A dual functional fluorescent sensor for the detection of Al3+ and Zn2+ in different solvents

Abstract

(E)-N′-((2-Hydroxynaphthalen-1-yl)methylene)imidazo[2,1-b]thiazole-6-carbohydrazide (X), a new fluorescent 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 towards 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 the B–H equation. The binding mode and sensing mechanism of X with metal ions (Al³⁺ and Zn²⁺) were verified by DFT/TDDFT calculations using Gaussian 09 based on the B3LYP/6-31G(d) basis set.