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SiO2 -TiO2 and SiO2-TiO2/CeO2 Multifunctional Nanocomposite Films Deposited by a Hybrid Plasma Methodology

Abstract

The growing demand for multifunctional materials of small dimensions has led to the development of nanostructured films. Among the different existing categories, those based on metal oxide nanoparticles have received growing attention. Specifically, structures composed of TiO2 nanoparticles dispersed in SiO2 matrix, SiO2-TiO2, are widely investigated considering the photocatalytic and bactericidal potential, optical and mechanical properties. In addition to providing mechanical reinforcement, TiO2 particles exhibits catalytic activity under ultraviolet light. Such nanocomposites are studied as alternatives for pollutant degradation, inactivation of biofilms and photogenerated barriers against corrosion. Nevertheless, the drawback still hampering the large diffusion of such nanocomposites rely on the need of ultraviolet light irradiation. To shift of the TiO2 photocatalytic effect to the visible region of the spectrum is one of the challenges for all mentioned applications of SiO2-TiO2 nanocomposites. Furthermore, different methodologies are proposed for preparation of such nanocomposites, but a simplified, economically feasible and ecologically correct methodology is still dependent on future advances. In this context, the proposal of the present project is to develop SiO2-TiO2 or SiO2-TiO2/CeO2 multifunctional nanocomposite films that could act as protective barriers against corrosion of metallic and polymeric surfaces at the same time that they present photocatalytic activity by incidence of ultraviolet or visible light. For this purpose, a hybrid one step plasma methodology based on the simultaneous deposition of hexamethyldisiloxane, HMDSO, by plasma enhanced chemical vapor deposition (PECVD) and of TiO2 (or the TiO2/CeO2 mixture) by Ar plasma sputtering is proposed. The use of TiO2/CeO2 hybrid nanocrystals is proposed as an attempt to make the nanocomposite catalytic under visible light. The effect of the process parameters on the properties of the resulting films and their photocatalytic activity, bactericidal potential and barrier properties will be investigated. Since there are no reports in the literature on the preparation of SiO2/TiO2 and SiO2-TiO2/CeO2 nanocomposites by the proposed technique, neither knowledge about the effect of the process parameters on the film forming mechanisms, the investigation will be conducted as a function of total gas pressure, plasma excitation power, Ar and CeO2 ratios in the mixture and deposition time. Chemical composition, structure, thickness, topography, morphology and surface thermodynamic, optical and barrier properties of the samples will be determined. The photocatalytic and bactericidal potential of coatings will be also assessed. (AU)