Multicolour electrochemiluminescence

Electrochemiluminescence (ECL) as a basis for chemical and biochemical measurement has risen to prominence in the last two decades, and is now firmly established as one of the most important means of achieving ultrasensitive bioanalytical detection. Until recently, it seemed that ECL was approaching the limits of its development as a technique, with the vast majority of applications being limited to derivatives of Ru(bpy)32+, the red-emitting standard ECL emitter. Recently, however, with the advent of new classes of electrochemiluminophores, notably cyclometalated iridium complexes, and various types of nanomaterials, new possibilities have arisen, which have stimulated new developments. Chief among these advances has been the ability to simultaneously detect more than one luminophore in the same solution, by exploiting differences in colour and/or redox potential. Combined with the emergence of new electrochemical methodologies, such as bipolar electrochemistry (BPE), and advances in spectroscopic, electrochemical and data acquisition hardware, this has resulted in a surge of research activity in recent years, related to multicolour ECL for potential multiplex detection applications. Here, we summarise and critically analyse the most important developments in the area, provide practical information related to instrumental aspects of potential-resolved and wavelength-resolved measurements and offer insights related to future directions in this field.