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 rice with a good linearity (R2 > 0.995 in the range of 1 to 8 ng; 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. [Display omitted] •Electrothermal solid sampling nanozyme colorimetric sensor was first designed.•Visualized detection of Hg is fulfilled within 25 min via AuNPs gas phase enrichment.•Hg LOD reaches 6 μg/kg in solid excluding complicated sample preparation.