A highly sensitive and selective fluorescent chemosensor for detection of Zn2+ based on a Schiff base

•A new chemosensor for Zn2+ has been synthesized and characterized.•Chemosensor showed very high selectivity to Zn2+ through fluorescence.•Chemosensor was able to distinguish Zn2+ from Cd2+ commonly having similar properties.•The stoichiometric ratio evaluated using both Benesi–Hildebrand relation and Job’s plot gives 1:1 stoichiometry.

A Schiff-base fluorescent probe – 2-((E)-(quinolin-8-ylimino)methyl)quinolin-8-ol (H7L) was synthesized and evaluated as a chemoselective Zn2+ sensor. Upon treatment with Zn2+, the complexation of H7L with Zn2+ resulted in a red shift with a pronounced enhancement in the fluorescence emission intensity in ethanol solution. Moreover, other common alkali, alkaline earth and transition metal ions failed to induce response or minimal spectral changes. Notably, this chemosensor could distinguish clearly Zn2+ from Cd2+. Fluorescence studies on H7L and H7L–Zn2+ complex reveal that the quantum yield strongly increases upon coordination. The stoichiometric ratio and association constant were evaluated using Benesi–Hildebrand relation giving 1:1 stoichiometry. This further corroborated 1:1 complex formation based on Job’s plot analyses. This chemosensor exhibits a very good fluorescence sensing ability to Zn2+ over a wide range of pH.

Graphical abstractA Schiff-base fluorescent probe – 2-((E)-(quinolin-8-ylimino)methyl)quinolin-8-ol (H7L) was synthesized and evaluated as a chemoselective Zn2+ sensor. Addition of Zn2+ to ethanol solution of H7L resulted in a red shift with a large increased in the fluorescence intensity while many other metal ions have no influence. Notably, this chemosensor could distinguish clearly Zn2+ from Cd2+.Figure optionsDownload full-size imageDownload as PowerPoint slide