In this study, we have used new approach for detection of the methyl parathion residues i.e., by inhibiting half of the peroxidase-like activity of gold nanoparticles. We have investigated the peroxidase like activity of gold nanoparticles by colorimetric assay and optimized the pH,
temperature, incubation time and different concentrations of H2O2 by using TMB as substrate as well as organophosphates effect on their enzyme mimetic activity. Kinetic study of gold nanoparticles has shown better catalytic activity than horseradish peroxidase at pH 3.5.
The peroxidase substrate TMB (3,3,5,5-tetramethylbenzidine) can be oxidized by H2O2 by the enzymatic action of the gold nanoparticles resulting in a blue-coloured product, oxidized TMB. The principle involved behind the inhibition of enzymatic activity of nanozyme is
due to hindrance of electron transfer mechanism TMB-H2O2-Au NPs system by the methyl parathion. The peroxidase activity is selectively reduced with increasing methyl parathion concentration. This sensing method has lowest limit of detection of 78.95 nM. This study can
be used for development of sensitive and cost effective technique for sensing of harmful pesticides.
