Large-scale oxide nanostructures grown by thermal oxidation

Large scale oxide nanostructures of CuO, Fe/sub 2/O/sub 3/, Co/sub 3/O/sub 4/, ZnO, etc. were prepared by catalyst-free thermal oxidation process in atmosphere using pure metal as the starting material. Various single crystalline nanostructure arrays, including nanowires, nanobelts, nononeedles, nanoflakes, and nanowalls were obtained. These nanostructures can be grown from bulk materials, like foils or sheet, or from the microsized metal powders and the pre-deposited metal film. The growth time, temperature and substrate have important effects on the morphology, size and distribution of the nanostructures. Different from V-S or V-L-S mechanisms, the growth of nanostructure is found to be based on the metal ion diffusion process. The gradual oxidation process of the metals was clearly demonstrated. The properties of these nanostructures including gas sensing, magnetism, photoluminescence, and field emission were extensively investigated. (author)