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 ?4, which is a typical marker of the redox state of the Iron center in a Hemin molecule. Based on the autocorrelation and crosscorrelation analysis of the single-molecule Raman spectral trajectories and the control measurements of single-molecule spectroelectochemistry and electrochemical STM, we suggest that 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 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 involving 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.

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

245th National Meeting (2013)

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