Electrochemical Au NPs sensor for rapid detection of emerging PFAS alternatives in aquatic food chains

Per-and polyfluoroalkyl substances (PFAS) are increasingly recognized as environmentally relevant compounds because of their extensive occurrence, limited degradability, bioaccumulation potential, and possible impacts on human health. The increasing use of short-chain and emerging PFAS alternatives further highlights the demand for rapid, sensitive, and selective detection methods applicable for environmental monitoring. Herein, a label-free electrochemical impedance spectroscopy (EIS) sensor based on a fluorinated thiol self-assembled monolayer formed on electrodeposited gold nanoparticles supported on a glassy carbon electrode (fluorinated SAM/AuNPs/GCE) is reported. The sensor design integrates nanostructured AuNPs with fluorinated interfacial chemistry to improve sensitivity and preferential response toward fluorine-containing analytes. The AuNPs layer facilitates an enlarged electroactive surface area and amplifies interfacial impedance responses, while the fluorinated SAM can promote PFAS adsorption via fluorophilic interactions. Perfluorooctanesulfonic acid (PFOS), one of the most regulated and environmentally relevant PFAS, was employed as the primary target analyte, and the sensing principle relied on adsorption-induced modulation of charge-transfer resistance measured by EIS. Under the optimal conditions, the sensor demonstrated a linear response toward PFOS in the concentration range of 0.01-600 ng L^-1 with a low limit of detection of 0.005 ng L^-1. The sensor revealed reproducibility, long-term stability, and the highest response to PFOS under the tested experimental conditions, with distinguishable responses across the examined PFAS panel. In addition, the adsorption-driven and label-free sensing mechanism eliminates the need for complicated recognition elements and minimizes sample preparation for aqueous samples. Recoveries were obtained in tap, river, and fish samples, confirming platform viability for rapid PFAS monitoring.