A naphthalimide appended rhodamine based biocompatible fluorescent probe: Chemosensor for selective detection of Hg2+ ion, live cell imaging and DFT study

In this work, we are presenting the design and synthesis of an innovative fluorescent chemosensor: NR-HG, established on a naphthalimide-based rhodamine platform for Hg2+ ion sensing. The probe operates via PET, CHEF, and FRET mechanisms. The fluorescent chemosensor shows an immense selectivity and sensitivity towards Hg2+ ion via the enhancement of ring-opening rhodamine spiro-cyclic structure, with a detection limit (LOD) of 491 nM. The DFT analysis strongly validates the experimental observations. The probe senses the Hg2+ ion reversibly upon the addition of potassium iodide (KI). From the analysis of Job's plot, it can be conclusively confirmed that the NR-HG-Hg2+ complex demonstrates a 1:1 stoichiometric ratio. We also conducted an MTT assay and cell imaging experiment to assess both the compatibility of the probe with living cells and its effectiveness in real-life imaging.