Ultrathin ZnO nanostructures synthesized by thermal oxidation of hexagonal Zn micro/nanostructures.

Ultrathin (<5 nm) ZnO nanobelts, as well as porous nanotubes/nanosheets were successfully synthesized via a very simple process: thermal oxidation of hexagonal Zn micro/nanostructures in a tube furnace in 50 sccm N2 flow. The ZnO nanobelt clusters were largely grown from the (0001) end surface of the Zn nanoprisms at 300 degrees C. The porous nanotubes and nanosheets were formed on the downstream substrate by 370-400 degrees C thermal oxidation of Zn films in low pressure. These structures are related to the anisotropic oxidation of Zn and differences of melting point between Zn and ZnO. We propose that the ultrathin nanobelts were formed in a vapor-liquid-solid process while the ultrathin nanotubes and nanosheets were formed via a vapor-solid-resublimation process. The structure of the nanostructures was characterized by transmission electron microscopy. The ultrathin mesoporous nanotubes and nanosheets have been found to possess rich surface defects. These structures may have potential applications in gas sensors, catalysts and hydrogen storage due to their large specific surface area.