The influence of gold nanoparticles on photoluminescence spectra on zinc oxide microspheres

We studied the influence on photoluminescence (PL) spectra of zinc oxide (ZnO) microspheres (MS) via decoration with gold nanoparticles (AuNP). Porous ZnO MSs with various sizes are prepared by hydrothermal method ^[1] . The diameter of MS ranges from 1μm to 4 μm. PL spectra of isolated ZnO MSs pumped with 325 nm laser were measured via a micro-PL setup. Multiple peaks corresponding to whispering gallery modes (WGMs) of various orders with TE and TM polarization were observed in the visible range. Three types of PL emission spectra are found. One has sharp resonant WGM modes similar to those observed for porous ZnO MSs without AuNPs, but with sharper peaks. Another has strong leaky modes with evenly spaced triangle-shape emission peaks. The third also shows a leaky mode pattern but with asymmetric sawtooth like s-lineshapes. Theoretical modeling ^[2] has been performed to simulated the emission pattern of various degrees of AuNP decoration, and the results are compared with experimental data to learn the effect of AuNP decoration on the emission spectra of ZnO MSs. From these studies, we can learn the change of emission spectra of ZnO MSs caused by foreign particles and the technique may find useful application in biosensing.