Surface synthesis of zinc oxide nanoparticles on silica spheres: Preparation and characterization

A new method for the preparation of SiO2/ZnO composite nanoparticles by the simplified controlled double-jet precipitation technique is described. The transmission electron microscopic and scanning electron microscopic images of SiO2/ZnO show that ZnO is coated on the silica (SiO2) surface as a thin layer or single nanoparticle, dependent on the reactant conditions. The powder X-ray diffraction of the initial zinc oxide-silica powder yields diffraction peaks corresponding to ZnO phase. Energy-dispersive X-ray analysis shows the presence of Zn, O, and Si elements. Infrared spectroscopy illustrates the structural changes that occurred in the siloxane network and surface silanol groups of SiO2 upon the deposition of ZnO. The photoluminescence spectrum of SiO2/ZnO shows two emission peaks centered around 360 and 400 nm, respectively, which is similar to that of ZnO nanoparticles. We propose that the process takes place via formation of ZnO clusters on the silica surface modified by triethanolamine, followed by collision with other ZnO clusters in the solution, resulting in the precipitation of ZnO on the silica surface.