Influence of the Percentage of Doped into Matrix on Photocatalysis

The sol-gel process was employed in the preparation of titania-doped spherical nanosilica for application in photocatalysis. To this end, the silica matrix was doped with 1 and 10% titania, and the catalytic activity of the resulting solids in the degradation of rhodamine was tested. The synthesized materials were thermally treated at 120, 400, and 800°C. Differential thermal analysis did not evidence the titania-phase transition from anatase to rutile. Scanning electron microscopy revealed the formation of monodisperse spherical nanoparticles with sizes varying between 400 and 500？nm. The UV-Vis absorption spectra showed that the silica doped with 10% titania promoted 86% rhodamine degradation within 90？minutes, as compared to 40% in the case of the silica containing 1% titania. The silica matrix was demonstrated to affect the titania-phase transformation. 1. Introduction Advances in nanotechnology have enabled production of nanosized silica via the sol-gel process, and this material has been widely employed in scientific research as well as in engineering development. Nowadays, the sol-gel technique is the method that is most commonly employed for the synthesis of silica nanoparticles. This route involves simultaneous hydrolysis and condensation of alkoxides, so that silica nanoparticles with several characteristics can be achieved [1]. The advantages of monodispersed nanometric particles have been demonstrated, and their importance for many industrial applications, for example, as catalysts, pigments, or pharmaceuticals, has been shown [2]. The sol-gel methodology is well known for being an easy and quick preparation method, and two routes can be used, namely, the hydrolytic and nonhydrolytic [3]. The hydrolytic sol-gel process is based on the inorganic polymerization of molecular precursors and involves evolution of a polymer through the sol and consequent formation of a network. The molecular precursor employed in the sol-gel process is essentially an alkoxide, and several combinations can be achieved, depending on the compound that is utilized in the reaction [4, 5]. The nonhydrolytic sol-gel process is based on the condensation reaction between a metallic or semimetallic halide and a metallic or semimetallic alkoxide, thereby generating an oxide [6, 7]. Titanium dioxide exists in two main forms, more specifically anatase and rutile. Countless applications have been described for these different phases, but titanium dioxide is mainly used in catalysis (photocatalysis) [8]. Various literature works have discussed about the photocatalytic efficiency