THE EFFECT OF ELECTRODE MATERIAL ON THE ELECTROGENERATED CHEMILUMINESCENCE OF LUMINOL

The oxidation of luminol and its concomitant electrogenerated chemiluminescence (ECL) were studied at several electrode materials by voltammetry and chronoamperometry. The ECL intensity (I(ECL)) was inversely related to the activity of the electrodes. The lowest I(ECL) was measured when luminol was oxidized to 3-aminophthalate (n = congruent-to 4 eq mol-1) at a nearly mass-transport limited rate at glassy carbon. The ECL kinetics were studied and the order of the reaction with respect to luminol was 3/2 at concentrations to ca. 1 mM when O2 was the coreactant. In the presence of H2O2, the ECL reaction was first order with respect to luminol. A reaction mechanism is proposed that is consistent with the kinetic data and the inverse relationship between electrode activity and I(ECL). The implications of these results are discussed with respect to imaging the spatial distribution of current density at electrode surfaces, including that of PbO2 films activated by adsorbed Bi(V). A value of 6.6 x 10(-6) cm2 S-1 was determined for the diffusion coefficient of luminol in 0.1M NaOH.