Novel rhodamine based chemosensor for detection of Hg2+: Nanomolar detection, real water sample analysis, and intracellular cell imaging

A novel fluorescent chemosensor PS founded on rhodamine 6G for Hg2+ has been synthesized and authenticated by employing H-1 NMR, C-13 NMR, and LC-MS skills. The fluorescent chemosensor displays an intense selectivity and sensitivity for Hg2+ over additional metal ions explored in the combined organic aqueous phase. A strong fluorescence enhancement was detected after the addition of Hg2+, which was accompanied by ring-opening of a rhodamine spiro-cyclic structure. The stoichiometric ratio of the PS-Hg2+ complexes was determined to be 1:1 according to Job's plot and H-1 NMR experiment. The binding constant and limit of detection (LOD) for PS-Hg2+ complexation is estimated to be 6 x 10(4) M-1 and 3.0375 x 10(-8) M (30.37 nM), respectively. The extreme fluorescent enhancement caused by Hg2+ binding in chemosensor PS occurred at a pH range of 6-8. Owing to practical application, the Hg2+ metal ion was efficiently determined using a spike and recovery approach from real water samples. Additionally, the probe PS was further used in the cell imaging experiment for the detection of the Hg2+ intracellularly using MDA-MB-231 and A375 breast cancer cells by MTT assay method with low cytotoxicity.