Surface and interaction effects of capping ligands (ammonia, methanol, methylamine and pyridine) influence the properties of semiconductor nanoclusters (NCs), which help to achieve the desired applications. The density functional theory (DFT) and time dependent density functional theory (TD-DFT) methods have been used to study the electronic properties of Zinc Oxide (ZnO) nanoclusters. The partial density of states (PDOS), HOMO-LUMO (E-g) gap, electrostatic potential map (ESP) and the optical absorption and emission spectra have been calculated and used for the opto electronic studies. Significant differences were observed in the electronic structure of passivated (ZnO)(6) NC because of the passivation of four different ligands with the NCs. We found that the pyridine (-C5H5N) passivated NC is the most stable, followed by ammonia (-NH3), methylamine (-MeNH2), and methanol (-MeOH). The partial density of states show that the pyridine (-C5H5N) passivated (ZnO)(6) nanoclusters exhibit wider band gap than the other NCs. The study of HOMO-LUMO gap and excitation spectra show that there is a blue shift in the absorption spectra of the NCs. The electrostatic potential map around the passivated NCs are plotted and the results are found that methanol (-MeOH) capped NC has weak electronegativity than that of the other NCs. This is due to electronic and nuclear charges of different arrangement on the surface structure of the passivated (ZnO)(6) NCs. (C) 2016 Published by Elsevier B.V.