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An aqueous sol-gel process, previously developed for producing undoped and Cu 2+ , Ni 2+ , Zn 2+ or Pb 2+ doped TiO 2 photocatalystswith remarkably high photocatalytic activity without requiring any calcination step, has been adapted to produce Fe 3+ , Cr 3+ , La 3+ or Eu 3+ singledoped TiO 2 photocatalysts as well as La 3+-Fe 3+ and Eu 3+-Fe 3+ co-doped TiO 2 catalysts. The physicochemical properties of the obtained catalysts have been characterized using a suite of complementary techniques, including ICP-AES, XRD, UV-Vis spectroscopy, nitrogen adsorption-desorption and Fe-57 Mössbauer. The active crystalline phase is obtained without requiring any calcination step and all the different catalysts are composed of nanocrystallites of anatase with a size of 6-7 nm and a high specific surface area varying from 181 to 298 m² g-1. In this study, the effect of the NO 3 :Ti(IV) mole ratio used to induce the peptisation reaction during the synthesis has been studied and the results revealed that this ratio can influence significantly the textural properties of the resulting catalyst. A screening of the photocatalytic activity of the undoped and Fe 3+ , Cr 3+ , La 3+ or Eu 3+ singledoped and co-doped photocatalysts has been performed by evaluating the degradation of 4nitrophenol under UV-Visible light (330 nm <λ< 800 nm). This study suggests that the photocatalytic activity is significantly influenced by the dopant nature and content with an optimal dopant content being observed in the case of Fe 3+ or La 3+ single-doped as well as in the case of La 3+-Fe 3+ and Eu 3+-Fe 3+ co-doped catalysts. In the case of Cr 3+ single-doped catalysts, a detrimental effect of the dopant on the photocatalytic degradation of 4-nitrophenol has been observed while no significant influence of the dopant has been detected in the case

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TiO 2 thin films have been produced by a dip-coating process using a non-aqueous sol-gel method. This study investigated the influence of the operating variables such as nature of the substrate, sol concentration, withdrawing speed of the dip-coater and number of layers on the physico-chemical properties of the films using XRD, GIXRD, UV-Vis spectroscopy, profilometry, spectroscopic ellipsometry and SEM. Photocatalytic activity of the films was * Corresponding author. The performances of the catalysts were compared through the reaction rate constants determined using an apparent first-order kinetic model adjusted on the experimental data.This study showed that the photocatalytic activity and the reaction rate constant depend on the film thickness through the synthesis and dipping variable, with an optimum thickness of 80 nm being observed. An optimized transparent film exhibiting a high adhesion, a well crystallized TiO 2 -anatase phase, a good photocatalytic activity and a reaction rate constant k equal to 0.126 h -1 was obtained using a simple process. The specific photocatalytic activity of this film was higher to the one measured for TiO 2 powders in previous works.

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