Luminescent Sensing, Selective Extraction and Recovery of Cu2+ 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 Cu2+ in aqueous environment. The receptor shows a prominent color change in presence of Cu2+ from yellow to reddish brown in DMSO-H2O (2:1) medium. Upon addition of Cu2+, a remarkable increment in emission intensity (phi=0.091, 11 fold) was observed probably due to intra-ligand charge transfer transition (ILCT). Interestingly, this sensor is capable to extract Cu2+ selectively from aqueous mixture of metal ions using dichloromethane solvent with the increased extraction efficiency from 85% (L:Cu2+, 1:1) to 95% (L:Cu2+, 2:1) in the pH range of 6.5-10.0. The extraction behavior of Cu2+ 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 Cu2+ (1.0x10(-5)M), no significant interference was observed after addition of 5-fold excess of other metal ions (Zn2+, Cd2+, Co2+, Fe2+, Fe3+, Ni2+, Hg2+, Sn2+, Al3+, Cr3+, Mn2+) in DMSO-H2O (2:1) medium. Moreover, the ligand was regenerated (> 98%) by adjusting the pH upto 4cycles and showed a good recyclability and reusability which might be helpful to extract Cu2+ efficiently from aqueous medium.