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

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 (K_a ) 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^- , CO₃^2- , HCO₃^- , SO₄^2- , HSO₄^- , CH₃ COO^- , PO₄^3- , HPO₄^2- , S^2- and S₂ O₃^2- 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.