Hg2--activated oxidase-like activity of Ag2S@graphene oxide nanozyme and its naked-eye monitoring Hg2+ application with obvious hyperchromic effect

To improve the selectivity and sensitivity for naked-eye detection of toxic Hg2+, water-soluble Ag2S nanoparticle stabilized by graphene oxide (Ag2S@GO) was identified by virtue of the high catalytic activity of nano Ag2S and the excellent physicochemical property of graphene oxide. After its structure and spectral performance were characterized and investigated, it was noted that the proposed Ag2S@GO possesses outstanding Hg2+-activated oxidase-like activity to oxidize the chromogenic substrate of 3,3',5,5',-tramethylbenzidine (TMB) with an obvious hyperchmmic effect from colorless to blue in the presence of Hg2+ exclusively. Under the optimized conditions, the Ag2S@GO+TMB system was successfully applied for naked-eye detection of heavy metal Hg2+ in real environmental samples, with a nmol.L-1-level detection limit of 9.8 x 10(-9) mol/L, an accurate recovery among 97.0-101.8% and a low standard deviation less than 3.3%. The Hg2+-activated oxidase-like activity of Ag2S@GO and its exclusive recognition mechanism to toxic Hg2+ were also proposed.

Automated summary

The combination of silver sulfide nanoparticles and graphene oxide enabled the naked-eye detection of toxic Hg2+ with high sensitivity and selectivity. The detection method showed a detection limit of 9.8 x 10(-9) mol/L, accurate recovery rates of 97.0-101.8%, and a low standard deviation of less than 3.3%.