A highly selective turn-on fluorescent probe for Al³⁺ in aqueous solution based on quinoline Schiff-base

A new Al³⁺-specific fluorescent probe NQ was designed and synthesized from 2-hydroxy-1-naphthaldehyde and 2-aminoquinoline. Upon the addition of Al³⁺, the fluorescent intensity of NQ was significantly enhanced compared with other examined metal ions in aqueous solution. The result of a Job's plot indicated the formation of a 1:1 complex between the probe and Al³⁺, and the possible binding mode of the system between NQ and Al³⁺ was clarified by IR analysis and ¹H NMR titration. Moreover, other metal ions examined had little effect on the detection of Al³⁺. The detection limit of NQ for Al³⁺ detection was 1.98 μM, which is lower than the level (7.4 μM) in drinking water defined by the World Health Organization. In addition, the fluorescent probe NQ could be recyclable simply through treatment with a proper reagent such as F^-, and could also be used for the detection of Al³⁺ in real samples.