How Extending Light Emission in Space and Time Transforms Electrochemiluminescence as a Powerful Chemical Imaging Platform

In electrochemiluminescence (ECL) reactions, light is emitted from reactions between electrogenerated, unstable, short-lived intermediates that are produced at an electrode surface. Thus, classically, the temporal and spatial characteristics of the emission layer are limited by the lifetime of these fleeting species. By extension, ECL emission is typically confined within micrometers of the electrode surface and requires an applied bias. Here, we present approaches that overcome the spatial and temporal constraints of traditional ECL platforms. Spatially, using unconventional reagent concentrations or reflection, axial resolution is enhanced to image objects up to hundreds of micrometers from the electrode surface. Furthermore, bimolecular solution reactivity can be leveraged via a freely diffusing, electrogenerated species, extending ECL emission millimeters away from the electrode and enabling minutes-long ECL-initiated afterglow chemiluminescence. Temporally, electroprecipitation of ECL-active species prolongs chemiluminescence by hundreds of seconds even after the applied bias ceases. Overall, this Perspective aims to conceptually separate the “E” from the “CL”, demonstrating that ECL emission extends beyond the electrode surface during an applied bias, allowing its benefits to be obtained whenever and wherever desired.