Luminescent Sensing, Selective Extraction and Recovery of Cu from Aqueous Environment by a Novel Turn-on Chemosensor.

A novel luminescent hydrazone ligand was synthesized via 1:1 condensation reaction of 9-anthracene aldehyde and 2-hydrazinobenzoic acid followed by its characterization with the help of absorption, emission, FTIR, NMR and mass studies. It was investigated as a reversible, ratiometric and turn-on luminescent chemosensor for Cu in aqueous environment. The receptor shows a prominent color change in presence of Cu from yellow to reddish brown in DMSO-HO (2:1) medium. Upon addition of Cu, a remarkable increment in emission intensity (Φ = 0.091, 11 fold) was observed probably due to intra-ligand charge transfer transition (ILCT). Interestingly, this sensor is capable to extract Cu selectively from aqueous mixture of metal ions using dichloromethane solvent with the increased extraction efficiency from 85% (L:Cu, 1:1) to 95% (L:Cu, 2:1) in the pH range of 6.5-10.0. The extraction behavior of Cu was monitored with the help of UV-Vis spectroscopy and a readily-usable smartphone to capture the RGB data which may be helpful as a field based analysis tool. In presence of Cu (1.0 × 10 M), no significant interference was observed after addition of 5-fold excess of other metal ions (Zn, Cd, Co, Fe, Fe, Ni, Hg, Sn, Al, Cr, Mn) in DMSO-HO (2:1) medium. Moreover, the ligand was regenerated (> 98%) by adjusting the pH upto 4 cycles and showed a good recyclability and reusability which might be helpful to extract Cu efficiently from aqueous medium.