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

TiO2-SiO2 core-shell particles include of monodisperse silica core and nanostructured titania shell were synthesized by a multi-step coating process. The monodisperse silica spheres were synthesized by Stöber method and titania shell was obtained of 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 activity of the core-shell particles was evaluated using methyl orange photodegradation 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 much higher photocatalytic activity than pure titania.