Dual-mode electrochemiluminescence and colorimetric detection of malathion based on a bifunctional rGO@ZnO/Zn-Fe3O4 nanozyme

A dual-mode sensing platform has been developed for ultrasensitive malathion (MAT) detection based on bifunctional rGO@ZnO/Zn-Fe 3 O 4 composites (reduced graphene oxide-supported ZnO nanorods and Zn-doped Fe 3 O 4 microspheres). The rGO@ZnO/Zn-Fe 3 O 4 nanozyme is fabricated via a one-pot hydrothermal strategy and integrates favorable electrochemiluminescence (ECL) emission and intrinsic peroxidase-mimicking activity to realize dual-signal readout. In the K 2 S 2 O 8 ECL system, Au NPs@UiO-66 serves as a coreactant booster to further magnify the ECL intensity of the composite. Meanwhile, the nanozyme catalyzes the H 2 O 2 -mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a colorimetric response. MAT suppresses both ECL and colorimetric responses by occupying Fe 2+ /Fe 3+ catalytic sites and scavenging of reactive radicals. The sensor achieves limits of detection as low as 2.8 × 10 –13  mol/L under ECL mode and 1.32 × 10 –6  mol/L under colorimetric mode. In practical testing of MAT-spiked vegetable samples, the sensor exhibits acceptable recoveries and low relative standard deviations, demonstrating its practicability for field food safety supervision and rapid pesticide residue screening. Graphical abstract