Electrochemical Light, From Laboratory Curiosity to Useful Analytical Technique

Electrochemiluminescence (ECL) is the process where species generated at electrodes undergo electron-transfer reactions to form excited states that emit light. Application of a voltage to an electrode in the presence of an ECL luminophore such as Ru(bpy)32+ (where bpy = 2,2′-bipyridine) or diphenylanthracene results in light emission and allows detection of the emitter at very low concentrations (≤10–12 mol dm–3). By employing ECL-active species as labels on biological molecules, ECL has found commercial application for immunoassays and DNA analyses. The history of ECL is presented including the earliest, curiosity driven experiments and the development of ECL into an analytical technique for clinical diagnostic applications. The development and use of ECL sensors is an excellent example of how, over time, a laboratory curiosity can become a useful, powerful, and commercially viable technique.