In-situ synthesis of chemically pure noble metal (Au, Pt, Pd, Ru) nanoparticles was performed via redox reaction under ambient conditions from aqueous noble metal salt solutions on non-porous fumed silica. Nanoparticles of average sizes < 5 and up to 19 nm were obtained. The nanostructured fumed silica with surface modified by triethoxysilane has been proven an effective support for noble metal nanoparticles synthesis. The silicon-hydride groups on the silica surface not only directly reduce noble metal ions from solution, but they also stabilize metal nanoparticles by bonding with the solid matrix. The nanocomposites were studied for the reduction of 2-nitrophenol showing very high activity at room temperature following the order Pd>Au>Ru>Pt.