Triplet-excited dye molecules (eosine and methylene blue) quenching by H2O2 in aqueous solutions

• Published in: Journal of photochemistry and photobiology. A, Chemistry. Vol. 116; no. 1; pp. 57 - 62
• Main Authors: Gak, V.Yu, Nadtochenko, V.A., Kiwi, J.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 30-06-1998; Elsevier Science
• Subjects: Chemistry; Dye decolorization; Dye oxidation; Eosine; Exact sciences and technology; General and physical chemistry; Hydrogen peroxide; Methylene Blue; Photochemistry; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Yield radical-formation; Methylene Blue; Yield radical-formation; Hydrogen peroxide; Eosine; Dye oxidation; Dye decolorization; Discoloration; Oxidation reduction; Extinction; Photochemical reaction; Experimental study; Methylene blue; Thiazine dye; Acid base balance; Triplet state; Visible radiation; Kinetic parameter; Aqueous solution; Rate constant; Xanthene dye; Excited state
• ISSN: 1010-6030; 1873-2666
• DOI: 10.1016/S1010-6030(98)00230-5

The quenching of the triplet-excited dyes eosine and methylene blue (MB) by H2O2 has been studied by laser and steady-state photolysis. The quenching rate constant of the eosine triplet is kq = 2.4 ± 0.3 × 105 (M s)−1 and rate constant of MB quenching with H2O2 was found to be kq = 6.5 ± 0.5 × 105 (M s)−1. The decolorization of both dyes is accelerated upon H2O2 addition under steady-state photolysis and the redox reaction mechanism is suggested. The quantum yield for ion-radicals formation obtained were: for eosine 0.01 ± 0.005 and 0.03 ± 0.01 for MB. This latter observation provides the evidence for stability of these dyes under light irradiation in the presence of H2O2.