Fluorene based fluorescent and colorimetric chemosensors for selective detection of cyanide ions in aqueous medium and application of logic gate

Abstract

Rising detrimental effects of cyanide due to its frequent large-scale utilization demand rapid and sensitive detection of cyanide ions. Herein, two new fluorene based chemosensors 1 and 2 have been developed through the Suzuki–Miyaura coupling reaction for fluorescence enhancement based selective detection of cyanide with sensitivity levels down to 0.2 ppb and 0.4 ppb, respectively. The plausible sensing mechanism is based on Michael type adduct formation due to the reaction of cyanide with chemosensors and was confirmed by 1H NMR titration, Job’s plot, dynamic light scattering (DLS), and density functional theory (DFT) calculations. Chemosensors 1 and 2 showed excellent linear response towards CN¯ ions (0–100 nM) in the Benesi–Hildebrand plot with association constants (Ka) 1.61 × 106 and 7.1 × 105 M¯1, respectively that corresponds to their favorable chemical reaction. Excellent selectivity of chemosensors for cyanide in the presence of other interferences was investigated through fluorescence emission, UV–Visible, and DFT analysis. Surprisingly, an immediate reversible colorimetric change upon alternate shaking and steadiness of chemosensor − CN¯ solution was noticed indicating that chemosensors can act as promising recyclable sensors for colorimetric on-site detection of CN¯. Meanwhile, chemosensors 1 and 2 displayed highly selective colorimetric detection of CN¯ under daylight and UV radiations (365 nm). Further, cyanide responsive test kits were fabricated that provided a low-cost and portable method for on-site detection of CN¯ ions in an aqueous medium. Finally, chemosensors were successfully applied for designing logic gates, and detection of cyanide in industrial waste and food samples.