Selective and sensitive colorimetric sensor for CN− in the absence and presence of metal ions (Cu2+/Ni2+): mimicking logic gate behaviour

Abstract

Enone based anion sensors have significance due to their colorimetric reaction upon deprotonation and variable occurrence in the conjugated moiety. We have designed a novel and easily forming cromene-isonicotinohydrazide based probe, exhibiting selectivity towards CN⁻ through the naked eye. A Job's plot displays 1 : 1 stoichiometry along with a 0.76/0.68 μM detection limit. The results accentuate that upon addition of cations (Cu²⁺/Ni²⁺) to the heteroatom of donor moiety, sensitivity improves. The limits of detection were found to be 3.5/6.3 μM in the presence of Cu²⁺/Ni²⁺. The mechanism was proved by FTIR, NMR, DFT and –OH titration.