Yolk-Shell Catalyst of Single Au Nanoparticle Encapsulated within Hollow Mesoporous Silica Microspheres

Synthesis and catalysis of yolk-microspheres containing single Au nanoparticle core and a mesopurous shell of hallow mesoporous silica microspheres (HMSM)are reported. This synthesis employs polystyrene-co-poly(4-vinylpyridne) micorsphereses both template to fabricate the HMSM shell through sol-gel process and scalffold to immobilize the Au nanoparticle. Since the single Au nanoparticle cor is supernatant within the inert HMSM shell, the yolk-shell catalyst has minimum support effect and is a promising model to explore the origin of Au catalysis. Catalyzed reduction of 4-nitorphenol with NaBH4 demonstrates size dependent induction or activation and size dependent activity of the Au nanoparticle of the yolk-shell catalyst.