To achieve rapid and accurate detection of mercury ions (Hg²⁺) in tap water by utilizing the peroxidase-like catalytic activity of AuRu bimetallic nanozymes (AuRuNPs).

Using AuCl₃ and RuCl₃ as precursors, the AuRuNPs was synthesized in one step by allowing the reaction to stand in ethanol solvent at room temperature in the dark for 12 h. Then, the L-cysteine (Cys) was added to the system and co-incubated with the AuRuNPs to inhibit its peroxidase-like activity. Subsequently, the water sample to be tested was mixed with the above inhibition system, allowing Hg²⁺ to specifically chelate with Cys to release inhibition. Finally, the substrates 3,3’,5,5’-tetramethylbenzidine and H₂O₂ were added. After a 40 min reaction at room temperature, the absorbance at 652 nm was measured, and the concentration of Hg²⁺ was quantified using a standard curve.

Following condition optimization, a linear detection range of 1–100 μmol/L was achieved for Hg²⁺, with a limit of detection of 3.03 μmol/L. Good selectivity toward common interfering ions was demonstrated. In tests performed on actual tap water samples, spiked recoveries ranged from 97.16% to 98.50%, with a relative standard deviation was less than or equal to 4.75%.

This method is simple to operate, low in cost and strong anti-interference ability, providing a new strategy for the on-site rapid screening of Hg²⁺ in tap water.