Controlled Synthesis of ZnO Nanospheres Using Hydrothermal Process

Abstract

A novel, versatile, and template-free method has been developed to synthesize solid crystalline zinc oxide (ZnO) spheres via hydrothermal process at a temperature of 100oC within 2h. Using an aqueous solution of zinc acetate dihydrate, ammonium hydroxide, ethanol, and urea, the effects of pH values and structure directing agents on the morphology of ZnO crystals were systematically investigated. We found that the key parameters affecting ZnO morphologies are the pH value of the solution as well as the structure directing agents. When the structure directing agents such as ethanol and urea were used, at a pH value of 12, isotropic growth of ZnO spheres was developed, while at pH value less than 12, anisotropic growth of ZnO structures was observed. Furthermore, by modulating the volume ratio of ethanol in the solution, the size of the ZnO spheres could be controlled from nanometer to micrometer range.