Zinc oxide (ZnO) nanoparticles have been investigated in depth, due to their potential as a semiconductor material in dye sensitized solar cell applications. In this current research, ZnO nanostructure was synthesized using a simple precipitation technique with the addition of citric acid (C6H8O7)as the capping agent. Various ratios of ZnO and citric acid were prepared, i.e. 1:1, 2:1, 4:1 and calcination temperatures of 150 and 400°C were used to investigate the effect of those parameters on the ZnO nanostructure and its crystallinity. The nanostructure characteristics, i.e. nanocrystallite size, crystallinity, and optical properties were determined by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and ultra-violet visible (UV-Vis) spectroscopy, respectively. The investigation results showed that ZnO nanostructure was formed as spherical shapes and rods in the range of 19.8–30.8 nm with the lowest band gap energy (Eg) of 3.15 eV obtained under conditions of a 4:1 ratio and calcined at 400°C. Considering nanostructural characteristics, the ZnO nanostructures in this study would be suitable for application as a semiconductor oxide layer in a dye sensitized solar cell.