Growth of porous ZnO nanowires by thermal oxidation of ZnS nanowires

The growth of porous ZnO nanowires (NWs) by thermal oxidation of ZnS NWs in air was studied. The ZnS NWs were first synthesized by thermal evaporation of ZnS powder at 1100°C in Ar. On subsequent annealing in air, the ZnS NWs transformed to porous ZnS-ZnO core-shell NWs and porous ZnO NWs at 600-700°C and 700-750°C, respectively. Higher annealing temperature suppressed the formation of porous structure in ZnO NWs. Two factors, the higher formation rate for SO₂ than for ZnO and the incompatible structure at the interface of epitaxial ZnS and ZnO, are beneficial to the formation of porous ZnO NWs from ZnS NWs on annealing in air. The mechanisms for the formation of porous ZnO NWs by thermal oxidation of ZnS NWs in air are discussed.