Department of Chemistry, Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA.
J Am Chem Soc. 2011 May 11;133(18):6989-96. doi: 10.1021/ja109306r. Epub 2011 Apr 12.
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.
我们通过单分子表面增强拉曼光谱（SMSERS）结合光谱电化学，研究了吸附在银纳米粒子表面的血红素（氯化物）的单分子氧化还原反应动力学。通过特定振动模式 ν(4)的拉曼频率的显著波动来识别和探测分子/Ag 界面处的氧化还原反应，ν(4)是血红素分子中铁中心氧化还原状态的典型标记。基于单分子拉曼光谱轨迹的自相关和互相关分析以及单分子光谱电化学和电化学 STM 的对照测量，我们提出血红素-Ag 界面处的单分子氧化还原反应动力学主要由热波动驱动。在分子-金属界面上没有外加电势的情况下测量单分子氧化还原反应的自发波动动力学，为在分子-金属界面处表征界面电子转移提供了一种新颖而独特的方法。我们展示的方法对于获得涉及界面电子转移过程的分子偶联和动力学非常有效。获得的新信息对于进一步理解、设计和操纵分子-金属界面或金属-分子-金属结处的电荷转移过程至关重要，这些过程是单分子电子学、催化和太阳能转换的基本要素。
