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Abstract: The structure, morphology and composition of pure WO3 thin films deposited onto vacuum-cleaved NaCl(001) single crystals have been studied at different substrate temperatures up to 580 K and under different oxidative and reductive treatments in the temperature range 373–873 K by Transmission Electron Microscopy, Selected-Area Electron Diffraction and X-ray Photoelectron Spectroscopy (XPS). A transition from an amorphous structure obtained after deposition at 298 K to a more porous structure with small crystallites at the highest substrate temperatures has been observed. XPS spectra reveal the presence of W6+ irrespective of the preparation procedure. Significant changes in the film structure were only observed after an oxidative treatment in 1 bar O2 at 673 K, which induces crystallization of a monoclinic WO3 structure. After raising the oxidation temperature to 773 K, the film shows additional reconstruction and a hexagonal WO3 structure becomes predominant. This hexagonal structure persists at least up to 873 K oxidation temperature. However, these structural transformations observed upon oxidation were almost completely suppressed by mixing the WO3 thin film with a second oxide, e.g. Ga2O3. Reduction of the WO3 films in 1 bar H2 at 723–773 K eventually induced the formation of the β-W metal structure, as evidenced by electron diffraction and XPS. [Copyright &y& Elsevier]

A facile gas-steamed strategy is reported for preparing heteroatom dual-doped hierarchical porous hollow carbon catalysts via carbonization of a mixture of carbon sphere precursor and ammonium fluoride (NH 4 F). Notably, NH 4 F can be decomposed into NH 3 and HF by pyrolysis, in which HF gas can etch SiO 2 pellets to form hollow structure while the N and F atoms can be introduced at the same time. The FCS-900 exhibits admirable electrocatalytic properties with the highest onset potential and limiting current density in neutral electrolytes (0.944 V vs. RHE and 6.44 mA cm−2). In comparison to MFC-Pt, much higher output voltage and power density (0.617 V and 1093.6 ± 6.26 mW m−2) are obtained by MFC-900. Such results can be attributed to the largest specific surface area of FCS-900 to supply exposed active sites and fast transportation channels. Based on X-ray photoelectron spectroscopy, the FCS-900 catalyst possesses the active substances of pyridinic/graphitic N and C-F bonds. The synergism of N and F can effectively facilitate the adsorption of O 2 during ORR, as further supported by density functional theory calculation. The facile and green synthesis strategy can be extended to design metal-free carbon-based electrocatalysts with superior electrocatalytic performance. [Display omitted] • A gas-steamed strategy is proposed to prepare N-F co-doped hollow carbon spheres. • NH 4 F is endowed with dual functions of etching SiO 2 and N-F co-doping. • The FCS-900 has highly active substances of pyridinic/graphitic N, C-F bonds. • The MFC-900 shows the highest power density of 1093.6 ± 6.26 mW m−2. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a high-performance, low-energy consumption, and environmentally friendly water treatment technology with a broad application prospect in heavy metal removal. Selecting electrode materials with high capacitance and low resistance is essential for improving CDI's desalting efficiency. This article discusses the utilization of sugarcane bagasse (C-N-X) and the production procedures of CDI materials. The unique 3D cross-linked structure of C-N-X provides excellent mass transfer properties and significant advantages in capacitance and conductivity. The results of X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectrometer (FTIR) show that bagasse biochar with graphene-like structure and abundant functional groups provides active sites for Cu2+ removal. In this paper, C-N-X is first used as CDI electrode material to remove Cu2+. Electrochemical tests show that the specific capacitance of C-N-X is still stable at about 47 F g−1, and the removal capacity of Cu2+ (25 mg L−1) reaches 66.79 mg g−1 within 4 h after 700 cycles. The experimental results and DFT calculations confirm the adsorption selectivity of C-N-700 for Cu2+. [Display omitted] [ABSTRACT FROM AUTHOR]

Ferromagnetic metal-organic semiconductor (FM-OSC) hybrid interfaces have been shown to play an important role for spin injection in organic spintronics. Here, 11,11,12,12-tetracyanonaptho-2,6-quinodimethane (TNAP) is introduced as an interfacial layer in Co-OSCs heterojunctions with an aim to tune the spin injection. The Co/TNAP interface is investigated by use of X-ray and ultraviolet photoelectron spectroscopy (XPS/UPS), near edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD). Hybrid interface states (HIS) are observed at Co/TNAP interfaces, resulting from chemical interactions between Co and TNAP. The energy level alignment at the Co/TNAP/OSCs interface is also obtained, and a reduction of the hole injection barrier is demonstrated. XMCD results confirm sizeable spin polarization at the Co/TNAP hybrid interface. [ABSTRACT FROM AUTHOR]

We study the filling of single-walled carbon nanotubes (SW- CNTs) with ferrocene molecules. Using e-DIPS SWCNTs with a mean diameter of 1.7 nm, we obtain a filling factor as high as 90%. At elevated temperatures in high vacuum the filled SWCNTs are transformed to double-walled carbon nanotubes (DWCNTs). Temperature dependence of inner tube growth is investigated by Raman spectroscopy. The electronic properties of the obtained nanostructures are studied by X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy. It is found that the growth temperature is higher for larger diameter inner tubes. It is demonstrated that ferrocene filling leads to electron doping of SWCNTs. [ABSTRACT FROM AUTHOR]

Abstract: The structure and morphology of mixed GaO x /WO x thin film systems prepared by either sequential or simultaneous oxide deposition has been studied by Analytical (High-Resolution) Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM). GaO x and WO x were prepared by thermal evaporation of the corresponding oxides (β-Ga2O3 and WO3, respectively) in 10−2 Pa oxygen onto a NaCl substrate, which was held at temperatures between 298 and 580K. The film morphology of differently prepared mixed GaO x /WO x films not only differs significantly from those of the pure oxides, but also strongly depends on the preparation conditions and the order of deposition. Upon co-deposition of GaO x /WO x films onto NaCl(001) at temperatures above 580K a gallia morphology was observed, which is strikingly different from hitherto reported pure GaO x films, i.e., growth of small-diameter (20–25nm) sub-stoichiometric gallia dendrites. The dendritic growth is apparently mediated by the GaO x /NaCl(001) contact area rather than being an intrinsic feature of the three-dimensional mixed-oxide bulk. In particular, neither sequentially deposited GaO x /WO x films nor co-deposited films on top of a pre-deposited WO x interlayer exhibited this peculiar morphology. [Copyright &y& Elsevier]

Abstract: Gallium oxide thin films were prepared by thermal evaporation and deposition of Ga2O3 on NaCl(001) cleavage planes at varying substrate temperatures, oxygen pressures and deposition rates. The structure of the so-prepared thin films was checked by Transmission Electron Microscopy and Selected Area Diffraction and also characterized by X-ray Photoelectron Spectroscopy and Atomic Force Microscopy, both in the as-deposited state and after different oxidative and reductive treatments. The substrate temperature proved to be most crucial for the structure of the gallium oxide films, ranging from low-contrast amorphous structures at low substrate temperatures (298 K) to nanosphere structures at higher temperatures (580 K). The stability of the films was found to be mainly determined by the interaction of substrate temperature and deposition rate. Crystalline β-Ga2O3 structures were obtained after oxidative, reductive and annealing treatments at and beyond 773 K suggesting that the crystallization is mainly a thermal annealing effect. [Copyright &y& Elsevier]

• Increased work function of the hybrid interface Si-SiO 2 /organic layer with acidic groups. • Surface band bending of the silicon crystal upward along with a negative surface dipole. • The protonation effect of the silicon oxide film by molecular acidic groups. • Increased depth of space charge region and height of Schottky barrier in Si semiconductor. The large photovoltaic response from homogeneous silicon wafer obtained upon deposition of a molecular layer on its surface remained an unexplained phenomenon so far. Here, we show by X-ray and ultraviolet photoelectron spectroscopy that deposition of species containing acidic groups on the surface of n -type silicon with native silicon oxide overlayer always results in increased work function of the hybrid interface. This effect is shown to originate due to the surface band bending of the silicon crystal upward, which is accompanied by a negative surface dipole formed. This effect is assigned to protonation of the silicon oxide film by molecular acidic groups, which in turn facilitates accumulation of a mirror negative charge at the Si-SiO 2 interface, thus increasing the depth of the depletion region and height of the Schottky barrier in the silicon semiconductor, respectively. Comparison of the work functions of the samples in the dark and under illumination confirms formation of a depletion region at the silicon surface upon molecular adsorption. [ABSTRACT FROM AUTHOR]

Doped semiconductors nanostructures (NSs) have shown great interest as a potential for green and efficient photocatalysis activities. Magnesium (Mg)-doped zinc oxide (ZnO) nanoparticles (NPs) has been synthesized by a one-step chemical low temperature (60 °C) co-precipitation method without further calcination and their photocatalytic performance for photodegradation of Methylene blue (MB) dye under the illumination of solar light is investigated. The crystal structure of the synthesized NPs is examined by X-ray diffraction (XRD). XRD data indicates a slight shift towards higher 2θ angle in Mg-doped samples as compared to the pure ZnO NPs which suggest the incorporation of Mg2+ into ZnO crystal lattice. X-ray photoelectron spectroscopy (XPS), UV–Vis spectrophotometer and cathodoluminescence (CL) spectroscopy, were used to study electronics, and optical properties, respectively. The XPS analysis confirms the substitution of the Zn2+ by the Mg2+ into the ZnO crystal lattice in agreement with the XRD data. The photocatalytic activities showed a significant enhancement of the Mg-doped ZnO NPs in comparison with pure ZnO NPs. Hole/radical scavengers were used to reveal the mechanism of the photodegradation. It was found that the addition of the Mg to the ZnO lattices increases the absorption of the hydroxyl ions at the surface of the NPs and hence acts as a trap site leading to decrease the electron-hole pair and consequently enhancing the photodegradation. Image 109 • Base and Magnesium doped ZnO NPs were synthesized by the chemical low-temperature co-precipitation route. • The photodegradation efficiency was found to be increasing with increasing the atomic concentration of Magnesium. • Trapping experiments indicated that holes are the major species that were responsible for the degradation of Methylene blue. • Methylene blue was found to degrade faster than the Congo red. [ABSTRACT FROM AUTHOR]