Deposition of silver nanoparticles on silica spheres and rods

Spherical and rod-like silica particles were used as cores to deposit shells of silver nanoparticles. Prior silver deposition the siliceous cores were modified with 3-aminopropyltrimetoxysilane to facilitate Ag deposition on the surface of silica particles. The process of Ag deposition was carried out in two consecutive steps: first, silver nanoparticles were deposited on the silica cores from silver nitrate solution in the presence of ammonia and Sn2+ ions. Next, further deposition of silver was achieved by reducing silver cations with formaldehyde. This process led to the formation of a densely packed silver layer that consisted of non-uniform silver nanoparticles (size from several to about 100 nm), on the surface of spherical and rod-like siliceous cores.