Growth of variable aspect ratio ZnO nanorods by hydrothermal technique

Abstract

Zinc oxide (ZnO) nanorods were successfully prepared by hydrothermal process. The influence of the solution temperature on the ZnO nanorods aspect ratio is investigated in the present work. The x-ray diffraction (XRD) and scanning electron microscopy (SEM) results and analysis reveal the formation of ZnO nanorods owing hexagonal Wurtzite structure with preferential orientation along the c-axis. We found that the solution temperature is a key parameter controlling the aspect ratio of the formed ZnO nanorods. The later increases linearly with the preparation temperature. The rod length is thermally activated with an activation energy of 0.48 eV, which corresponds to the activation energy of the reaction forming ZnO, indicating that the nanorods growth is controlled by the surface reaction rather than by mass transport. While, the rods diameter is reduced with increasing temperature, its activation energy of 0.23 eV is equal to the species diffusion activation energy in the solution and to the crystallite size activation energy suggesting, thereafter that the rod diameter variation is controlled by the nucleation dynamic.