Rapid and Accurate Detection of Perfluorooctanesulfonic Acid in Environmental Samples via Chemiresistive Sensor Integrating Molecular Imprinting and Fluorine–Fluorine Interactions

In this study, we developed a chemiresistive sensor based on a dual-recognition interface engineered on a self-assembled Ti₃C₂T_<i>x</i> film as an electrical transfer channel. The interface integrates a polydopamine-based molecularly imprinted polymer (PDA MIP) and a perfluorinated probe-1H,1H,2H,2H-perfluorodecylthiol (PFDT). Perfluorooctanesulfonic acid (PFOS) is specifically captured through a synergistic mechanism: molecular imprinting within the MIP cavities and fluorine-fluorine (F···F) interactions between the fluorinated chains of PFOS and PFDT. This binding event induces a measurable and rapid change in the electrical conductivity of the Ti₃C₂T_<i>x</i> channel. The sensor achieved a detection limit of 1.3 ng·L^-1 and an average selective factor of 12.0, enabling the differentiation of PFAS compounds with different C-F chain lengths and head groups. Density functional theory calculations confirmed the weak interactions between the F atoms of PFDT and PFOS, as well as the binding sites for hydrogen bonding and electrostatic interactions between PFOS and PDA. This collectively contributed to the strong binding of PFOS within the imprinted cavities. The sensor was successfully utilized to detect PFOS in environmental samples, including waters and soils in active fluorine chemical industrial parks, showing good agreement with LC-MS/MS results. This study demonstrates the promising potential of the proposed sensor for sensitive and accurate on-site detection of PFOS in environmental samples.