Sensitive colorimetric detection of mercury ions based on Au nanoparticles anchored yolk-shell ZIF-67 nanocubes

Abstract

Mercury ion (Hg2+) determination is vital for safeguarding water environments and living organisms. Yet, existing methods can't achieve on-site Hg2+ detection due to instrument reliance. Herein, we fabricated a colorimetric sensor based on nanozymes for sensitive Hg2+ detection. Au NPs-decorated ZIF-67 yolk-shell nanocubes (ZIF-67@PTA@Au) were prepared via sequential-etching, showing enhanced oxidase (OXD)-like activity, and could catalyze 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation without H2O2. This enhanced activity can be attributed to the synergistic effects of the components within the ZIF-67@PTA@Au nanocomposite. And the addition of Hg2+ specifically boosted its catalytic activity due to Au-Hg amalgam formation. The established Hg2+ sensor based on ZIF-67@PTA@Au nanozyme presented a wide linear range of 1-50 μM and a low detection limit (LOD) of 0.097 μM. The application of the ZIF-67@PTA@Au nanozyme-based Hg2+ sensor in tap water and lake water samples demonstrates its practical utility. The colorimetric assay provides a visual and selective method for Hg2+ detection, making it an attractive alternative to traditional analytical methods with extra potential for environmental monitoring.