An OFF-ON-OFF type fluorescent probe based on a naphthalene derivative for Al3+ and F- ions and its biological application.

A novel fluorescent probe-based naphthalene Schiff, 1-(C2-glucosyl-ylimino-methyl)-naphthalene-2-ol (L) was synthesized by coupling d-glucosamine hydrochloride with 2-hydroxy-1-naphthaldehyde. It exhibited excellent selectivity and highly sensitivity for Al3+ in ethanol with a strong fluorescence response, while other common metal ions such as Pb2+ , Mg2+ , Cu2+ , Co2+ , Ni2+ , Cd2+ , Fe2+ , Mn2+ , Hg2+ , Li+ , Na+ , K+ , Fe3+ , Cr3+ , Zn2+ , Ag+ , Ba2+ and Ca2+ did not cause the same fluorescence response. The probe selectively bound Al3+ with a binding constant (Ka ) of 5.748 × 103  M-1 and a lowest detection limit (LOD) of 4.08 nM. Moreover, the study found that the fluorescence of the L - Al3+ complex could be quenched after addition of F- in the same medium, while other anions, including Cl- , Br- , I- , NO2- , NO3- , ClO4- , CO32- , HCO3- , SO42- , HSO4- , CH3 COO- , PO43- , HPO42- , S2- and S2 O32- had nearly no influence on probe behaviour. Binding of the [L - Al3+ ] complex to a F- anion was established by different fluorescence titration studies, with a detection limit of 3.2 nM in ethanol. The fluorescent probe was also successfully applied in the imaging detection of Al3+ and F- in living cells.