Facile ‘embedding’ of Au nanocrystals into silica spheres with controllable quantity for improved catalytic reduction of p-nitrophenol

Abstract

Gold nanocrystals (NCs) supported on silica spheres or encapsulated in thin silica shells both have their own merits for catalytic applications. Development of sandwich nanostructures is a good solution to combine their advantages for recycling. Herein, we present a facile route to synthesize SiO₂@Au@r-SiO₂ (‘r-’ means redeposition) nanoparticles (NPs) using organic–inorganic silica spheres as templates. It is interesting to find that a thin silica layer can be spontaneously redeposited during the growth of Au NCs on the templates by partially etching the organic–inorganic silica spheres. The number of Au NCs embedded in the sandwich structures can be facilely controlled by adjusting the amount of HAuCl₄ solution added. The effect of Au particle number on their catalytic activity in these SiO₂@Au@r-SiO₂ NPs has been evaluated by the reduction of p-nitrophenol. The developed SiO₂@Au@r-SiO₂ NPs show controllable activity in the dark and enhanced activity under visible light due to the localized surface plasmon resonance (LSPR) of Au NCs.