Synergistic Integration of Aggregation-Induced Emission and FRET Mechanisms in Conjugated Polymers via Molecular Engineering for Ultrasensitive, Rapid, and Discriminative Detection of Perfluoroalkyl Substances

The global contamination of water bodies by persistent organic pollutants (perfluoroalkyl substances (PFAS)) has generated significant societal concern, emphasizing the urgent need for smart strategies for their rapid, ultratrace, and on-site detection. Conjugated polymers (CPs) are exceptional fluorescence sensing materials with signal-amplification properties, yet their performance is often hindered by a conventional aggregation-caused quenching (ACQ) effect. Herein, we present two acceptor-engineered aggregation-induced emission (AIE)-active CPs (FTD-MI and FTD-C8-MI) integrated with efficient Förster resonance energy transfer (FRET) mechanisms for ultralow detection of PFAS. FTD-MI exhibits a turn-off (cyan to dark) fluorescence response, while FTD-C8-MI shows a ratiometric (cyan to red) response to PFAS due to the synergistic effect of AIE and efficient interchain FRET, facilitated by electrostatic and hydrophobic interactions upon binding. Both CPs demonstrate excellent sensitivity at the subnanomolar level toward the most abundant PFAS, perfluorooctanoic acid (PFOA), and perfluorooctanesulfonic acid (PFOS). The sensing mechanism has been thoroughly investigated by both experimental and simulation studies. Additionally, an optical sensor array coupled with machine learning algorithms is established for the discriminative detection of six types of PFAS. Finally, a portable smartphone platform with a custom-designed "app" was developed for real-time, on-site, and semiquantitative analysis of PFAS in actual water samples. Thus, by providing a sensitive, portable, cost-effective, and user-friendly solution, this work offers a powerful tool for monitoring PFAS pollution, ensuring water safety, and reducing risks to public health.