Structural and optical properties of ZnO nanorods: influence of reaction temperature

ZnO nanorods have been prepared by hydrothermal method and the reaction temperatures are 120, 140, 160 and 180 °C, respectively. Microstructure, morphology, chemical composition and optical properties of the samples were investigated in detail. XRD and Raman spectrum analysis shows that the best crystal performance of ZnO obtained at 140 °C. The samples are mainly composed of morphology nanorods and abundant ZnO nanorods with hexagon-shaped crystallites structure are emerged at all reaction temperatures. XPS measurement indicates that the Zn and O surface atom ratio is estimated about 1.13:1 for the sample prepared at 140 °C. Compared with the UV–Visible absorption spectra of the samples obtained at 120, 140 and 180 °C, absorption edge appears slight blue shift phenomenon with reaction temperature increasing and the absorption intensity reduces at the same time. These analyses reveal that the optical band gap increases with increasing of reaction temperature and all the gaps are less than the standard value 3.2 eV of ZnO.