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 st?ber 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.