Indirect fabrication of Ag nanoparticle-immobilized hollow silica composite particles and their catalysis

A simple and effective method is proposed to prepare Ag nanoparticle-immobilized hollow silica particles (SiO 2 HP/AgNP composite particles). Ag 2 O nanoparticles are first immobilized on hollow silica particles (SiO 2 HP) by in situ thermolysis of AgNO 3 to get SiO 2 HP/Ag 2 ONP composite particles. Then, the Ag 2 ONPs immobilized on SiO 2 HP are translated to AgNPs by chemical or thermal reduction to obtain SiO 2 HP/AgNP composite particles. The resultant AgNPs have ultrafine nano-size and uniform and dense distribution, which benefits from the slow and moderate reaction in the formation of Ag 2 ONPs. The influencing factors including the surface property of SiO 2 HP, mass proportion of silver salt to silica, and reaction temperature have been studied. The composite particles exhibit excellent catalytic efficiency and repeatability in 4-nitrophenol reduction. Moreover, the catalytic activity can be further enhanced by adding a trace amount of NH 3 into the system, which has obvious synergies for catalysis with AgNPs.