Highly ordered superlattice of gold nanoparticles confined in porous silica matrix

Abstract

A new synthesis method for the highly ordered superlattice of 12 nm gold nanoparticles confined in po-rous silica has been developed. The gold nanoparticle superlattice showed a highly ordered FCC symmetry and the unit cell size was controllable by adopting different molecular weights of polyethylene glycols that were an-chored to the surface of gold nanoparticle. The superlattice contained the hierarchical pore structure of meso-pores and micropores, which provides the efficient access of fluids to the gold nanoparticle surface. The synthet-ic method for highly ordered nanoparticle superlattice is applicable to various species of nanoparticles, and that can open a new regime of nanoparticle superlattice. The gold nanoparticle superlattice in porous silica exhibited exceptionally high catalytic activity for CO oxidation in contrast to the known tendency about gold catalysts. The superlattice was also stable enough against the high temperatures and against the catalytic reaction. Currently the mechanism of CO oxidation by the superlattice is also yet to be understood, but the superlattice can be used as a good test bed for studying the mechanism of CO oxidation over AuNP catalysts. The high catalytic activity for CO oxidation over the superlattice is a new example of collective behavior that has not been shown by the individual gold nanoparticles.