Preparation of Raspberry-Like Silica-Titania Hybrid Particles with Photocatalytic Activity by Catalytic Templating Core-Shell Particles

Raspberry-like silica-titania composite particles (SiO2 @ TiO2) were prepared by catalytic hydrolysis and subsequent polycondensation of tetra-n-butyl titanate (TnBT) in poly[2-(N, N-dimethylamino) ethyl mathacrylate] (PDMAEMA) shell layers grafted on silica core particles, followed by calcination. Core-shell particles composed of a colloidal silica core and a PDMAEMA shell were first synthesized by surface-initiated atom transfer radical polymerization (ATRP) of DMAEMA on SiO2 particles with a diameter of 101 nm. The PDMAEMA-grafted SiO2 particles obtained had a hydrated graft layer 140 nm thick on a SiO2 core. The titania-hybridized silica particles were prepared by simply adding TnBT to water/methanol dispersions of core-shell particles. After calcination, the amorphous titania shell transformed into superficial anatase particles, resulting in raspberry-like SiO2 @ TiO2 particles. These particles were characterized by means of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and UV-vis spectroscopy. The photocatalytic activity of SiO2/TiO2 was examined by photodegradation behavior of methylene blue under UV irradiation.