Electrochemiluminescence in single entities, microscopicimaging and ratiometric analysis

Exciting research progresses have advanced the limits of electrochemiluminescence related techniques in several forefronts recently. This minireview starts from the efforts toward resolving the activities of single luminophores, the ultimate limit of detection. Strategies to measure single catalysts, single cells or organelles, and other single events/entities that affect the ensemble responses from a plural of luminophores are discussed next. Another area of extensive growth is the ratiometric approaches to improve the signal specificity in complex measurement matrix. More than one emission signals are employed either from two luminophore centers coupled for energy- or electron transfers or from the same luminophores activated differently. Improved signal-to-noise and/or specificity from the ratio of those emissions, often with opposite responses to target analyte, are categorized in biomacromolecules and ions/small molecules. Perspectives emphasize the needs to better understand the reaction kinetics for greater temporal and spatial resolutions needed for mechanistic understandings and broader applications.