Novel method to fabricate SiO2/Ag composite spheres and their catalytic, surface-enhanced Raman scattering properties

This paper presents a novel method for the fabrication of SiO2/Ag composite spheres with the aid of the reducing and stabilizing function of polyvinylpyrrolidone (PVP). In this approach, [Ag(NH3)(2)](+) ions were first adsorbed on the surfaces of silica spheres via electrostatic attraction between the silanol groups and ions; these [Ag(NH3)(2)](+) ions adsorbed on silica spheres were then reduced and protected by PVP to obtain SiO2/Ag composite spheres. Neither additional reducing agent nor core surface modification was needed; the particle size and the coverage degree of silver nanoparticles on the silica spheres could be easily tuned by altering the concentration of the precursor-[Ag(NH3)(2)](+) ions. UV-visible spectrometer analysis showed these composite spheres had very good catalytic property; Raman spectrometer measurement showed that these composite spheres exhibited excellent surface-enhanced Raman scattering (SERS) performance.