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Ultrafast Electron Transfer from Photoexcited CdSe Quantum Dots to Methylviologen

Authors

  • Frank Scholz,

    1. Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe University Frankfurt/M, Max-von-Laue-Strasse 7, 60438 Frankfurt (Germany), Fax: (+49) 69 798 29
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  • Lars Dworak,

    1. Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe University Frankfurt/M, Max-von-Laue-Strasse 7, 60438 Frankfurt (Germany), Fax: (+49) 69 798 29
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  • Dr. Victor V. Matylitsky,

    1. Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe University Frankfurt/M, Max-von-Laue-Strasse 7, 60438 Frankfurt (Germany), Fax: (+49) 69 798 29
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  • Prof. Dr. Josef Wachtveitl

    Corresponding author
    1. Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe University Frankfurt/M, Max-von-Laue-Strasse 7, 60438 Frankfurt (Germany), Fax: (+49) 69 798 29
    • Institute of Physical and Theoretical Chemistry, Johann Wolfgang Goethe University Frankfurt/M, Max-von-Laue-Strasse 7, 60438 Frankfurt (Germany), Fax: (+49) 69 798 29
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Abstract

The ultrafast charge separation at the quantum dot (QD)/molecular acceptor interface was investigated in terms of acceptor concentration and the size of the QD. Time-resolved experiments revealed that the electron transfer (ET) from the photoexcited QD to the molecular acceptor methylviologen (MV2+) occurs on the fs time scale for large acceptor concentrations and that the ET rate is strongly reduced for low concentrations. The increase in the acceptor concentration is accompanied with a growth in the overlap of donor and acceptor wavefunctions, resulting in a faster reaction until the MV2+ concentration reaches a saturation limit of 0.3–0.4 MV2+ nm−2. Moreover, we found significant QD size dependence of the ET reaction, which is explained by a change of the free energy (ΔG).

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