AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS-WeP

Paper SS-WeP39
Surface Diffusion of Photogenerated Hydroxyl Radicals as Probed by FTIR

Wednesday, October 27, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: Y. Paz, Technion-IIT, Israel
Authors: Y. Paz, Technion-IIT, Israel
H. Haick, Technion-IIT, Israel
Correspondent: Click to Email
Titanium Dioxide is a well-known photocatalyst for water and air treatment as well as for catalytic production of gases. For many organic materials, destruction of contaminants occurs through an oxidation mechanism, where hydroxyl radicals formed on the surface of the catalyst attack adsorbed compounds. Structures comprised of photoactive titanium dioxide and inert adsorbents may promote the overall performance of the photocatalyst by concentrating molecules, that usually do not adsorb on TiO@sub 2@, at the vicinity of the photocatalyst. Furthermore, one may consider the modification of the inert domains to achieve selective physisorption of contaminants of interest. This selectivity can be achieved by coating the inert areas with chemisorbed organic molecules, tailored for specific physisorption of the contaminants. The growing interest in such combined structures is strongly coupled with the debate over possible surface diffusion of the oxidizing species (namely OH radicals), which might migrate to the inert domains where they might mineralize the organic templates. The destruction of templates of alkyl-trichlorosilane organized organic monolayers, chemisorbed in the vicinity of TiO@sub 2@ domains, is studied. Based on in-situ FTIR measurements, it is shown that OH radicals, formed on the titanium dioxide micro-domains, are capable of inducing the mineralization of the fixed chemisorbed aliphatic chains, within minutes, even when these chains are located as much as 20 microns away from the titanium dioxide domains. These results, measured as a function of domain size and surface temperature, are now being evaluated in order to deduce surface diffusion parameters.