(596f) First Imprinting of Silica with a Nanoparticle Template

Organically-functionalized silica is widely used in binding and catalysis for a diverse portfolio of applications. Here we demonstrate the imprinting of bulk silica using a nanoparticle template, which consists of an organically-capped gold nanoparticle and organizes thiol groups on its external periphery. The resulting nanometer-size confined thiol functional groups are synthesized within a convergent shell of organization within porous silica. Our procedure relies on treatmemt of existing 5-nm gold nanoparticles with mercaptopropyltriethoxysilane (MPTES). The resulting postsynthetically modified particles are then incorporated into bulk a silica network via sol-gel hydrolysis/condensation using a biphasic mixture consisting of toluene and water. With catalytic amounts of hydrochloric acid, the resulting silica containing gold nanoparticles (Au@SiO₂) is synthesized to have a uniform porous structure, and gold is subsequently etched via diffusion of cyanide through the pores. The gold etching process does not significantly alter the porous silicate structure. With selective removal of gold, densely-packed thiol groups from MPTES ligand remain on the confined surface of porous silica, which is confirmed via steady-state fluorescence of pyrene fluoroprobe molecules chemisorbed on the silica surface.