A ninhydrin–thiosemicarbazone based highly selective and sensitive chromogenic sensor for Hg2+ and F− ions

Abstract

This study demonstrates the design, synthesis and sensing applications of a simple and efficient chemosensor, 2-(1,3-dioxo-1H-inden-2(3H)-ylidene)hydrazinecarbothioamide (R) for quick detection of Hg2+ and F− in aqueous media using a colorimetric test, UV–Vis spectral analysis, and silica gel support. Sensor R showed the typical absorption peak at 305 nm for Hg2+ which is responsible for color change from yellow to colorless, while in the case of F−, R exhibits a major peak at 415 nm and a color change from yellow to red. The limit of detection (LOD) of R for the analysis of Hg2+ was calculated as 1×10−6 M while for F−, it was found to be 3.4×10−7 M. The binding modes of R with Hg2+ and F− have been investigated by the Job’s plot, Benesi–Hildebrand (BH) method, 1H NMR, FTIR and theoretical studies. The sensor R was reversible after treating it with reagents such as EDTA and calcium nitrate solution after contacting with Hg2+ and F−, respectively. The performance of R can be successfully applied for the analysis of F− contents present in toothpastes. A simple and efficient receptor ninhydrin-based Schiff’s base (R) for quick detection of Hg2+ and F− in aqueous medium using colorimetric and UV–Vis spectral analyses.