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Chemical modifications on recessed microelectrode array, achieved via electrodeposition techniques are reported here. Silicon-based gold microelectrode arrays of 10 μm microband and microdisc array were selected and functionalised using sol-gel and nanoporous gold (NPG) respectively. For electrochemically assisted self-assembly (EASA) formati6154on of sol-gel, electrode surface was first pre-treated with a self-assembled partial monolayer of mercaptopropyltrimethoxysilane (MPTMS) before transferring it into the sol containing cetyltrimethyl ammonium bromide (CTAB)/tetraethoxysilane (TEOS):MPTMS (90:10) precursors. A cathodic potential is then applied. It was found that larger current densities were required in ensuring successful film deposition when moving from macro- to micro- dimensions. For NPG modification, a chemical etching process called dealloying was employed. NPG of three different thicknesses have been successfully deposited. All the modified and functionalized microelectrode arrays were characterized by both optical (SEM) and electrochemical analysis (cyclic voltammetry and impedance spectroscopy). An increase in surface area and roughness has been observed and such will benefit for future sensing application.

Publisher Summary The detection of many pesticides at extremely low levels can be best achieved not by direct detection of the pesticide itself but rather by detection of its inhibitory effects on enzyme reactions. The detection of organophosphate and other pesticides based on the inhibition of the enzyme acetylcholinesterase by these compounds has received considerable attention primarily because of high specificity and sensitivity. Other techniques such as use of multiple electrodes, pattern recognition software and flow-injection techniques have enabled the subtraction of matrix effects such as heavy metals from the system as well as the determination of pesticides in systems containing more than one compound. The signal processing algorithms allow automation of the pesticide quantification enabling use of the instrumentation by unskilled personal, thereby removing this sensing platform from specialized laboratories and making it available to the end-users. Thus this application could conceivably be utilized in the field as well as under laboratory conditions. The relative low cost of electrochemical technology compared with many of the other technologies used makes it an attractive alternative, especially if the enzyme electrodes can be inexpensively mass-produced using screen-printing to allow single-shot use.