Adsorption Behavior Of Oxathiazolinone Pesticides On SERS Substrate And Construction Of Residual Detection Metho

Surface-enhanced Raman spectroscopy（SERS）combines the advantages of Raman spectroscopy and nanotechnology to provide information for the molecules adsorbed on the surface of metal substrates.SERS is both a promising detection technique with broad application and one of the spectroscopic means to study molecular adsorption.At present,SERS technology is widely used in the detection of pesticides,but there are fewer studies on the mechanism of molecular adsorption of pesticides,which is more complex and needs to be described by means of quantum mechanics.In this paper,the pyridaben and pymetrozine were selected as the representatives for investigating the adsorption behaviors of azidone pesticides on the surface of metal substrates and establishing SERS detection methods for pyridaben and pymetrozine in real samples.This paper will provide theoretical guidance for the practical application of SERS detection technology for pesticide residues.The main research contents and results of this paper were as follows:（1）The adsorption behavior of pyridaben on the surface of silver nanoparticles（AgNPs）and its application in SERS detection.Combining the density functional theory（DFT）and SERS to study the adsorption behavior of pyridaben on the surface of AgNPs.And based on the results of the adsorption behavior study,a SERS method for the residue detection of pyridaben in apples was established.The results showed that the S atom of pyridaben was deduced to be the adsorption site of the AgNPs.Meanwhile,the physical parameters of the adsorption model showed that the pyridaben-Ag₄ complex was an ideal adsorption model.Then the"selective"enhancement of the spectral peaks was investigated by comparing the Raman activity spectra of pyridaben and pyridaben-Ag₄.Based on the results of the adsorption mechanism,a SERS method established for the determination of pyridaben residues in apples with the range of 0.10～10.00 mg/kg and the LOD of 0.08 mg/kg.（2）The adsorption behavior of pymetrozine on the surface of AgNPs and its application in SERS detection.The adsorption behaviors of pymetrozine on the surface of AgNPs and its theoretical spectra were investigated by DFT and SERS,and based on this,a SERS method for the detection of pymetrozine residue in apples was established.The result showed that the pymetrozine molecule was adsorbed with the AgNPs by the N4 atom,and the adsorption model of the pymetrozine-Ag₄ complex was the most stable.The linear range of the SERS method for the determination of pymetrozine residues in apples based on AgNPs was 0.10～10.00 mg/kg,and the LOD was 0.20 mg/kg.（3）The adsorption behavior of pymetrozine on the surface of Au@AgNPs and its application in SERS detection.The adsorption behaviors of pymetrozine on the surface of Au@AgNPs under different solutions were investigated,and based on this,a SERS method for the determination of pymetrozine residues in apples was established.The results showed that pymetrozine was adsorbed on the surface of Au@AgNPs with different types and obtained high SERS sensitivity by synergistic interaction with Au@AgNPs and NaOH.The linear range of the SERS method for the determination of pymetrozine residues in apples based on Au@AgNPs was 0.05～1.00 mg/kg and the LOD was 0.04 mg/kg.