Fluorine-Free Conjugated Polyelectrolyte Optical Nanosensor Array Enables Trace PFAS Detection and Discrimination

Environmental contamination of per- and polyfluoroalkyl substances (PFAS) into water supplies has become a global concern due to their toxicity, incidental discharge, and long halflife. Despite advancements in portable sensors, the simultaneous detection and discrimination of diverse PFAS at sub-nanomolar concentrations remains challenging without material fluorination, which further generates unintended PFAS waste. Here, the design, synthesis, and analytical performance of three emissive fluorine-free conjugated polyelectrolytes (CPEs) are demonstrated. Three CPEs with robust luminescence were synthesized with varying cationic ammonium side-chains to enable pronounced differences in each polymer's spectroscopic behavior upon electrostatic interaction with each PFAS. When coupled with array-based sensing methods, these polymeric sensors discriminated among seven PFAS (PFBA, PFOA, PFNA, PFBS, PFOS, PFDS, PFHxS) with interferents. To improve limits of detection (LODs), the CPEs were immobilized within hydrogels to enhance polymer-analyte interactions, thereby demonstrating extraordinary sensitivity (LOD = 63 pM) and selectivity without generating fluorinated waste.