Observing Single, Heterogeneous, One-Electron Transfer Reactions

Understanding electrochemical events on the single-molecule level is crucial for fields such as catalysis and biological systems. A variety of techniques exist to study the electrochemistry of single molecules, but few provide correlated chemical information. Herein, we study the electrochemistry of rhodamine 6G in nonaqueous conditions and demonstrate the first statistic electrochemical single-molecule SERS (EC-SMSERS) proof of single-electron transfer events. We find that the distribution of reduction events is broader than that in a bulk electrochemical experiment. The distribution of the reduction potentials can be explained by molecular reorientation and variations of the local surface site or chemical potential of the Ag nanoparticle. Our results contribute toward understanding electrochemical behavior of single molecules on the nanoscale monitored by SERS and the ultimate goal of controlling single-electron transfer processes.