The Application Of Precious Metal Nanomaterial In The Analysis Of Organophosphorus Pesticide Residue

Organophosphates(OPs)pesticides are widely applied in agriculture for their high activity and relatively low persistence in insects-controlling and agricultural productivity increasing.However,exposure to even a little amount of OPs pesticides is still fatal.OPs pesticides could phosphorylate the serine hydroxyl group in the active site of nervous system enzyme acetylcholinesterase(AChE),and irreversibly inhibit the activity of AChE.As a result,this make the neurotransmitter acetylcholine(Ach)disorder and cause injurious effects,such as asthma,teratogenesis,and even death happened.Therefore,rapid and sensitive detection of OPs pesticides is of vital importance to body health and environmental preservation.This thesis focuses on the fabrication of colorimetric biosensors for rapid detection of organophosphorus pesticide by using precious metal nanoparticles as optical probe.The details are summarized as follows:(1)First,we build a colorimetric sensor for the determination of organophosphorous pesticides(OPs)based on the inhibition of enzyme-triggered formation of gold-silver core-shell nanoparticles(Au@Ag NP).In our method,alkaline phosphatase(ALP)catalyzes the dephosphorylation of p-Aminophenyl phosphate monohydrate(p-APP)substrate to p-aminophenol(p-AP).As a reductive agent,p-AP reduced Ag+ to Ag0 on the outer surface of AuNPs to form the core-shell structured Au@Ag NPs.The color of Au@Ag NP changed from red to yellow,with the increasing Ag shell thick,which could be discerned by naked eye.OPs pesticides,the enzyme inhibitor,would block the dephosphorylation of p-APP and prevent the enzyme-stimulated silver deposition reaction,which exerted obvious effects on the formative Ag shell thick and led to decreased color intensity and UV absorbance of Au@Ag NPs.This finding forms the basis for the determination of OPs.(2)Next,we developed a colorimetric biosensor for OPs pesticides detection based on the enzymatic etching of gold nanorods(AuNRs)which displays vivid color responses.In the presence of acetylcholinesterase(AChE)and choline oxidase(CHO),the substrate acetylcholine(ACh)was catalyzed to generate H2O2 and betaine.The resulting H2O2 could etch AuNRs and lead to the decrease of the aspect ratio of AuNRs,which lead to the blue shift of LSPR and distinct color change form brownish to gray,green,violet,red,and yellow,respectively.After incubation with the organophosphorus pesticides(OPs),the activity of AChE was inhibited.As a result,the generation of H2O2 decreased,which prevented the etching of AuNRs and blocked color change.The accuracy of visual semi-quantitative determination of OPs was significantly improved,due to multiple colors are presented in this biosensor.And the LSPR shift(△W),the difference between the LSPR band of AuNRs after and before AChE inhibited by OPs,was utilized to quantitatively determination of OPs.