Anodic Potential Driven Electrochemiluminescence of Luminol/O2 System with the Immobilized TEMPO Mediator

Abstract

The oxygen reduction reaction (ORR) has been recognized well as an essential step to trigger the electrochemiluminescence (ECL) of the luminol/O₂ system but suffers from sluggish reaction kinetics. Herein, ECL of the luminol/O₂ system without involving ORR is reported by using a 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) grafted glassy carbon electrode (4-amino-TEMPO/GCE). This electrode exhibits high catalytic activity toward the oxidation of luminol, though it is covered with an organic film. Such promoted luminol oxidation on the electrode results in a 5.0-fold ECL enhancement at an anodic potential, ensuring the ECL detection as more sensitive. The mechanism studies indicate that the catalysis of 4-amino-TEMPO/GCE can provide additional luminol anion radical (L^–•) for enhancing the ECL of the luminol/O₂ system. Hence, this work introduces a different approach to modulate luminol oxidation for enhancing ECL emission based on an immobilized organic oxidation catalyst.