Electrografted Molecular Layers as Selective and Sustainable Electrochemical Platforms for the Detection of GenX or Perfluorobutanesulfonic Acid

Per- and polyfluoroalkyl substances (PFAS) are persistent pollutants of global concern due to their extreme resistance to degradation, toxicity, and widespread occurrence. Alternatives to legacy PFAS, GenX, and PFBS (perfluorobutanesulfonic acid) have emerged as equally hazardous, reinforcing the urgent need for sensitive, selective, and sustainable monitoring strategies. Here, we introduce molecular electrografted layers for sensing (MELS), fabricated on gold and glassy carbon electrodes via the electrografting of fluorinated precursors in the presence of PFAS templates. Utilizing rationally designed fluorine–fluorine interactions and the hydrogen evolution reaction as a green, nontoxic redox probe, the sensors achieve detection limits of 1 ppt (Au/MELS-TFA) and 4 ppt (GCE/MELS-TFTA) for GenX, meeting former regulatory limits. Both sensors exhibit strong selectivity toward structurally similar PFAS, excellent stability with less than 5% variation across 300 measurements, and robust performance across environmental matrices, with recoveries within 15% of the deviation in deionized, tap, and brackish waters relative to the concentrations measured by LC-MS/MS. Extending the approach to PFBS yields comparably low detection limits, highlighting the versatility of the proposed sensing platforms. These findings establish MELS as a new generation of sustainable electrochemical sensors for PFAS monitoring, combining chemical robustness, environmental compatibility, and regulatory compliance.