Fluorescence turn-on probe for Hg²⁺ based on schiff base derivative containing sulfur

A novel fluorescence turn-on probe based on a new schiff base derivative CzSB containing sulfur atoms is designed and prepared for detection of Hg²⁺ in the presence of other competing metal ions in acetonitrile. The addition of Hg²⁺ significantly enhances the fluorescence emission intensity of CzSB. The turn-on behavior of the probe is ascribed to the metal ion-induced conformational changes from the weak N-phenyl carbazole monomer emission to intensive excimer emission. The photophysical properties and Job plot of CzSB toward Hg²⁺ confirme a 1:2 (CzSB-Hg²⁺) binding mode and a possible binding mechanism.