Oxygen Reduction Reaction-Regulated Paper-Based Bipolar Electrochemiluminescence Biosensor for Sensitive Detection of Carbendazim

Herein, we present a highly efficient electrochemiluminescence (ECL) sensor on a paper-based closed bipolar electrode (CBPE) for the sensitive detection of carbendazim (CBZ). This work leverages the tunable dynamics of the cathodic oxygen reduction reaction (ORR) to regulate the emission of anodic luminescence. The innovative design of the CBPE eliminates the need for analytes to directly participate in redox reactions, as required in conventional three-electrode-based ECL systems, while also minimizing interference between the sensing and reporting poles by physically decoupling the two electrodes, greatly improving sensitivity. To further improve the ECL performance, novel ECL-emitting copper nanoclusters (CuNCs_Assy), with excellent stability and strong anodic luminescence characteristics, were synthesized and employed as the ECL emitter in the anodic cell, effectively preventing hydrogen evolution associated with the cathodic ECL mode. For target analysis, a Cl-doped metal-free porous electrocatalyst (<i>mf</i>-pClNC), labeled with an aptamer that specifically recognizes CBZ, is introduced into the sensing electrode. Upon target binding, the electrocatalyst <i>mf</i>-pClNC dissociates from the electrode surface, increasing the reaction energy barrier of the ORR and consequently weakening the anodic CuNCs_Assy ECL signal, enabling ultrasensitive target quantification. As a proof-of-concept, the proposed CBPE sensor was effectively applied to detect CBZ in crops, achieving a broad linear range of 10^-11 to 10^-5 g mL^-1 and an exceptionally low detection limit of 3.33 pg mL^-1. This study establishes a sensitive platform for rapid pesticide residue detection and offers a universal strategy for reaction-regulated CBPE-ECL, with strong potential for detecting a broad range of targets in bioanalysis and clinical diagnostics.