Papers by Author: S. Castillo

Abstract: Nanocrystalline TiO2 powders were prepared by the sol-gel method and evaluated in the NO photocatalytic oxidation. Samples annealed at 200 and 500°C (TiO2-P-200, TiO2-P-500) were characterized by nitrogen adsorption, XRD-Rietveld refinements, TEM, FTIR and UV-vis spectroscopies. The photocatalytic test of the sol-gel TiO2 samples was carried out in an insulated chamber with 10 ppm of NO, using a 365-nm UV light lamp; the test results were compared with those obtained with a commercial catalyst (P25). Improved photoactivity (89 % of NO oxidized in 60 min) was obtained with the TiO2-P-200 solid which showed high surface area, small crystallite size, higher amount of OH and highly abundant brookite phase (37.2 %) coexisting with the anatase phase (62.8 %). The photo-oxidation activity of the sol-gel catalyst annealed at 500 °C (TiO2-P-500) showed changes in its textural and morphologic properties and therefore, less photoactivity. Sol-gel photocatalysts could be a good option for abating pollution in both indoor and outdoor environments at room temperature.

Abstract: We report the findings concerning the preparation and characterization of Au nanoparticles deposited on sol-gel derived TiO2, TiO2-Al2O3 and TiO2-In2O3 semiconductors. The gold nanoparticles were obtained by the deposition-precipitation method using urea. The mean particle size was determined by HAADF-STEM. The gold nanoparticles ranged form 2.4 to 4.4 nm, and the smallest corresponding to the TiO2-Al2O3 support was 2.4 nm. The effect of support on the growth of the gold nanoparticles was analyzed by HRTEM. The gold nanoparticles showed different shapes depending on the semiconductor supports. Truncated cuboctahedral gold nanoparticles were identified and analyzed.