Perylene diimide based fluorescent sensors for aqueous detection of perfluorooctane sulfonate (PFOS).

Background: Perfluorooctane sulfonate (PFOS), one of the most harmful members of the large group of per- and poly-fluoroalkyl substances (PFAS), is notorious for its environmental persistence, bioaccumulation, and toxic effects, raising serious environmental and health concerns. Developing rapid and sensitive methods to detect PFOS in water is critical for effective monitoring and protection against this hazardous chemical.

Results: In this study, we developed rapid and highly sensitive fluorometric sensors (PDI-2+ , PDI-6+ ) for detecting PFOS. We also investigated the influence of the sensor's molecular structure on its performance. Our findings reveal that the formation of a supramolecular complex between PFOS and the cationic fluorophores, facilitated by the synergistic interplay of electrostatic, hydrophobic and π-π stacking interactions, enables a quick and efficient fluorometric sensing response for the detection of PFOS in aqueous systems. Remarkably, the detection limit for PFOS was found to be as low as 3.5 nM (1.9 ppb) for PDI-2+ and 2.7 nM (1.4 ppb) for PDI-6+ , showcasing the high sensitivity of the sensor. The PDI sensors also demonstrate a high level of selectivity for PFOS against PFOA (another top two PFAS designated as hazardous substances by the U.S. EPA), other PFAS like GenX, structurally similar detergents, and inorganic salts typically found in water. Furthermore, the sensor's successful detection of PFOS in real water samples underscores its potential for environmental monitoring.

Significance: The development of novel, water-soluble fluorometric sensors offers a promising solution for the rapid and sensitive detection of PFOS in water. Their high selectivity and low detection limits make them valuable tools for environmental monitoring and pollution control. The findings of this study contribute to the advancement of analytical techniques for PFAS detection and support ongoing efforts to mitigate the environmental and health risks posed by PFOS contamination.