Mimetic peroxidase based on a gold amalgam for the colorimetric sensing of trace mercury(II) in water samples

The development of an efficient protocol to achieve the precise monitoring of trace Hg²⁺ is of great significance. In this work, a colorimetric sensing platform for Hg²⁺ monitoring was constructed via modifying gold nanoparticles (Au NPs) and hemin/reduced graphene oxide (H-rGO) onto carbon cloth (CC) (AuNPs/H-rGO/CC). The Au NPs, anchored on the surface of the interlaced fibers of CC without aggregation, showed high peroxidase-mimetic catalytic activity. The formed Au amalgam and the synergistic effect of Au NPs and H-rGO enhanced the peroxidase-mimetic activity of AuNPs/H-rGO/CC and enabled the sensing platform to achieve the colorimetric detection of Hg²⁺ over a wide range of 3.2 × 10⁻¹⁰ M–1.0 × 10⁻⁶ M. AuNPs/H-rGO/CC exhibited high selectivity towards Hg²⁺ due to the high special affinity between Au NPs and Hg²⁺. The sensing platform was further successfully applied to the determination of Hg²⁺ in different water samples via a simplified operation involving just tweezers. The present sensing protocol is expected to provide an efficient way to construct colorimetric sensors and to promote the sensitive determination of Hg²⁺ for a variety of relevant applications.