Silica-coating of Coinage Metal Nanoparticles

Nanometer-scale coinage metal particles were coated with silica by a modified Stöber method. Silica shell thickness was varied from 30 to 90nm for Au core particles and from 28 to 76nm for Ag core particles. The optical spectra of the silica-coated Au and Ag nanoparticles agreed with predictions by Mie theory. For Cu nanoparticles, silica-coating was also successfully performed with the use of silane coupling agent as a stabilizer.