Effect of pH on sonication assisted synthesis of ZnO nanostructures: Process details

Abstract

A facile sonication assisted fabrication of zinc oxide nanostructures (plate, rod and spherical) were successfully accomplished by changing the pH of the reaction mixture (acidic, neutral and basic). Starch was used as a capping agent. Mixing time was determined to decide the rate of addition of Zn(NO3)2 solution into the NaOH base solution. In a sonication method, the system was irradiated by ultrasound for a total duration of 20min. The effect of pH on the yield (%), crystallite size, crystallinity (%), structures and band gap energy of ZnO were measured and compared using different characterization tools. The yield evaluated accounts for material balance in sonochemically prepared ZnO sample. A probable mechanism was proposed to explain the formation of tailored ZnO morphology based on the concentration of zinc species present in the solution. It was revealed from the X-ray diffraction data, that conventional magnetic stirring technique needs calcination for ZnO formation. However, sonochemical method leads to direct synthesis of ZnO. It was observed that the quantum of energy required for sonochemical method of synthesis is comparable to the energy required for agitation and calcination (together) during conventional method of ZnO synthesis.