Sensitive colorimetric detection of mercury ions using Au nanoparticle-anchored yolk–shell ZIF-67 nanocubes

Abstract

Mercury ion (Hg²⁺) determination is vital for safeguarding water environments and living organisms. Yet, existing methods cannot achieve on-site Hg²⁺ detection due to instrument reliance. Herein, we fabricated a colorimetric sensor based on nanozymes for sensitive Hg²⁺ detection. Au NP-decorated ZIF-67 yolk–shell nanocubes (ZIF-67@PTA@Au) were prepared via sequential-etching, which exhibit enhanced oxidase (OXD)-like activity and can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) 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 the ZIF-67@PTA@Au nanozyme demonstrated 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.