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

Three isatin appended Schiff's base chemosensors (CS1-CS3) were synthesized and characterized by FT-IR, H-1-NMR, C-13-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 H-1-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 approximate to > 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-.