(337f) The Colorimetric Response of Borohydride Stabilized Silver Nanoparticle on Interaction with Organophosphates

Detection of residual organophosphates in food is of paramount importance in the current scenario. Biosensors for pesticide detection may be developed by monitoring the interaction of nanoparticles with pesticides. In this report, we have studied the colorimetric response of pesticides phorate, chlorpyrifos and malathion with borohydride stabilized silver nanoparticle. The colorimetric changes are corroborated with UV-Visible spectra along with the change in particle size and zeta potential. Nanoparticle on interaction with phorate show visible change in color to dark green while other two pesticides haven’t shown any visible color change. The colorimetric response of nanoparticle pesticide mixture was further studied for 12 hours of incubation and it was observed that nanoparticle-phorate mixture started decolorizing after an hour and becomes colorless after 12 hours of incubation, while other two pesticide mixtures remains same. This decolorization of phorate was correlated with the degradation of pesticide in the presence of bare silver nanoparticle. The reaction mechanism was explained by the formation of silver and sulfur atom (Ag→S) complex. The uncapped nanoparticles get stabilized by pesticides over time for chlorpyrifos and malathion while phorate undergoes degradation due to scission of S-CH₂ present in the molecule. This color change may be utilized as a colorimetric method for the detection of phorate pesticide.