Femtomolar Congener-Selective Detection of Perfluoroalkyl Substances in Water by a Cyclodextrin-Oriented Molecularly Imprinted Transistor Sensor

Perfluoroalkyl substances (PFASs) pose significant environmental risk due to their persistence and toxicity, while the structural similarity among congeners complicates selective detection in complex matrices. This study presents a β-cyclodextrin (β-CD)-oriented molecular imprinting strategy integrated with an extended gate field-effect transistor (EGFET) sensor. The approach leverages the hydrophobic cavity of β-CD to achieve preorientation of PFAS template molecules followed by electropolymerization of <i>o</i>-phenylenediamine (o-PD) in the presence of [BMIM][BF₄] ionic liquid (IL) to form molecularly imprinted polymers (MIPs) with enhanced recognition specificity. PFAS binding to imprinted sites induces interfacial charge redistribution, which is amplified through field-effect modulation and converted to measurable threshold voltage shift. This multiple recognition enables differential binding patterns for structurally similar PFAS molecules, achieving femtomolar detection limits (25 fM for perfluorooctanesulfonate, 73 fM for perfluorodecanoic acid) with excellent selectivity. The sensors demonstrate robust performance across diverse environmental matrices, including tap water, river water, chromium electroplating wastewater, and surrounding groundwater. Real-world application of the sensor to industrial electroplating sites reveals distinct contamination levels spanning 10^-9 to 10^-5 M in wastewater and 10^-12 to 10^-7 M in groundwater, which represent outstanding analytical correlation validated against liquid chromatography-tandem mass spectrometry (LC-MS/MS). The developed sensor provides a practical solution for rapid, simplified PFAS screening in a contaminated environmental medium.