Controlled transformation of ZnO nanobelts into CoO/Co sub(3)O sub(4) nanowires

Highly crystalline CoO and Co sub(3)O sub(4) nanowires were prepared by vapor-phase conversion of ZnO nanobelts. The ZnO nanobelts were successfully transformed into highly crystalline CoO nanowires by thermal evaporation of CoCl sub(2) at 700 degree C in Ar, which were subsequently converted to Co sub(3)O sub(4) nanowires by oxidative annealing at 600 degree C. The reactions at 500 and 550 degree C in 0.5% O sub(2) led to the formation of well-defined oxide p-n junction nanostructures such as Co sub(3)O sub(4)-decorated ZnO nanobelts and ZnO-ZnCo sub(2)O sub(4) core-shell nanocables, respectively, as the reaction intermediates. The evolutions of phase and residual Zn component during the conversion were investigated in relation to the reaction temperature and oxygen partial pressure.