SELECTIVITY AND SENSITIVITY OF SELF-ASSEMBLED THIOCTIC ACID ELECTRODES

The design of electrodes with controllable surface properties continues to be a major challenge. This study was undertaken to evaluate the possibility of self-assembly of thioctic acid (1,2-dithiolane-3-pentanoic acid) on a smooth gold electrode to form an organized monolayer with the carboxylic acid terminal in contact with solution controlling the response of the electrode. This surface is shown schematically in Figure 1. Li and Weaver have exploited spontaneous strong adsorption of thioctic acid on gold through its two sulfur atoms in order to attach pentaamminecobalt(III) to the surface. The electrodes were designed to study intramolecular electron transfer, no particular effort was made to control surface roughness, and the electrochemical behavior of solution species at thioctic acid modified gold was not reported.1Selfassembly of thioalkyl derivatives is emerging as a practical way to modify gold electrodes. Applications of the self-assembled monolayer electrodes (SMEs) to pH and metal sensing have been reported.2,3Sun et al. have shown that a self-assembled monolayer of 4-aminothiophenol can be used, by controlling solution pH, to electrostatically bind solution species.4Electron transfer through the monolayers has been investigated, and a number of factors have been found to influence it including the chain length of the assembled derivatives5and the density of packing of the monolayer.6. © 1992, American Chemical Society. All rights reserved.