Plasmon mediated enhancement of visible light emission of Au-ZnO nanocomposites

We report on the enhancement of the visible luminescence of Au-ZnO nanocomposites synthesized via a simple photoreduction method. The attachment of Au nanoparticles on the surface of ZnO nanostructures has been observed using transmission electron microscopy. Raman analysis reveals an increase in disorderness via lattice defect formation due to Au attachment and thus results in the appearance of silent modes of ZnO. The photoluminescence spectra of ZnO is found to be dominated by defect related visible emission, which is enhanced with the inclusion of Au nanoparticles. At room temperature, the green emission for nanocomposites has been found to be enhanced by seven times as compared to the pristine ZnO. Temperature dependent photoluminescence of Au-ZnO nanocomposites has been investigated to elucidate the origin of green luminescence and the enhancement of intensity. The gradual dominance of the green emission is originated from the surface plasmon oscillation of Au followed by the electron capture at the singly ionized oxygen vacancies of ZnO. The observed enhancement of visible light emission of ZnO using Au nanoparticles can establish the platform to fabricate efficient ZnO based visible light emitting devices and display systems.