Fig. 2. Schematic of the system used to measure ECL of individual DPA molecules. The Au UME is facing a PMT. A 20 femtoliters solution containing few tens of mM of DPA dissolved in acetonitrile with 0.1 M of tetrabutylammonium hexafluorophosphate (TBAPF6) is introduced into the gap under flow conditions. Potential pulses applied to the UME produce a cascade of reactions that lead to light emission measured by the PMT. Reproduced from ref. 54 with permission from the Royal Society of Chemistry, copyright [2020].