Defect engineering-mediated OER-enhanced ECL for ultrasensitive detection of E.coli

The electrochemiluminescence (ECL) system of Luminol is frequently constrained by its sluggish reaction kinetics and strong dependence on dissolved oxygen in practical applications. Herein, we report an innovative strategy for enhanced oxygen evolution reaction (OER) catalysis mediated by defect engineering, which provides a new insight into boosting the kinetic process of ECL performance in the Luminol/H₂O system. In this study, Ferrocene monocarboxylic acid (FcCA) was coordinatively linked to the topological framework of nickel-based metal-organic frameworks (NiBDC MOFs) to construct Fc-NiBDC MOFs, achieving a significant improvement in the OER performance, leading to a 4-fold increase in the ECL intensity of Luminol. This is mainly because FcCA induces coordination defects at adjacent Ni sites, creating a high density of oxygen vacancies to facilitate the conversion of reactive oxygen species (ROS). At the same time, by utilizing its strong adsorption ability for hydroxyl groups, it can significantly increase the local concentration of ROS at the active sites. Furthermore, the introduced Fc/Fc⁺ redox cycle continuously accelerates the generation and transformation of ROS, thereby constructing an efficient ROS cyclic regeneration mechanism. This triple synergistic enhancement effect can effectively promote the sustained generation and efficient enrichment of ROS, thereby significantly improving the ECL efficiency of Luminol immobilized on NiBDC MOFs through amide bonds. The biosensor constructed on this basis was applied for the highly sensitive detection of E.coli, with a limit of detection (LOD) as low as 0.33 CFU mL^-1. This strategy pioneers a new pathway for the defect engineering in MOF-based ECL systems, offering a versatile platform for pathogen diagnostics.