TiO2-Assisted Photodegradation of Dyes. 9. Photooxidation of a Squarylium Cyanine Dye in Aqueous Dispersions under Visible Light Irradiation
TiO2-Assisted Photodegradation of Dyes. 9. Photooxidation of a Squarylium Cyanine Dye in Aqueous Dispersions under Visible Light Irradiation
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DOI：
10.1021/es980923i
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发表时间：
1999-03
影响因子：
11.4
通讯作者：
Taixing Wu;Tong Lin;Jincai Zhao;H. Hidaka;N. Serpone
中科院分区：
文献类型：
--
作者：
Taixing Wu;Tong Lin;Jincai Zhao;H. Hidaka;N. Serpone
在可见光（λ ≥ 430 nm）照射下，通过紫外维斯、质子核磁共振、电子自旋共振（ESR）和气相色谱-质谱联用（GC-MS）、过氧化物酶和过氧化氢酶存在下的过氧化氢含量测定以及化学需氧量（COD）法研究了TiO 2对方酸菁染料（SQ）的光降解作用。获得了有关TiO 2辅助光降解机理的重要结果。当含有SQ的水性TiO 2分散体被可见光照射时，首先产生的活性氧物种是超氧自由基阴离子，其在甲醇溶剂中稳定，但在水性介质中非常不稳定，并且容易通过H2 O2的形成和随后的还原而转化为·OH自由基。在光降解过程中，H2 O2的量增加;虽然预期，但未检测到有机过氧化物。重要的是，SQ染料中的花青CC双键的断裂主导了整个降解过程，产生1-磺丙基-3，3-二甲基-5-溴吲哚-2-酮，其主要组分是1-磺丙基-3，3-二甲基-5-溴吲哚-2-酮。
The TiO2-assisted photodegradation of a squarylium cyanine dye (SQ) has been examined under visible light irradiation (λ ≥ 430 nm) by UV−vis, proton-NMR, ESR, and GC-MS spectroscopies, by peroxide assays in the presence of peroxidase and catalase enzymes, and by chemical oxygen demand (COD) methods. Significant results were obtained relevant to the 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 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 CC 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 i...