SERS Detection Of Biomarkers And Trace Nitrite Based On Functionalized Nanoparticle

Surface Enhanced Raman Spectroscopy（SERS）detection technology has the characteristics of fast,sensitive,accurate,non-destructive,and rich fingerprint information.In analytical applications,SERS can distinguish itself from many other methods by utilizing the rich vibrational spectral information it provides,and has broad application prospects in biology,medicine,environment,and other fields.Due to the small molecular weight and low Raman activity of some biomarkers or inorganic substances,it is difficult to achieve direct detection even using excellent SERS substrates.Therefore,researchers used the labeling method to modify the SERS substrate with some probe molecules to obtain functional nanoparticles.The reaction between the labeled SERS substrate and the object to be measured can change the area of the Raman scattering cross section of the object to be measured,improve the adsorption of the determinand on the SERS substrate,and realize the SERS sensitive detection of such substances.In this paper,starting from the functional modification of SERS substrate,the chemical reaction and SERS method are combined to detect trace amounts of the analyte.The specific research contents and conclusions are carried out from the following three aspects:1.Due to the small molecular weight and low Raman activity of 4-Aminobutyric acid（GABA）,a Schiff base reaction was introduced.In chapter one,4-mercaptobenzaldehyde（4-MBA）was assembled onto AuNPs via Au-S bond to form functional nanoparticles（AuNPs@4-MBA）.Then,under certain conditions,it reacts with GABA to form a Schiff base,which increases the Raman scattering cross section area and enhances the Raman signal of GABA.In addition,because 4-MBA was assembled on AuNPs in advance through Au-S bond,the characteristic peak at 1080cm^-1was selected as the internal standard,and compared with the characteristic peak at 1560 cm^-1of the newly generated C=N double bond.A linear standard curve was drawn between the peak intensity ratio of I₁₅₆₀/I₁₀₈₀and the concentration of GABA.The linear relationship between 1×10^-5and 1×10^-9mol/L was good,R²was 0.9942,and the detection limit was 3.2×10^-11mol/L.SERS detection of GABA was realized,and it was successfully applied to the detection of GABA in human serum that has important application value for future practical detection.2.Because the sol system is prone to"coffee ring effect",the chapter two is to introduce inositol hexaphosphate internal gap（IP₆）on the basis of the first work to prepare AuNPs@IP₆.Due to its special structural properties,sodium phytate can be used as a stabilizer to prevent the aggregation of gold nanoparticles.Then the AuNPs@IP₆film self-assembles onto the surface of silicon wafer,and constructs Si/AuNPs@IP₆2D SERS substrate.The substrate detection dopamine（DA）has a good linear relationship between 1×10^-4and 1×10^-8mol/L,R²is 0.9823,and the detection limit is 2.85×10^-10mol/L,which meets the practical application detection of DA and realizes the direct detection of dopamine.In addition,Si/AuNPs@IP₆2D SERS substrate can be prepared on a large scale with strong reproducibility.The silicon wafers used in the experiment were cleaned and reused,reducing costs.3.In chapter three,we first improved on the base of chapter two,formed a layer of gold nanoparticles on the surface of silver nanoparticles coated with sodium phytate,and synthesized nanoparticles with IP₆Ag@Au core-shell structure.The SERS substrate with core-shell structure plays a role in enhancing Raman signal.Then,the IP₆Ag@Au film was self-assembled onto silicon wafer by phase conversion method to prepare Si/IP₆Ag@Au 2D SERS substrate.In addition,inspired by chapter one and according to the principle of Azo reaction that PATP and nitrite ion under acidic conditions will generate DMAB,so p-aminophenylmercaptan（PATP）was modified on Si/IP₆Ag@Au two-dimensional SERS substrate,the specific detection of nitrite ion was realized.On the one hand,the Raman signal is improved by improving the substrate,and on the other hand,the specific detection of nitrite ion is improved.The specific detection of NO₂^-can be achieved by modified PATP with Si/IP₆Ag@Au,and has a good linear relationship between 5×10^-5and 5×10^-7mol/L,The R²of the newly generated characteristic peaks of 1145 cm^-1,1394 cm^-1and 1438 cm^-1are0.9794、0.9855 and 0.9719 respectively,and the detection limit is 3.04×10^-9mol/L、2.89×10^-9mol/L and 2.99×10^-9mol/L respectively.In addition,this method has a short detection time and has been successfully applied to the detection of nitrite ion in tap water,which has a good application prospect.