Tuning of electronic energy levels of NH3 passivated ZnO nanoclusters: A first principle study

We have investigated the optical structural and electronic properties of NH3 capped (ZnO)(21) and (ZnO)(34) nanoclusters of varying sizes, and their complexes by using density functional theory (DFT. B3LYP functional with LANL2DZ basis set which are implemented in the Gaussian09 package. Structural study of bond length, bond angle and bond distortion increases slightly with increase in the surface passivation. From PDOS there is merely an equivalent contribution to the surface states from ZnO and NH3 molecules except for 3 NH3 capping where contribution of ZnO is very less. Surface of nanoclusters is capped upto five NH3 molecules for both nanoclusters have been examined. The band gap of ZnO clusters decreases with the increase in particle size, illuminating quantum confinement in nanoclusters. The band gap becomes reliable with increase in the surface passivation. Additionally, the uv-vis spectra delivers blue shift of the entire absorption spectra. The amount of spectral displacement from red to blue shift happens due to increase in NH3 . Also the presence of amine group on Zn atom will extensively increases its nucleophilicity.