Controlled synthesis of low polydispersity Ag@SiO2 core-shell nanoparticles for use in plasmonic applications

A novel methodology was developed for the synthesis of tuneable silver-silica core-shell nanoparticles (Ag@SiO2). The use of tannic acid and sodium citrate to reduce and stabilize silver atoms allowed the controlled synthesis of silver cores ranging from 26-118 nm in diameter, and silica shells of tuneable thicknesses from 6-51 nm were deposited using a combination of tetraethyl orthosilicate and sodium citrate. Both core size and spacer thickness can be tuned over a wide range of diameters and thicknesses by the simple variation of the reagent stoichiometric ratios, and mg range quantities of highly uniform core-shell nanoparticles can be prepared with excellent repeatability and reproducibility. To ascertain the usefulness of the core-shell nanoparticles for plasmonic enhancement studies, fluorescence measurements were performed on core-shell and coreless nanoparticles coated with a molecular fluorophore.