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Abstract: The preparation of multiphase CdS/TiO2 photocatalysts by the deposition of cadmium sulfide nanoparticles on the surface of commercial titania Hombifine N and Degussa P25 in the presence of a chelating agent (ammonia) was carried out. The photocatalysts were characterized by a wide range of experimental techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) combined with energy-dispersive X-ray (EDX) spectroscopy, X-ray fluorescence (XRF) spectroscopy, and UV/VIS spectroscopy. The photocatalytic activity was tested in the reaction of ethanol gas-phase oxidation under visible light irradiation (λ >420nm) in a batch reactor. The deposition of cadmium sulfide on the surface of anantase/rutile titania Degussa P25 was found to produce higher activity in comparison to the deposition on anatase Hombifine N. The good stability and activity of the multiphase system seem to be caused by the formation of hetero-junctions between CdS and TiO2 nanoparticles resulting in the efficient charge separation and decreased electron–hole recombination. [Copyright &y& Elsevier]

Abstract: Nanocrystalline cadmium sulfide CdS thin films with relevance for optical applications were synthesized from aqueous solutions by chemical bath deposition. Grazing incidence X-ray diffraction shows that the films formed on glass or silicon substrates are made up of nanocrystalline particles. About 80% of the particles have a diameter of 5±1 nm. The nanoparticles have either sphalerite or wurtzite structure. The presence of the sphalerite phase is a signature of a highly non-equilibrium state of the nanocrystalline film. Kinetic studies show that the size of the nanocrystals and the relative fraction of the two phases do not depend on the deposition time once it exceeds a duration of 30 min. For longer times, the particle characteristics remain constant while the thickness of the film grows. Thermodynamical analysis of ionic equilibria allows to choose the reaction bath composition for the formation of cadmium hydroxide Cd(OH)2. The experiments provide strong evidence that the beginning of the deposition of CdS is accompanied by a formation of cadmium hydroxide Cd(OH)2. [Copyright &y& Elsevier]

The analysis of X-ray diffraction patterns showed that the geometry of PbS nanoparticles with a structure of NaCl is a nonlinear function of particle size for PbS particles smaller than 82nm. [Copyright &y& Elsevier]