(742c) Quantum Statistical Mechanics of Charge Transfer Processes At Electrode-Electrolyte Interfaces

Authors: 
Gupta, C., Stanford University
Howe, R. T., Stanford University



Charge transfer at an electrochemical solid-liquid interface is a complex physical phenomenon characterized by an interdependence of microscopic electronic and chemical processes.  The inherent coupling of chemistry with the nanoscale charge transport dynamics at electrochemical interfaces yields a unique physical platform capable of electrical transduction of chemical information at the molecular level.  However, this “information-rich” phenomenon has usually been described experimentally by measurements of observables like the current flowing across the interface, the voltage drop across the interface and/or the charge accumulated at the interface. The traditional measurements and their subsequent analyses present a macroscopic, ensemble-averaged description of the transfer process wherein the microscopic information is often obfuscated in the background signal that is often discarded.  Therefore, sensing platforms utilizing the charge transfer process as an information transduction mechanism tend to be limited in the scope of analytes that can be investigated.  Typically, electrochemical sensors are deployed for the detection of redox-active species that are capable of direct electronic interaction with metallic or semi-conducting electrodes through available valence and/or d-shell electrons within the useful electronic energy ranges, which is usually within +-0.7eV relative to an electrolytic reference for an aqueous system.  We propose here a design methodology for electrochemical systems wherein the engineered charge transfer process enables transduction of chemical information, like inter-molecular bond vibration frequency, about non-redox-active analyte species.  The proposed design strategy leverages a quantum statistical model of the charge transfer process at the electrochemical interface developed by the authors, where the critical parameters affecting the information transduction mechanism are identified and quantified.  We will discuss the implications of the critical parameters on the engineering of the physical sensor front-end, as well as on the engineering of the instrumentation necessary for the information acquisition.  Preliminary experimental data will also be presented that will highlight the capability to distinguish structural isomers and single-atom-mass-isotope substituents of the detected analytes from an all-electronic signal generated by the sensor front-end.