STUDY OF OPTICAL ENERGY GAP AND QUANTUM CONFINMENT EFFECTS IN ZINC OXIDE NANOPARTICLES AND NANORODS

Abstract

ZnO sol-gel nanoparticles (NPs) and nanorods (NRs) were prepared by simple chemical method. The resulting NPs and NRs have been characterized by X-Ray Diffraction, TEM, UV-Vis absorption and steady-state photoluminescence (PL) spectroscopy.(XRD) results showed that all samples were single phase wurtzite structure and broadening peaks for ZnO nanoparticles as compared to NRs. The morphology of the nanostructures was observed in transmission emission microscope. The NPs have average diameter ~ 4 nm and the NRs have ~ 18 nm diameter and ~ 100 nm length. The band gap was calculated from the UV-Visible spectrum and found to be 3.39 eV for NPs and 3.2 eV for NRs. This variation of optical energy gap is due to quantum confinement effect when is the material changed from nanoparticles to nanorods. However, the measured NPs and NRs diameters indicate that the charge carriers are located in a strong and weak confinement regime, respectively.The PL reveals that the ultraviolet emission intensity of ZnO nanoparticles decreases from 396 to 367 nm and shifts towards the blue region by reducing the size as compared to nanorods which is consistent with UV-visible absorption