Highly selective and sensitive detection of Hg²⁺ by a novel fluorescent probe with dual recognition sites

A novel thionocarbonate-coumarin-thiourea triad-based probe with dual recognition sites for sensing mercury (Hg²⁺) ion was developed. The synthesized probe possessed both fluorogenic ("off-on") and chromogenic (from colorless to blackish brown) sensing performance towards Hg²⁺ ions. The fluorescence intensity was increased by 70 fold after the addition of Hg²⁺. As expected, the probe exhibited excellent selectivity and sensitivity for Hg²⁺ compared to other common competitive metal ions. The fluorescence intensity of the probe improved linearly with the increase of the concentration of Hg²⁺ (0-40 μM). Also, the minimum limit of detection (LOD) of the synthesized probe was 0.12 μM. Considering the importance of test feasibility in the harsh environment, the developed probe was applicable for detecting Hg²⁺ ions over a broad working pH range of 3-11. It is reliable and qualifies for the quantitative determination of Hg²⁺ concentrations in actual water samples. Finally, the probe achieved the bioimaging performance of Hg²⁺ in living cells and plants with good biocompatibility.