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Molecules 2014, 19(11), 17279-17304; doi:10.3390/molecules191117279

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology in Bratislava, Radlinského 9, Bratislava SK-812 37, Slovakia
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Received: 13 August 2014 / Revised: 29 September 2014 / Accepted: 22 October 2014 / Published: 28 October 2014
(This article belongs to the Special Issue Photocatalysis)
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Abstract

The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent). The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol) in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen- and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents. View Full-Text
Keywords: titanium dioxide; hydroxyl radical; reactive oxygen species; EPR spectroscopy; spin trapping technique; sterically hindered amines titanium dioxide; hydroxyl radical; reactive oxygen species; EPR spectroscopy; spin trapping technique; sterically hindered amines
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Dvoranová, D.; Barbieriková, Z.; Brezová, V. Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study). Molecules 2014, 19, 17279-17304.

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