Fabrication and characterization of silver core and porous silica shell nanocomposite particles

The nanocomposite particles of silver core and silica shell have been successfully prepared. Silver colloids are synthesized using polymer polyvinylpyrrolidone (PVP) as protecting agent and the silica shell is then coated by means of the Stöber process to fabricate Ag@SiO2 core shell particles. The shell thickness can be easily controlled by the amount of tetraethyl orthosilicate (TEOS). TEM results indicate that the silica shell uniformly encapsulates the silver core particles. During the silica growth, PVP molecules will be trapped and dispersed in the silica shell. As a result, porous silica shell structure is obtained after burning off the PVP molecules and a positive correlation exists between the specific surface area of core shell particles and PVP quantity in the original silver colloids. The silica shell, even at a thickness of 25 nm, can maintain the original shape of Ag@SiO2 particles up to 1000 °C, and prohibit silver from sintering effects.