Dual-signal molecularly imprinted electrochemical sensor based on bimetallic organic framework/AuNPs synergistic...

Semicarbazide (SEM), a metabolite of nitrofurazone, poses potential risks as a carcinogen and teratogen in animal-derived foods. This research is centered on creating a homemade electrochemical sensor with high sensitivity for detecting SEM with dual signals. The working electrode was modified through the in-situ growth of a copper-iron bimetallic organic framework (Cu/Fe-BTC) on carbon cloth (CC), followed by the decoration of gold nanoparticles (AuNPs) on the Cu/Fe-BTC/CC surface. The Cu/Fe-BTC component provides abundant metallic active sites, resulting in a distinct [Fe(CN)₆]^3-/4- peak observed at 0.67 V (I₁, vs. SCE). Concurrently, the incorporation of AuNPs enhances the electrode high electron transfer capacity, which amplifies the signal peaked at 0.18 V (I₂, vs. SCE), thereby establishing an effective dual-signal detection system. Furthermore, a molecularly imprinted polymer (MIP) layer was electropolymerized onto the modified electrodes, utilizing resorcinol as the functional monomer and SEM as the template. Then, the peak intensities of the dual signals decreased upon target (SEM) recognition and increased during template elution, generating a measurable detection signal. By calculating the current changes, ΔI_D = ΔI₁ + ΔI₂, the adsorbed template molecule concentration could be quantified. Under optimal conditions, the sensor has excellent stability, accuracy, and repeatability in analyzing various samples, including serum, urine, meat, egg, honey, canned food, flour, milk powder, fish, and shrimp. The determination range is linear, spanning from 0.005 to 100 nM, with a limit of detection at 3.9 pM. Therefore, the Cu/Fe-BTC and AuNPs-based MIP sensor represents a reliable dual-signal strategy for the quantitative determination of SEM.