COLL 378 |
| Chuan-yi Wang, Henning Groenzin, and Mary Jane Shultz. Chemistry Department, Tufts University, Pearson Laboratory, 62 Talbot Ave., Medford, MA 02155 |
| Optically transparent TiO2 films are characterized at a molecular level using vibrational sum frequency generation (SFG) spectroscopy. TiO2 films are known to switch between being hydrophobic and hydrophilic upon UV irradiation and to switch back on exposure to ambient conditions. Previously attributed to generation of oxygen vacancies by UV irradiation, we have shown that the switchable wettability is due to an aliphatic hydrocarbon that adsorbs to the surface. UV irradiation oxidizes this hydrocarbon rendering the surface hydrophilic. The nature and evolution of the surface active sites are further studied using methanol as a molecular probe. Both physical and chemical adsorption of methanol on TiO2 is confirmed by changes in the SF-signal with surface temperature (T) and methanol pressure (P). In comparison with molecular methanol methoxy, the chemisorbed product, is more sensitive to surface treatment. Specifically, the aliphatic hydrocarbon poisons the surface for methoxy adsorption. |
|
Vibrational Analyses of Dry and Wet Surfaces
8:30 AM-11:30 AM, Wednesday, March 31, 2004 Marriott -- Grand Ballroom H, Oral
Division of Colloid and Surface Chemistry |