A rhodamine-phosphonate off–on fluorescent sensor for Hg2+ in natural water and its application in live cell imaging

A novel rhodamine-based fluorescent probe 3 was designed and synthesized, which contained a hydrophilic group, were designed as fluoroionophores and chromophores for the optical detection of Hg2+ ions in water with a broad pH span (3–10). As expected, it exhibited high selectivity and sensitivity for Hg2+ over other commonly coexistent metal ions in water. Its selectivity was excellent, and the detection limit was measured to be 0.2 ppm. The significant changes in the fluorescence color could be used for naked-eye detection. Furthermore, fluorescence imaging experiments of Hg2+ ions in living MGC803 cells demonstrated its value of practical applications in biological systems.