Dye sensitization of a zinc oxide electrode studied by a potential modulation technique

Matsumura, Michio; Mitsuda, Kenro; Tsubomura, Hiroshi

doi:10.1021/j150643a038

Cited by 18 publications

(5 citation statements)

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“…2). This value of k, is of the same magnitude as the bimolecular rate constant for the oxidation of nitroxyl radicals by R~( b p y ) ,~+ (4.9 X lo8 M-I S-I ) (36), but it is three orders of magnitude higher than that for electron transfer from TRP to the oxidized state of rose bengal adsorbed onto ZnO electrodes reported by Matsumara et al who studied the electron transfer from reductants to oxidized dyes using the potential modulation technique (37).…”

Section: Sensitization Of Trp+ By R~(bpy)~+/snomentioning

confidence: 77%

Photooxidation of Tryptophan: O₂(1Δ_g) versus Electron‐Transfer Pathway

Wessels

Foote

Ford

et al. 1997

Photochem & Photobiology

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Tris (2,2'-bipyridyl)ruthenium(II)chloride hexahydrate (Ru[bpy]3(2+)) free in solution and adsorbed onto antimony-doped SnO2 colloidal particles was used as a photosensitizer for a comparison of the O2(1 delta g) and electron-transfer-mediated photooxidation of tryptophan (TRP), respectively. Quenching of excited Ru(bpy)3(2+) by O2(3 sigma g-) in an aerated aqueous solution leads only to the formation of O2(1 delta g) (phi delta = 0.18) and this compound was used as a type II photosensitizer. Excitation of Ru(bpy)3(2+) adsorbed onto Sb/SnO2 results in a fast injection of an electron into the conduction band of the semiconductor and accordingly to the formation of Ru(bpy)3(2+) and was used for the sensitization of the electron-transfer-mediated photooxidation. The Ru(bpy)3(3+) is reduced by TRP with a bimolecular rate constant kQ = 5.9 x 10(8) M-1 s-1, while O2(1 delta g) is quenched by TRP with kt = 7.1 x 10(7) M-1 s-1 (chemical + physical quenching). Relative rate constants for the photooxidation of TRP (kc) via both pathways were determined using fluorescence emission spectroscopy. With Np, the rate of photons absorbed, being constant for both pathways we obtained kc = (372/Np) M-1 s-1 for the O2(1 delta g) pathway and kc > or = (25,013/Np) M-1 s-1 for the electron-transfer pathway, respectively. Thus the photooxidation of Trp is more than two orders of magnitude more efficient when it is initiated by electron transfer than when initiated by O2(1 delta g).

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Section: Sensitization Of Trp+ By R~(bpy)~+/snomentioning

confidence: 77%

Photooxidation of Tryptophan: O₂(1Δ_g) versus Electron‐Transfer Pathway

Wessels

Foote

Ford

et al. 1997

Photochem & Photobiology

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“…Comparison with Previous Studies. Previous studies of the charge recombination dynamics for dye-sensitized TiO 2 differ widely both in the typical time constants for charge recombination and their dependence upon applied bias voltage. − ,,,, While a comprehensive review of these studies is beyond the scope of this paper, two points can be made which are of particular relevance. First, considerable care was taken for the results reported here to minimize the light incident upon the sample.…”

Section: Discussionmentioning

confidence: 99%

Charge Recombination Kinetics in Dye-Sensitized Nanocrystalline Titanium Dioxide Films under Externally Applied Bias

et al. 1998

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The kinetics of charge recombination were determined following low intensity optical excitation of RuII(2,2‘-bipyridyl-4,4‘dicarboxylate)2(NCS)2 sensitized nanocrystalline TiO2 films as a function of externally applied bias voltage V. These kinetics were found to be multiexponential. The median time (t 50%) for charge recombination was found to depend strongly upon bias voltage, reducing from t 50% ∼ 200 ms for V = 0 V versus Ag/AgCl to < 30 ns for V ≤ −500 mV. This reduction in t 50% was found to follow the equation t 50% ∝ exp(qV/1.7k B T). These results are consistent with the charge recombination kinetics being strongly dependent upon the accumulation of electrons in intraband/conduction band states of the TiO2 film. For biases V ≤ −400 mV, the rate of charge recombination was found to exceed the rate of rereduction of the dye cation by an I-/I3- redox couple in solution.

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“…), in which data on the chemisorption and catalytic properties are also presented. 3 The surface area of the powder was approximately 5 m2/g. In the present work, the powder was heated to 900 K under ultrahigh vacuum and leached with ultrahigh-purity 3 N HC1 to remove small amounts of calcium.…”

Section: Methodsmentioning

confidence: 99%

Photoemission studies of physisorbed xenon atoms on ruthenium/copper surfaces

Kim¹,

Sinfelt²,

Eder³

et al. 1987

J. Phys. Chem.

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Studies of Ru-Cu surfaces were made by applying ultraviolet photoelectron spectroscopy (UPS) to xenon physisorbed on the surfaces. Experiments were conducted on samples prepared by depositing copper on the (001) plane, i.e., the basal plane, of a ruthenium single crystal and on the surface of a ruthenium powder as well. When the amount of copper present on the surface was approximately one-third to one-half of a monolayer, the xenon photoemission spectrum obtained with the ruthenium powder differed significantly from that obtained with a well-annealed, smooth (001) surface plane. The copper appears to form islands on the smooth (001) plane, but on the surface of the ruthenium powder it is not present in this form. Consequently, copper deposited on a smooth (001) plane of ruthenium would not seem to be a good model of a ruthenium-copper catalyst. Introduction of defects into the (001) plane prior to copper deposition yields a surface which corresponds more closely to that of typical catalysts. These findings provide a reasonable way of rationalizing differences observed when studies of the effect of copper on the ethane hydrogenolysis activity of a ruthenium single crystal are compared with studies of the influence of copper on hydrogenolysis activity in actual ruthenium-copper catalysts.

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Dye sensitization of a zinc oxide electrode studied by a potential modulation technique

Cited by 18 publications

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Photooxidation of Tryptophan: O₂(1Δ_g) versus Electron‐Transfer Pathway

Photooxidation of Tryptophan: O₂(1Δ_g) versus Electron‐Transfer Pathway

Charge Recombination Kinetics in Dye-Sensitized Nanocrystalline Titanium Dioxide Films under Externally Applied Bias

Photoemission studies of physisorbed xenon atoms on ruthenium/copper surfaces

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Dye sensitization of a zinc oxide electrode studied by a potential modulation technique

Cited by 18 publications

References 0 publications

Photooxidation of Tryptophan: O2(1Δg) versus Electron‐Transfer Pathway

Photooxidation of Tryptophan: O2(1Δg) versus Electron‐Transfer Pathway

Charge Recombination Kinetics in Dye-Sensitized Nanocrystalline Titanium Dioxide Films under Externally Applied Bias

Photoemission studies of physisorbed xenon atoms on ruthenium/copper surfaces

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Photooxidation of Tryptophan: O₂(1Δ_g) versus Electron‐Transfer Pathway

Photooxidation of Tryptophan: O₂(1Δ_g) versus Electron‐Transfer Pathway