Microdisk electrodes: Part II. Fast-scan cyclic voltammetry with very small electrodes

Cyclic voltammetry has been investigated at inlaid disk electrodes with nominal radii of 0.3, 1.0, and 5.0 μm. The electrode capacitance is found to be much larger than expected for the two smaller radii electrodes. This effect is attributed to the capacitance between the inner conductor and the electrolyte solution. The excess capacitive current is minimized by the use of a conductive shield around the electrode which is connected to ground potential. Criteria are investigated for the degree of filtering of steady-state voltammograms to minimize noise while avoiding distortion of the experimental data. Experimental voltammograms for the oxidation of ferrocene in acetonitrile solutions are found to be in good agreement with existing theories for scan rates in which linear and convergent diffusion occur. The factors which limit the use of very small electrodes are discussed in terms of signal-to-noise, ohmic drop, and linear diffusion.