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.

Inspired by the properties of natural chitin, the present work provides the first solid foundation for growing conformal ultrathin antibacterial films of organic chitin through a solvent-free molecular layer deposition (MLD) process. This work establishes the initial groundwork for growing biomimetic hybrid cuticles by combining sugar-type molecules with vapor-phase metal-organic precursors, which we term metallochitins or, more generally, metallosaccharides. The MLD process, featuring mild temperatures and solvent-free conditions, provides exceptional conformality and thickness precision, ensuring highly conformal coatings on diverse high aspect ratio substrates. In vitro testing confirmed that the MLD-grown metallochitins not only promote the growth of various cell lines but also prevent adhesion of both Gram-negative and Gram-positive bacteria. The choice of the metal in the hybrid enables selective antimicrobial activity against Gram-negative bacteria or comprehensive antibacterial effects, which can be controlled as desired.

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.

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.

The Pt/SnO2 (SP-samples) and Pt/alpha-Fe2O3 (FP-samples) with platinum loadings between 1 and 10 mol% were synthesized mechanochemically starting from platinum(II) acetylacetonate dissolved in toluene and from SnO2 and alpha-Fe2O3 powders obtained from tin(II) and iron(II) acetates. The STEM results show that the ultrasmall platinum nanoparticles (PtNPs) are well dispersed on the SnO2 and alpha-Fe2O3 supports. The PtNPs size distribu-tions calculated with lognormal functions ranged from 1.0 to 1.3 nm. The results of temperature programmed reduction in hydrogen showed maxima at 120-160 degrees C due to the reduction of PtOx to Pt0. The Pt-4f-XPS results showed that the dispersed platinum on the SnO2 and alpha-Fe2O3 supports consisted of all three oxidation states of platinum: Pt4+, Pt2+ and Pt0. The average oxidation state of platinum as a function of molar fraction of Pt loading in the SP samples varies from 1.69 to 2.11, whereas the oxidation state of Pt in the FP samples varies more linearly and steeply from 1.42 to 2.58. The synthesized samples showed high catalytic activity for the reduction of 4-nitropenol (4-NP) to 4-aminophenol (4-AP), which can be explained by the high dispersion of non -aggregated ultrasmall PtNPs with a size of about 1 nm on the SnOx and FeOx supports.

The in situ free carbon formation in polymer-derived ceramics (PDCs) is essential for its microstructure evolution and resulting unique characteristics. This study advances the phenomenon of surface graphenization with the first silicon-based conformal preceramic polymer thin films deposited by molecular layer deposition (MLD). In situ thermal annealing transmission electron microscopy (TEM) investigation was performed to study the evolution of carbon on the nanoscale during high-temperature postprocessing of the hybrid organic-inorganic siloxane-alumina (SiAlCHO) in vacuum. The e-beam exposure during annealing induced the knock-on damage process, i.e., direct displacement/ emission of an atom as a result of the collision with a fast electron. The emission of hydrogen atoms of the preceramic MLD film led to a loss of hydrogen from the organic groups within the film, which determined the first stage of the observed phenomenon, the carbonization of the film. The relatively high annealing temperature of the sample provided the carbon mobility to form an energetically favorable sp2-bonding arrangement of carbon, which led to the formation of up to four graphene layers. The amount of carbon in the preceramic SiAlCHO, which is the source for the graphene layer formation, and consequently the resulting number of surficial graphene layers can be reduced by increasing the MLD process temperature so that it forms even a single layer. MicroRaman mapping was performed to confirm the chemical nature of the e-beam-induced graphene formation. The resulting SiAlCO PDCs withstand annealing temperatures as high as 1200 degrees C without crystallization and phase separation. The investigation allows for a better understanding of the microstructural evolution of carbon in the near-surface region and its associated properties, which are essential for various applications of PDCs.

Hybrid materials are a merger of inorganic and organic materials and, as such, have the potential to outperform the characteristics and functionalities of conventional, that is, inorganic or organic materials. Consequently, various routes for their synthesis are being explored. However, despite the enormous recent progress in synthetic strategies, the pool of successfully hybridized materials is still very limited, thereby lowering their practical applicability since the functionality of the materials relies on the choice of the organic and inorganic constituents and their interplay. This work demonstrates the hybridization of indium oxide with ParyleneC upon vapor phase infiltration (VPI) of the metal-containing precursor trimethylindium into the polymer and its reaction with a counter precursor in its subsurface. We found that the choice of hydrogen peroxide instead of water vapor as the oxygen source substantially influences the hybrid material formation, resulting in a hybrid with an increased infiltration depth down to 300 nm, a narrower band gap, and stable sheet resistance values over a broad range of infiltration temperatures, from 135 to 210 & DEG;C. Electron microscopy and chemical analysis revealed the formation of indium oxide nanoparticles (NPs) within the ParyleneC with a capping layer of indium oxide. The flexible hybrid withstands at least 7000 bending events over a curvature with a radius of 5.5 mm. The redistribution of the NPs inside the polymer matrix upon bending even leads to a decrease of the electrical sheet resistance, which makes this flexible conductive hybrid (FCH) material opting for applications as robust flexible transparent electrodes.

A series of semi-transparent W-incorporated TiO2 thin films (TxW; x = 0,1,2,5, and 10) were fabricated by anodizing co-sputtered titanium-tungsten (WiTi1_ i (0 <= i <= 0.05)). Field emission gun scanning electron mi-croscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Grazing incidence X-ray diffraction, and Raman spectroscopy were used to characterize TxW thin films, which confirmed the anatase form of TiO2 as well as the presence of W in the thin films. Optoelectronic and photoelectrochemical charac-terization showed that TxW thin films are markedly beneficial for reducing photo generated charges recombi-nation. T1W exhibited the maximum charge carrier lifetime (0.29 mu s) which is over two times of pristine T0W (0.13 mu s). Methylene blue (MB) and imidacloprid (IMI) were selected as the target pollutants for the study of photocatalytic effectiveness of TxW under solar light. T1W showed maximum removal efficiency for MB at pH8. Moreover, response surface methodology analyses revealed that IMI removal efficiency enhanced about three times at pH 4 with adding 255 mu M of H2O2.

In the present study, we investigate the photocatalytic activity of ZnO thin films doped by copper atoms in successive steps during the film growth by the atomic layer deposition method. Scanning electron microscopy and x-ray diffraction measurements reveal a polycrystalline structure of samples with degrading crystallinity for films with higher Cu content. X-ray photoelectron spectroscopy analysis is consistent with the presence of copper in the Cu+ state for samples with a relative Cu content lower than 1 at.%. Those samples exhibit p-type conductivity indicating that copper ions occupy substitutional, CuZn, acceptor sites in ZnO. As established from UV-vis measurements, Cu-doped ZnO films also show enhanced optical absorption in the visible region. A reduced electron-hole recombination rate, due to much lower intrinsic free charge carrier concentrations in the doped samples, and the increased light absorption in the visible region, lead to a large enhancement of photocatalytic efficiency observed in doped films under simulated sunlight irradiation.

Among transition metal oxides, manganites have attracted significant attention because of colossal magnetoresistance (CMR)—a magnetic field-induced metal–insulator transition close to the Curie temperature. CMR is closely related to the ferromagnetic (FM) metallic phase which strongly competes with the antiferromagnetic (AFM) charge ordered (CO) phase, where conducting electrons localize and create a long range order giving rise to insulator-like behavior. One of the major open questions in manganites is the exact origin of this insulating behavior. Here we report a dc resistivity and magnetization study on manganite La1−xCaxMnO3 ceramic samples with different grain size, at the very boundary between CO/AFM insulating and FM metallic phases x=0.5. Clear signatures of variable range hopping (VRH) are discerned in resistivity, implying the disorder-induced (Anderson) localization of conducting electrons. A significant increase of disorder associated with the reduction in grain size, however, pushes the system in the opposite direction from the Anderson localization scenario, resulting in a drastic decrease of resistivity, collapse of the VRH, suppression of the CO/AFM phase and growth of an FM contribution. These contradictory results are interpreted within the standard core-shell model and recent theories of Anderson localization of interacting particles.

The photocatalytic activity of thin zinc oxide (ZnO) films grown by atomic layer deposition (ALD) and plasma-enhanced ALD (PEALD) was investigated under UV and simu-lated solar illumination. Optimal deposition temperatures were chosen for each method (200°C for ALD and 60°C for PEALD). Under UVC light, the PEALD ZnO thin film showed higher photocatalytic activity, while the activity of the ALD film was better under sun-simulating light. At UVA, the results were similar for the two types of thin films. We have shown that the photocatalytic activity depends on both optical properties and crystal structure, with neither of them having a dominant impact.

Enabling self-healing of materials is crucially important for saving resources and energy in numerous emerging applications. While strategies for the self-healing of polymers are advanced, mechanisms for semiconducting inorganic materials are scarce due to the lack of suitable healing agents. Here a concept for the self-healing of metal oxides is developed. This concept consists of metal oxide nanoparticle growth inside the bulk of halogenated polymers and their subsequent entropy-driven migration to externally induced defect sites, leading to recovery of the defect. Herein, it is demonstrated that the pool of self-healing materials is expanded to include semiconductors, thereby increasing the reliability and sustainability of functional materials through the use of metal oxides. It is revealed that electrical properties of tin-doped indium oxide can be partially restored upon healing. Such properties are of immediate interest for the further development of transparent flexible electrodes.

Salt-affected and sandy pedospheres low in complex organic and mineral matrices critical for metal sorption (e.g. humics, aluminosilicates) could exacerbate metal transfer into the food chain. To test this hypothesis, a 3-factor study with salinity (0–50 mM NaCl), humates (HA; 0–150 mg/kg) and Cd contamination (0–9 mg/kg) was conducted in sandy substrate with strawberry. Cadmium phytoaccumulation decreased in the order roots > crowns > leaves > fruits. In comparison to the control, tissue Cd concentration was influenced by the NaCl × HA × Cd interaction, increasing Cd in leaves (up to 241-fold) and fruits (up to 135-fold) and exceeding the European maximum limit of 0.05 mg Cd/kg w wt. Surface analyses (XRD, SEM–EDX, FTIR, SIMS) revealed that the growth substrate rich in SiO2 (> 87% w/w) had uniform, nonporous and chemically unreactive surface structure. In contrast, the more complex HA matrix featuring abundant and heterogeneous micro-porosity and a large content of reactive radicals. Chemical speciation modelling of the rhizosphere solutions showed that almost all Cd was dissolved and distributed among the bioavailable Cd2+, Cl-complexed and HA-complexed pools, with small amounts of Cd adsorbed to K/Na-aluminosilicates. Slightly acidic pH (5.4–6.2) and complexation with Cl and HA in the rhizosphere favoured Cd solubility and its transfer to plants. The assessment of health risk of strawberry fruit consumption indicated a relatively higher the Estimated Daily Intake (EDI) in children (5% of provisional tolerable daily Cd intake) vs adults (< 1%), with the Dietary Risk Coefficient (DRC) < 0.1 in both populations, suggesting a low risk. However, given Cd intake from other sources and its cumulative effects, precautions are needed when consuming strawberries grown in salt-affected sandy soils.

Silicon-based polymers show great promise for various applications in biomedicine, nanotechnology, tissue targeting, and drug deliv e r y . The use of such materials as functional coatings on surfaces requires the development of strongly adhering and flexible conformal films, which is challenging for conventional wet-chemical coating techniques. We have developed a facile, solvent-free molecular layer deposition (MLD) process to grow environmentally stable hybrid alumosilazane thin films. Exceptionally good biocompatibility is testified with significantly higher proliferation of human embryonic kidney (HEK293T) cells than that on glass, which was used as a reference. Such highly biocompatible and conformal films show great promise as functional coatings for scaffolds or implantable devices with complex topologies or high-aspect-ratio structures.

Thin films containing 3D-ordered semiconductor quantum wires offer a great tool to improve the properties of photosensitive devices. In the present work, we investigate the photo-generated current in thin films consisting of an interconnected 3D-ordered network of Ge quantum wires in an alumina matrix. The films are prepared using nitrogen-assisted magnetron sputtering co-deposition of Ge and Al2O3. We demonstrate a strong photocurrent generation in the films, much stronger than in similar films containing Ge quantum dots. The enhanced photocurrent generation is the consequence of the multiple exciton generation and the films' specific structure that allows for efficient carrier transport. Thin film with the largest nitrogen content showed enhanced performance compared to other thin films with 1.6 excitons created after absorption of a single photon at an energy nearly equal to the double bandgap value. The bandgap value depends on the geometrical properties of the quantum wires, and it is close to the maximum of the solar irradiance in this case. In addition, we show that the multiple exciton generation is the most pronounced at the photon energy values equal to multiple values of the thin film bandgap.

The success of the osseointegration process depends on the surface characteristics and chemical composition of dental implants. Therefore, the titanium dental implant was functionalised with a composite coating of alendronate and hydrolysed collagen, which are molecules with a positive influence on the bone formation. The results of the quantum chemical calculations at the density functional theory level confirm a spontaneous formation of the composite coating on the titanium implant, ∆G*INT = −8.25 kcal mol−1. The combination of the results of X-ray photoelectron spectroscopy and quantum chemical calculations reveals the structure of the coating. The alendronate molecules dominate in the outer part, while collagen tripeptides prevail in the inner part of the coating. The electrochemical stability and resistivity of the implant modified with the composite coating in a contact with the saliva depend on the chemical nature of alendronate and collagen molecules, as well as their inter- and intramolecular interactions. The formed composite coating provides a 98% protection to the implant after the 7-day immersion in the artificial saliva. From an application point of view, the composite coating could effectively promote osseointegration and improve the implant’s resistivity in contact with an aggressive environment such as saliva.

Microstructure and morphology of particles play key roles in optimizing the properties of shape-selected ZnO particles, which are essential factors for flexible and reliable applications. In particular, chemical understanding and physical measurement with scientific theory must be further integrated for the realization of finely tuned ZnO nano microstructures with desired sizes and shapes. Herein, we deliver a detailed description of the mechanism that mimics the formation of finely-tuned, spherical ZnO nanoparticles (NPs) at the computational level. We tackled issues that significantly affect the favorable structural motifs of the spherical ZnO NPs grown hydrothermally from ethanolic solution leading to their advancing chemical and physical properties. The excellent photocatalytic activity of the spherical ZnO was addressed by an apparent-rate constant of 9.7(2)x10(-2) min(-1) efficiently degrading the Rhodamine B solution by similar to 99% in 50 min. The apparent-rate constant for tubular ZnO particles is almost six times lower than that of spherical ZnO NPs. Comparative results revealed that the diversity of size and shape of ZnO particles distinguishes the wurtzite-to-rocksalt transformation reversibility phenomena by dictating the microstructure-dependent deformation behavior and ultimately leading to different transition-induced elastic strain responses to hydrostatic pressure up to 30 GPa. (C) 2021 Elsevier B.V. All rights reserved.

We have studied the oxidation kinetics of initial stages of oxide formation on clean metallic copper surfaces during low-energy O2+ bombardment at room temperature using X-ray photoelectron spectroscopy around Cu 2p and O 1s core-levels and Auger Cu LMM peaks. Two stages in the oxidation process of Cu were observed. For the lower oxygen doses, a single, Cu2O, phase was formed, while the growth of the second, CuO, phase preferentially forms at higher doses. The relative contributions of Cu2O and CuO phases were determined from the deconvolution of Auger Cu LMM spectra, while the thickness of the oxides was estimated from the intensity of the underlying metallic Cu LMM signal and in-depth profiles obtained by secondary ion mass spectrometry. While the growth of the Cu2O layer follows the linear oxidation kinetics, characteristic of the fast chemical reactions of oxygen with the host atoms around the penetration depth of impinging oxygen atoms, the logarithmic law was found for the CuO growth, consistent with the formation of CuO nuclei within the Cu2O matrix.

In this work, we present a large, tenfold enhancement in the photocatalytic activity of thin ZnO films grown by plasma-enhanced atomic layer deposition (PE-ALD) at 100 degrees C, compared to values obtained for thin ZnO films deposited by a conventional thermal ALD method at the same temperature. Thus, we have demonstrated that we can deposit thin ZnO films using the PE-ALD method both at low temperatures and with a high photocatalytic ability. A number of structural (SEM, EDX, HRTEM, GIXRD, XRR, XPS, SIMS) and optical (UV-Vis, PL) experimental techniques have been employed to elucidate a possible physical origin of the observed remarkable difference in the photocatalytic activity of thin ZnO films grown by the PE-ALD method compared to those grown by the thermal ALD method.

Pure and Co3+-doped BaAl2O4 [Ba(Al1-xCox)2O4, x = 0, 0.0077, 0.0379] powder samples were prepared by a facile hydrothermal route. Elemental analyses by static secondary ion mass spectrometry (SIMS), X-ray absorption spectroscopy (XAS) measurements at the Co K-edge, and X-ray diffraction studies were fully correlated, thus addressing a complete description of the structural complexity of Co3+-doped BaAl2O4 powder. Powder X-ray diffraction (PXRD) patterns indicated that prepared samples were nanocrystalline with a hexagonal P63 symmetry. The X-ray absorption near-edge structure (XANES) measurements revealed the presence of cobalt in a +3 oxidation state, while the rarely documented, tetrahedral symmetry around Co3+ was extracted from the extended X-ray absorption fine structure (EXAFS) oscillation patterns. Rietveld structure refinements showed that Co3+ preferentially substitutes Al3+ at tetrahedral Al3 sites of the BaAl2O4 host lattice, whereas the (Al3)O4 tetrahedra remain rather regular with Co3+-O distances ranging from 1.73(9) to 1.74(9) Å. The underlying magneto-structural features were unraveled through axial and rhombic zero-field splitting (ZFS) terms. The increased substitution of Al3+ by Co3+ at Al3 sites leads to an increase of the axial ZFS terms in Co3+-doped BaAl2O4 powder from 10.8 to 26.3 K, whereas the rhombic ZFS parameters across the series change in the range from 2.7 to 10.4 K, showing a considerable increase of anisotropy together with the values of the anisotropic g-tensor components flowing from 1.7 to 2.5. We defined the line between the Co3+ doping limit and influenced magneto-structural characteristics, thus enabling the design of strategy to control the ZFS terms' contributions to magnetic anisotropy within Co3+-doped BaAl2O4 powder.