A reversible colorimetric chemosensor for “Naked Eye” sensing of cyanide ion in semi-aqueous solution

A new and simple receptor HL derived from quinoline-2-carbaldehyde and 2,4-dinitrophenylhydrazine was synthesized and explored as a colorimetric sensor for cyanide ion in DMSO/H 2 O (7:3, v/v) medium. Addition of cyanide ion to HL resulted in a color change from yellow to wine red with a significant bathochromic shift (∼125   nm) in the absorption maxima, which makes naked eye detection possible. The experimental results reveal that the formation of anionic species from deprotonation of the hydrazone N H moiety by CN − is responsible for the spectral changes. The sensor exhibits high selectivity and sensitivity for CN − ion and the detection limit were found to be 0.37   ×   10 −6   M. Moreover, the HL–CN − complex was reversibly bound and HL could be recovered by treatment with Ag + or Cu 2+ and reused without loss of sensing ability. Finally, the use of a test strip of probe HL to detect cyanide was reported.