3 research outputs found

    Structural and Kinetic Studies of Intermediates of a Biomimetic Diiron Proton-Reduction Catalyst

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    One-electron reduction and subsequent protonation of a biomimetic proton-reduction catalyst [FeFeĀ­(Ī¼-pdt)Ā­(CO)<sub>6</sub>] (pdt = propanedithiolate), <b>1</b>, were investigated by UVā€“vis and IR spectroscopy on a nano- to microsecond time scale. The study aimed to provide further insight into the proton-reduction cycle of this [FeFe]-hydrogenase model complex, which with its prototypical alkyldithiolate-bridged diiron core is widely employed as a molecular, precious metal-free catalyst for sustainable H<sub>2</sub> generation. The one-electron-reduced catalyst was obtained transiently by electron transfer from photogenerated [RuĀ­(dmb)<sub>3</sub>]<sup>+</sup> in the absence of proton sources or in the presence of acids (dichloro- or trichloroacetic acid or tosylic acid). The reduced catalyst and its protonation product were observed in real time by UVā€“vis and IR spectroscopy, leading to their structural characterization and providing kinetic data on the electron and proton transfer reactions. <b>1</b> features an intact (Ī¼<sup>2</sup>,Īŗ<sup>2</sup>-pdt)Ā­(Ī¼-H)Ā­Fe<sub>2</sub> core in the reduced, <b>1<sup>ā€“</sup></b>, and reduced-protonated states, <b>1H</b>, in contrast to the Feā€“S bond cleavage upon the reduction of [FeFeĀ­(bdt)Ā­(CO)<sub>6</sub>], <b>2</b>, with a benzenedithiolate bridge. The driving-force dependence of the rate constants for the protonation of <b>1<sup>ā€“</sup></b> (<i>k</i><sub>pt</sub> = 7.0 Ɨ 10<sup>5</sup>, 1.3 Ɨ 10<sup>7</sup>, and 7.0 Ɨ 10<sup>7</sup> M<sup>ā€“1</sup> s<sup>ā€“1</sup> for the three acids used in this study) suggests a reorganization energy >1 eV and indicates that hydride complex <b>1H</b> is formed by direct protonation of the Feā€“Fe bond. The protonation of <b>1<sup>ā€“</sup></b> is sufficiently fast even with the weaker acids, which excludes a rate-limiting role in light-driven H<sub>2</sub> formation under typical conditions

    Detection and Identification of Cu<sup>2+</sup> and Hg<sup>2+</sup> Based on the Cross-reactive Fluorescence Responses of a Dansyl-Functionalized Film in Different Solvents

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    A dansyl-functionalized fluorescent film sensor was specially designed and prepared by assembling dansyl on a glass plate surface via a long flexible spacer containing oligoĀ­(oxyethylene) and amine units. The chemical attachment of dansyl moieties on the surface was verified by contact angle, XPS, and fluorescence measurements. Solvent effect examination revealed that the polarity-sensitivity was retained for the surface-confined dansyl moieties. Fluorescence quenching studies in water declared that the dansyl-functionalized SAM possesses a higher sensitivity towards Hg<sup>2+</sup> and Cu<sup>2+</sup> than the other tested divalent metal ions including Zn<sup>2+</sup>, Cd<sup>2+</sup>, Co<sup>2+</sup>, and Pb<sup>2+</sup>. Further measurements of the fluorescence responses of the film towards Cu<sup>2+</sup> and Hg<sup>2+</sup> in three solvents including water, acetonitrile, and THF evidenced that the present film exhibits cross-reactive responses to these two metal ions. The combined signals from the three solvents provide a recognition pattern for both metal ions at a certain concentration and realize the identification between Hg<sup>2+</sup> and Cu<sup>2+</sup>. Moreover, using principle component analysis, this method can be extended to identify metal ions that are hard to detect by the film sensor in water such as Co<sup>2+</sup> and Ni<sup>2+</sup>

    Efficient Dye-Sensitized Solar Cells with Voltages Exceeding 1 V through Exploring Tris(4-alkoxyphenyl)amine Mediators in Combination with the Tris(bipyridine) Cobalt Redox System

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    Tandem redox electrolytes, prepared by the addition of a trisĀ­(<i>p</i>-anisyl)Ā­amine mediator into classic trisĀ­(bipyridine)Ā­cobalt-based electrolytes, demonstrate favorable electron transfer and reduced energy loss in dye-sensitized solar cells. Here, we have successfully explored three trisĀ­(4-alkoxyphenyl)Ā­amine mediators with bulky molecular structures and generated more effective tandem redox systems. This series of tandem redox electrolytes rendered solar cells with very high photovoltages exceeding 1 V, which approaches the theoretical voltage limit of trisĀ­(bipyridine)Ā­cobalt-based electrolytes. Solar cells with power conversion efficiencies of 9.7ā€“11.0% under 1 sun illumination were manufactured. This corresponds to an efficiency improvement of up to 50% as compared to solar cells based on pure trisĀ­(bipyridine)Ā­cobalt-based electrolytes. The photovoltage increases with increasing steric effects of the trisĀ­(4-alkoxyphenyl)Ā­amine mediators, which is attributed to a retarded recombination kinetics. These results highlight the importance of structural design for optimized charge transfer at the sensitized semiconductor/electrolyte interface and provide insights for the future development of efficient dye-sensitized solar cells
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