Abstract: This study developed a simple, rapid and visual approach for colorimetric detection of organophosphorus pesticide. Positively-charged gold nanoparticles (AuNPs) with an average diameter of 25 nm were synthesized by seed growth method which possessed intrinsic peroxidase-like activity. AuNPs were demonstrated to have the highest oxidase activity at pH 4.0, 35 ℃ in the presence of 1 mmol/L 3,3’,5,5’-tetramethylbenzidine (TMB) and 10 mmol/L H2O2. It was shown that the nanozyme activity of AuNPs could be inhibited by its surface passivation with rogor, and so an inverse relationship between AuNPs catalytic activity and rogor concentration in the range from 1 to 80 mmol/L was found. The correlation coefficients and sensitivity of the assay were 0.985 and 1.39 mmol/L, respectively. Recoveries from tea samples spiked with different concentrations of rogor were in the range of 91.36%–102.56%. The effective peroxidase-like activity of AuNPs was kept for 1 month at room temperature. Adsorption of rogor onto AuNPs via amide bond was confirmed by Fourier transform infrared (FTIR) spectroscopic analysis. This assay may have potential application in environmental pollutant detection.

Key words: gold nanoparticles, peroxidase mimetics, organophosphorus pesticides, colorimetric analysis