A Dicyanoisoflurone-based Near-infrared Fluorescence Probe for Highly Sensitive Detection of Hg²

Due to its high toxicity, long durability, easy absorption by aquatic organisms, and significant bioaccumulation, Hg²⁺ has caused substantial environmental damage and posed serious threats to human health. Therefore, effective detection of Hg²⁺ is of utmost importance. In this study, a turn-on fluorescent probe based on dicyanoisoflurone was developed for the detection of Hg²⁺. The probe exhibited near-infrared fluorescence signal at 660 nm upon excitation by 440 nm UV light in a mixture of CH₃CN and HEPES buffer (4:1, v/v, 10 mM, pH = 7.5), with selective binding to Hg²⁺ in a molar ratio of 1:1. This binding event was accompanied by a visible color change from light yellow to orange. By utilizing the enhanced fluorescence signal change, this probe enables highly sensitive analysis and detection of Hg²⁺ with excellent selectivity (association constant = 1.63 × 10⁴ M^- 1), large Stokes shift (220 nm), high sensitivity (detection limit as low as 5.6 nM), short reaction time (30 s), and a physiological pH range of 7.5-9.5. The probe was successfully employed for detecting of Hg²⁺ in real water and living cells.