Selective colorimetric chemosensor for the detection of Hg2+ and arsenite ions using Isatin based Schiff's bases; DFT Studies and Applications in test strips

Abstract Three isatin appended Schiff's base chemosensors (CS1-CS3) were synthesized and characterized by FT-IR, 1 H-NMR, 13 C-N MR, and LC–MS. The sensing ability of the synthesized chemosensors towards Hg 2+ and AsO 2 − ions was established through colorimetric / UV–vis techniques and achieved detection limit at ppm levels. All chemosensors CS1-CS3 exhibited rapid colorimetric / UV–vis response with Hg 2+ , also, CS1 and CS3 displayed dual-ion selectivity towards AsO 2 − (colour changes orange to aqua-blue) and Hg 2+ (from orange to colorless). The binding properties and detection limit has been examined through the UV–vis instrument. The mechanism of binding was investigated using various analytical techniques like FT-IR, UV–vis, mass and 1 H-NMR titration experiments. The experimental results were supported by theoretical DFT study. The developed colorimetric chemo-sensors showed a good binding affinity towards metal ions and exhibited good linearity (R 2 ≈ >0.99). Further, the developed sensors were used for test strips application to detect the Hg 2+ , AsO 2 − ions and achieved naked-eye detection at ppm levels. Hence, CS1-CS3 sensors find its practical application in efficient detection of toxic metals like Hg 2+ and AsO 2 − .