Spatial and Temporal Electrochemical Control of Singlet Oxygen Production and Decay in Photosensitized Experiments

Ijeri, Vijaykumar S.; Daasbjerg, Kim; Ogilby, Peter R.; Poulsen, Lars

doi:10.1021/la7028577

Cited by 10 publications

(8 citation statements)

References 39 publications

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“…Molecular oxygen may be produced in the processes of singlet oxygen quenching (36) also in argon saturated solutions, e.g. the superoxide radical anion is a very effective quencher of singlet oxygen (54).…”

Section: Resultsmentioning

confidence: 99%

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Barbieriková

Mihalíková

Brezová³

2012

Photochem & Photobiology

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The reactions of sterically hindered amines (SHA) were investigated in acetonitrile solutions and TiO(2) suspensions upon exposure to monochromatic radiation, λ=365 nm, by means of in situ EPR spectroscopy. The formation of singlet oxygen, as one of the possible oxidation agents for SHA, in these systems is affected significantly by solvent used and the experimental conditions. Experiments in homogeneous media evidenced alternative pathways for the SHA oxidation with a variety reactive oxygen species involved. In anhydrous acetonitrile solutions containing KO(2), the SHA oxidation was negligible not only in the dark but also on continuous exposure. However, the presence of water, even at low concentrations, led to the transformation of O(2)(•-) to singlet oxygen and hydrogen peroxide, which served as a source of hydroxyl radicals. These species participated in oxidation of SHA resulting in the generation of nitroxide radicals. To investigate the influence of different competitive reactions of SHA with other ROS formed upon TiO(2) photoexcitation, a series of experiments using different additives (e.g. KO(2), H(2)O(2), NaN(3), dimethylsulfoxide, methanol as organic cosolvents) under air or argon were performed. The detailed analysis of paramagnetic intermediates formed upon the irradiation of the studied systems was accomplished using EPR spin trapping technique.

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Section: Resultsmentioning

confidence: 99%

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Barbieriková

Mihalíková

Brezová³

2012

Photochem & Photobiology

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“…45 However, the 1 O 2accepting level is shifted approximately +1 V with respect to ground-state (triplet) O 2 . 46 On the basis of the electrochemical data in Figure 5, this would place the 1 O 2 accepting level and the Au 25 0/−1 (HOMO) redox peak at nearly identical potentials. As such, and any charge transfer between Au 25 − and 1 O 2 should be reversible, 39 precluding significant 1 O 2 contribution to the irreversible cluster oxidation observed in this study.…”

Section: The Journal Of Physical Chemistry Lettersmentioning

confidence: 98%

Photomediated Oxidation of Atomically Precise Au₂₅(SC₂H₄Ph)₁₈^– Nanoclusters

Kauffman

Alfonso

Matranga

et al. 2012

J. Phys. Chem. Lett.

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The anionic charge of atomically precise Au25(SC2H4Ph)18(-) nanoclusters (abbreviated as Au25(-)) is thought to facilitate the adsorption and activation of molecular species. We used optical spectroscopy, nonaqueous electrochemistry, and density functional theory to study the interaction between Au25(-) and O2. Surprisingly, the oxidation of Au25(-) by O2 was not a spontaneous process. Rather, Au25(-)-O2 charge transfer was found to be a photomediated process dependent on the relative energies of the Au25(-) LUMO and the O2 electron-accepting level. Photomediated charge transfer was not restricted to one particular electron accepting molecule or solvent system, and this phenomenon likely extends to other Au25(-)-adsorbate systems with appropriate electron donor-acceptor energy levels. These findings underscore the significant and sometimes overlooked way that photophysical processes can influence the chemistry of ligand-protected clusters. In a broader sense, the identification of photochemical pathways may help develop new cluster-adsorbate models and expand the range of catalytic reactions available to these materials.

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“…The mean radial diffusion length of O 2 ( 1 Δ g ), l r , can be estimated using the equation l r = (6D 0 τ Δ ) 1/2 , where D 0 is the diffusion coefficient for oxygen in water (2.07 × 10 −9 m 2 s −1 ) 36 and τ Δ is the lifetime of O 2 ( 1 Δ g ). The low value of l r ∼ 200 nm for O 2 ( 1 Δ g ) in H 2 O produced by AE(TPP) or TPPS-AE indicates that the adsorption on the surface or the close contact of target molecules with nanofibers is a fundamental prerequisite for the effective course of photooxidation reactions.…”

Section: Preparation Of the Photoactive Anion-exchange Materialsmentioning

confidence: 99%

Anion exchange nanofiber materials activated by daylight with a dual antibacterial effect

Plíštil

Henke

Kubát

et al. 2014

Photochem Photobiol Sci

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Anion exchange polystyrene nanofiber materials (AE) were prepared by electrospinning followed by two-step functionalization of the nanofiber surface by chlorosulfonic acid and ethylendiamine. The photoactive character of these materials was introduced through adsorption of the tetra-anionic 5,10,15,20-tetrakis-(4-sulfonatophenyl)porphyrin photosensitizer (TPPS-AE) on the nanofiber surface or by encapsulation of the nonpolar 5,10,15,20-tetraphenylporphyrin photosensitizer (AE(TPP)) into the nanofibers. Anion exchange nanofiber materials with porphyrins are characterized by a high ion-exchange capacity, photogeneration of singlet oxygen O2((1)Δg), and singlet oxygen-sensitized delayed fluorescence. Due to the photogeneration of cytotoxic O2((1)Δg), the nanofibers exhibited oxidation of the external substrates in aqueous solution and an efficient antibacterial effect when activated by simulated daylight. Adsorption of both TPPS and I(-) on the surface of AE led to the formation of more efficient I-TPPS-AE materials. Rapid photooxidation of I(-) by O2((1)Δg), and the formation of another cytotoxic species, I3(-), on the surface of the nanofibers were responsible for the increased antibacterial properties of I-TPPS-AE and the prolonged antibacterial effect in the dark.

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Spatial and Temporal Electrochemical Control of Singlet Oxygen Production and Decay in Photosensitized Experiments

Cited by 10 publications

References 39 publications

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Photomediated Oxidation of Atomically Precise Au₂₅(SC₂H₄Ph)₁₈^– Nanoclusters

Anion exchange nanofiber materials activated by daylight with a dual antibacterial effect

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Spatial and Temporal Electrochemical Control of Singlet Oxygen Production and Decay in Photosensitized Experiments

Cited by 10 publications

References 39 publications

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Photoinduced Oxidation of Sterically Hindered Amines in Acetonitrile Solutions and Titania Suspensions (An EPR Study)

Photomediated Oxidation of Atomically Precise Au25(SC2H4Ph)18– Nanoclusters

Anion exchange nanofiber materials activated by daylight with a dual antibacterial effect

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Photomediated Oxidation of Atomically Precise Au₂₅(SC₂H₄Ph)₁₈^– Nanoclusters