Thiocarbohydrazide based Schiff Base as a Selective Colorimetric and Fluorescent Chemosensor for Hg2+ with "Turn‐Off" Fluorescence Responses. Issue 13 (6th April 2020)

• Record Type: Journal Article
• Authors: Bhaskar, R.; Sarveswari, S.
• Is Part Of: ChemistrySelect. Volume 5:Issue 13(2020)
• Page Start: 4050
• Page End: 4057
• Publication Date: 2020-04-06
• Subjects: Colorimetric -- CHEQ -- DFT -- Hg2+ Sensing -- Fluorescence -- Quenching; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.202000652
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: An efficient thiocarbohydrazide based fluorescencesensor S5 for the selective detection of Hg 2+ in semi‐aqueous medium has been successfully designed and synthesized. The absorption (UV‐Vis) and emission (fluorescence) properties of S5 were studied in various solvents. The sensor S5 displayed no distinct changes in absorption with various solvents; however some remarkable changes were noticed in fluorescence studies. Solvent dependent spectral characterization of S5 was explored via the Lippert‐Mataga plot. UV‐Vis and fluorescence studies also revealed that the sensor S5 could selectively detect Hg 2+ ion over the other tested metal ions. The interaction of S5 with Hg 2+ leads to colour change from colourless to yellow. The observed quenching in fluorescence intensity may be due to chelation enhanced fluorescence quenching (CHEQ). The sensing mechanism was arrived through DFT and 1 H NMR titration studies. The limit of detection was found to be 1.26 nM with a wide pH range of 4–10. Moreover, sensor S5 could demonstrate sensing efficiency for lower concentrations of Hg 2+ in real sample analysis. Its performance, as a test strip and in analysis of various water samples conferred its superior selectivity. Abstract : An efficient chromogenic and fluorogenic chemosensor S5 for selective recognition of Hg 2+ ion was successfully designed, synthesised, and characterised through various spectroscopic techniques. The photophysical characterisation and sensing mechanism of S5 was studied by using 1 H NMR and DFT studies. The sensors S5 could detect Hg 2+ down to 1.26 nM in a semi‐aqueous medium.