Visualizing Interfacial Dynamics and Reaction Kinetics in Electrochemiluminescence via Reflective Impedance Microscopy

Abstract Electrochemiluminescence microscopy (ECLM) represents one of the most widely used techniques for mechanistic studies in electrochemiluminescence (ECL) systems. However, the ECLM output relies predominantly on the intensity of the ECL signal, often without fully accounting for the reaction kinetics and diffusion dynamics of the reacting species. In this work, we introduced reflective impedance microscopy (RIM) as an orthogonal technique for the investigation of ECL systems. RIM is an imaging technique capable of spatially resolving the impedance of the electrode-solution interface. Specifically, we employed the electrochemical mapping of impedance in the presence of magnetic microbeads to uncover diffusion dynamics in a bead-based ECL assay. We then coupled RIM measurements with finite element simulations, demonstrating that the bead acted as a physical boundary that reduced the thickness of the ECL-emitting layer in its surroundings. Furthermore, we combined RIM and ECLM to study modified electrodes and visualize variations in the TPrA oxidation rate across different materials. In these systems, graphene particles act as catalytic sites that accelerate the oxidation of TPrA, resulting in a localized emission enhancement from beads in their vicinity. Beyond these specific findings, this study establishes RIM as a versatile and powerful imaging technique, unlocking further possibilities for mechanistic investigations of electrochemiluminescence and other complex electrochemical systems.