Paper SS-TuP2
Photocatalytic Degradation of Self-Assembled Monolayers Anchored at the Vicinity of Titanium Dioxide Domains, as a Probe for Surface Diffusion
Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D
The presented work demonstrates the ability of self-assembled monolayers to serve as a tool for gaining information on surface diffusion of oxidizing species formed photocatalitically on titanium dioxide. In order to study the photodegradation of molecules located at the vicinity of a titanium dioxide photocatalyst, well-defined structures comprised of alternating micro-stripes of TiO2 and silicon were prepared on silicon wafers. Onto these structures, a cross-linked self-assembled monolayer (SAM) of Octadecyltrichlorosilane (OTS) was chemisorbed. The kinetics of the photodegradation of the anchored SAM on the hybrid structure was then measured in-situ by FTIR under controlled humidity. It was found that the photogenerated oxidizing species, formed on the titanium dioxide well-defined micro-domains, are capable of inducing, within minutes, the mineralization of the aliphatic chains anchored to the inert silicon domains, even when these chains were located as far as 20 microns away from the titanium dioxide micro-zones. In contrast, no remote mineralization could be observed when the same experiments were performed with alkanethiols on gold, in Au/TiO2 hybrid systems. A mechanism, explaining these results and their dependency upon various parameters (diffusion length, temperature, humidity) is presented. The implications of these observations on the design and modeling of porous photocatalysts having "dark" pores are discussed as well.