Electrochemically, spectrally, and spatially resolved annihilation-electrogenerated chemiluminescence of mixed-metal complexes at working and counter electrodes

Previously dismissed as an unwanted and unpredictable artifact of electrogenerated chemiluminescence (ECL) systems, emission at the counter electrode has new importance in the context of the emerging multicolor and potential-resolved ECL systems in which a much wider range of potentials are applied at the working electrode. Herein, we explore the annihilation ECL from a mixture of two electrochemiluminophores at both the working and counter electrodes of a three-electrode electrochemical cell. The potentials at the working and counter electrodes were both measured, and the simultaneous spatially resolved ECL was captured with a digital camera. The factors that determine the dominant emitter (and therefore the observed emission color) at the working electrode can be applied to the counter, albeit with a less well-defined potential range. A variety of color combinations from the luminophores can be elicited at the two electrode surfaces through the selection of applied potentials.