Control of Stepwise Hg²⁺ Reduction on Gold to Selectively Tune its Peroxidase and Catalase-Like Activities and the Mechanism

The flexible regulation of enzyme-like activities of nanozyme is of great importance in biomedical applications. However, the current modulation strategies usually lack activity specificity to reveal precise tuning of the desired activity. In this work, it is demonstrated for the first time that the Hg²⁺ on surfaces of Au film can be reduced in a chemical path of Hg(II) → Hg(I) → Hg(0) via anti-Galvanic reaction. Furthermore, it is amazing that the generated Hg⁰ via Hg(NO₃)₂ treatment contributes to greatly boosted peroxidase and catalase activities of Au films due to the formation of Au@Hg amalgam, while the main Hg⁺ species on Au formed by HgCl₂ modification results in only catalase-like activity acceleration. Based on this, the peroxidase- and catalase-like activities of gold can be selectively modulated by controlling the stepwise reduction of Hg²⁺. Further density functionality theory (DFT) calculations reveal that it is the significantly lowered activation energy by Au@Hg amalgam that accounts for the acceleration of both peroxidase and catalase reaction. These results demonstrate a novel avenue to specifically modulate the enzyme-mimicking activities of Au, which not only facilitates the design of nanozymes with specific activity, but also broadens their biological usage.