Preparation and characterization of SiO2/TiO2 core-shell particles with controlled shell thickness

SiO2/TiO2 core-shell particles with controlled shell thickness were prepared by a multistep coating process. The thickness of the titania coating layer was varied from 9 to 57 nm depending on the number of coating steps, from 1 to 5 times. The titania coating resulted in a rough and textured surface of the core-shell particles, increasing the specific surface areas 5–25 times depending on the coating thickness with respect to those of silica particles. FT-IR and XPS results confirmed the existence of Tisingle bondOsingle bondSi chemical bonding at the interface between the titania coating layer and silica particle surface. The apparent surface coverage was estimated using isoelectric point data.