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Titolo:
TiO2-assisted photodegradation of dyes. 9. Photooxidation of a squarylium cyanine dye in aqueous dispersions under visible light irradiation
Autore:
Wu, TX; Lin, T; Zhao, JC; Hidaka, H; Serpone, N;
Indirizzi:
Chinese Acad Sci, Inst Photog Chem, Beijing 100101, Peoples R China Chinese Acad Sci Beijing Peoples R China 100101 100101, Peoples R China Meisei Univ, Dept Chem, Hino, Tokyo 191, Japan Meisei Univ Hino Tokyo Japan 191 Univ, Dept Chem, Hino, Tokyo 191, Japan Concordia Univ, Dept Chem & Biochem, Montreal, PQ H3G 1M8, Canada Concordia Univ Montreal PQ Canada H3G 1M8 m, Montreal, PQ H3G 1M8, Canada
Titolo Testata:
ENVIRONMENTAL SCIENCE & TECHNOLOGY
fascicolo: 9, volume: 33, anno: 1999,
pagine: 1379 - 1387
SICI:
0013-936X(19990501)33:9<1379:TPOD9P>2.0.ZU;2-Z
Fonte:
ISI
Lingua:
ENG
Soggetto:
COLLOIDAL TIO2 PARTICLES; PHOTOASSISTED DEGRADATION; ENVIRONMENTAL PHOTOCHEMISTRY; SEMICONDUCTOR SURFACES; ELECTRON-TRANSFER; CATIONIC DYES; EXCITED-STATE; ACIDIC MEDIA; RHODAMINE-B; SURFACTANTS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Agriculture,Biology & Environmental Sciences
Engineering, Computing & Technology
Citazioni:
31
Recensione:
Indirizzi per estratti:
Indirizzo: Zhao, JC Chinese Acad Sci, Inst Photog Chem, Beijing 100101, Peoples R China Chinese Acad Sci Beijing Peoples R China 100101 Peoples R China
Citazione:
T.X. Wu et al., "TiO2-assisted photodegradation of dyes. 9. Photooxidation of a squarylium cyanine dye in aqueous dispersions under visible light irradiation", ENV SCI TEC, 33(9), 1999, pp. 1379-1387

Abstract

The TiO2-assisted photodegradation of a squarylium cyanine dye (SQ) has been examined under visible light irradiation (lambda greater than or equal to 430 nm) by UV-vis, proton-NMR, ESR, and GC-MS spectroscopies, by peroxideassays in the presence of peroxidase and catalase enzymes, and by chemicaloxygen demand (COD) methods. Significant results were obtained relevant tothe mechanism(s) of TiO2-assisted photodegradations. The active oxygen species produced first when an aqueous TiO2 dispersion containing SQ is irradiated by visible light is the superoxide radical anion, which is stable in methanol solvent but very unstable in aqueous media, and is readily converted to (OH)-O-. radicals via formation and subsequent reduction of H2O2 The quantity of H2O2 increased during the photodegradation; though expected, no organoperoxides were detected. Of import, cleavage of the cyanine C=C double bond in the SQ dye dominated over the whole degradation process yielding 1-sulfopropyl-3,3-dimethyl-5-bromoindolenium-2-one, the predominant component in the dispersion. This intermediate is not excited by visible light anddegrades no further. A sequence of steps is proposed in the initiation of the TiO2-assisted photochemical transformation.

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Documento generato il 25/09/20 alle ore 00:13:49