Effect of Alkali Concentration and Reaction Time on the Morphology of ZnO Nano-Microparticles Prepared by Hydrothermal Method

A low-temperature hydrothermal method was used to prepare ZnO nano-microparticles using surfactant-free solutions. The effect of the alkali concentration (Zn2+/OH- = 1:1, 1:2, 1:4 and 1:8) and reaction time (1,2 and 3 hours) on the morphology of the ZnO was studied. The structure and the morphology of the ZnO obtained were investigated by means of XRD and SEM techniques, respectively. The results revealed that the solution basicity and reaction time were important factors affecting the morphology. With an increase in the reaction time, the crystallinity of the phases formed was enhanced. At a low alkali concentration, i.e. 1:1, a ZnO hexagonal prism-like structure with a crystal size of 300 nm - 1.5 mu m and Zn(OH)(2) amorphous phase were formed. With a further increase to Zn2+/OH- = 1:2, some nanorods and flakes appeared beside the ZnO nanoparticles. When the ratio reached Zn2+/OH- = 1:4, different morphologies such as nanorods, slices and nanoflakes were obtained. At Zn2+/OH- = 1:8, the morphology changed into microflowers as the major structure with some nanoparticles and nanosheets as the minor structure.