Synthesis And Photoluminescence Properties Of Au–ZnO Heterogeneous Nanostructures

Zinc oxide(ZnO)is a group II?VI direct band gap inorganic oxide semiconductor.Compared with other materials,ZnO has a wide band gap(3.37 eV),and it has good electrical conductivity,biocompatibility,and thermal stability.Metal–zinc oxide hybrid nanomaterials have attracted more and more attention due to their novel physical and chemical properties.Compared to pure metal or zinc oxide materials,metal–zinc oxide hybrid nanomaterials have different application potential,and may play important roles in the fields of optoelectronic devices,photocatalysis,photovoltaic industries,and medical treatments.Although the preparation process of metal–zinc oxide hybrid nanomaterials is not difficult,there still exist many controversies about their formation mechanisms and luminescence mechanisms.In this paper,we shall study the morphological characteristics and related optical properties of ZnO and Au–ZnO heterogeneous nanocrystals.We have synthesized ZnO nanoparticles and Au nanocrystals with small size and good crystallinity by using the bottom–up chemical synthesis method.By using characterizations of the fluorescence and UV–vis absorption spectra,we study the exication wavelength dependence of the resonance absorption peak of the Au nanocrystals and the intrinsic absorption peak of ZnO nanocrystals.We have successfully syntheiszed the Au–ZnO heterogeneous nanocrystals with shape of hexagonal pyramid by using the two–step synthesis method.By means of the characterizations of transmission electron microscopy and the fluorescence spectroscopy,the morphology and luminescent properties of ZnO nanoparticles are studied.We analyze the reasons of decrease of the intensity of the defect luminescence relative to that of intrisinc luminescence of zinc oxide as well as the red shift of the resonance absorption peak of Au in the hybrid nanostructures.We propose a possible theoretical model and explain the phenomena of weakening of defect luminescence of ZnO and the formation mechanism of the Au–ZnO heterogeneous nanocrystals by using theoretical calculations.