Fabrication Of Complex Microelectrode Array And Its Application To Electrochemical Detection

Electrochemical methods have been widely used for detecting electroactive species due to their advantages of simplicity, easy operation, low cost and variety of methods. It is challenging for researchers to develop electrochemical methods for achieving detection with high sensitivity and selectivity. In recent years, a number of new electrochemical detection methods have been developed, which are based on electrochemical reaction kinetics or diffusion layer.This work achieves high detection sensitivity and selectivity of the target in the coexistence of interfering species by the overlap of the diffusion layer and the interaction between the reactants. Firstly, plane-band-recessed microdisk electrode array was designed and fabricated by micro-electromechanical systems. Based on the electrode configuration, we propose two working modes (separation potential mode and oxidation-reduction mode) which can not only eliminate interferent but also enhance signal by redox cycling in diffusion layer. Moreover, interference from EC mechanism can be avoided. The oxidation-reduction mode is further proposed for eliminating interferent in the diffusion layer and achieving selective detection using conventional electrode. Detailed contents are as follows:1. Plane-band-recessed microdisk electrode array is composed of a plane electrode, a band electrode, and an array of microcavities. The three electrodes are separated by insulating layers. After exploring pre-processing wafers, sputtering, introducing an insulating layer, lithography and etching processes, we developed a relatively simple method to fabricate plane-band-recessed microdisk electrode array that are successfully used for electrochemical detection. In the structure of the electrode, the plane electrode is mainly used for depleting interferent, the band electrode is used for enhancing the signal by redox cycling and recessed microdisk electrodes for detecting analyte.2. Two operating modes are proposed for plane-band-recessed microdisk electrode array detection. Using the separation potential mode, we can achieve selective detection of the target analyte dopamine (DA) in the presence of ascorbic acid (AA), redox cycling enhancement in the diffusion. Oxidation-reduction mode can eliminate interferences, enhance the signal by redox cycling in the diffusion lyaer, and avoid the influence of EC mechanism. The advantage of oxidation-reduction mode is that it can be more widely applied.3. The oxidation-reduction mode is applied to commercial electrode. The selective detection of dopamine in the presence of ascorbic acid can be achieved. The effect of the step potential, duration time and sweep rate on detection sensitivity and selectivity was investigated. Since the oxidation product of AA is not stable, the influence of AA on the detection can be avoided. Because only easily achievable potential control and commonly used electrode without modification are required, the proposed method is facile and thus high reproducibility is expected.