Reaction-based ratiometric chemosensor for instant detection of cyanide in water with high selectivity and sensitivity.

A highly selective chemosensor 1 based on an acylhydrazone group as binding site and naphthalene group as the fluorescence signal group were described, which could instantly detect CN(-) in water with specific selectivity and high sensitivity. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the carbonyl group, which could be confirmed by (1)H NMR, (13)C NMR, ESI-MS and DFT calculations. The addition of CN(-) to sensor 1 induced a remarkable color change from colorless to yellow and generated a blue fluorescence, these sense procedure could not interfered by other coexistent competitive anions (F(-), Cl(-), Br(-), I(-), AcO(-), H2PO4(-), HSO4(-), ClO4(-), SCN(-), S(2-), NO3(-) and SO4(2-)). The detection limits were 5.0×10(-7) M and 2.0×10(-9) M of CN(-) using the visual fluorescent color changes and fluorescence spectra changes respectively, which is far lower than the WHO guideline of 1.9×10(-6) M. Test strips based on sensor 1 were fabricated, which could act as a convenient and efficient CN(-) test kit to detect CN(-) in pure water for "in-the-field" measurement.