Metallic particles from complexing microcapsules dispersed in a silica gel

A new process to control the distribution of metal nanoparticles is proposed. It involves the use of complexing microcapsules obtained by interfacial polycondensation. The latter are hollow spheres constituted of a polymer membrane, containing an insoluble active ingredient, such as a polyacrylic acid, which can complex Co2+ ions. These capsules are dispersed in a silica sol followed by thermal treatments and reduction under H2 which results in metallic Co nanoparticles confined in the capsules domains. The particles do not diffuse in the matrix.