Monodispersed silica-titanyl sulfate microspheres

We report on the synthesis of monodispersed individual silica-titanyl sulfate (SiO2-TS) spheres with the dimensions varying from 350 to 900 nm. An important factor leading to complete and uniform coating Of SiO2 spheres with a ca. 40 nm thick layer of TS is the ratio, phi, between the amount of TS added to the silica dispersion and the total available surface area Of SiO2 spheres. For the size range Of SiO2 particles varying between ca. 300 and 800 nm, the optimum value of phi varied from 0.05 to 0.09 g/cm(2), above which extensive aggregation of composite particles occurred. The encapsulation of SiO2 microspheres, was driven by heterocoagulation between the positively charged TS clusters and the negatively charged SiO2 particles.