Simple route to prepare different core–shell structured silica‐based microspheres

Abstract

Different core–shell structured silica–titania (SiO2–TiO2) nanocomposites were successfully synthesised in two successive stages. In the first stage, the core was synthesised by preparing poly[oligo(ethylene glycol)monomethyl ether methacrylate] (POEOMA) on the modified surface of silica nanoparticles (SiO2–POEOMA). In the second stage, the shell was formed by depositing or coating tetrabutyl titanate (TBT) with SiO2-polymer to obtain cauliflower-like, cauliflower–pomegranate-like and pomegranate-like SiO2–POEOMA–TiO2 microspheres; the weight ratio of added SiO2–POEOMA to TBT (1:0.146, 0.293 and 0.439) was then adjusted. Later, the polymer layer was removed to obtain the cauliflower-like, cauliflower–pomegranate-like and pomegranate-like core–shell structured SiO2–TiO2 microspheres (CMs, CPMs and PMs). X-ray diffraction results showed that the TiO2 shell was a pure anatase phase. SiO2–TiO2 microspheres were also characterised by N2 adsorption–desorption; the results showed that a pore structure was found in the porous shell. Extensive porosity was generated in the shell because POEOMA was used as a template and pore-forming agent; the structure of CMs, CPMs and PMs remained almost unchanged. These results also showed that pore volumes and specific surface areas of the final products derived from N2 sorption decreased as the content of TBT increased. PMs with the highest content of TiO2 showed the most efficient photocatalytic activity.