Comparative studies on the electrochemiluminescence of the luminol system at a copper electrode and a gold electrode under different transient-state electrochemical techniques

The electrochemiluminescence (ECL) and amperometric behaviors of the luminol system at a copper electrode and at a gold electrode were studied under different transient-state electrochemical techniques such as linear sweep voltammetry, normal pulse voltammetry, differential pulse voltammetry, chronoamperometry and cyclic-square potential. Under linear sweep voltammetry, normal pulse voltammetry and differential pulse voltammetry, three and one ECL peaks were obtained at a gold electrode and at a copper electrode, respectively. The ECL intensity, peak number and peak potential were well comparable with each electrochemical technique. Under chronoamperometry and cyclic-square potential, only one ECL peak was found and the ECL intensity decreased as the pulse potentials became more positive at a copper electrode with chronoamperometry, whereas, the ECL intensity increased as the pulse potentials became more positive at a gold electrode. Moreover, at a gold electrode, chronoamperometry and cyclic-square potential under high potentials show higher ECL sensitivity than other three techniques mentioned above. The repetitions of the ECL responses from pulse to pulse at both electrodes were observed under normal pulse voltammetry, differential pulse voltammetry and cyclic-square potential. The mechanisms for these ECL peaks were proposed due to the reactions of luminol radical anion formed by electro-oxidation of luminol with various electrogenerated oxygen-containing species such as O2, gold oxides, and O2- at different potentials. These studies on luminol electrochemiluminescence under different electrochemical techniques may be valuable for expanding the field and application of electrochemiluminescence reactions, especially for enriching the explanations of the mechanism of luminol electrochemiluminescence.