Identification of multifunctional graphene-gold nanocomposite for environment-friendly enriching, separating, and detecting Hg²⁺ simultaneously

By virtue of the specific amalgam of mercury with gold and high specific area of a graphene scaffold, an environment-friendly multifunctional graphene-gold nanocomposite (G-AuNPs) has been identified and prepared by a simple one-pot redox reaction. The resultant G-AuNPs can reversibly enrich about 94% of Hg²⁺ in water samples, which can be further separated by only a simple filtration. Importantly, the color of the G-AuNPs suspension exclusively changes from purple-red to light brown upon the addition of Hg²⁺ in the presence of ascorbic acid, which can be applied for colorimetric detection of Hg²⁺ with a detection limit (3σ, n = 20) of 1.6 × 10^-8 mol·L^-1. Furthermore, using ascorbic acid as reducing agents, both the preparation process and the resultant nanocomposite are nontoxic. To the best of our knowledge, this is the first report to enrich, separate and detect Hg²⁺ contaminant simultaneously without causing any secondary pollution.