Characterization of titanium dioxide photoactivity following the formation of radicals by EPR spectroscopy

Characterization of titanium dioxide photoactivity following the formation of radicals by EPR... In order to find ways to characterize oxygen-saturated aqueous TiO2 suspensions, the formation of photo-induced free radicals was followed by EPR spectroscopy, using as indicators N-oxide and nitrone spin trapping agents, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 3,3,5,5-tetramethyl-1-pyrroline N-oxide (TMPO), α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POB N), 4-(N-methylpyridyl)-N-tert-butylnitrone (MePyBN), as well as semi-stable free radicals, 4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxyl (TEMPOL), cation radical of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), diammonium salt (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH). DMPO and TMPO are efficiently oxidized to the EPR-silent products via radical in termediates. Conversely, the nitrone spin traps (POBN and MePyBN) showed selective formation of hydroxyl radical spin adducts upon continuous irradiation of oxygenated TiO2 suspensions. Their concentrations increased proportionally with the amount of photocatalyst and irradiation time. The EPR spectrum of the semi-stable free radicals TEMPOL, ABTS·+ or DPPH is gradually eliminated during irradiation, and this system represents a simple technique for the evaluation of TiO2 activity. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Research on Chemical Intermediates Springer Journals

Characterization of titanium dioxide photoactivity following the formation of radicals by EPR spectroscopy

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Publisher
Springer Netherlands
Copyright
Copyright © 2007 by Springer
Subject
Chemistry; Catalysis; Physical Chemistry; Inorganic Chemistry
ISSN
0922-6168
eISSN
1568-5675
D.O.I.
10.1163/156856707779238630
Publisher site
See Article on Publisher Site

Abstract

In order to find ways to characterize oxygen-saturated aqueous TiO2 suspensions, the formation of photo-induced free radicals was followed by EPR spectroscopy, using as indicators N-oxide and nitrone spin trapping agents, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 3,3,5,5-tetramethyl-1-pyrroline N-oxide (TMPO), α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POB N), 4-(N-methylpyridyl)-N-tert-butylnitrone (MePyBN), as well as semi-stable free radicals, 4-hydroxy-2,2,6,6-tetramethylpiperidine N-oxyl (TEMPOL), cation radical of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), diammonium salt (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH). DMPO and TMPO are efficiently oxidized to the EPR-silent products via radical in termediates. Conversely, the nitrone spin traps (POBN and MePyBN) showed selective formation of hydroxyl radical spin adducts upon continuous irradiation of oxygenated TiO2 suspensions. Their concentrations increased proportionally with the amount of photocatalyst and irradiation time. The EPR spectrum of the semi-stable free radicals TEMPOL, ABTS·+ or DPPH is gradually eliminated during irradiation, and this system represents a simple technique for the evaluation of TiO2 activity.

Journal

Research on Chemical IntermediatesSpringer Journals

Published: Apr 15, 2009

References

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