Fabrication and photocatalytic activity of Ag-immobilized TiO2-coated SiO2 nanoparticles under visible light

This study details the fabrication of metal-silver nanoparticle-immobilized titania-coated silica nanoparticles for photocatalytic applications under visible light. The immobilization process was performed at four distinct stages. Initially, SiO 2 nanoparticles were synthesized using the Stöber method. Subsequently, the SiO 2 nanoparticles were coated with TiO 2 shells (SiO 2 /TiO 2 ) through a sol-gel process utilizing an alkoxide, followed by annealing to crystallize the shells into anatase TiO 2 . In the third stage, Sn 2+ ions were adsorbed onto the surfaces of SiO 2 /TiO 2 nanoparticles. In the final stage, Ag + ions are introduced, which are reduced and concurrently adsorbed onto the nanoparticle surfaces through the action of Sn 2+ . Comprehensive characterization using transmission electron microscopy, visible spectroscopy, and X-ray photoelectron spectroscopy confirmed the immobilization of Ag nanoparticles on the nanoparticle surface (SiO 2 /TiO 2 /Ag). Reiteration of the Ag immobilization process increased the quantity of metallic Ag nanoparticles on the nanoparticles (SiO 2 /TiO 2 /Ag/Ag). In a comparative analysis involving an equivalent number of particles, the photoactivity of SiO 2 /TiO 2 /Ag/Ag under visible light surpassed those of SiO 2 , Ag-immobilized SiO 2 , SiO 2 /TiO 2 , and P25 (commercially available TiO 2 ). This enhancement in photocatalytic activity can be attributed to the role of metal Ag nanoparticles in electron trap action, facilitation of electron-hole separation, and promotion of the interfacial electron transfer process. • This study was conducted using metal Ag-immobilized TiO 2 -coated SiO 2 nanoparticles. • SiO 2 nanoparticles were coated with TiO 2 shells using a sol-gel method. • The TiO 2 shells crystallized into anatase TiO 2 by annealing at 600°C. • Ag immobilization was performed using a pre-treatment step for metal plating. • High photoactivity of the Ag-immobilized TiO 2 -coated SiO 2 under visible light was confirmed.