Selective and sensitive turn on fluorescence cyanide recognition in aqueous medium based on Zn(II)-hydrazone metal...

Detection and quantification of the cyanide ion (CN^- ) has attracted considerable attention because of its extreme toxicity. A novel Zn(II)-complex, applicable as a fluorescent chemosensor for CN^- recognition, was synthesized in excellent yields from the reaction of zinc sulfate with the novel hydrazone: 3-(amino-9H-purin-yl)-N'-(hydroxybenzylidene) propanehydrazide. The structures of the hydrazone (L) and the zinc-hydrazone complex (L.Zn) were characterized by ultraviolet-visible spectrophotometry, Fourier-transform infrared spectrometry, mass spectrometry, proton- and carbon-13-nuclear magnetic resonance. The sensing performance of the proposed chemosensors, L and L.Zn, towards common ions was investigated via naked-eye studies as well as absorption and emission spectral analysis. Hydrazone (L) efficiently functioned as a fluorescence sensor for aluminum ions (Al³⁺ ) and zinc ions (Zn²⁺ ) with large binding constants, and exhibited colorimetric and fluorometric responses for several basic anions: OH^- , CO₃ ^2- , HCO₃ ^- , HSO₃ ^- , CH₃ COO^- and CN^- . However, L.Zn showed quick, sensitive and specific enhancement of fluorescence intensity towards CN^- anion, and a linear relationship was observed as the concentration of CN^- varied from 1 to 14 μM. The detection limit was determined to be 0.14 μM, which is lower than the 1.9 μM maximum value recommended by the World Health Organization for drinking water. The practical performance of the sensor was successfully demonstrated using various environmental water samples spiked with cyanide ion.