Integrated Analysis Method Of Microextraction-surface Enhanced Raman Spectroscopy Based On Ag@WS₂QD Nanocomposite And Its Applications

The migration,enrichment,and metabolism of pollutants in the environment cause soil,water and air pollution,and bring negative influence to environmental ecology and human health.Therefore,the development of fast and efficient analysis methods for trace environmental pollutants is an important research content in the field of analytical chemistry.Surface enhanced Raman spectroscopy(SERS)has high sensitivity,provides compound fingerprint information,and allows direct analysis without sample preparation.The SERS instrument is portable for on-site analysis.In this thesis,with the goal at improving the affinity of precious metal SERS substrates,the extraction-SERS integrated analysis was studied and applied in environmental analysis.1.Ag@WS2QD nanocomposites were prepared by modifying WS2 quantum dots(WS2QD)on the surface of silver nanoparticles,and the SERS enhancement properties of Ag@WS2QD were studied.The WS2QD extraction layer on the Ag@WS2QD surface layer can selectively adsorb and enrich certain analytes,thereby improving the affinity of the silver SERS substrate for such analytes.This chapter evaluated the composition,pH and electrolyte concentration on SERS enhancement properties of Ag@WS2QD.The DFT calculation confirmed that the charge transfer number in the "Ag@WS2QD-analyte" system was higher than that in the"Ag-analyte" system.This chapter also confirmed the ability of Ag@WS2QD used as SERS substrate in qualitative and quantitative analysis.2.Based on Ag@WS2QD composite material,a dispersive solid phase microextraction-surface enhanced Raman spectroscopy(dSPME-SERS)integrated analysis method was developed.This method takes advantage of the highly dispersive property of Ag@WS2QD in aqueous solution and the selective adsorption of thiram by the WS2QD extraction layer.The adsorption equilibrium and detection of thiram can be achieved within 2 minutes.Thiram was analysed from 4 kinds of juice and honey based on the dSPME-SERS method.Linear range of the dSPME-SERS method was 12-1200 ppb,and the recoveries were between 86.0-98.1%.Due to the adsorption selectivity of thiram by the WS2QD extraction layer,common components from honey and fruit juice did not interfere with the SERS signal of thiram.The Ag@WS2QD based dSPME-SERS method was proved fast,sensitive,anti-interference,and has potential in the field of food analysis.3.Based on the Ag@WS2QD extraction membrane,an integrated analysis method of solid phase extraction and surface enhanced Raman spectroscopy(SPE-SERS)was developed.This chapter focuses on the types of Ag@WS2QD extraction membrane support media and the influence of sample volume on the repeatability and sensitivity of SPE-SERS integrated analysis.Ag@WS2QD/Nylon6 extraction membrane is used as the extraction medium and SERS substrate,combining the advantages of SPE and SERS technology,and can realize the integrated analysis of the enrichment and detection of trace components in large-volume samples.The SPE-SERS integrated analysis method has a linear range of 20-1000 ppb for trace nitrofurazone in Heihu spring water and fish pond water,the relative recovery rate is 88.3%-96.7%,and the RSD is less than 6.2%.In summary,the SPE-SERS integrated analysis method based on Ag@WS2QD/Nylon6 filter extraction membrane is expected to become a rapid analysis and in-situ monitoring platform for trace contaminants in complex water samples.