A Simple and Rapid Quinoline Schiff Base as a Fluorescent Probe for Zn²⁺ and Its Application in Test Strips

A simple fluorescent probe, (E)-N-(3-methoxy-4-methylphenyl)-1-(quinolin-2-yl)methanimine (L), was synthesized via Schiff base condensation reaction between quinoline-2-carboxaldehyde and 3-methoxy-4-methylaniline. L can be used as a ' turn-on ' fluorescent probe for the selective and sensitive detection of Zn2+ ions in a CH3OH/HEPES medium. The detection limit was 1.04x10(-7) M. Job plot analysis shows that the binding stoichiometry of L and Zn2+ is 1 : 1, further verified by the single crystal structure. The fluorescence-enhanced response of L towards Zn2+ ions may be related to the chelation-enhanced fluorescence (CHEF) supported by theoretical calculations. By adding EDTA, the reversibility of the probe binding to Zn2+ ions is demonstrated, enabling the construction of a functional molecular logic circuit. In addition, probe L was successfully incorporated into test strips for the quantitative detection of Zn2+.