CYCLIC VOLTAMMETRIC RESPONSES FOR INLAID MICRODISKS WITH SHIELDS OF THICKNESS COMPARABLE TO THE ELECTRODE RADIUS - A SIMULATION OF REVERSIBLE ELECTRODE-KINETICS

Given common methods of preparing inlaid microdisk electrodes, shield thicknesses are often comparable to disk radii. Equations appropriate to characterizing the steady state, cyclic voltammetric response for microdisks embedded in infinite insulating planes poorly approximate the steady state response at these electrodes because, on the time scale to achieve steady state, diffusion around the shield from behind the plane of the electrode contributions to the flux. A finite difference simulation with a nonuniform, expanding spatial grid is presented for reversible electrode kinetics over a range of scan rates sufficient to follow the transition from linear to radial diffusion, including nux around the edge of the shield. The voltammetric response is influenced critically by shield thickness and electrode radius; a method is proposed and verified experimentally to determine radius and shield thickness. The equations for infinitely thick insulators underestimate the current at a thinly shielded microdisk by less than or equal to 49%. Generation of a nonuniform, expanding grid is presented.