Transition from stochastic events to deterministic ensemble average in electron transfer reactions revealed by single-molecule conductance measurement

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 116; no. 9; pp. 3407 - 3412
• Main Authors: Li, Yueqi, Wang, Hui, Wang, Zixiao, Qiao, Yanjun, Ulstrup, Jens, Chen, Hong-Yuan, Zhou, Gang, Tao, Nongjian
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 26-02-2019
• Subjects: Conductance; Dependence; Electrochemical potential; Electrochemistry; Electron transfer; Electrons; Kinetics; Physical Sciences; Rate constants; Reaction kinetics; Resistance; Stochasticity; Variation; single molecule; ensemble averaging; electron transfer reactions; stochastic electron transfer; molecular electronics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1814825116

Electron transfer reactions can now be followed at the single-molecule level, but the connection between the microscopic and macroscopic data remains to be understood. By monitoring the conductance of a single molecule, we show that the individual electron transfer reaction events are stochastic and manifested as large conductance fluctuations. The fluctuation probability follows first-order kinetics with potential dependent rate constants described by the Butler–Volmer relation. Ensemble averaging of many individual reaction events leads to a deterministic dependence of the conductance on the external electrochemical potential that follows the Nernst equation. This study discloses a systematic transition from stochastic kinetics of individual reaction events to deterministic thermodynamics of ensemble averages and provides insights into electron transfer processes of small systems, consisting of a single molecule or a small number of molecules.