Preparation of silica-coated rhodium nanoparticles using water-in-oil microemulsion

Monodispersed silica-coated rhodium nanoparticles were synthesized by using the w/o microemulsion of polyoxyethylene (15) cetyl ether / cyclohexane / water system. By hydrolysis of tetraethyl orthosilicate in the presence of rhodium complex nanoparticles followed by thermal treatment, the silica-coated metallic rhodium nanoparticles were obtained in the microemulsion. In the composite nanoparticles, a metallic rhodium particle with a diameter of 4 nm was located nearly at the center of a spherical silica particle. The thickness of silica layer was 14 nm.