Fabrication of tailored imprinted layer and cladded layer on magnetic nanomaterials with enhanced specificity for recognition of PFOS

Background: Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant with significant risks to ecosystems and human health. Magnetic molecularly imprinted polymers (MIPs) provide a promising solution for selectively extracting PFOS from contaminated water. However, while bifunctional monomer imprinting improves the imprinting effect by introducing diverse functional groups, it can also increase non-specific adsorption. To address this problem, a surface cladding strategy was applied after polymerization, forming an inert cladding layer to reduce non-specific binding and improve specificity. Results: The magnetic MIPs with a cladding layer (Fe₃O₄@PFOS-cMIPs) exhibited enhanced adsorption performance, achieving a high adsorption capacity of 135.1 mg g⁻¹, an imprinting factor of 3.19, and a selectivity factor greater than 1.3, surpassing most reported PFOS-MIPs. The interactions between Fe₃O₄@PFOS-cMIPs and PFOS were confirmed to be a synergistic combination of electrostatic and hydrophobic interactions, as evidenced by FTIR analysis, zeta potential measurements, and pH studies. Additionally, Fe₃O₄@PFOS-cMIPs demonstrated excellent reusability, with stable performance across six adsorption-desorption cycles using a regeneration solution of acetone and NaCl. Furthermore, when coupled with LC-MS, Fe₃O₄@PFOS-cMIPs successfully detected trace levels of PFOS in complex environmental water samples. The method demonstrated high precision (RSD, 6.0 %), excellent recoveries (90.9 %–103.3 %), a low limit of detection (LOD, 0.06 ng L⁻¹), and an enrichment factor of 299. Significance: This study presents a practical and efficient strategy for developing magnetic MIPs with enhanced molecular recognition. The enhanced specificity and adsorption capacity highlight the strong potential of these MIPs for the targeted extraction of PFOS from various contaminated water sources, offering significant contributions to environmental analysis and remediation.