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

<div>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 <em>N</em>,<em>N</em>′-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.</div>