DNA-Mediated Graphene Oxide/Platinum Nanozymes for Label-Free Colorimetric Detection of Hg²⁺

Abstract

Mercury ions (Hg2+) have persistent bioaccumulation and high toxicity, which can severely damage the ecological system and human health. Therefore, sensitive methods are required for Hg2+ analysis. Herein, a DNA-mediated growth strategy was developed for the synthesis of platinum nanoparticles (PtNPs) on the surface of graphene oxide (GO). The resulting GO-DNA-PtNPs displayed excellent peroxidase-mimicking activity in a sequence-dependent manner. The peroxidase-mimicking activity could be significantly inhibited by Hg2+ because of the specific trapping of Hg2+ by thymine bases (T–Hg2+–T) and in situ reduction of Hg2+ by PtNPs on the GO surface. Under optimal conditions, there was a good linear range from 1 pM to 1 μM with a detection limit of 2.2 pM for Hg2+ analysis. This sensor demonstrated excellent analytical performance for assessing Hg2+ in complex lake waters. This work provides an effective strategy for the preparation of PtNP-based nanozymes and broadens the applications of PtNPs for biosensing.