Fabrication and Characterization of Ultrathin-ring Electrodes for Pseudo-steady-state Amperometric Detection

Abstract

The fabrication of ultrathin-ring electrodes with a diameter of 2 mm and a thickness of 100 nm is established. The ultrathin-ring electrodes provide a large density of pseudo-steady-state currents, and realize pseudo-steady-state amperometry under quiescent conditions without a Faraday cage. Under the limiting current conditions, the current response at the ultrathin-ring electrode can be well explained by the theory of the microband electrode response. Cyclic voltammograms at the ultrathin-ring electrode show sigmoidal characteristics with some hysteresis. Numerical simulation reveals that the hysteresis can be ascribed to the time-dependence of pseudo-steady-state current. The performance of amperometry with the ultrathin-ring electrode has been verified in its application to redox enzyme kinetic measurements.

Diffusion-controlled Mediated Electron Transfer-type Bioelectrocatalysis Using Microband Electrodes as Ultimate Amperometric Glucose Sensors

“…An ultrathin-ring electrode with a thickness of 100 nm was fabricated as described in a previous report 32 with slight modifications. Firstly, a UV-resin rod with the diameter of 2 mm was fabricated and bound with a copper wire.…”

“…35 Because of the difference in the geometrical symmetry, the steady-state characteristics of a microband electrode is weaker than those of the microdisk electrode. 32 Numerical simulations were performed to elucidate the pseudosteady-state characteristics of the mediated enzymatic reaction on a microband electrode. Figure 2a shows the effect of the microband electrode thickness on the numerically calculated amperograms for a catalytic oxidation current at microband electrodes of varying w; the triangles, squares, and circles represent w = 0.1, 1, and 10 μm, respectively.…”

“…32 However, fabricating thicker ring electrodes was difficult using this methodology because of poor reproducibility.…”

“…32 The thickness of the ring must be quite small (~100 nm) compared with its diameter to sufficiently form a toroidal diffusion layer. The electrochemical behavior of ultrathin-ring electrodes is similar to that of band electrodes.…”

“…33 The current response of an ultrathin-ring electrode is sufficiently large for detection without a Faraday cage. 32 In addition, decreasing the ring thickness decreases the response time, which is defined as the time that the variation of current is less than the threshold.…”