Metal Oxide Nanostructures from Simple Metal-oxygen Reaction in Air

Metal oxide nanostructures（CuO,Co;O;,ZnO andα-Fe;O;）have been successfully fabricated by a sim- ple and efficient method:heating the appropriate metals in air at low temperatures ranging from 200 to 400℃.The chemical composition,morphology and crystallinity of the nanostructures have been characterized by micro-Raman spectroscopy,X-ray diffraction,scanning electron microscopy and transmission electron mi- croscopy.Two mechanisms:vapor-solid and surface diffusion play dominant roles in the growth of metal oxide nanostructures starting with low melting point metals（Zn and Cu）and high melting point metals（Fe and Co）,respectively.With sharp ends and large aspect ratio,the metal oxide nanostructures exhibit impressive field-induced electron emission properties,indicating their potentials as future electron source and displays. The water wettability and anti-wettability properties of iron oxide nanoflakes were also discussed in this work.