Near-infrared fluorescent probe visual detection of Hg²⁺ and its application in biological system and ecological system

Mercury ion (Hg²⁺), a heavy metal cation with greater toxicity, is widely present in the ecological environment and has become a serious threat to human health and environmental safety. Currently, developing a solution to simultaneously visualize and monitor Hg²⁺ in environmental samples, including water, soil, and plants, remains a great challenge. In this work, we created and synthesized a near-infrared fluorescent probe, BBN-Hg, and utilized Hg²⁺ to trigger the partial cleavage of the carbon sulfate ester in BBN-Hg as a sensing mechanism, and the fluorescence intensity of BBN-Hg was significantly enhanced at 650 nm, thus realizing the visualization of Hg²⁺ with good selectivity (detection limit, 53 nM). In live cells and zebrafish, the probe BBN-Hg enhances the red fluorescence signal in the presence of Hg²⁺, and successfully performs 3D imaging on zebrafish, making it a powerful tool for detecting Hg²⁺ in living systems. More importantly, with BBN-Hg, we are able to detect Hg²⁺ in actual water samples, soil and plant seedling roots. Furthermore, the probe was prepared as a test strip for on-site determination of Hg²⁺ with the assistance of a smartphone. Therefore, this study offers an easy-to-use and useful method for tracking Hg²⁺ levels in living organisms and their surroundings.