Investigations of nonstoichiometric tungsten oxide nanoparticles

Recently, pure phases of hollow multi-walled WS2 nanotubes were prepared from a surface reaction with reduced tungsten oxide nanowhiskers. During the process, which starts with WO3-x nanoparticles and finishes with WS2 nanotubes, particular care has been devoted to the evolution of the tungsten oxide cores once the first encapsulating WS2 layer has been formed. The reduced tungsten oxide phases were previously studied by a combination of techniques, including high-resolution transmission electron microscopy and X-ray diffraction. In the present study, Raman spectroscopy combined with the previous two techniques is used to give further detail concerning the structure of the reduced oxide phases. This study sheds some further light on the reduction process of the tungsten suboxide phases and the growth mechanism of oxide nanowtiskers and subsequently WS2 nanotubes from quasi-isotropic tungsten oxide nanoparticles. (C) 2001 Elsevier Science.