Surfactant-Free In Situ Synthesis of Sub-5nm Silver Nanoparticles Embedded Silica Sub-Microspheres as Highly Efficient and Recyclable Catalysts

A novel surfactant-free in situ synthesis approach of 'naked' small silver nanoparticles (2.63 nm.d) supported by silica sub-microspheres was demonstrated. When this catalyst was used for 4-nitrophenol catalytic reduction, the rate constant k reached 0.42 s(-1) even when the catalyst concentration was low (10 mg.L-1). Meanwhile, the catalysts also maintained their high catalytic efficiency even after 25 repeated reaction cycles. Our approach therefore provided a way to generate 'clean' Ag nanoparticles supported catalyst without any post-treatment, which exhibited outstanding catalytic activity and could potentially extend to the heterogeneous catalysts development based on other noble metals.