conductivity, forming 1-8wt% rGO-(Fe2/Ni)MOF composites. These hybrids serve as supports for Pt catalysts, producing Pt/ [1-8wt% rGO-(Fe2/Ni)MOF] electrocatalysts. The synthesized materials were characterized using FT-IR, XRD, SEM, TEM, EDS mapping, XPS, cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy, and direct ethanol fuel cell performance testing. Among the prepared catalysts, Pt/[5 wt% rGO-(Fe2/Ni) MOF] exhibited the highest electrocatalytic activity toward ethanol oxidation, achieving a current density of 50.37 mA cm-2 at 0.86 V. In DEFC testing at 60 degrees C with 3M ethanol, this catalyst delivered a power density three times higher than the Pt/CC as control catalyst, with an open-circuit voltage of 0.54 V compared to 0.35 V for Pt/ CC. These results demonstrate that the designed rGO-MOF hybrid is an efficient and durable Pt support, offering significant potential for DEFC applications and sustainable energy conversion.

A novel bimetallic metal-organic framework (MOF), MIL-88B(Fe2/Ni)-NH2 ((Fe2/Ni)MOF), representing a new generation of MOFs, was synthesized and combined with CuO nanoparticles to produce a hybrid support for platinum-based catalysts in direct methanol fuel cells (DMFCs). The (Fe2/Ni)MOF provides a high surface area and abundant anchoring sites for Pt dispersion, while CuO nanoparticles improve electrical conductivity and facilitate charge transfer. Pt catalysts were deposited on (Fe2/Ni)MOF@CuO composites with varying CuO loadings (9, 13, 17 and 21 wt%). The synthesized materials were characterized by FTIR, XRD, SEM, TEM, EDS mapping, XPS and electrochemical techniques including cyclic voltammetry, chronoamperometry, electrochemical impedance spectroscopy in acidic media, and were evaluated in single-cell DMFC tests. The Pt/(Fe2/Ni) MOF@CuO (17 wt%) sample exhibited the best performance, with the highest anodic current density (45.20 mA cm-2), the lowest onset potential and improved long-term stability. As the anode in a membrane electrode assembly (MEA) using optimized 2 M methanol, this catalyst delivered a maximum power density of 2.58 mW & sdot;cm-2and an open circuit voltage of 0.56 V, significantly outperforming the Pt/CC control electrode (1.34 mW cm-2 and 0.40 V). These results demonstrate that (Fe2/Ni) bimetallic MOF@CuO hybrid supports are efficient and low-cost platforms for enhancing Pt anode activity and stability in DMFCs.

Engineering efficient photoelectrodes requires precise control over the structure, interfaces, and optoelectronic properties of thin semiconductor films. Here, reactive magnetron co-sputtering (RMS), combined with post-deposition annealing, was used to achieve in situ formation of Bi2O3-BiVO4 thin films with tunable phase composition and p-n heterojunctions. Unlike conventional wet-chemical methods, this approach allows direct control of Bi/V ratios during deposition, while annealing governs phase evolution on the substrate. By adjusting the Bi/V target power ratio and annealing temperature, Bi2O3-dominant, pure BiVO4, and mixed-phase Bi2O3--BiVO4 heterojunction films were synthesized, as confirmed by X-ray diffraction and X-ray photoelectron spectroscopy. High-temperature grazing incidence X-ray diffraction revealed phase transitions, with Bi2O3 stable at lower temperatures and BiVO4 forming above similar to 400 degrees C. Photoelectrochemical characterization showed that Bi2O3-BiVO4 heterojunction films outperform single-phase films, owing to enhanced charge separation driven by internal electric fields at the p-n interface. The optimized BO/BVO-1 film exhibited photocurrent densities 2.5-9 times higher than pure BiVO4, depending on applied bias. Electrochemical impedance spectroscopy indicated reduced charge transfer resistance and suppressed recombination in the heterojunction samples. These findings demonstrate that RMS combined with annealing provides a scalable route for phase engineering and hetero-junction design in thin-film photoelectrodes.

Pt-free and Pt-decorated α-Fe2O3 nanotubes containing 1 and 5 mol% Pt were hydrothermally synthesized to investigate how Pt decoration influences low-temperature hydrogen sensing beyond simple catalytic enhancement. Unlike many previous studies that focus primarily on sensing performance, this work correlates Pt-induced microstructural and magnetic ordering with sensor behavior. Structural characterization confirmed retention of the hematite phase after Pt modification, while XPS revealed both metallic and oxidized Pt species, along with an increased concentration of surface oxygen species. Mössbauer spectroscopy, EPR, and magnetic measurements showed that Pt decoration, assisted by heat treatment, partially restores the Morin transition and improves magnetic ordering, which directly correlates with the observed enhancement in sensing performance. Compared to Pt-free hematite, Pt-decorated nanotubes exhibited significantly improved hydrogen detection, achieving a detection limit of 1.0 ppm at 463 K with a fast response of 3.6 s. Notably, efficient sensing was achieved at lower operating temperatures (down to 363 K), with only 1 mol% Pt required to obtain high sensitivity and rapid response. Measurements performed in nitrogen further revealed enhanced responses due to reduced oxygen competition and promoted hydrogen spillover on Pt sites. These results demonstrate that Pt decoration of reducible α-Fe2O3 nanotubes links structural and magnetic ordering with hydrogen sensing performance, providing guidance for the rational design of advanced hydrogen sensors.

The deposition of thin active layer of zinc oxide (ZnO) on thermally sensitive substrates represents a major challenge. For this purpose, atomic layer deposition (ALD) is the most suitable deposition technique. Since both the growth rate and the quality of thin films synthesised by the conventional ALD method at temperatures near the room temperature are low, the plasma-enhanced version of the method (PEALD) is used at ambient temperatures, with which we increase the chemical reactivity of the precursors. In this work, we present the structural, optical and photocatalytic properties of thin ZnO films deposited by PEALD at room temperature. We show that the properties of the films strongly depend on the applied RF power of the plasma. The films synthesised with a plasma RF power below 200 W have an amorphous structure and a weaker photocatalytic activity. The films obtained with an RF power of 200 W or more consist of nano-sized crystallites. Compared to the amorphous films, they show significantly higher photocatalytic activity.

Industrial water pollution caused by persistent organic contaminants remains a major environmental concern, necessitating the development of efficient and advanced photocatalytic materials. In this study, we present a novel photocatalytic system based on ultrathin ZnO coatings deposited on microstructured gamma-Fe2O3 films by atomic layer deposition (ALD). The microstructured gamma-Fe2O3 films were prepared by the drop-casting of gamma-Fe2O3-SiO2 core-shell structures with controlled shape, size and silica shell thickness. Our results demonstrate that the ALD growth rate of ZnO films is strongly influenced by the concentration of surface hydroxyl (-OH) groups on the microstructured gamma-Fe2O3 films. Detailed structural and surface characterization were performed using SEM, TEM, AFM, XPS and GIXRD. Under UV irradiation, the ZnO/gamma-Fe2O3 heterostructures exhibited up to threefold higher methylene blue degradation rates compared to ZnO films on flat silicon. This enhancement arises from two distinct factors observed in different samples: increased surface roughness and microstructured morphology led to larger catalytic surface area in case of samples with the intermediate silica layer; and the formation of a type I heterojunction between ZnO and gamma-Fe2O3-enabled by the direct contact between the two metal oxides for samples without an intermediate silica layer-promoted efficient separation of photogenerated charge carriers. These results demonstrate how both surface architecture and band alignment engineering can independently contribute to improved photocatalytic performance.

Zinc oxide (ZnO) thin films have attracted considerable attention due to their versatile applications in optoelectronic devices, transparent electrodes and surface acoustic wave devices. In particular, their photocatalytic properties make them interesting for wastewater treatment. In this study, we investigate the influence of substrate and film thickness on the structure and photocatalytic activity of ZnO thin films prepared by atomic layer deposition (ALD). The photocatalytic activity of ZnO films on Si, glass, Al, and porous Al substrates was investigated under UV irradiation, focusing on the decomposition of methylene blue (MB) as a model for an organic pollutant. To understand the mechanism of photodegradation, detailed information on the morphology of the nanostructured ZnO surface and the surface chemistry was obtained by scanning electron microscopy (SEM), secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS). We have shown that the photocatalytic activity depends on ZnO film thickness and that it reaches saturation at a film thickness of about 20 nm, independent of the substrate. Furthermore, we compared the photocatalytic activity of ZnO films on flat substrates and porous aluminum (prepared by electrochemical anodization) at an optimal film thickness of 20 nm. Our results show that the ZnO thin film on porous aluminum has a significantly higher photocatalytic activity. After 300 minutes of UV lamp exposure, the ZnO thin film deposited on flat aluminum demonstrated the least photocatalytic activity, leading to a reduction of approximately 35% in the concentration of the MB solution. In contrast, the ZnO film coated on a porous anodic aluminum substrate exhibited the highest photocatalytic efficiency, with a reduction in the MB solution concentration by approximately 85%.

An anion exchange-assisted technique was used for the synthesis of platinum-decorated SnO2 supports, providing nanocatalysts with enhanced activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). In this study, a series of SnO2 supports, namely SnA (synthesized almost at room temperature), SnB (hydrothermally treated at 180 °C), and SnC (annealed at 600 °C), are systematically investigated, all loaded with 1 mol% Pt from H2PtCl6 under identical mild conditions. The chloride ions from the SnCl4 precursors were efficiently removed via a strong-base anion exchange reaction, resulting in highly dispersed, crystalline ~5 nm cassiterite SnO2 particles. All Pt/SnO2 composites displayed mesoporous structures with type IVa isotherms and H2-type hysteresis, with SP1a (Pt on SnA) exhibiting the largest surface area (122.6 m2/g) and the smallest pores (~3.5 nm). STEM-HAADF imaging revealed well-dispersed PtOx domains (~0.85 nm), while XPS confirmed the dominant Pt4+ and Pt2+ species, with ~25% Pt0 likely resulting from photoreduction and/or interactions with Sn–OH surface groups. Raman spectroscopy revealed three new bands (260–360 cm−1) that were clearly visible in the sample with 10 mol% Pt and were due to the vibrational modes of the PtOx species and Pt-Cl bonds introduced due the addition and hydrolysis of H2PtCl6 precursor. TGA/DSC analysis revealed the highest mass loss for SP1a (~7.3%), confirming the strong hydration of the PtOx domains. Despite the predominance of oxidized PtOx species, SP1a exhibited the highest catalytic activity (kapp = 1.27 × 10−2 s−1) and retained 84.5% activity for the reduction of 4-NP to 4-AP after 10 cycles. This chloride-free low-temperature synthesis route offers a promising and generalizable strategy for the preparation of noble metal-based nanocatalysts on oxide supports with high catalytic activity and reusability.

We have studied the impact of nanosized grains of copper oxides, grown by atomic layer deposition (ALD), on photocatalytic activity of thin titanium dioxide (TiO 2 ) films under visible-light irradiation. The size of grains and the crystal phase of copper oxide were controlled by the number of ALD deposition cycles. The x-ray diffraction and x-ray photoelectron measurements revealed preferential formation of CuO for a small number of deposition cycles, while Cu 2 O forms preferentially for a larger number of cycles. The photocatalytic efficiency of pristine TiO 2 has been enhanced for copper oxide/TiO 2 structures in which the nanosized copper oxide grains do not cover the entire TiO 2 surface. At the same time, the large increase of the current measured across the copper oxide/TiO 2 structures is consistent with the charge transfer from copper oxide grains to TiO 2 , essential for the observed increase of photocatalytic activity.

Thin films with self-assembled quantum dots (QDs) featuring a semiconductor core and a metallic shell possess unique properties that can be precisely adjusted by altering the size, spacing, and structure of the QDs. In this study, we concentrate on the properties related to efficient photoelectric conversion and thermoelectric sensitivity of Ge and Ge/Al core/shell QD lattices within a SiC matrix. These nanostructured materials are fabricated by using the magnetron sputtering technique, which facilitates their formation and self-assembly during the deposition process. We explore various Ge QD sizes and Al shell thicknesses in films deposited on a p-type Si substrate. Our findings demonstrate that the optical, thermoelectric, and photoelectric conversion properties of these simple devices can be extensively tuned by modifying the core size and shell thickness. Notably, an enhanced photoelectric conversion of approximately 130% was observed in the material with the thinnest Al shell, explained by a theoretical model for electric field enhancement in core-shell structured QDs and multiple exciton generation, which is enhanced in nanoscaled Ge. Additionally, materials with Al-shell QDs exhibit a significantly high temperature coefficient of resistance, above 8%/K, surpassing that of Ge, SiC, or pure Ge QDs. These insights are vital for advancing and optimizing devices based on Ge QDs, offering valuable contributions to both QD physics and materials engineering. The materials produced hold great potential for applications in light-sensitive devices and temperature sensors.

Tungsten trioxide (WO 3 ) is widely known for its technological importance in electrochromic sensors and catalytic devices. The incorporation of hydrogen into WO 3 can strongly influence the material's electrical, optical, and structural properties. This study investigates the evolution of different tungsten oxidation states and the mechanism of oxide reduction of polycrystalline WO 3 thin films induced by low-energy H 2 + irradiation at room temperature. The reduction investigation was conducted in situ using X-ray photoelectron spectroscopy (XPS) measurements around W 4 f and O 1 s core levels. The hydrogen-implanted film, which was irradiated with 5 keV H 2 + ions for 180 minutes, was subsequently characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy and secondary ion mass spectrometry (SIMS). During the initial phase of H 2 + irradiation, the W 6+ oxidation state in WO 3 is reduced to W 5+ and W 4+ , while the prolonged hydrogen bombardment leads to further reduction and the formation of W 2+ and W 0 states. SEM reveals crystallinity loss in the irradiated WO 3 sample, while Raman and XRD indicate a phase transformation from monoclinic to tetragonal after hydrogen bombardment. Our analysis shows that WO 3 reduction is confined to the surface while hydrogen-tungsten bronze (H x WO 3 ) is formed in the bulk of the material.

When measured in vitro, the release of metal ions from orthodontic alloys is typically carried out in artificial saliva (AS), a medium with many advantages but lacking the biological complexity of natural human saliva. In this study, we measured ion release profiles from the complete orthodontic fixed appliance, comprising stainless steel and NiTi parts, in a proteinaceous media (yeast extract peptone dextrose, YPD) and compared it to AS. Two immersion models were used, differing in medium replenishment dynamics. To elucidate the metal release results, surface chemistry and topography were analysed using atomic force microscopy (AFM) followed by roughness analysis, and elemental analysis of the top micrometric and nanometric layer (SEM/EDX and XPS analyses).The results showed that proteinaceous media promoted the leaching of Fe, Cu, and Al while suppressing Ni and Cr. Ni2+ and Cr3+ ions were detected in the top layer on NiTi in AS, but not in YPD. A rough "wavy" surface layer was formed in AS, as opposed to smaller sharper entities formed in YPD. Cu(I) compounds on orthodontic bands were detected in both media. The replenishment of the media during immersion influenced the development of surface chemistry and ion leaching for both types of media, AS and YPD. The results obtained in this study are expected to provide a significant advancement over previous studies using artificial saliva (only).

The structural, optical and photocatalytic properties of ZnO thin films synthesised by plasma-enhanced atomic layer deposition (PEALD) at different temperatures between 60 degrees C and 250 degrees C were investigated to better understand their enhanced photocatalytic properties. We found that the photocatalytic activity of the films synthesised at the lowest temperatures was superior among thin ZnO films synthesised by the ALD method. The polycrystalline structure of these films consists of small grains of about 5 nm in size with a high surface-to-volume ratio and a high proportion of inter-grain spaces. Such a structure contains a high concentration of surface trapping sites for excited charge carriers and thus reduces their recombination rate. A higher surface concentration of active charge carriers leads directly to increased photocatalytic activity.

Molybdenum-doped bismuth vanadate photoanodes (Mo-BiVO4) were prepared by reactive magnetron sputtering of pure metal targets and subsequent annealing at 500 degrees C in vacuum. The undoped and doped photoanodes were characterised by XRD and photoelectrochemical (PEC) linear sweep voltammetry to find optimal deposition conditions for the highest photocurrent density. It was shown that similar to 2 at. % Mo-doped BiVO4 photoanode significantly increased its photoelectrochemical water oxidation efficiency compared to the pristine BiVO4 photoanode. We performed an in-depth analysis by cyclic voltammetry and electrochemical impedance spectroscopy, supported by X-ray photoelectron spectroscopy, to elucidate the positive effect of Mo doping on the improvement of PEC activity. We found three key effects resulting from the additional electrons after substitution of V5+ by Mo6+: (i) reduced Fermi level pinning effect after passivation of recombination surface centres, (ii) enhanced bulk charge transport, and most importantly (iii) part of the additional electrons localise at the V5+ lattice sites and reduce vanadium to V4+, leading to numerous oxygen vacancies. At the surface, these vacancies form adsorption sites for intermediates involved in the oxygen evolution reaction and thus play a crucial role in enhancing the photocurrent.

Three-dimensional ZnO structures were prepared by both thermal atomic layer deposition (ThALD) and plasma-enhanced atomic layer deposition (PEALD) on a sacrificial cellulose template. The synthetic approach consisted of ALD of conformal ZnO nanofilms on the fibrous cellulose template, followed by thermal removal of the polymer. The resulting calcinated samples, consisting of a scaffold of fused polycrystalline ZnO nanoparticles, showed a sevenfold and ninefold increase in photocatalytic activity against methyl orange under ultraviolet-A light, for the ThALD and PEALD samples, respectively, compared to the non-calcined samples prior to cellulose removal. In addition to the improved three-dimensional surface exposure and accessible active sites, it was suggested that the amount of hydroxyl groups on the surface and the density of nanoparticle packing in 3D ZnO structures are critical parameters for improving the photoinduced degradation of the dye.

The evolution of different W oxidation states and the oxide reduction mechanism of polycrystalline WO3 thin films, induced by low-energy H-2(+) bombardment at room temperature, was investigated in situ by X-ray photoelectron spectroscopy around W 4f and O 1s core levels and the valence band. A hydrogen tungsten bronze is formed at the beginning of the reduction process, as is evident from the development of the W5+ oxidation state and the creation of the O-H bonds. With the higher H implantation dose, reduction proceeds with the creation of H2O gas molecules, whose evolution with the bombardment time correlates with the cumulative concentration fractions of W4+, W2+, and W-0 oxidation states. The generation of H2O molecules removes O atoms from the WO3 matrix, inducing the reduction of WO3 to lower oxides and, subsequently, metallic W, which is the dominant phase on the surface after 180 min of bombardment.