Controllable Fabrication of Ag Nanoparticles-Coated Silica Core-Shell Microspheres and Its Optical Properties

This paper described a one-step shell growth and extraordinarily facile method for the preparation of Ag nanoparticles-coated silica core-shell microspheres. The Ag nanoparticles could deposit on the silica microspheres to form continuous and compact shell layers at a balanced amount of polyvinyl pyrrolidone after the surface modification of the silica microspheres by (3-Mercaptopropyl) trimethoxysilane. The strong interactions between the thiol groups and Ag nanoparticles make it difficult to peel off the Ag shell from the core microspheres, obtaining extremely stable and homogeneous Ag nanoparticles-coated silica core-shell microspheres. Besides, the coating effect was controlled by varying the content of coupling agent, the type and amount of stabilizing agent, the quantity of silica microspheres as well as the mixing time between silica and silver ammonia solution. In addition, these Ag nanoparticles-coated silica core-shell microspheres were characterized using laser particle size analyzer (LPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical properties of the composite microspheres were observed by UV-vis spectroscopy.