Double modifications of TiO2 by doping with WO3 and by dispersing on a SiO2 support were made by the one-pot sol-gel method. Doping with W shifts the TiO2 band gap energy from 3.2 eV to around 3.06 eV. The surface area of the supported W-TiO2/SiO2 material was significantly increased, by approximately 3 times, in comparison to the bare TiO2. The photocatalytic activities of the catalysts were evaluated in the degradation reaction of p-nitrophenol in aqueous solution and basic medium. After 240 min of photodegradation, more than approximately 99% p-nitrophenol could be mineralized with the most active W-TiO2/SiO2 catalyst. Under UV irradiation, p-nitrophenol was initially photodegraded into hydroquinone and benzosemiquinone intermediates, which were further degraded into smaller fragments such as organic carboxylic acids and finally completely mineralized. A proposed photoreaction mechanism was presented based on the key roles of the surface hydroxyl species and superoxide radicals such as O2- and ⋅OH, together with W6+/W5+ couples and e-/h+ pairs in the catalysts in the p-nitrophenol photodegradation. The one-pot sol-gel synthesis method was proven to be effective to obtain W-TiO2/SiO2 catalyst with large surface area and high photocatalytic activity, and it can be also used for the preparation of other heterogeneous catalysts.

A series of Ag 0 nanoparticle materials supported in SiO 2 were synthesized by the sol-gel method, with contents of 2, 5 and 10% w/w. The fresh samples were calcinated and reduced with H 2 at 500 °C in order to obtain Ag 0 . The materials obtained were studied by X-ray diffraction, N 2 physisorption, UV-vis spectroscopy, electronic transmission microscopy and EDS (energy dispersive spectrometer). The antibacterial activity was observed in the deactivation of E. coli in its liquid phase, using the plate count method to identify viable CFU (colony forming units). The results show that the materials containing Ag nanoparticles dispersed in SiO 2 increase their bactericidal efficiency on the increase of the content and size of Ag nanoparticles.

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