Probing ground-state single-electron self-exchange across a molecule-metal interface

J Am Chem Soc. 2011 May 11;133(18):6989-96. doi: 10.1021/ja109306r. Epub 2011 Apr 12.

Abstract

We have probed single-molecule redox reaction dynamics of hemin (chloride) adsorbed on Ag nanoparticle surfaces by single-molecule surface-enhanced Raman spectroscopy (SMSERS) combined with spectroelectrochemistry. Redox reaction at the molecule/Ag interface is identified and probed by the prominent fluctuations of the Raman frequency of a specific vibrational mode, ν(4), which is a typical marker of the redox state of the iron center in a hemin molecule. On the basis of the autocorrelation and cross-correlation analysis of the single-molecule Raman spectral trajectories and the control measurements of single-molecule spectroelectochemistry and electrochemical STM, we suggest that the single-molecule redox reaction dynamics at the hemin-Ag interface is primarily driven by thermal fluctuations. The spontaneous fluctuation dynamics of the single-molecule redox reaction is measured under no external electric potential across the molecule-metal interfaces, which provides a novel and unique approach to characterize the interfacial electron transfer at the molecule-metal interfaces. Our demonstrated approaches are powerful for obtaining molecular coupling and dynamics involved in interfacial electron transfer processes. The new information obtained is critical for a further understanding, design, and manipulation of the charge transfer processes at the molecule-metal interface or metal-molecule-metal junctions, which are fundamental elements in single-molecule electronics, catalysis, and solar energy conversion.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Electron Transport
  • Electrons*
  • Hemin / chemistry*
  • Oxidation-Reduction
  • Silver / chemistry*
  • Spectrum Analysis, Raman
  • Vibration

Substances

  • Silver
  • Hemin