A Highly Selective and Sensitive Fluorescent Turn-on Probe for Al3+ Based on Naphthalimide Schiff Base


A simple and highly selective aluminium ion fluorescent probe (N-n-butyl-4-[3,3′-((2-aminoethyl)azanediyl)bis(N′-(2-hydroxy-3-methoxybenzylidene)-propanehydrazide)]-1,8-naphthalimide) (P-1) employing 1,8-naphthalimide as the fluorophore group and Schiff base as the recognition group has been successfully synthesized and systemically characterized. The structure of probe P-1 has been established by single crystal X-ray. The photophysical properties of probe P-1 revealed that the values of the fluorescence quantum yield are higher in non-polar solvents than in polar solvents. Compared with the free P-1, the fluorescence intensity of P-1 shows a significant fluorescence enhancement in the presence of Al3+ without any significant interference from other cations and anions. In addition, from the UV–vis titration, fluorescence titration,Job’s plot and 1H NMR spectra analysis, we could primarily confirm that three important coordinative sites of P-1 for Al3+ were from imine nitrogen and tertiary amine nitrogen and formed a 1:1 complex. The fluorescence intensity for the (P-1) showed a good linearity with the concentration of Al3+ in the range of 3.0–10.0 μM, with a detection limit of 8.65 × 10−8 M and a binding constant (Kb) of 4.95 × 104 M−1. It is worthy of note that the probe P-1 was successfully applied in detection of Al3+ in Yellow River and tap water samples.


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