A novel ratiometric imprinted electrochemical sensing bisphenol A using MIP with alkenyl ferrocene as a functional monomer and COF-derived porous carbon as a sensitive element

Free radical polymerization is widely used for preparing molecularly imprinted polymers (MIPs) by copolymerizing alkenyl functional monomers and cross-linkers with the template molecules. However, these monomers based electrochemical sensors can only construct single-signal electrochemical sensors, making them vulnerable to various interferences. Therefore, this work aims to construct a ratiometric molecularly imprinted (RMI) electrochemical sensor by free radical polymerization. First, 3-butenoic acid (ferrocenyl) methyl ester (BA-Fc) as an alkenyl ferrocene was synthesized using hydroxymethylferrocene as a reactant. A new ferrocene-based molecularly imprinted polymer (Fc-MIP) was then synthesized by free radical polymerization with BA-Fc as functional monomer. To enhance the electrical conductivity of the covalent organic framework (COF), COF-derived porous carbon (COF-PC) was synthesized through pyrolysis. A RMI electrochemical sensor was then constructed to detect bisphenol A (BPA). For this construction, COF-PC and Fc-MIP served as the sensitive and selective elements, respectively. The oxidation peaks of BPA and Fc were utilized for the response and internal reference signals, respectively. This sensor displayed a linear ratiometric signal (IBPA/IFc) in response to BPA concentrations from 0.1 to 10 µM with detection limit of 0.03 µM. The relative standard deviation of the non-ratiometric and ratiometric sensors was 6.71% and 3.10%, respectively, demonstrating the advantage of the RMI sensor. This proposed sensor, exhibiting satisfactory reproducibility, sensitivity, and selectivity, was successfully applied in detecting BPA in samples of industrial wastewater, soil, and plastic bottles.