Surfactant-Assisted Sol-Gel Synthesis of TiO2 with Uniform Particle Size Distribution.

TiO2 materials were prepared froma titanium isopropoxide precursor by sol-gel processing in watermedia with or without various templates (polyethylenimine or Pluronic P-123). The photocatalytic efficiency of the samples was found to depend strongly on the use of and type of template added. Titania/Pluronic sols resulted in homogeneous anatase TiO2-rutile with uniform particle size distribution after calcination (400°C). Optical properties of the samples were characterized by UV-Vis spectroscopy and crystalline structures by X-ray diffraction. A surfactant-assisted sol-gel process retarded crystallization of the anatase and rutile titania, which resulted in smaller grain sizes and presumably a larger active surface area. The morphology of the surfaces was obtained by AFM techniques. The highest photobleaching rate was found for samples deposited from the sol with the addition of the Pluronic P-123 surfactant, and it was almost twice as high as that for films deposited from sols with polyethylenimine. 1. Introduction Titania coatings with high specific surface area and with narrow pore size distribution have a big prospect of practical application in such areas as solar energy transformation [1] and photocatalysis [2-7] for water and air clearing and processing, as self-cleaning coatings for windows and tiles [8]. The pore size and specific surface area substantially affect the physical properties of these materials and can play a significant role in their activity. For example, catalytic application demands an adjustable porosity for optimization of rate of reagent diffusion towards adsorption centers and a large surface area for the maximum interaction between the reagent flow and the catalyst surface. Titania-based coatings can be synthesized by various methods, but sol-gel process is the most applied as this method possesses some advantages, such as homogeneity at molecular level, a wide range of a precursor selection, control over microstructure, low demands upon reagent purity, possibility of a fine adjustment of the end product properties, simplicity of process, and low temperature and cost. Synthesis of titania by sol-gel method is usually attained by hydrolysis of titanium alkoxide precursors. Nevertheless, two various approaches can be applied accordingly to process parameters. So far, the most [ABSTRACT FROM AUTHOR]