To study NPs and their antimicrobial properties theoretically, the Zn6O6 and Zn6S6 hexagonal clusters were selected as models for the ZnO and ZnS wurtzite systems, which are known to exhibit good agreement between theoretical and experimental results . Thus, the optimised clusters involving no imaginary frequencies were obtained using density functional theory (DFT) at the B3LYP/6-31+G(d,p) level. The electronic structures and spectroscopic properties were determined using time-dependent DFT (TD-DFT) calculations.