Cyanide‐Ion‐Induced J‐Aggregation of Merocyanine Dye for Paper‐Based Colorimetric Detection in Water.

A probe based on merocyanine dye was synthesized as a salt of p‐toluenesulfonate. Owing to the high solubility of merocyanine dye in water and H‐bonding ability, it was investigated for anion‐induced aggregation properties in the buffered medium [CH3CN: water (1 : 1/v: v)]. The probe recognized the existence of cyanide ion by forming an H‐bond and displacing the p‐toluenesulfonate group. The probe displayed a bluish‐purple color in response to cyanide ion addition, which was initially light pink. The complex formation and aggregation properties of the probe were investigated using techniques like naked eye detection, digital colorimetry, UV‐Visible, 1H‐NMR, and dynamic light scattering (DLS). Paper and solution‐based techniques aided by a smartphone were also used successfully in the determination process. An excellent limit of detection value (LOD) was witnessed in all the techniques exploited for sensing cyanide ions. Methods based on density functional theory (DFT) were also used to investigate the complex formation and observed a good correlation in experimental and theoretical results. [ABSTRACT FROM AUTHOR]