A near-infrared fluorescent ratiometric probe with large Stokes shift for multi-mode sensing of Pb²⁺ and bioimaging

Pb²⁺ is a heavy metal ion pollutant that poses a serious threat to human health and ecosystems. The conventional methods for detecting Pb²⁺ have several limitations. In this study, we introduce a novel fluorescent probe that enables the detection of Pb²⁺ in the near-infrared region, free from interference from other common ions. A unique characteristic of this probe is its ability to rapidly and accurately identify Pb²⁺ through ratiometric measurements accompanied by a large Stokes shift of 201 nm. The limit of detection achieved by probe was remarkably low, surpassing the standards set by the World Health Organization, and outperforming previously reported probes. To the best of our knowledge, this is the first organic small-molecule fluorescent probe with both near-infrared emission and ratiometric properties for the detection of Pb²⁺. We present a triple-mode sensing platform constructed using a probe that allows for the sensitive and selective recognition of Pb²⁺ in common food items. Furthermore, we successfully conducted high-quality fluorescence imaging of Pb²⁺ in various samples from common edible plants, HeLa cells, Caenorhabditis elegans, and mice. Importantly, the probe-Pb²⁺ complex exhibited tumour-targeting capabilities. Overall, this study presents a novel approach for the development of fluorescent probes for Pb²⁺ detection.