Green synthesis of fluorescent N,O-chelating hydrazone Schiff base for multi-analyte sensing in Cu2+, F− and CN− ions

Abstract A colorimetric and fluorometric hydrazone Schiff’s base derived from dehydroacetic acid by three-steps and high-yield syntheses under green approach employing ethanol as a solvent has been prepared. Multi-analyte sensing for both metal cation (Cu 2+ ) and anions (F − and CN − ), with high sensitivity and competitive selectivity, was encountered. The sensing mechanism of anion detection found to be deprotonation of N H and O H moieties in the presence of ions. However, metal cation like copper(II) ions chelation with sensor, leads to diminish intra-molecular charge transfer (ICT) with chelation induced quenching of fluorescence (CHQF). Contrary, anionic interaction ensued in heightened ICT as well as photo-induced electron transfer (PET) processes. The Job’s plots interpretation rendered stoichiometry of 2:1 with Cu 2+ /F − and 1:1 with CN − . Moreover, the detection limits of 0.962 ppm (Cu 2+ ), 0.023 ppm (F − ) and 0.073 ppm (CN − ) were much lower than WHO guidelines. Further, either water or methanol was employed to differentiate F − /CN − ions with sensor in THF, with prominent visible naked eye and fluorometric responses.