Donor–acceptor conjugated and triazine-containing covalentorganic framework: Construction of a signal “on–off–on” electrochemiluminescence immunosensor for efficiently detecting zearalenone

We utilized a novel signal “on–off–on” electrochemiluminescence (ECL) immunosensing strategy for the accurate and sensitive detection of trace zearalenone (ZEN) by using a triazine-containing covalent organic framework (COF) as luminophore and a complex of CuFe2O4 and polydopamine (CuFe2O4@PDA) as the quencher. The triazine-containing COF, which was synthesized by reacting 2,4,6-tris (4-formyl-phenyl)-1,3,5-triazine (TFPT) and 1,3,5-tris (4-aminophenyl) benzene (TAPB) (denoted as TFPT-TAPB-COF), exhibited the advantages of large specific surface area and pore size, extended π-conjugated skeletons, long-range order structure, donor–acceptor (D–A) conjugated structure, and high intramolecular charge transfer, thus achieving an enhanced ECL emission ability in the presence of K₂S₂O₈. Moreover, CuFe2O4@PDA has demonstrated the trimodal quenching effects of resonance energy transfer, electron transfer, and efficient scavenging ability toward electrogenerated coreactant radicals. The ECL emission mechanism of the D–A conjugated TFPT-TAPB-COF and the merged quenching effect of CuFe2O4@PDA were clarified. By combining the trimodal ECL quenching mechanism and competitive immunosensing strategy, the constructed “on–off–on” TFPT-TAPB-COF-based ECL immunosensor exhibited a wide dynamic range of 10 fg mL−1 to 100 ng mL−1 with an ultralow detection limit of 7.9 fg mL−1, high selectivity, good accuracy, high stability, and acceptable practicality for the detection of ZEN from food products. This work provides a new COF-based ECL immunosensing method for the efficient detection of mycotoxins in food items.