The influence of photoluminescence (PL) spectra from two same-sized zinc oxide (ZnO) microspheres (MS), made by hydrothermal growth, coupling with each other is studied. It is shown that the difference of the PL spectra between single ZnO MS and coupling ZnO MSs can be observed. Coupled ZnO MSs leads to peak splitting of whispering gallery modes (WGMs) for both TE and TM polarization. The PL spectra were obtained by illuminating coupled ZnO MSs directly by 325 nm laser source via a micro-PL setup. First, we inject the laser into the one of the coupling ZnO MSs with 1.72 μm diameter, the PL spectra has few difference between single ZnO MS because the other MS makes less influence on the spherical resonator. Second, by injecting the laser which covers the coupling ZnO MSs, it’s surprising that the PL spectra shows various splitting peaks in the visible region. The phenomenon tells these two coupling MSs lose their symmetry which exist if they are separated, thus, the angular momentum of one ZnO MS is destroyed by another attached ZnO MS. To sum up, the PL spectra of ZnO MS is sensitive to the surface-decorated particles, which can be applied in biosensing to detect various molecules.
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  . 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  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.