Highly sensitive colorimetric detection of HgII and CuII in aqueous solutions: from amino acids toward solid platforms

Abstract

A chemosensor (NBD-H) based on an amino acid with 7-nitro-2,1,3-benzoxadiazole was used for selective detection of Hg^II and Cu^II among 15 metal ions in aqueous solutions by a colorimetric change. NBD-H sensitively differentiated Hg^II and Cu^II in aqueous solutions by a color change; a pink color for Hg^II and an orange color for Cu^II. NBD-H showed nanomolar detection limits for Hg^II (176 nM, R² = 0.996) and Cu^II (163 nM, R² = 0.996). The detection limit for Cu^II was much lower than the maximum allowable level of Cu^II in drinking water recommended by the U.S. EPA. The binding mode study showed that deprotonation of the NH group of NBD-H played a critical role in the binding and sensing of metal ions. NBD-H immobilized on PEG-PS resin maintained the potent binding affinity and sensing ability for the metal ions. The resin with NBD-H was recyclable for the detection of metal ions in 100% aqueous solutions.