Preparation and self-assembly of uniform TiO2/SiO2 composite submicrospheres

Monodisperse spheres of silica were uniformly coated with titania through the hydrolysis of titanium alkoxide in order to increase the refractive index of complex submicrospheres and keep their monodispersity as well as their surface morphology. On the basis of the hydrolysis of tetrabutyl orthotitanate (TBOT), a continuous-feeding procedure was used to fabricate 10-nm titania coatings on monodisperse colloidal silica submicrospheres of diameter 200 nm. The TiO2/SiO2 composite spheres were assembled to achieve structures with three-dimensional order by gravity sedimentation and vertical deposition. The complex sphere composition, quality, and morphology were characterized by different techniques.