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-10H-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 Hg2+ ion. The PHT was fully characterized by FT-IR, 1H-NMR, and ESI-Mass spectral analysis. The PHT probe was efficiently used for the selective detection of Hg2+ ion in the presence of other metal ions. Further, the stoichiometry of the PHT with Hg2+ 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.