TiO 2 -based photocatalyst layers are still highly favored materials for photocatalysis on immobilized semiconductor electrodes because of their favorable electronic band positions, high corrosion stability, cost efficiency, and readily available titanium. Since chemical synthesis of nanocrystalline TiO 2 layers from alkoxide precursors is usually complex and of low reproducibility, new methods are required to enable large-scale production of immobilized titania catalyst layers for practical applications. The synthesis of TiO 2 -layers on fluorine doped tin oxide (FTO) by means of a reactive sputtering process is reported here, with stable operation being implied by the means of a λ-sensor. Structural, electrochemical, and photocatalytic properties were investigated for different layer thicknesses and postdeposition annealing temperature of the deposited TiO 2 by means of SEM, TEM, XRD, XPS, UV/vis spectroscopy, and a range of photochemical measurements including iE curves, acIS, IMVS and IMPS, and IPCE.

For nanoparticles with sub-10 nm diameter, the electronic bandgap becomes size dependent due to quantum confinement; this, in turn, affects their electro-optical properties. Thereby, MoS 2 and WS 2 monolayers acquire luminescent capability, due to the confinement-induced indirect-to-direct bandgap transition. Rolling up of individual layers results in single wall inorganic nanotubes (SWINTs). Up to the present study, their luminescence properties were expected to be auspicious but were limited to theoretical investigations only, due to the scarcity of SWINTs and the difficulties in handling them. By optimizing the conditions in the plasma reactor, relatively high yields of WS 2 SWINTs 3-7 nm in diameter were obtained in this work, compared to previous reports. A correlative approach, transmission electron microscopy coupled with a scanning electron microscope, was adapted to overcome handling obstacles and for testing individual nanotubes by lowtemperature cathodoluminescence. Clear cathodoluminescence spectra were obtained from WS 2 -SWINTs and compared with those of WS 2 multiwall nanotubes and the corresponding bulk material. Uniquely, the optical properties of INTs acquired from cathodoluminescence were governed by the opposite impact from quantum size effect and strain in the bent triple S-W-S layers. The experimental findings were confirmed by the Density Functional and Time-Dependent Density Functional theoretical modeling of monolayer and bilayer nanotubes of different chiralities and diameters. This study provides experimental evidence of the quantum confinement effect in WS 2 SWINTs akin to WS 2 monolayer. The ability to tune the electronic structure with morphology or number of layers may be exploited toward photoelectrochemical water splitting with WS 2 catalysts, devising field effect transistors, photodetectors, and so on.

Metal nanoparticles are commonly used for a wide range of applications. This paper presents a novel synthesis method using plasma vapor deposition and a subsequent thermal treatment to produce homogeneous particles within the nanometer range. A combination of high resolution transmission electron microscopy and scanning electron microscopy studies as well as ultraviolet/visible light transmission measurements are employed in order to characterize crystallographic, microstructural, and optical properties of gold, silver, and core−shell bimetallic nanostructures on a titania surface. The nanostructural size and composition of the core−shell nanostructures and therefore their optical properties could be directly adjusted by the plasma process parameters and/or the postdeposition thermal treatment of the samples.

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Plasma chemical reactions in CH4/Ar and C2Hm/Ar (m = 2, 4, 6) gas mixtures in a dielectric barrier discharge at medium pressure (300 mbar) have been investigated. From mass spectrometry the production of H2 and formation of larger hydrocarbons such as CnHm with up to n = 12 is inferred. Hydrogen release is most pronounced for CH4 and C2H6 gas mixtures. Fourier Transform InfraRed (FTIR) spectroscopy reveals the formation of substituted alkane (sp3), alkene (sp2), and alkyne (sp) groups from the individual gases which are used in this work. Abundant formation of acetylene occurs from C2H4 and to a lesser extent from C2H6 and CH4 precursor gases. The main reaction pathway of acetylene leads to the formation of large molecules via C4H2 and, eventually, to nano‐size particles. The experimental results are in reasonable agreement with simulations which predict a pronounced electron temperature and gas pressure dependency. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)