Titanium dioxide-photocatalysis has been studied extensively over the past few decades as an advanced oxidative process in the destruction of environmental contaminants. The photocatalyst titanium dioxide in conjunction with UV light has proven to be an effective process with various chemical and biological contaminants. Recently in our laboratories, titanium dioxide photocatalysis using sunlight as the source of energy was found to effectively limit the viability of Cladophora, a filamentous, green algal that has been growing uncontrollably in certain areas of the Great Lakes. However, since titanium dioxide is activated mainly by ultraviolet light, its ability to utilize sunlight is limited; the solar spectrum consists of typically 2-5% UV light. Modifications in the structure of the titanium dioxide by incorporation of different atoms extend the utilization of light from the sun into the visible region for the photocatalytic processes. Namely, N-doped TiO2 exhibits absorption in the visible region. We have utilized the synthesis of N-TiO2 published by C.S. Gopinath and co-workers1 that begins with TiCl3. The modified TiO2 exhibits a light yellow tint and shows extended UV-VIS absorption. We have also carried out another synthetic procedure which requires titanium isopropoxide, oxalic acid and urea and leads to an N-doped TiO2 material with a deeper yellow color. The further challenge is to form N-doped TiO2 which will permanently adhere to glass, work which is in progress in our laboratories. We have compared the photocatalytic performances of the various N-doped TiO2 samples with both Degussa P-25 and synthesized colloidal TiO2. An enhancement in the photocatalytic performance of the modified titanium dioxide has been realized using the methylene blue dye and using winter samples of Cladophora, with both UV and visible light.

(1) Sathish, M.; Viswanathan, B.; Viswanath, R. P.; Gopinath, C. S. Chem. Mater. 2005, 17, 6349.