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, 1H-NMR, 13 C-N MR, and LC–MS. The sensing ability of the synthesized chemosensors towards Hg2+ and AsO2− 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 Hg2+, also, CS1 and CS3 displayed dual-ion selectivity towards AsO2− (colour changes orange to aqua-blue) and Hg2+ (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 1H-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 (R2 ≈ >0.99). Further, the developed sensors were used for test strips application to detect the Hg2+, AsO2− ions and achieved naked-eye detection at ppm levels. Hence, CS1-CS3 sensors find its practical application in efficient detection of toxic metals like Hg2+ and AsO2−.