Manipulation of monomer-aggregate transformation of a heptamethine cyanine ligand: near infrared chromogenic recognition of Hg2+†
Abstract
A novel near infrared optical molecular probe (CyL) derived from heptamethine cyanine dye was developed for the selective detection of Hg2+ over other metal ions in aqueous solutions. The detection conditions for Hg2+ were optimized. A linear range from 1.0 × 10−7 M to 5.0 × 10−6 M and a detection limit of 1.93 × 10−8 M with a correlation coefficient of 0.9992 were achieved under the optimal conditions. In the recognition of Hg2+, CyL alone peaks at 760 nm and exhibits a shoulder at 690 nm. Hg2+ can modulate the aggregation state of CyL through coordination of thiosemicarbazide on CyL and Hg2+, and thus results in an obvious shift in the maximal absorption wavelength of CyL in the NIR region. The ESI mass spectra of CyL–Hg2+ solution have been used to prove the conversion of CyL from monomers to aggregates. Finally, the proposed method has been successfully applied to the determination of Hg2+ in cosmetic samples.