Elaboration et caractérisation des nano-cristaux à base de TiO2.

Abstract

The aim of this thesis is to study the structural, optical and photoelectrochemical properties of porous titanium dioxide thin (PTiO2) films decorated with silver nanoparticles (Ag NPs). TiO2 films were prepared by sol-gel dip-coating technique and the porous TiO2 films (PTiO2) were elaborated by adding polyethylene glycol (PEG) to the starting solution. Ag NPs were deposited on PTiO2 films by photodeposition technique with different UV irradiation time (t UV). The study was split into two parts. The first was devoted to the optimization of the elaboration conditions of TiO2 films by sol-gel dip-coating technique. In this part, the effect of thickness and annealing temperature on structural and optical properties of titanium dioxide thin films was studied. The second part deals with the effect of UV irradiation time (t UV), used for the deposition of Ag NPs, on structural, optical and photoelectrochemical (PEC) properties of silver loaded porous TiO2 films (Ag/PTiO2). Several analysis techniques have been used to characterize our samples. Structural analysis includes X-ray diffraction, Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Optical study was based on UV-Visible spectrometry and cyclic voltammetry was used to investigate photoelectrochemical properties of silver loaded PTiO2 films in dark and under simulated solar light. It was found that PTiO2 films present a higher photoelectrochemical response compared with TiO2 film. Ag loaded PTiO2 films exhibit an enhancement in the visible light absorption due to the LSPR effect. Ag/PTiO2 films present a higher PEC activity compared with bare PTiO2 film. The highest PEC response was obtained for the sample prepared with 15 minutes of UV irradiation time. It was found that longer UV illumination lead to a decrease in PEC activity. The photocurrent values of the sol-gel prepared Ag/PTiO2 films are comparable to those obtained for Ag NPs loaded TiO2 nanotubes elaborated with the relatively complex metallic Ti anodization technique.