A New Thiophene-Appended Fluorescein-Hydrazone-Based Chromo-Fluorogenic Sensor for the Screening of Hg 2+ Ions in Real Water Samples

Abstract

A simple yet efficient, Hg2+ selective sensor, based on a fluroescein-thiophene conjugate, namely, (Z)-3′,6′-dihydroxy-2-(((3-methylthiophen-2-yl)methylene)amino)spiro[isoindoline-1,9′-xanthen]-3-one (FT) has been designed and synthesized. The compound was well characterized by analytical techniques such as HR-MS, FTIR, UV-visible absorption, steady-state fluorescence and time-resolved spectrophotometric techniques. Comprehensive analysis demonstrated FTas a highly specific and ultra-sensitive sensor towards Hg2+ ions in presence of several other interfering metal ions in ethanol/H2O (9 : 1, v/v) at pH=7.2 buffered with 10 mM HEPES buffer at room temperature. The complexation of the probe FT with Hg2+ was well confirmed by ESI-MS and FTIR spectral analysis. The detection limit of the probe FT towards Hg2+ was achieved down to 137 nM. The structure of ligand FT and FT-Hg2+ complex were well corroborated by theoretical studies as well. In addition, the FT-Hg2+ complex was found to be reversible in presence of di-sodium EDTA and hence decipher its recyclability capabilities. The significance of the present probe FT lies in its successful application for the detection and quantification of Hg2+ in real water samples and logic gate fabrication for future incorporation in small organic molecule based efficient molecular devices.