Abstract
Electrochemiluminescence (ECL) of 0.01 M luminol in NaOH medium of pH 12.0 on a boron-doped diamond (BDD) thin-film anode was studied in the absence and presence of H2O2. Here we show a new characteristic property of BDD allowing light emission in a wide potential range of 0.5–5.0 V vs Ag|AgCl, KCl(sat.), a behavior not observed for other anodes. Maximum ECL intensity was found at 2.2–2.8 V without H2O2, which became 63 times more intense after adding 0.05 M H2O2. The strong enhancement of ECL in the presence of H2O2 is attributed to the larger production of emitter 3-aminophthalate dianion, formed by selective nucleophilic attack of superoxide radical anion (O2•–) to the radical electrogenerated from one-electron oxidation of the monoanionic form of luminol. Linear sweep voltammetry showed that •OH was not generated from OH– oxidation, whereas O2•– can be produced from HO2– oxidation. The performance of O2•– in ECL was confirmed by p-benzoquinone quenching.
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