Selective and Sensitive Fluorescent Detection of Cyanide Ions and their Estimation in a Highly Alkaline Medium.

Abstract

Accurate detection of cyanide ions in food and water is indispensable to avert detrimental effects on human health and minimize environmental defilement. In response to this pressing need, we reported a novel fluorescent chemosensor (PPL1) to detect cyanide ions in highly alkaline solutions with a unique and instant fluorescence response (dull green to bright yellow) with great selectivity and sensitivity. The 1:1 binding fashion of PPL1 with CN- was signified by Job analysis. The limit of detection (0.49 µM) and the interference assay of PPL1 certified its selectivity and suitability for the detection of CN- in actual samples. The selectivity of PPL1 towards CN- was ascribed to the deprotonation followed by nucleophilic addition mechanism as proven by 1H and 13C NMR and LC-MS. The PPL1 demonstrated exceptional performance even under extreme pH circumstances and enabled us to quantify cyanide in alkaline water samples in line with the US EPA standard cyanide estimation protocol and in food samples such as sprouting potatoes, cassava, and almonds. The DFT/TD-DFT computations that shed light on the electronic transitions and interaction sites involved in the sensing process robustly validate our experimental findings and proposed mechanism. The PPL1 emerges as an advancing candidate for environmental monitoring and food safety applications due to its strong mechanistic validation (deprotonation followed by nucleophilic addition), low detection limit (0.49 µM), rapid response time (instant response), and swift fluorescence switching with CN- ions (green to yellow instantaneously in contact with CN-).