A dual functional fluorescence sensor for detection of Al3+ and Zn2+ in different solvent
(E)-N'-((2-hydroxynaphthalen-1-yl)methylene)imidazo[2,1-b]thiazole-6-carbohydrazide (X), a new fluorescence sensor, was designed and synthesized based on imidazo[2,1-b]thiazole and 2-hydroxy-1-naphthaldehyde, which could be used to detect Al3+ in methanol buffer solution and detect Zn2+ in ethanol buffer solution with detection limits of 1.45 × 10-7 M and 1.29 × 10-8 M, respectively. X showed high sensitivity and selectivity for Al3+ and Zn2+ in the presence of other metal ions. The fluorescence intensity of X was reversible even after six cycles with the sequentially alternative addition of metal ions (Al3+ and Zn2+) and PPi, showing an efficient “off-on-off” fluorescence behavior. The complexation ratio of X to Al3+ and Zn2+ was 1:1, which was proved by mass spectrometry and B-H equation. The binding mode and sensing mechanism of X with metal ions (Al3+ and Zn2+) was verified by DFT/TDDFT calculations using Gaussian 09 based on B3LYP/6-31G(d) basis.