ABSTRACT
Upon bringing an electrode into contact with an electrolyte solution, electron transfer (ET) occurs because of the mismatch of the electronic energy level in the electrode and that in solution, which are controlled and measured, respectively, by the electrode potential (E) and the redox potential of the electroactive species in electrolyte solution.1,2 As a result, charges are produced at electrode surfaces, and in the meantime, electrolyte ions are accumulated and/or depleted near electrodes due to electrostatic interaction, thus forming electrical double layers (EDLs) (Figure 2.1), which
2.1 Introduction ............................................................................................................................29 2.2 Mass Transport and Electron Transfer (ET) Processes at Nanoscale Electrodes .................. 33
2.2.1 Coupling between the Electrostatic Potential and Concentration Distributions at Nanoscale Electrode/Electrolyte Interfaces and the Dynamic Electrical Double Layer (EDL) Nature of Interfaces .................................................................. 33
2.2.2 Coupling between the Electrostatic Potential and Solvent Dielectric Distribution at Nanoscale Electrode/Electrolyte Interfaces ....................................... 35
2.2.3 EDL Effects on Mass Transport Rates at Nanoscale Electrodes................................ 38 2.2.4 EDL Effects on Heterogeneous ET Kinetics at Nanoscale Electrodes ...................... 41 2.2.5 Heterogeneous ET Kinetics at Nanoscale Electrodes: Beyond the Electrical
Double Layer (EDL) Effect ........................................................................................44 2.2.5.1 Failure of the Linear Free Energy and Quasi-Two-State ET
Assumptions ................................................................................................44 2.2.5.2 Importance of Long-Distance Electron Tunneling ...................................... 47
2.3 EDL Effects on Ion Transport and Solution Flow in Nanopores ........................................... 49 2.3.1 Ion Current Rectication (ICR) in Conical Nanopores .............................................. 49
2.3.1.1 ICR: Theory and Simulation ........................................................................50 2.3.1.2 Electrolyte Flow Coupled with the EDL within a Nanopore ...................... 52
2.3.2 Negative Differential Resistance in Nanopores Resulting from the EDL .................. 55 2.3.3 EDL Effects in Nanopore-Based Particle Analysis ....................................................60 2.3.4 EDL Gating of Redox Transport at Recessed Conical Nanopore Electrodes ............ 61
2.4 Conclusions ............................................................................................................................. 63 Acknowledgments ............................................................................................................................64 References ........................................................................................................................................64
are nanoscale in nature because they are dened by high electric elds screened by mobile charges (ions in solution and electrons in the electrode) and solvent dipoles over distances on the order of 0.1-100 nm in common situations.1
