title: Radical intermediates in photoinduced reactions on TiO2 (an EPR spin trapping study).
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.
authors.affiliation: 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.
authors.forename: Dana
authors.initials: D
authors.lastname: Dvoranová
authors.affiliation: 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.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Barbieriková
authors.affiliation: 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. vlasta.brezova@stuba.sk.
authors.forename: Vlasta
authors.initials: V
authors.lastname: Brezová
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D002244:Carbon / Q000737:chemistry; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004583:Electrons; D000431:Ethanol / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D010087:Oxides / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D019097:Spin Trapping / Q000379:methods; D013481:Superoxides / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*
chemical_list: D000097:Acetonitriles; D010087:Oxides; D012997:Solvents; D013481:Superoxides; C009495:titanium dioxide; D017665:Hydroxyl Radical; D000431:Ethanol; D002244:Carbon; D014025:Titanium; D010100:Oxygen; D000432:Methanol; D004121:Dimethyl Sulfoxide; C032159:acetonitrile