Enhanced photoluminescence in Ag@SiO2 core-shell nanoparticles coated ZnO nanorods

ZnO nanorods (NRs) of diameter ~50 nm are coated with Ag@SiO2 NPs by the two-step chemical method. The structural and morphological properties of the Ag@SiO2 NPs coated ZnO NRs confirm its structural purity as well as adhesion of Ag@SiO2 NPs onto the NRs׳ surface where thickness of the SiO2 coating has been changed. The photoluminescence (PL) properties of the coated NRs show that the intensity of the near band edge emission peak has been enhanced to as high as 7 times as compared to only ZnO NRs when a ~12 nm thick SiO2 shell exists around Ag core which acts as a spacer layer in between Ag and ZnO. The mechanism behind the enhancement is has been successfully explained by interpreting the PL results with a model which would further help one to understand similar PL enhancement in similar metal-semiconductor systems.