Preparation and photocatalytic activity of fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposite-encapsulated low molecular weight aromatic compounds

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposite-encapsulated low molecular weight aromatic compounds R_F-(VM-SiO₂)_n-R_F/an-TiO₂/Ar-H] were prepared by the sol–gel reactions of the corresponding oligomer in the presence of anatase titanium oxide nanoparticles (an-TiO₂) and the aromatic compounds such as bisphenol A BPA], 1,1′-bi(2-naphthol) BINOL], and fullerene under alkaline conditions. Thermogravimetric analyses measurements show that R_F-(VM-SiO₂)_n-R_F/an-TiO₂ nanocomposite-encapsulated BPA and BINOL, in which the theoretical contents in the composites are 25?～?32 %, were found to give no weight loss corresponding to the contents of these aromatic compounds even after calcination at 800 °C. On the other hand, the corresponding nanocomposite-encapsulated fullerene exhibited weight loss behavior related to the presence of fullerene under similar conditions; however, UV–vis spectra showed the presence of the residual fullerene in the composites even after calcination. An-TiO₂ in these fluorinated nanocomposites can keep its crystalline structure without phase transformation into rutile even after calcination at 1,000 °C, although the parent an-TiO₂ nanoparticles underwent a complete phase transformation into rutile under similar conditions. Notably, R_F-(VM-SiO₂)_n-R_F/an-TiO₂/Ar-H nanocomposites can give a good photocatalytic activity even after calcination at 1,000 °C for the decolorization of methylene blue under UV light irradiation. More interestingly, these fluorinated nanocomposites before and after calcination were found to exhibit a higher photocatalytic activity at the initial UV light irradiation from 1 to 3 min than that of the corresponding R_F-(VM-SiO₂)_n-R_F/an-TiO₂ nanocomposites under similar conditions.