Lethicia Gueneau

Synthesis and characterization of crystalline tin oxide nanoparticles

Monodisperse non-aggregated spheroidal nanoparticles of SnO2 cassiterite are prepared through hydrolysis of tin isopropoxide in the presence of acetylacetone and p-toluenesulfonic acid, followed by ageing at 60 °C. The obtained sols remain stable for several months at 4 °C. The nanoparticles have been characterized in the solid state (xerosol) by powder X-ray diffraction, TEM, FTIR, TGA-DTA, and 119Sn MAS and 13C CP-MAS NMR. The mean size of the cassiterite oxide core is about 1–2 nm. These particles do not aggregate in suspension because their surfaces are protected by an hybrid organic–inorganic layer containing acetylacetonate ligands, acetylacetone, p-toluenesulfonates and water.

Photocatalytic decomposition of fatty stains by TiO2 thin films

Anatase TiO2 nanoparticles have been prepared as aqueous colloidal solutions by a conventional sol-gel process. Thin films have been deposited onto glass substrates by dip-coating and eventually further crystallized by heat-treatment up to 300∘C. The effect of the TiO2 film thickness, porosity and particle size on the reaction kinetics has been studied as well as the starting thickness of the fatty acid layer. The photocatalytic activity of the films has been measured through the decomposition of artificial stains formed by fatty acids deposited onto the TiO2 layer (adipic or stearic acid). The kinetics of stain photodecomposition has been studied in details by in-situ infrared spectroscopy absorption studies. This allows to discuss the role of UV light absorption and the interdiffusion of radicals and oxygen across the interfaces. The mechanism for stain decomposition is shown to be associated to a shrinkage of the solid film at the surface of the porous oxide film after a diffusion of the excited radicals from the oxide.