title: Electrochemistry in nanometer-wide electrochemical cells.
abstract: The electrochemical properties of an electrochemical cell defined by two concentric spherical electrodes, separated by a 1 to 20-nm-wide gap, and a freely diffusing electrochemically active molecule (e.g., ferrocene) have been investigated by coupling of Brownian dynamics simulations with long-range electron-transfer probability values. The simulation creates a trajectory of a single molecule and calculates the likelihood that the molecule undergoes a redox reaction during each time interval based on a probability-distance function derived from literature first-order kinetic data for a surface-bound ferrocene. Steady-state voltammograms for the single-molecule concentric spherical electrochemical cell are computed and are used to extract a heterogeneous electron-transfer rate for the freely diffusing molecule redox reaction. The Brownian dynamics simulations also indicate that long-range electron transfer, between the redox molecule and electrode, leads to nonsigmoidal-shaped i-E characteristics when the distance between electrodes approaches the characteristic redox tunneling decay length. The long-range electron transfer generates a "tunneling depletion layer" that results in a potential-dependent diffusion-limited current.
authors.affiliation: Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, USA.
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: White
authors.forename: Henry S
authors.initials: HS
authors.lastname: White