A rapid and solid sampling colorimetric sensor of Hg in food based on thermo-release coupled with Au nanozyme trap

Considering complicated matrices, solid sampling analysis of heavy metals in food is almost impossible for ionic nanocolorimetric methods. Here, a novel approach is proposed to fulfill Hg analysis in solid sample based on Au nanozyme colorimetry following thermo-release (TR) and gas phase enrichment (GPE). Gold nanozyme was synthesized to both enable Hg trapping and nanozyme reaction. Furthermore, the presence of Hg⁰ enhances the POD activity of Au nanozymes and thereby oxidizes TMB under H₂O₂, resulting in color change to blue. The method LOD₃₇₀ for Hg reached 6 μg/kg in 200 mg rice sample with a good linearity (R² > 0.995); the analysis time was less than 25 min excluding digestion or extraction. Mg²⁺, Fe³⁺, and Cr⁻ interference was effectively eliminated via thermo-release, GPE and AuNPs amalgamation. It was for the first time rapid and colorimetric detection of Hg in solid sample was achieved for nanozyme, holding a great potential for visualized elemental detection in food.