Study on the properties and reaction mechanism of polypyrrole@norfloxacin molecularly imprinted electrochemical sensor based on three-dimensional CoFe-MOFs/AuNPs

Coated with polypyrrole (Ppy)-based molecularly imprinted polymer (MIP), 3D CoFe-metal organic frameworks (CoFe-MOFs) with gold nanoparticles (AuNPs) was developed for electrochemical trace detection of norfloxacin (NOR). On one hand, the trace detection of NOR was realized with MIP/CoFe-MOFs/AuNPs/Glassy carbon electrode (GCE). The effective surface area of the imprinted cavities capable of identifying NOR on MIP/CoFe-MOFs/AuNPs/GCE increased to 0.1058 cm2 after 3D CoFe-MOFs/AuNPs was modified, which indicates that CoFe-MOFs/AuNPs could generate more imprinted cavities, thus contributing to a lower limit of detection (LOD) of 0.131 pmol L−1 (S/N = 3) with a wider linear range (5–100, 100–1000 and 1000–6000 pmol L−1). On the other hand, the recognition reaction to NOR by MIP/CoFe-MOFs/AuNPs/GCE is an irreversible electrochemical oxidation reaction involving an electron and a proton, controlled by a mixed adsorption-diffusion mechanism. Rapid and precise detection of NOR in prescription (norfloxacin capsules with the specification of 0.1 g) and pure milk with the recovery rates between 97.04 and 110.2% and the relative standard deviations (RSD) were less than 5.7%. The measured results by MIP/CoFe-MOFs/AuNPs/GCE were close to the commercial norfloxacin enzyme-linked immunosorbent assay (ELISA) kit, demonstrates its high potential to NOR trace detection in environmental and animal foods.