"Reactive" optical sensor for Hg²⁺ and its application in environmental aqueous media and biological systems

A new rhodamine B-based "reactive" optical sensor (1) for Hg²⁺ was synthesized. Sensor 1 shows a unique colorimetric and fluorescent "turn-on" selectivity to Hg²⁺ over 14 other metal ions with a hypersensitivity (detection limits are 27.6 nM (5.5 ppb) and 6.9 nM (1.4 ppb), respectively) in neutral buffer solution. To test its applicability in the environment, sensor 1 was applied to quantify and visualize low levels of Hg²⁺ in tap water and river water samples. The results indicate sensor 1 is a highly sensitive fluorescent sensor for Hg²⁺ with a detection limit of 1.7 ppb in tap water and river water. Moreover, sensor 1 is a convenient visualizing sensor for low levels of Hg²⁺ (0.1 ppm) in water environment (from colorless to light pink). In addition, sensor 1 shows good potential as a fluorescent visualizing sensor for Hg²⁺ in fetal bovine serum and living 293T cells. The results indicate that sensor 1 shows good potential as a highly sensitive sensor for the detection of Hg²⁺ in environmental and biological samples. Graphical Abstract A new rhodamine B-based "reactive" optical sensor (1) for Hg²⁺ was synthesized. 1 shows a unique colorimetric and fluorescent "turn-on" selectivity to Hg²⁺ over 14 other metal ions with a hypersensitivity in water environment. And it is a convenient visualizing probe for low levels of Hg²⁺ in environment aqueous media, fetal bovine serum and living 293T cells.