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  • Wiley-Blackwell  (4)
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  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a single picosecond pulse from a frequency-doubled Nd:YAG-mode-locked laser for excitation, we measured directly the rate of electron injection from the excited singlet state of eosin in the conduction band of colloidal TiO2 particles. The rate constant for interfacial electron transfer is 9.5 × 108s-1 at 25°C and pH 3.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1596-1604 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The subtitutional doping of 120-Å- sized TiO2 Particles with Fe(III)ions has a profound effect on the charge carrier recombination time in this colloidal semiconductor. In undoped particles, the mean lifetime of an electronhole pair is ca. 30 ± 15 ns. Doping with 0.5% Fe(III) drastically augments the charge-carrier lifetime which is extended to minutes or hours. The slow character of the recombination dynamics in Fe(III)-doped colloids was confirmed by laser photolysis using the characteristic optical of electrons in TiO2 to monitor the time course of the reaction. EPR studies showed the Fe(III) ions to enter the host lattice on Ti(IV) sites, charge compensation taking place through the formation of oxygen vacancies. Valence-band holes produced under band-gap excitation react with these centers it the bulk forming Fe(IV), the conduction band electrons being trapped by Ti(IV) at the particle surface. Presumably, the spatial separation of the trapped electron and hole sites inhibits their recombination.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of CN-bridged trinuclear Ru complexes of the general structure [RuL2(μ-(CN)Ru(CN)L2′)2] where L is 2,2′-bipyridine-4,4′-dicarboxylic acid and L′ is 2,2′-bipyridine (1)2,2′-bipyridine-4,4′-dicarboxylic acid (2), 4,4′-dimethyl-2,2′-bipyridine (3), 4,4′-diphenyl-2,2′-bipyridine (4), 1,10-phenanthroline (5), and bathophenanthrolinedisulfonic acid (6) have been synthesized, and their spectral and electrochemical properties investigated. The two carboxylic functions on the 2,2′-bipyridine ligand L serve as interlocking groups through which the dye is attached at the surface of TiO2 films having a specific surface texture. The role of these interlocking groups is to provide strong electronic coupling between the π* orbital of the 2,2′-bipyridine and the 3d-wave-function manifold of the conduction band of the TiO2, allowing the charge injection to proceed at quantum yields close to 100 %. The charge injection and recombination dynamics have been studied with colloidal TiO2, using laser photolysis technique in conjunction with time-resolved optical spectroscopy. Photocurrent action spectra obtained from photo-electrochemical experiments with these trinuclear complexes cover a very broad range in the visible, making them attractive candidates for solar light harvesting. Monochromatic incident photon-to-current conversion efficiencies are strikingly high exceeding 80% in some cases. Performance characteristics of regenerative cells operating with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have been investigated. Optimal results were obtained with complex 1 which gave a fill factor of 75 % and a power conversion efficiency of 11.3% at 520 nm.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1436-1444 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aqueous sols of TiO2 (anatase, particle radius 25 Å) were excited with (347.1 nm)-laser light and the reaction of valence-band holes with halide ions (X = I-, Br-, Cl-) was investigated. Hole transfer takes place within the duration of the (10 ns)-laser pulse and results in the formation of anion radicals according to the sequence:The quantum yield of X-2 increases in the order Cl-2 〈 Br-2 〈 I-2, attaining 0.8 for I-2 at pH 1. It is affected by pH, halide concentration and the presence of a protective agent for the sol.RuO2 deposited onto TiO2 enhances markedly Cl-2 and Br-2 -formation, but has no effect on the yield of I-2.Laser-photolysis investigation of halide oxidation were also carried out with colloidal Fe2O3 (particle radius 600 Å). For I2-formation, the quantum yield exceeds 0.9 indicating almost quantitative hole scavenging by iodide.
    Additional Material: 5 Ill.
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