Enhancement of plasmonic resonance through an exchange reaction on the surface of silver nanoparticles: application to the highly selective detection of triazophos pesticide in food and vegetable samples

We report a simple and novel colorimetric assay for the highly selective detection of triazophos pesticide using the localized surface plasmon resonance (LSPR) of citrate capped silver nanoparticles (AgNPs) as a sensing probe. To the best of our knowledge, to date there is no report for the colorimetric detection of triazophos pesticide in food and vegetable samples using AgNPs as a colorimetric probe. The proposed method is based on the aggregation of AgNPs through a selective interaction of both sulfur and nitrogen moieties of triazophos with the NPs. The color change and red shift of the LSPR of AgNPs in the UV-visible region is due to the exchange of citrate capped ions with triazophos from the surface of NPs. Control experiments and theoretical investigations were also carried out to confirm the interactions and exchange reaction between AgNPs and triazophos pesticide. The calibration curve was found to be linear over the range of 10-300 ng mL(-1) with a limit of detection (LOD) of 3 ng mL(-1). Good recovery percentage (92.4-96.0%) and RSD (2.4-3.6%) showed the selectivity with better precision for the determination of the target pesticide from complex sample matrices. The advantages of the proposed method are simple, rapid and highly selective detection of triazophos from food and vegetable samples.