Beyond the lab: A field-deployable microfluidic platform for on-site detection of PFOA in water enabled by a fluorinated TICT probe

A fluorinated TICT probe enables low-background turn-on PFOA detection. • Dispersion-driven F⋯F contacts mediate selective probe-PFOA recognition. • Robust PFOA detection in complex waters with an LOD of 593 nM in surface water. • A microfluidic platform delivers < 10 min PFOA screening at suspected sites. Fluorescent sensors based on intramolecular charge transfer (ICT) are commonly used to detect environmental pollutants like perfluorooctanoic acid (PFOA), yet their typical fluorescence “turn-off” response often leads to high background and a limited signal-to-noise ratio, constraining sensitivity. In this study, we present a fluorinated fluorescent probe, DMASP-F, which operates via a fluorescence “turn-on” mechanism mediated by twisted intramolecular charge transfer (TICT), significantly reducing background interference for PFOA sensing. Integrating with dichloromethane-based liquid-liquid extraction, we demonstrate the probe with a limit of detection (LOD) of 37.9 nM. More importantly, implementation into a compact microfluidic platform also enables rapid (within minutes) and on-site PFOA detection, achieving excellent LODs of 87.7 nM in deionized water and 593 nM in actual water samples from Xiangjiang. The on‑site sensing performance competes favorably with, and often surpasses, that of most reported fluorescent PFOA sensors. Furthermore, energy decomposition analysis and molecular dynamic simulations reveal that the sensing performance arises from dispersion dominated F⋯F interactions, which promote probe-analyte binding, restrict molecular torsion, and thereby enhance fluorescence. This work showcases a TICT-based sensing strategy for rapid PFAS analysis and provides a field-deployable platform for monitoring PFOA contamination. Download: Download high-res image (211KB) Download: Download full-size image