A novel phenanthroline-based colorimetric turn-off optical sensor for Zn2+

Abstract

In this study, a new Zn2+-selective sensor (PCA) was developed by linking 4-(dimethylamino) cinnamaldehyde with 2,9-dimethyl-1,10-phenanthroline in a one-step reaction. The colorimetric and optical sensing properties of PCA were investigated by utilizing UV–Vis, fluorescence spectroscopy and the naked eye. The sensor PCA displayed high selectivity and sensitivity to Zn2+ over a wide range of the other metal ions in acetonitrile (ACN)/Tris-HCl buffer (10 mM, pH 7.39, v/v 2:1) solution. The sensor showed a clear visual change from yellow to orangish-red with Zn2+. In addition, PCA could detect Zn2+ with fluorescence quenching. The complex (PCA/Zn2+) stoichiometry was found to be 1:1 and the binding constant of the complex was calculated as 1.30 × 106 M−1. PCA displayed a low detection limit (0.835 µM) which is much lower than the value recommended by WHO. PCA was also used to detect Zn2+ in tap water samples using filter paper strips and UV–Vis spectroscopy.