Mechanism of photoluminescence quenching in visible and ultraviolet emissions of ZnO nanowires decorated with gold nanoparticles

Decorating with metal nanoparticles (NPs) is an effective way to tune the photoluminescence (PL) properties of ZnO nanowires (NWs), but the mechanism for this is insufficiently understood. In this study, ZnO NWs with lower work function were synthesized on Si substrates using thermal oxidation. Au NPs were incorporated onto the surface of the ZnO NWs. The PL properties of ZnO NWs decorated with Au NPs of different sizes were systematically investigated. Quenching rather than enhancement of both the near-band-edge and visible emission of ZnO NWs was observed after decoration with Au NPs. Introducing an approximately 2-nm-thick Al2O3 insulating layer between the ZnO NWs and Au NPs caused the quenching phenomenon to disappear. These results suggest that the quenching was caused by electron transfer from ZnO to the Au NPs under UV irradiation and the PL properties of ZnO NWs decorated with Au NPs are also related to the band structure of ZnO.