A robust ruthenium nanozyme-powered visual platform for thiram residues assay in foods.

A highly efficient peroxidase (POD)-like ruthenium nanoparticles loaded oxidized multi-walled carbon nanotubes (Ru/OMWCNTs) nanozyme was synthesized for the determination of thiram residues in foods. The resulting nanozyme exhibits broad pH and temperature tolerance, scalable production, and enhanced affinity toward 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2 compared to natural horseradish peroxidase (HRP). The incorporation of an OMWCNT substrate also confers excellent stability under harsh conditions, including high salinity, thermal variation, pH fluctuations, and long-term storage. A colorimetric sensing platform was developed based on the thiram-inhibited oxidation of TMB, achieving a detection range of 0.03 ~ 1.2 µg/mL and a low limit of detection (LOD) of 11.7 ng/mL. The sensor also shows satisfactory anti-interference ability against common metal ions, biomolecules, and other pesticides. When applied to the analysis of fruit and vegetable juices, the method delivered high recoveries and yielded results in close agreement with those obtained by the reference HPLC method, confirming its practicality for real-sample analysis. This study provides a robust and visual sensing tool that holds great potential for rapid thiram detection in food safety monitoring.