The effect of process parameters on the size of ZnO nanoparticles synthesized via the sol-gel technique

This article describes the controlled size of ZnO nanoparticles when they are synthesized using the sol- gel method without the involvement of a capping agent. The effects of process parameters such as the molar ratio, pH of reactants and calcination temperatures on the size of the synthesized ZnO nanoparticles were investigated. The hexagonal wurtzite phase structure of ZnO nanoparticles was obtained in the form of spherical shapes for all samples. It was found that the ZnO nanoparticles were small in size and experienced reduced agglomeration at a 1:2 molar ratio of the starting material and pH of 2.0 +/- 0.2. The results showed that the ZnO nanoparticles had increased in size and experienced a larger agglomeration when the ratio and pH were at higher or lower than the optimal condition. The morphological observations showed increase in particle size when the calcination temperature was increased. The functional group for the ZnO nanoparticle showed a peak in the range of 494-500 cm(-1). The optical properties of the ZnO nanoparticles with the best band gap of 3.19 eV were also evaluated under the optimal experimental conditions. The surface charge of the ZnO nanoparticles did not change, which indicated that there was no relationship between surface charge and particle size for the same type of catalyst. (C) 2012 Elsevier B.V. All rights reserved.