Control of shell thickness in silica-coating of Agl nanoparticles

Silica-coating of Agl nanoparticles with a Stober method was carried out to find out reaction conditions for control of the shell thickness. The Agl nanoparticles were prepared from AgClO4 and KI with the use of 3-mercaptopropyltrimethoxysilane (MPS) as a silane coupling agent and dimethylamine (DMA) catalyst for alkoxide hydrolysis. The silica-coating was performed at 4.5 x 10(-6)-4.5x10(-5) M MPS, 11-20 M water, 0.002-0.1 M DMA and 0.005-0.04 M tetraethylorthosilicate at Agl concentrations of 0.1-1 mM. Consequently, Agl-silica core-shell particles could be prepared with the use of 4.5 x 10(-5) M MPS, 20 M water, 0.01 M DMA and 1 mM Agl. Silica shell thickness could be varied from 15 to 28 nm with an increase in the TEOS concentration from 0.005 to 0.04 M.