The Controlled Growth of Silica Shell from Barium Titanate and Silver Nanoparticles Cores via Sol-Gel Reaction

Energy harvesting and conversion devices have made a progress by implementing a nanocomposite approach which requires compatibility between nanoparticles and a host matrix. Various reaction conditions for the formation of silica coated silver and barium titanate (BaTiO₃) core-shell nanoparticles using a modified Stöber process were investigated. The sol-gel reaction has been utilized to coat the surface of commercially available barium titanate and silver nanoparticles, synthesized using well-known citrate method. This coating inhibits the aggregation of particles and provides compatible interactions between the host polymer matrix and the nanoparticles. The silica coating process is initiated by hydrolysis and condensation of tetraethyl orthosilicate (TEOS). The characterizations of the silica core-shell particles included: Ultraviolet-Visible spectroscopy for examining aggregation among core-shell particles, Infrared spectroscopy for detecting silica formation, Scanning Electron Microscope and Transmission Electron Microscope for determining morphology and shell thickness, and zeta-potential and Dynamic Light Scattering for evaluating the stability of nanoparticles suspensions. The various pretreatments of barium titanate were completed before sol-gel reaction to maximize the stability of the nanoparticles dispersion. The barium titanate and silver nanoparticles have been successfully coated with silica. The silica shell thickness was controlled by varying the concentration of TEOS and the reaction time. Further functionalization of the silica coated nanoparticles using functional silanes will be investigated in the future.