Nanostructures constituted by unusually small silica nanoparticles modified with metal oxides as support for ultra-small gold nanoparticles

Mesoporous silica composed by small nanoparticles has been synthesized by a modified neutral S⁰I⁰ templating route method (S⁰, neutral primary amine surfactant; I⁰, neutral inorganic precursor). Decreasing the polarity of the medium and tuning the composition of the S⁰I⁰ pair allow the formation of silica nanoparticles that are agglomerated into silica fractal or sponge-like structures. Those nanoparticles conform the building blocks of the neutral S⁰I⁰ method. In this work for the first time they are observed isolated by HRTEM. On the other hand, the addition of metal oxides triggers the formation of aggregates containing unusually small silica nanoparticles, i.e. smaller building blocks that in bare silica, in the range of 2-4nm. Further, through the impregnation of a gold precursor post-synthesis, ultra small gold nanoparticles (1nm) were embedded in the final silica nanostructures upon calcination of the organic precursors. FTIR and UV-vis spectroscopies, TEM and SEM, XRD and N₂ absorption were used to characterize the resultant materials.