Enhancement of Electrochemiluminescence by Au Paste Electrode for Bipolar Electroanalysis (Supporting Information)

Carbon paste electrodes (CPEs) are widely used because of their malleability and ease of modification of functional molecules. This study introduces the application of Au paste electrodes (AuPEs) as a method for amplifying electrochemiluminescence (ECL), with a focus on bipolar electrochemical analyses. First, the ECL intensities generated by the cathodic and anodic reactions of [Ru(bpy)₃]²⁺ at the glassy carbon disc electrode, Au disc electrode, carbon paste electrode, and AuPE was compared using a three-electrode system. We confirmed that the utilization of the AuPEs resulted in ECL intensities that were 1.4–1.7 times higher than those achieved through the use of other electrodes. A similar ECL enhancement effect was observed with the AuPE mixed with N,N′-dimethyl-3,4,9,10-perylenetetracarboxylicdiimide (PDI-CH₃) as a cathodic luminophore. This PDI-CH₃ mixed AuPE was used as the cathode in a closed bipolar electrode system. The system successfully detected dopamine concentrations of 1.0 mmol dm⁻³ in a sample cell. We hypothesize that the observed enhancements in the ECL were attributable to the surface plasmon field-enhancement effect of the Au particles. These results can be applied to highly sensitive bipolar electrochemical microscopy for imaging the dynamics of intracellular transmitter molecules.