A novel naphthalimide-rhodamine dye: Intramolecular fluorescence resonance energy transfer and ratiometric chemodosimeter for Hg2+ and Fe3+

A novel ratiometric fluorescent chemodosimeter REPN based on 1,8-naphthalimide-rhodamine was successfully synthesized. Two different strategies of fluorescence resonance energy transfer (FRET) and photo-induced electron transfer (PET) for ratiometric detection of Hg 2+ /Fe 3+ were designed into one sensing system. REPN exhibits typical FRET signal from pyridine-naphthalimide moiety to rhodamine moiety which was induced by Hg 2+ with a detection limit of 2.72 × 10 −6  M in EtOH/PBS buffer (1:1, v/v, pH = 7.4) solution. However, the probe REPN performed ratiometric detection behavior via PET process combined with the classical ring-opening sensor system in the presence of Fe 3+ , the detection limit was 5.7 × 10 −7  M. REPN emitted bright yellow fluorescence in solid state and the maximum emission wavelength was 538 nm. Besides, the silica nanoparticles loaded AIE dye REPN maintained and further reinforced the AIE effect with higher water solubility.