Zinc oxide (ZnO) powders were synthesized by a simple hydrothermal process in the temperature range of 50 to 100 oC. Nanocrystallites were formed by a simple hydrothermal route from aqueous solutions of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and NaOH under controlled process conditions such as precursor concentration (0.07 to 1 mol/L), reaction pH (7 to 11) and temperatures. Single phase ZnO particles can be easily synthesized at low precursor concentration, high reaction pH and high temperature. The synthesized powders prepared at 80 oC exhibited short hexagonal tablet, tapered multipod, or rod-shaped morphologies. The particles, primarily, had a nanometric three-dimensional six-fold symmetry, which was related to the hexagonal wurtzite structure and the particle morphologies were largely influenced by the hydrothermal processing parameters. Rod-shaped ZnO particulates consisting of the elongated crystals of interconnected or separate forms were predominantly developed at high precursor concentration and high pH condition. Consequently, it has been proposed that the morphological features could be tailored by changing the process parameters.

Keywords: Hydrothermal synthesis, ZnO, Crystal morphology, Nanostructures, Nano-rod