Semi-quantitative And Quantitative Analysis Of Trace Chemicals Based On Surface Enhanced Raman Scattering Effect

Trace detection method based on surface enhanced Raman scattering?SERS?effect is very potential in application for it is accurate and rapid.Herein,two kinds of SERS substrates employing Au and Ag as SERS active materials respectively were fabricated.With these SERS substrates,trace polychlorinated biphenyls?PCBs?which were environmental pollutants and food antiseptics were detected efficiently.By improving the principal component analysis?PCA?method,the SERS spectra of mixture were analyzed semi-quantitatively,and the mixture composition was calculated.Besides,the solution concentration was quantified with partial least squares regression?PLSR?method.The following matters were discussed in the thesis:SiO₂ NRs?nanorods?@ Au NPs?nanoparticles?substrate was fabricated by sputtering Au nanoparticles on the SiO₂ nanorods array which was deposited with the glancing angle deposition?GLAD?method.Through optimizing the fabrication technology,effective SERS substrate performing an enhancement factor of 108 was obtained.With the substrate,1×10-6M 4-monochlorobiphenyl could be detected requiring no surface modification,and the substrate could be reused to detect 4-monochlorobiphenyl or 2-monochlorobiphenyl,3-monochlorobiphenyl,4-monochlorobiphenyl which were congeners benefiting from being easy to clean.5?g/g pentachlorobiphenyl in soil sample could also be detected with the substrate.Ultrathin HfO₂ film coated Ag nanorods substrate was also fabricated.The HfO₂ film coating the Ag nanorods completely and evenly with atomic layer deposition method,thus the Ag nanorods were protected from being oxidized,and the substrate became heat and acid resistant that its enhancing effect remained after 300? and 10 mM HCl treatment.The substrate could be reused multi-times to detect potassium sorbate which was food antiseptics,by being heated to remove the analytes.SERS spectra of mixtures were analyzed semi-quantitatively with the PCA method.The ternary and binary mixtures' compositions were calculated according to “triangle rule” and “balance rule” respectively.Proportion of each component in mixtures of three kinds of dyes and mixtures of 2-monochlorobiphenyl,3-monochlorobiphenyl,4-monochlorobiphenyl congeners were calculated accurately.Taking the composition difference between analytes on the SERS substrate and in the solution caused by different adsorbability and adsorption process of kinds of molecules into consideration,a relative adsorption coefficient k was defined,and the “triangle rule” and “balance rule” were corrected.Resultly,the compositional analysis of mixture got more accurate.Quantitative analysis of food antiseptics' SERS spectra was also conducted with the method of PLSR.The concentration of 0.3¹0mg/L potassium sorbate was quantified accurately.Moreover,focusing on the compounding application of potassium sorbate and sodium benzoate,the two components' concentrations were modelled and calculated respectively with PLSR method,and the model performed satisfactory accuracy and stability while the peak overlap caused little impact.