Shape Transformation of ZnO Nanorods /Nanotubes at Low Temperature

We report the shape transformation of ZnO nanorods/nanotubes at temperatures (∼700 °C) much lower than the bulk melting temperature (1975 °C). With increasing annealing temperature, not only does shape transformation take place but the luminescence characteristics of ZnO are also modified. It is proposed that the observed shape transformation is due to surface diffusion, contradicting the previously reported notion of melting and its link to luminescence. Luminescence in the green-to-red region is observed when excited with a blue laser, indicating the conversion of blue to white light.