Cobalt nanoparticles were prepared at room temperature by reducing cobalt sulfate heptahydrate with sodium borohydride using functionalized SBA-15 mesoporous silica as a hard template. It was found that both external and internal fuctionalization of silica walls play a crucial role on the infiltration and reaction of the reagents in the silica framework. Subsequent heat treatment of the impregnated silica at 500 degrees C in air or nitrogen atmospheres leads to growth of crystals of the deposited cobalt and formation of cobalt oxide and cobalt nanoparticles, respectively. Dissolution of the silica template by NaOH resulted in well dispersed Co and Co3O4 nanoparticles ranging in size between 2 and 4 nm. The functionalization of the silica was studied by FTIR, N-2-physisorption, and thermogravimetric techniques and the obtained nanoparticles were characterized by XRD, TEM and EDX analysis. (c) 2012 Elsevier B.V. All rights reserved.