Preparation Of Functionalized Gold Nanoparticles SERS Substrate And Application In Food Analysis

Surface enhanced Raman spectroscopy（SERS）is a powerful optical technology,which has the advantages of rich information,high sensitivity and convenient operation in analytical chemistry.However,there are some limitations of SERS technology in small molecule detection,self-assembly function and economy.The multifunctional gold nanoparticle assembly substrate with the functions of enrichment,recovery and self-assembly can enable SERS to obtain higher sensitivity and stability by generating more"hot spots",which broadening the application range of SERS.Therefore,this study focused on the self-assembly and functionalization of gold nanoparticle substrate to has higher SERS activity and a wider range of applications,and explore its detection performance and principle in the analysis of pollutants.The main research contents are as follows:1.Sensitive surface-enhanced Raman scattering for the quantitative detection of formaldehyde in foods using gold nanorods substrateFormaldehyde（HCHO）is a common poisonous and harmful substance in food.It is a great significance to detect formaldehyde in food analysis.In this chapter,a rapid and sensitive quantitative detection method for formaldehyde has been developed based on surface-enhanced Raman scattering（SERS）using a4-amino-3-hydrazino-5-mercapto-1,2,4-triazol（AHMT）-formaldehyde derivative reaction.Gold nanorods（GNRs）were synthesized by a seed growth method to facilitate the collection of the SERS spectra of the extracts.The influence of parameters such as the aspect ratio of GNRs,the solvent and the surrounding microenvironment,the dosage of different reagents,the selectivity and uniformity of the method on the analysis results was optimized and explored.The results showed that the SERS analysis of the pure formaldehyde solution used a wide dynamic concentration range from 1.089 n M to 1.089 m M,with the limit of detection（LOD）as low as 0.86 n M and an enhancement factor of 3.9×10⁷.The recovery of this quantification method was calculated to be between 89.45%and103.2%,and the relative standard deviation（RSD）was not more than 6.74%for intentionally contaminated rice noodles,steamed buns,and liquor.Compared to previous reports,this analytical method made full use of the enhanced function of GNRs to further reduce the detection limit of formaldehyde.In summary,the developed method has the advantages of simplicity,rapid performance,and cost effectiveness.2.Using acupuncture magnetic force to assemble SERS substrate and detect malachite green by surface-enhanced Raman spectroscopyThe morphology and assembly structure of the SERS substrate play a vital role in SERS detection.Needle-like magnetic nanoparticles can generate more hot spots due to the special optical and magnetic properties of the tip,the material itself and self-assembly aggregation,thereby increasing the activity of the SERS substrate,making it more sensitive in analysis and detection.Therefore,a Fe₃O₄@Au SERS substrate was developed.The SERS function is realized by coating gold on the iron core.The iron nanocore can realize the magnetic assembly function,and the needle-like nano-gold structure coated on the outside greatly increases the SERS activity of the material,making the enhancement effect of the substrate equivalent to that of pure gold nanoparticles.This versatile substrate provides a new idea for SERS detection.In the quantitative detection of malachite green,the linear range was between 1 n M and 100 n M.The linear equation was y=130.52x+448.82,R²=0.9357,The detection limit was as low as0.74 n M.3.Construct a fully recovered surface-enhanced Raman spectroscopy detection method by constructing a multifunctional magnetic SERS substrateGold and silver nanoparticles are the most common enhancement substrates in SERS due to their unique optical properties for a long time.However,the dispersion and stability of gold and silver nanoparticles are poor without surfactant,which affects the reproducibility and stability in practical application,and has the risk of biological hazards,high cost and poor economy.Therefore,a needle like structure of core-shell nanoparticles（Fe₃O₄@Au@Si O₂）with magnetic assembly and core-shell isolation was designed.A method for SERS analysis of core-shell nanoparticles was developed.The iron core plays the role of magnetic assembly and substrate recovery,the needle like gold interlayer plays the role of enhancement,and the silica shell improves the stability of the nanoparticles sol.This isolation property not only plays the role of isolation,but also avoids the"quenching"phenomenon of hot spots caused by the direct contact of nanoparticles,and improves the SERS activity of the substrate to a certain extent.This method can complete the purification process by simple ultrasonic elution.The full recovery mode of substrate and analyte can not only improve the sensitivity,stability and environmental protection of SERS detection,but also solve the long-standing problem of substrate economy.