The potential-resolved electrochemiluminescent behavior of calcein in aqueous alkaline solutions at a glassy carbon electrode

In aqueous alkaline solutions, the potential-resolved electrochemiluminescent (ECL) behavior of calcein at a glassy carbon electrode was investigated. A sharp ECL light emission peak appeared near 0.8 V (vs. Ag/AgCl) under cyclic voltammogram (CV) conditions. In order to obtain a better understanding of the light emission, we investigated the effects of supporting electrolytes, the pH value, the presence of O2 or N2, and the concentration of calcein. The oxidative form of calcein reacted with hydroxyl radicals and oxygen, producing singlet excited oxygen that was identified as the emitter using the ECL, UV–vis absorption and fluorescence spectra. A possible mechanism for the behavior of calcein in this system was also proposed.