Phenothiazine-Thiophene Hydrazide Dyad: An Efficient “On-Off” Chemosensor for Highly Selective and Sensitive Detection of Hg2+ Ions

A new phenothiazine-thiophene hydrazone based ((10-ethyl-10 H -phenothiazine-3,7-diyl)bis(methanylylidene))bis(thiophene-2-carbohydrazide) ( PHT ) chemosensor was synthesized via a single-step reaction and utilized as fluorescence “On-Off” sensor towards Hg 2+ ion. The PHT was fully characterized by FT-IR, 1 H-NMR, and ESI-Mass spectral analysis. The PHT probe was efficiently used for the selective detection of Hg 2+ ion in the presence of other metal ions. Further, the stoichiometry of the PHT with Hg 2+ complex was confirmed by Job’s plot analysis. The limit of detection (LOD) value of the probe PHT was found to be 0.44 × 10 −8 M. Graphical abstract