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

► ZnO nanoparticle was synthesized by the sol gel method without capping agents. ► Effects of process parameters on size of ZnO nanoparticle was investigated. ► The pH and calcination temperatures indicates more effecting on band gap was observed. ► The optimum condition for mimimal size of 1:2 ratio, pH of 2.0 ± 0.2 and calcined at 400 °C were found.