TiO2–mesoporous silica nanocomposites: cooperative effect in the photocatalytic degradation of dyes and drugs†
TiO2–SiO2 composites containing 10 wt%, 20 wt%, 30% and 40 wt% of TiO2, obtained by using preformed mesoporous silica nanoparticles (MSNs) and titanium isopropoxide as titanium source, have been investigated in detail using a variety of techniques. All the samples were characterized by N2-physisorption, X-ray powder diffraction (XRPD), diffusive reflective UV-vis spectroscopy (DRUV-vis), X-ray photoelectron spectroscopy (XPS) and imaged using transmission electron microscopy (TEM). The TiO2–MSN composites, that exhibited a spherical morphology, high specific surface areas and titania in the anatase phase, owing to their specific chemical–physical properties were studied as catalysts in the photocatalytic degradation of methylene blue, methyl orange and paracetamol, as examples of polluted wastewaters. The well-defined porous structures of MSNs may offer a special environment for titania nanoparticles, increasing the specific surface area and the thermal stability of the composite, thus modifying the photocatalytic behavior of the materials. The TiO2 loading, the particle size and the surface characteristics were related to the degree of UV absorption and the measured energy band gap of the nanocomposites. A cooperative effect between the two components (TiO2 and SiO2) could be the key factor at the basis of the good photocatalytic performances: nanostructured TiO2 in intimate contact with MSN provides the sites for generation of OH˙ radicals by oxidation of water and the SiO2 skeleton is able to adsorb the molecules of cationic dyes and prevent poisoning of the TiO2 surface.