The Study on the Growth Process of ZnO Nanorods

The authors synthesized ZnO nanorods by calcining the precursor composed of PVP and Zn(CH_3COO)_2·2H_2O at 300 ℃. In order to investigate the growth process of ZnO nanorods, the precursor was calcined for different time (0.5, 3, 12, 24 h) and the corresponding products were measured by TEM, HR-TEM (high-resolution transmission electron microscopic), SAED (selected-area electron diffraction pattern) and XRD. The result showed that there were ZnO crystallites in the precursor of PVP and Zn(CH_3COO)_2·2H_2O, which was dried at 110 ℃. When the precursor was calcined at 300 ℃ for 0.5 h, ZnO nanorods could be observed with diameter of 50 nm and the nanorods consisted of two parts. One was compact nanorod with diameter of about 30 nm and the other part was ZnO crystallites attaching around the nanorod. This phenomenon indicated that there might be a transverse growth direction of ZnO nanorods at early time of crystal growth. When the precursor was calcined for 3 h, the products were direct and smooth single crystal ZnO nanorods. Further increasing the calcining time at 300 ℃ could improve the length of the ZnO nanorods in a certain extent while the diameter changed a little. The HR-TEM results showed that the growth direction of ZnO nanorods was along c axis.