A new Al³⁺ selective fluorescent turn-on sensor based on hydrazide-naphthalic anhydride conjugate and its application...

In this communication, we have developed an optical chemosensor 2-amino N-(6-bromo-1,3-dioxo-1H-benzo[de]isoquinolin-2(3H)-yl)benzamide (NAPH) for selective detection of Al³⁺ by reacting 4-bromo-1,8-naphthalic anhydride with 2-aminobenzohydrazide. In (DMSO:H₂O, 1:1, v/v) medium, the selective and specific nature of NAPH towards Al³⁺ was observed by the quenching along with a blue-shift in the absorption of NAPH at 465 nm that resulted in the distinct colour change from light brown to colourless. The selective complexation that occurred between NAPH and Al³⁺ was investigated by ¹H NMR and DFT methods. Under similar conditions, the weakly fluorescent receptor NAPH showed a distinct fluorescence enhancement at 555 nm in the presence of Al³⁺ among the other tested metal ions and anions. The NAPH·Al³⁺ complex formation is reversible upon addition of strong chelating agent EDTA. The receptor NAPH can be applied to detect Al³⁺ down to 2.9 μM without any interference from other tested metal ions. In addition, the receptor NAPH was successfully applied to detect Al³⁺ in live HeLa cells.