Ultrasensitive near-infrared fluorescent probe for precise fluoride detection and its application in bioimaging

Fluoride ions play vital roles in biological and industrial processes but pose health and environmental risks at elevated levels. Traditional detection methods are often hampered by inability for real-time monitoring and complex instrumentation. In contrast, fluorescent probes offer a simple, rapid, and non-invasive alternative, ideal for applications like live-cell imaging. Herein, we report a near-infrared (NIR) fluorescent probe engineered from dicyanomethylene-4H-benzopyran scaffold for highly selective fluoride detection. The probe employs a silyl-ether-gated intramolecular charge transfer (ICT) mechanism: fluoride-triggered desilylation restores ICT and switches on NIR emission with an exceptionally large Stokes shift of 205 nm. The probe features excellent selectivity for fluoride (LOD = 11.3 nM) and strong resistance to interference from complex biological matrices, enabling high-contrast imaging of fluoride dynamics in HeLa cells. Furthermore, density functional theory calculations elucidate, the unique mechanism of steric-hindrance-controlled ICT. These findings provide a more comprehensive understanding of ICT and underscore the NIR probe as a powerful tool for fluoride monitoring with excellent optical performance.