In situ EPR study of UV irradiated TiO2 suspensions with spin traps

ANYL 148

I-Hsiang Tseng, ihsiang.tseng@nist.gov and Stephanie J. Scierka. National Institute of Standards and Technology, Gaithersburg, MD 20899
Electron paramagnetic resonance (EPR) spectroscopy with a “Spin Trap” technique was applied to monitor photoinduced radicals. The use of 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) produced specific hydroxyl and/or superoxide spin adducts. 3-carboxyproxyl (3CP) and 3-aminoproxyl (3AP) produced decay curves from their initial concentrations over UV-irradiation time. This decay was a result of photogenerated radicals from TiO2 and spin traps. A closer interaction with the spin trap and TiO2 particle resulted in efficient charge transfer and more radicals. The greatest hydroxyl radical concentration was generated on catalytic anatase/rutile (A/R), followed in rank by anatase (A), sol-gel (SG) and nanosize anatase (NA). Superoxide radicals were observed on A and SG suspended in methanol. The trends of the decay rate in 3AP and the generation rate in DMPO-OH seemed related to the photoactivity of TiO2. Surface-treated rutile with silica, alumina or zirconia (SR, AR or AZNR) showed better photostability under UV application.
 

General Papers
7:00 PM-9:00 PM, Sunday, 28 August 2005 Washington DC Convention Center -- Hall A, Poster

Division of Analytical Chemistry

The 230th ACS National Meeting, in Washington, DC, Aug 28-Sept 1, 2005