Cyanide recognition using chalcone-based Colourimetric and fluorescent Chemosensor

In this work, the (Z)-3-(2-oxo-phenylethylidene)indoline-2-one (IsCh) chemosensor was successfully synthesized. The synthesized IsCh was characterized by FTIR, UV-Vis, and ¹H NMR spectroscopy, showing characteristic IR bands at 3153, 1710, 1648, and 1611 cm^-1, absorption maxima at 331 and 258 nm, and an NH resonance at δ 8.55 ppm. IsCh exhibited a spontaneous naked-eye colour change from orange to colourless upon addition of CN^-. This response was further supported by UV-vis absorption (333-403 nm) and fluorescence (FT_431nm = 25,014-63,749) spectroscopic studies. The binding interaction between IsCh and CN^- was quantitatively analyzed using the Benesi-Hildebrand method and found 2.9 × 10⁴ M^-1 with a nanomolar range of detection limit (75 nM). The selectivity of the chemosensor toward CN^- was evaluated in the presence of a range of competing anions, including F^-, Cl^-, Br^-, I^-, AcO^-, SO₄^2-, and HCO₃^-, through interference and competitive interference studies. Additionally, pH-dependent UV-Vis absorption experiments were performed to assess the stability and sensing performance of IsCh over a broad pH range, with particular emphasis on physiologically relevant conditions. The ICT mechanism underlying the CN^- recognition by IsCh was elucidated and supported by DFT calculations.