Highly sensitive detection to gallic acid by polypyrrole-based MIES supported by MOFs-Co2+@Fe3O4

Abstract Supported by metal-organic frameworks (MOFs), a new molecular imprinted electrochemical sensor (MIES) taking nano-structure Co2+@Fe3O4 as the support point of receptor was developed for highly sensitive detection of GA in this paper. Gold electrode was modified with Co2+@Fe3O4, then Co2+@Fe3O4/Au was soaked and compounded to Fe3O4@ZIF-67/Au. MIPs film was obtained by potentiostatic polymerization with polypyrrole as monomer and GA as template. SEM, EDS, FTIR, XRD, DPV and EIS characterizations indicate the success of the preparation of the modified electrode. By optimization, the Δi response of MIP/Fe3O4@ZIF-67/Au was strengthened from 25.38 μA to 30.84 μA. The MIP/Fe3O4@ZIF-67/Au sensor showed a superior sensitivity with a lower LOD of 0.297pM (S/N = 3) and a wider linear range of 6–600pM for GA detection, which profits from the combination of high surface area of Co2+@Fe3O4 and high porosity of MOFs. Because of the specificity of molecular imprinted polymers (MIPs), our sensor showed advanced selectivity and not affected by similar structure interfering substances. In addition, the stability, reproducibility and real-sample detection were also satisfactory with the recovery rates between 89.5% and 118.4% and the RSD were lower than 5.5%. This sensitive and simple method can be further used to prepare polypyrrole-based MIES suported by MOFs-Co2+@Fe3O4 for highly sensitive detection of other small and weight molecules.