Multi-Step Coating of Monodisperse Silica Spheres by Titania Nanoparticles Base on Electrostatic Attraction Strategy

TiO2-SiO2 core-shell particles with monodisperse silica core and nanostructured titania shell were synthesized by a multi-step coating process. The monodisperse silica spheres were prepared by Stöber method and titania shell obtained from a colloidal sol prepared by a hydrolysis– condensation reaction. The titania sol was deposited on monodisperse silica spheres by a multi-step coating method based on electrostatic attraction. Characterization was performed by DLS, SEM, DTA-TG, FT-IR and XRD. Also, the photoactivity of the core-shell particles was evaluated using methyl orange degradation by UV–visible spectrophotometer. The mean particle size of the colloidal titania sol was determined about 20 nm. The particle size of TiO2-SiO2 core-shell was about 500 nm. The deposit of titania nanoparticles on silica spheres was caused to delay anatase-rutile transformation. The core-shell particles calcined at 650°C showed a higher photocatalytic activity than that of pure titania.