Record number :
Title of article :
Irradiation of titanium dioxide generates both singlet oxygen and superoxide anion
Author/Authors :
Ryusei Konaka، نويسنده , , Emiko Kasahara، نويسنده , , Walter C. Dunlap، نويسنده , , Yorihiro Yamamoto، نويسنده , , Kuang Chang Chien، نويسنده , , Masayasu Inoue، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 1999
Pages :
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Abstract :
Although photoexcited TiO2 has been known to initiate various chemical reactions, such as the generation of reactive oxygen species, precise mechanism and chemical nature of the generated species remain to be elucidated. The present work demonstrates the generation of singlet oxygen by irradiated TiO2 in ethanol as measured by ESR spectroscopy using 2,2,6,6-tetramethyl-4-piperidone (4-oxo-TMP) as a 1O2-sensitive trapping agent. Under identical conditions, the superoxide ion was also detected by spin trapping agent 5,5-dimethyl-pyrroline-N-oxide (DMPO). Kinetic analysis in the presence of both 4-oxo-TMP and DMPO revealed that singlet oxygen is produced directly at the irradiated TiO2 surface but not by a successive reaction involving superoxide anion. The basis for this view is the fact that DMPO added in the mixture increased the signals responsible for 4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy (4-oxo-TEMPO), a reaction product of 4-oxo-TMP and 1O2. The detailed mechanism for the generation of 1O2 and superoxide ion by irradiated TiO2 and reactions between these species and DMPO are discussed.
Keywords :
Titanium dioxide , Singlet oxygen , superoxide anion , ESR , spin trapping , Photodynamic reaction , free radicals
Journal title :
Free Radical Biology and Medicine
Link To Document :