The combination of tri-n-propylamine (TPrA) and tris(2,2'-bipyridyl)ruthenium(II) is one of the most historically relevant electrochemiluminescence (ECL) systems, as it is used in hospitals all over the world to test for myocardial infarction. In developing novel diagnostic tools or improving upon standard ones, it is important to investigate historic systems in new ways. We demonstrate the precipitation of an ECL-active solid by using this historic ECL system. Even after the potential is ended, an emission persists for 100s of seconds, corresponding to a million times increase in ECL lifetime through this afterglow chemiluminescence process. This fractures the dogma of ECL, where classically an applied electric potential is assumed to be a requirement for light emission. Beyond proof of concept, experimental parameters such as pH, potential waveform, applied potential, TPrA concentration, and supporting electrolyte were changed and showed the ability of this system to be tunable between two regimes: ECL intensity and afterglow chemiluminescence time. Additionally, we offer a probable mechanism for the formation of this precipitate that effectively extends the utility of ECL in space and time. When looking at the necessary technological advancements needed in bioanalysis, fundamental steps forward, such as those presented in this study, are required to enable leaps in applied knowledge.
Layman et al. (2026) studied this question.