Monitoring the Formation and Decay of Singlet Molecular Oxygen in TiO2 Photocatalytic Systems and the Reaction with Organic Molecules

Daimon, Toshihiro; Hirakawa, Tsutomu; Nosaka, Yoshio

doi:10.5796/electrochemistry.76.136

Cited by 14 publications

(6 citation statements)

References 16 publications

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“…The irradiation of titanium dioxide nanoparticles in the presence of molecular oxygen results in the generation of singlet oxygen, but the specific mechanism of 1 O 2 formation is not straightforward and alternative reaction pathways have been suggested [88,89,90]. The direct detection of 1 O 2 is based on the phosphorescence measurement at 1270 nm corresponding to the radiative transition O 2 ( 1 ∆ g )→O 2 ( 3 Σ g ) [89,91].…”

Section: Resultsmentioning

confidence: 99%

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

2014

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Abstract:The radical intermediates formed upon UVA irradiation of titanium dioxide suspensions in aqueous and non-aqueous environments were investigated applying the EPR spin trapping technique. The results showed that the generation of reactive species and their consecutive reactions are influenced by the solvent properties (e.g., polarity, solubility of molecular oxygen, rate constant for the reaction of hydroxyl radicals with the solvent). The formation of hydroxyl radicals, evidenced as the corresponding spin-adducts, dominated in the irradiated TiO2 aqueous suspensions. The addition of 17 O-enriched water caused changes in the EPR spectra reflecting the interaction of an unpaired electron with the 17 O nucleus. The photoexcitation of TiO2 in non-aqueous solvents (dimethylsulfoxide, acetonitrile, methanol and ethanol) in the presence of 5,5-dimethyl-1-pyrroline N-oxide spin trap displayed a stabilization of the superoxide radical anions generated via electron transfer reaction to molecular oxygen, and various oxygen-and carbon-centered radicals from the solvents were generated. The character and origin of the carbon-centered spin-adducts was confirmed using nitroso spin trapping agents.

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Section: Resultsmentioning

confidence: 99%

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

2014

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“…At this pH, the TiO 2 surface is negatively charged, 18 and electrostatic repulsion orients the negatively charged phenolic moiety of the tyrosine residue and the negatively charged phosphate group at the phosphorylated tyrosine out from the TiO 2 surface, which results in decreased interaction and oxidation of tyrosine residues of the peptides with the holes. It has also been suggested that organic molecules should be adsorbed onto the TiO 2 surface 19 to react with the short-lived singlet oxygen (lifetime 2−3 μs). 20 Hence, hydroxyl radicals obviously play the major role in initiating oxidation reactions of the tyrosine residue of the studied peptides.…”

Section: •−mentioning

confidence: 99%

Oxidation of Tyrosine-Phosphopeptides by Titanium Dioxide Photocatalysis

et al. 2016

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Protein phosphorylation has a key role in cell regulation. Oxidation of proteins, in turn, is related to many diseases and to aging, but the effects of phosphorylation on the oxidation of proteins and peptides have been rarely studied. The aim of this study was to examine the mechanistic effect of phosphorylation on peptide oxidation induced by titanium dioxide photocatalysis. The effect of phosphorylation was compared between nonphosphorylated and tyrosine phosphorylated peptides using electrospray tandem mass spectrometry. We observed that tyrosine was the most preferentially oxidized amino acid, but the oxidation reaction was significantly inhibited by its phosphorylation. The study also shows that titanium dioxide photocatalysis provides a fast and easy method to study oxidation reactions of biomolecules, such as peptides.

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“…The detection of singlet oxygen phosphorescence in the near infrared (NIR) is the most straightforward one. Below we will consider the previous results − of the application of this technique to the study of singlet oxygen generation with the use of TiO 2 as a sensitizer.…”

Section: Introductionmentioning

confidence: 99%

Singlet Oxygen ¹O₂ in Photocatalysis on TiO₂. Where Does It Come from?

et al. 2019

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Features of the near-infrared phosphorescence of singlet oxygen 1 O 2 photosensitized by TiO 2 in solutions have been investigated. The short-lived phosphorescence of 1 O 2 with spectral maximum at approximately 1300 nm is observed to follow excitation by pulsed laser radiation at 355 nm of TiO 2 suspended in CCl 4 and water H 2 O. The shorter lifetime and spectral shift of this phosphorescence, as compared with phosphorescence of 1 O 2 sensitized by phenalenone in these solvents, are attributed to the adsorbed state of emitting singlet oxygen. The observed laser pulse energy dependence indicates the two-photon and three-photon nature of this phosphorescence initiation in CCl 4 and H 2 O, respectively. The formation of 1 O 2 in CCl 4 is assumed to be provided by the sequence of one-photon excitation of TiO 2 , giving rise to superoxide anion O 2 − and one-photon photodetachment of electron from O 2 − . The photodetachment of electron from O 2 − in water H 2 O is a two-photon process because of higher solvation energy of superoxide anion in water. The processes that govern the rise and decay of singlet oxygen phosphorescence sensitized by TiO 2 are discussed. The factors affecting the yield of singlet oxygen provided by electron photodetachment are also considered.

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Monitoring the Formation and Decay of Singlet Molecular Oxygen in TiO2 Photocatalytic Systems and the Reaction with Organic Molecules

Cited by 14 publications

References 16 publications

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

Oxidation of Tyrosine-Phosphopeptides by Titanium Dioxide Photocatalysis

Singlet Oxygen ¹O₂ in Photocatalysis on TiO₂. Where Does It Come from?

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Monitoring the Formation and Decay of Singlet Molecular Oxygen in TiO2 Photocatalytic Systems and the Reaction with Organic Molecules

Cited by 14 publications

References 16 publications

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

Radical Intermediates in Photoinduced Reactions on TiO2 (An EPR Spin Trapping Study)

Oxidation of Tyrosine-Phosphopeptides by Titanium Dioxide Photocatalysis

Singlet Oxygen 1O2 in Photocatalysis on TiO2. Where Does It Come from?

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Singlet Oxygen ¹O₂ in Photocatalysis on TiO₂. Where Does It Come from?