Simultaneously colorimetric detection and effective removal of mercury ion based on facile preparation of novel and green enzyme mimic.

Abstract In this work, an environmentally-friendly and cost-effective enzyme mimic was obtained by facile one-pot preparation of chitosan/Cu/Fe (CS/Cu/Fe) composite. This composite exhibited significantly enhanced oxidase-mimicking activity during catalyzing the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB). The CS/Cu/Fe composite was comprehensively characterized and the possible catalytic mechanism was reasonably explored and discussed. Benefiting from the thermal stability and the compatibility with carbohydrate, the CS/Cu/Fe composite was further integrated with agarose hydrogel to fabricate a portable analytical tube containing oxidase mimic. Based on the inhibition of the catalytic oxidation of TMB in the presence of cysteine, as well as the recovery of oxidase-like activity of CS/Cu/Fe due to the specific complexation of cysteine and mercury ion (Hg2+), the rapid colorimetric detection of Hg2+ was successfully carried out in the analytical tube. This colorimetric method showed good linear response to Hg2+ over the range from 40 nM to 8.0 μM with a detection limit of 8.9 nM. The method also revealed high selectivity and satisfactory results in recovery experiments of Hg2+ detection in tap water and lake water. Furthermore, it was found that the effective removal of Hg2+ could be realized in the analytical tube based on efficient Hg2+ adsorption by CS/Cu/Fe composite and agarose hydrogel. This study not only prepared a robust and low-cost enzyme mimic, but also proposed a smart strategy to simultaneously monitor and remove toxic Hg2+ from contaminated water.