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.