A Carbonate-Involved Amplification Strategy for Cathodic Electrochemiluminescence of Luminol Triggered by the Catalase-like CoO Nanorods

The lumiol-O-2 electrochemiluminescence (ECL)systemconstantly emits bright light at positive potential. Notably, comparedwith the anodic ECL signal of the luminol-O-2 system, thegreat virtues of cathodic ECL are that it is simple and causes minordamage to biological samples. Unfortunately, little emphasis has beenpaid to cathodic ECL, owing to the low reaction efficacy between luminoland reactive oxygen species. The state-of-the-art work mainly focuseson improving the catalytic activity of the oxygen reduction reaction,which remains a significant challenge. In this work, a synergisticsignal amplification pathway is established for luminol cathodic ECL.The synergistic effect is based on the decomposition of H2O2 by catalase-like (CAT-like) CoO nanorods (CoO NRs)and regeneration of H2O2 by a carbonate/bicarbonatebuffer. Compared with Fe2O3 nanorod (Fe2O3 NR)- and NiO microsphere-modified glassy carbonelectrodes (GCEs), the ECL intensity of the luminol-O-2 systemis nearly 50 times stronger when the potential ranged from 0 to -0.4V on the CoO NR-modified GCE in a carbonate buffer solution. The CAT-likeCoO NRs decompose the electroreduction product H2O2 into OH & BULL; and O-2 (& BULL;) (-), which further oxidize HCO3 (-) and CO3 (2-) to HCO3 (& BULL;) and CO3 (& BULL;) (-). These radicalsvery effectively interact with luminol to form the luminol radical.More importantly, H2O2 can be regenerated whenHCO(3) (& BULL;) dimerizes to produce (CO2)(2)*, which provides a cyclic amplification of the cathodicECL signal during the dimerization of HCO3 (& BULL;). This work inspires developing a new avenue to improve cathodicECL and deeply understand the mechanism of a luminol cathodic ECLreaction.

Automated summary

A synergistic signal amplification pathway was established for luminol cathodic electrochemiluminescence (ECL) by decomposing H2O2 with catalase-like cobalt oxide nanorods (CoO NRs) and regenerating H2O2 with carbonate/bicarbonate buffer. Compared with other nanomaterial-modified electrodes, the CoO NR-modified electrode exhibited nearly 50 times stronger ECL intensity of the luminol-O2 system in a carbonate buffer solution. This work provides a new avenue to improve cathodic ECL and understand the mechanism of luminol cathodic ECL.