On the Hopping Efficiency of Nanoparticles in the Electron Transfer across Self-Assembled Monolayers

Authors

  • Dr. Feng Liu,

    1. State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian (China)
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  • Kamran Khan,

    1. State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian (China)
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  • Jing-Hong Liang,

    1. State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian (China)
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  • Prof. Jia-Wei Yan,

    1. State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian (China)
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  • Prof. De-Yin Wu,

    1. State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian (China)
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  • Prof. Bing-Wei Mao,

    Corresponding author
    1. State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian (China)
    • State Key Laboratory of Physical Chemistry of Solid Surfaces and College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, Fujian (China)
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  • Dr. Palle Skovhus Jensen,

    1. Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)
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  • Prof. Jingdong Zhang,

    Corresponding author
    1. Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)
    • Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)
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  • Prof. Jens Ulstrup

    1. Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)
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Abstract

Redox reactions of solvated molecular species at gold-electrode surfaces modified by electrochemically inactive self-assembled molecular monolayers (SAMs) are found to be activated by introducing Au nanoparticles (NPs) covalently bound to the SAM to form a reactive Au–alkanedithiol–NP–molecule hybrid entity. The NP appears to relay long-range electron transfer (ET) so that the rate of the redox reaction may be as efficient as directly on a bare Au electrode, even though the ET distance is increased by several nanometers. In this study, we have employed a fast redox reaction of surface-confined 6-(ferrocenyl) hexanethiol molecules and NPs of Au, Pt and Pd to address the dependence of the rate of ET through the hybrid on the particular NP metal. Cyclic voltammograms show an increasing difference in the peak-to-peak separation for NPs in the order Au<Pt<Pd, especially when the length of the alkanedithiol increases from octanedithiol to decanedithiol. The corresponding apparent rate constants, kapp, for decanedithiol are 1170, 360 and 14 s−1 for NPs of Au, Pt and Pd, respectively, indicating that the efficiency of NP mediation of the ET clearly depends on the nature of the NP. Based on a preliminary analysis rooted in interfacial electrochemical ET theory, combined with a simplified two-step view of the NP coupling to the electrode and the molecule, this observation is referred to the density of electronic states of the NPs, reflected in a broadening of the molecular electron/NP bridge group levels and energy-gap differences between the Fermi levels of the different metals.

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