A correlation between crystal structure and catalytic activity in the solid solutions CdMoxW1−xO4

Two CdMo_xW_1−xO₄ solid solutions with the scheelite and the wolframite structures were synthesised via different techniques and their structures were determined from powder refinements. The limit of the reciprocal solubility of Mo in CdWO₄ has been checked. Several compositions of the solid solutions have been tested in the catalytic mild oxidation of propane or propene and relations between the structures and the catalytic activity are proposed.     

In situ sulfurization to generate Sb2(Se1 − xSx)3 alloyed films and their application for photovoltaics

Because of its tunable band gap and band position, Sb₂(Se_{1 − x} S_x )₃ (0 ≤ x ≤ 1) is a promising light‐absorbing material for photovoltaic device applications. However, no systematic study on the synthesis and characterization of single‐phase polycrystalline Sb₂(Se_{1 − x} S_x )₃ thin films has been reported. Through introducing in situ sulfurization into the rapid thermal evaporation process, a series of single‐phase, highly crystalline Sb₂(Se_{1 − x} S_x )₃ films with x = 0.09, 0.20, 0.31, and 0.43 were successfully obtained, with the corresponding band gap, band position and film morphology fully revealed. Futhermore, solar cells with superstrate ITO/CdS/Sb₂(Se_{1 − x} S_x )₃/Au structure were fabricated and carefully optimized. Finally, a champion device having 5.79% solar conversion efficiency was obtained employing uniform Sb₂(Se_0.80S_0.20)₃ absorber layer. Our experimental investigation confirmed that Sb₂(Se_{1 − x} S_x )₃ is indeed a very promising absorber material worth further optimization. Copyright © 2016 John Wiley & Sons, Ltd.     

Reduction of NOx over Fe/ZSM-5 catalysts: mechanistic causes of activity differences between alkanes

Fe/ZSM-5 catalysts prepared by sublimation of FeCl₃ onto H/ZSM-5 catalyze the selective reduction of NO_x by hydrocarbons to N₂. The order of the relative rates and N₂ yields obtained with different alkanes reveals a non-trivial chemistry. The maximum yield is lower for propane than for n-butane but about the same for n- and iso-butane. However, at temperatures below this maximum, the N₂ yield is higher for propane and n-butane than for iso-butane. Deposits are formed on the catalyst that contain N atoms in a low-oxidation state which are able to react with NO₂ to form N₂. TPO and FTIR results show that the amount and also the character of the deposits depend on the nature of alkanes. The change of the oxidation state of nitrogen from a high value in NO or NO₂ to a lower value in nitrile and amino groups of the deposit is rationalized by applying mechanistic concepts of organic chemistry, including the Beckmann rearrangement and fragmentation. FTIR spectra and the observed oxygen- and nitrogen-containing compounds by GC-MS are potential clues to the reaction mechanism.     

Molecular simulation study of the structural properties in InxGa1−xAs alloys: Comparison between Valence Force Field and Tersoff potential models

The thermodynamic and structural properties of compound semiconductor alloys have been generally modelled using either the Valence Force Field model or the Tersoff potential model. This work compares the properties, such as lattice constant and bond length, of the In_xGa_1−xAs alloy as predicted by Monte Carlo simulations in the semigrand isothermal isobaric ensemble using both the potential models, with experimental data. The lattice constants are expected to follow the Vegard’s law at any given temperature. Valence Force Field model predicts bond length data which follows the experimentally determined values at 300 K; whereas the Tersoff model forecasts that the virtual crystal approximation will be followed. The VFF model, with its experimentally determined parameters, is found to be better for modelling the alloy at room temperature. The Tersoff model, with its fitted parameters, on the other hand predicts the effect of temperature on the microscopic structure of the alloy better. The parameters of the Tersoff potential characterizing the In–Ga interactions can be further improved to predict bond lengths more accurately.     

Magnetic and optical characterization of Mn-doped PbS nanocrystals supported in oxide glass matrix

The evidence of successful growth of Mn-doped PbS (Pb_1−xMn_xS) nanocrystals (NCs) in SiO₂–Na₂CO₃–Al₂O₃–PbO₂–B₂O₃ template, using the fusion method, is reported on in this study. The as-grown Pb_1−xMn_xS NC is characterized using optical absorption, electron paramagnetic resonance, and atomic force microscopy. The data are discussed in terms of two distinct scenarios, namely a core-doped and a shell-doped nanostructure.     

The start gene CDC28 and the genetic stability of yeast

The cdc28-srm mutation in Saccharomyces cerevisiae decreases spontaneous and induced mitochondrial rho- mutability and the mitotic stability of native chromosomes and recombinant circular minichromosomes. The effects of cdc28-srm on the genetic stability of cells support the hypothesis that links cell cycle regulation in yeast to changes in chromatin organization dependent on the start gene CDC28 (Hayles and Nurse, 1986).     

Characterization of GaN epitaxial layers on SiC substrates with AlxGa1−xN buffer layers

High quality GaN epitaxial layers were obtained with Al_xGa_1−xN buffer layers on 6H–SiC substrates. The low-pressure metalorganic chemical vapor deposition (LP-MOCVD) method was used. The 500 Å thick buffer layers of Al_xGa_1−xN (0≤x≤1) were deposited on SiC substrates at 1025°C. The FWHM of GaN (0004) X-ray curves are 2–3 arcmin, which vary with the Al content in Al_xGa_1−xN buffer layers. An optimum Al content is found to be 0.18. The best GaN epitaxial film has the mobility and carrier concentration about 564 cm² V⁻¹ s⁻¹ and 1.6×10¹⁷ cm⁻³ at 300 K. The splitting diffraction angle between GaN and Al_xGa_1−xN were also analyzed from X-ray diffraction curves.     

Preparation of CuIn1−xGaxSe2 thin films by sputtering and selenization process

CuIn_1−xGa_xSe₂ polycrystalline thin films were prepared by a two-step method. The metal precursors were deposited either sequentially or simultaneously using Cu–Ga (23 at%) alloy and In targets by DC magnetron sputtering. The Cu–In–Ga alloy precursor was deposited on glass or on Mo/glass substrates at either room temperature or 150°C. These metallic precursors were then selenized with Se pellets in a vacuum furnace. The CuIn_1−xGa_xSe₂ films had a smooth surface morphology and a single chalcopyrite phase.     

Solid-state photoelectrochemical device based on poly(3-hexylthiophene) and an ion conducting polymer electrolyte, amorphous poly(ethylene oxide) complexed with I3/I redox couple

The photoelectrochemical properties of a solid-state photoelectrochemical cell (PEC) based on poly(3-hexylthiophene), P3HT, and an ion-conducting polymer electrolyte, amorphous poly(ethylene oxide), POMOE, complexed with I₃⁻/I⁻ redox couple has been constructed and studied. The current–voltage characteristics in the dark and under white light illumination, transient photocurrent and photovoltage studies, photocurrent action spectra for front and back side illuminations and an open-circuit voltage and short-circuit current dependence on light intensity have been studied. An open-circuit voltage of 130 mV and a short-circuit current of 0.47 μA cm⁻² were obtained at light intensity of 100 mW/cm². IPCE% of 0.024% for front side illumination (ITO/PEDOT) and IPCE% of 0.003% for backside illumination (ITO/P3HT) were obtained.