Room temperature direct space-selective growth of gold nanoparticles inside a silica matrix based on a femtosecond laser irradiation

A one-step procedure without heat-treatment was carried out to yield the space-selective growth of gold nanoparticles inside a transparent silica matrix. A silica porous monolith was prepared via a sol–gel route and then post-doped with an aqueous solution of hydrogen tetrachloroaurate (HAuCl4) as a gold precursor, in the presence of sodium carbonate as an additive. Direct and local precipitation of gold nanoparticles inside the deep volume of the silica matrix was induced by a femtosecond laser irradiation at room temperature. Gold nanoparticles with size of about 50–60 nm were evidenced by absorption spectroscopy and transmission electron microscopy. The additive is assumed to be involved in a photo-electrochemical mechanism including redox reactions, which is necessary to the formation of gold nanoparticles.