Fabrication of surface-enhanced Raman scattering-active ZnO/Ag composite microspheres

We show in this paper how zinc oxide (ZnO)/silver (Ag) composite microspheres can be prepared by the reduction of Ag(NH3)(2+) with the reducing agent formaldehyde in aqueous solution on the surface of ZnO microspheres. During the preparation, Sri 21 was absorbed on the surface of ZnO microspheres for sensitization and activation, and then Ag(NH3)(2+) was reduced to Ag nanoparticles by the reducing agent to obtain ZnO/Ag composite microspheres. SEM and TEM images revealed silver nanoparticles with a diameter ranging from tens to 100 nm. X-Ray photoelectron spectra (XPS), X-ray diffraction (XRD) patterns and UV-vis spectra were used to characterize the structure of the ZnO/Ag composite microspheres. The origin of the surface-enhanced Raman scattering properties was traced to the surface of the ZnO/Ag composite microspheres. The enhancement factor was estimated in detail, and the enhancement mechanism for the SERS effect was also investigated. Copyright (c) 2007 John Wiley & Sons, Ltd.