title: Probing ground-state single-electron self-exchange across a molecule-metal interface.
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.
authors.affiliation: Department of Chemistry, Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA.
authors.forename: Yuanmin
authors.initials: Y
authors.lastname: Wang
authors.forename: Papatya C
authors.initials: PC
authors.lastname: Sevinc
authors.forename: Yufan
authors.initials: Y
authors.lastname: He
authors.forename: H Peter
authors.initials: HP
authors.lastname: Lu
mesh_terms: D004579:Electron Transport; D004583:Electrons; D006427:Hemin / Q000737:chemistry*; D010084:Oxidation-Reduction; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D012834:Silver; D006427:Hemin