Radii of Microelectrodes Undervalued from Steady-state Currents

Abstract

We examined Saito's equation for diffusion-controlled current at a microdisk electrode. We measured steady-state currents of a ferrocenyl derivative at glass-coated Pt electrodes with various sizes, of which radii were evaluated with a scanning electron microscope. The relation between the currents and the radii less than 2 m deviated downward from the proportionality, whereas the proportionality was maintained accurately for the radii more than 5 m. Radii of invisible electrodes which have been so far evaluated from the steady-state currents should be smaller than the geometrical values. The lower deviation of the proportionality was explained in terms of memory diffusion of the Fick's first law under the steady state.