Unusual properties and reactivity at the nanoscale

Ready transformation and reactivity is observed at the nanoscale. Silica/silicon (SiOx) nanospheres of diameter <= 30 nm generated from equimolar Si/SiO2 mixtures are found to display enhanced catalytic and reactive properties relative to commonly employed silica support surfaces including fumed silica. A unique oxygen deficient synthesis has been used to generate SnO2-x, nanowires, nanoribbons, and nanotubes displaying the phase coalescence of both ground state rutile and orthohombic structures at pressures well below 0.5 bar. This is in contrast to the bulk where 150 kbar of pressure must be used to generate the orthohombic structure. This unique reactivity and ready transformation is found to accompany the facile (seconds) room temperature nitridation of TiO2 nanocolloids, efficiently producing photocatalytically active TiO2-xNx nanoparticles absorbing light well into the visible region. In distinct contrast the direct nitridation of TiO2 submicron particles does not produce the conversion to the oxynitride at room temperature. (c) 2004 Elsevier Ltd. All rights reserved.