Raman Detection of Pyrethroid Pesticides from Cypermethrin Molecular Imprinting onto Gold Nanospheres Surface

Abstract

Pesticide residues detection draws more and more attention by combining Surface-enhanced Raman Scattering (SERS) and Molecularly Imprinted Technique (MIT) which could provide trace molecule detection In this study the surface imprinted layer (MIP) of Cypermethrin was synthesized on the surface of the gold nanoparticles and the MIP was used to increase the hot spots of the analyte Medium preparation has the advantages of simplicity and low cost Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the MIP-SERS particle size was 16±1 nm and the outer MIP layer thickness was 1 nm Since the gate effect of the outer MIP layer enhances the Raman effect the MIP-SERS system exhibits a Raman scattering enhancement effect superior to that of the individual gold spheres In this study a detailed comparison of SERS enhancement effects using different molar amounts of MIP-SERS substrates was carried out and analysis and interpretation were carried out in the experimental results and the SERS effect was verified by using CYP as a probe molecule The MIP-SERS active substrate is suitable for Raman scattering enhancement detection an estimated value of the enhancement factor (EF) of the MIP-SERS substrate was calculated through the following equation: EF = (ISERS/ NSERS)/ (IRS/NRS) Both ISERS and IRS are intensities obtained from SERS and normal Raman conditions respectively NSERS and NRS represent the number of adsorbed target molecules; N can be determined by considering the target molecule size with respect to the geometries of both SERS and non-SERS substrates For NRS it is assumed that the target molecules arrange in a single layer on a flat surface while for NSERS the surface area created by the MIP-SERS was calculated first before determining the number of target molecules that could be adsorbed onto the said surface With this two main assumptions were made: 1 MIP-SERS were arranged on a single layer and 2 the Raman laser spot having a diameter of 1 ?m could cover an estimate of 2890 MIP-SERSand the EF value is 2 88×106 The pesticides which similar to the pyrethroid structure were compared The similar structure can make the MIP-SERS substrate with the high-intensity Raman peak in the detection of pyrethroid pesticides And it was applied to the mixed pesticide and tea inspection which proved that the SERS active substrate of this study is a forward-looking detection tool

Date of Award	2020
Original language	English
Supervisor	Jiunn-Der Liao (Supervisor)