Potential-Dependent Electrochemiluminescence for Selective Molecular Sensing of Cyanide

Although tremendous efforts have been devoted to providing specificity for molecular sensors, most of the methods focus on the structural variation of the binding or reaction site to improve selectivity. Herein, we report a new approach in which a chemical probe, possessing a mediocre recognition site, can successfully discriminate a target among various interferences only with electrochemical manipulation. The synthetic probe (1) was designed to react with a cyanide anion (CN^-), and its dicyanovinyl group has selectivity toward CN^- along with sulfides and biothiols resulting in similar adducts. However, the binding adduct between 1 and CN^- (1-CN^-) has significantly different energy levels that are only able to undergo electrochemical oxidation under ∼1.2 V (vs Ag/AgCl), generating strong electrochemiluminescence (ECL). The ECL emission from 1-CN^- successfully discriminates CN^- without any interferences from other analytes including sulfides and thiols and exhibits a linear correlation with CN^- in a range of 1-400 μM (LOD = 0.04 μM, n = 5). Density functional theory (DFT) calculations and electrochemical studies supported the mechanism of CN^- discrimination. The approach was finally applied to direct trace analysis of CN^- in tap water (≥1 μM) and showed excellent performance suggesting a new, versatile, and rapid determination method for molecular toxins in real samples.