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

被引:81
作者
Brezova, V. [1 ]
Dvoranova, D. [1 ]
Stasko, A. [1 ]
机构
[1] Slovak Univ Technol Bratislava, Dept Phys Chem, Fac Chem & Food Technol, SK-81237 Bratislava, Slovakia
关键词
titanium dioxide; EPR spectroscopy; free radicals; hydroxyl radical; spin-trapping technique; TEMPOL; DPPH; ABTS(center dot.);
D O I
10.1163/156856707779238630
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
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), alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN), 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 TWO are efficiently oxidized to the EPR-silent products via radical intermediates. 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(center dot+) or DPPH is gradually eliminated during irradiation, and this system represents a simple technique for the evaluation of TiO2 activity.
引用
收藏
页码:251 / 268
页数:18
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