Design And Preparation Of Core-shell Nano-structure SERS Substrates

In recent years,surface enhanced Raman scattering has attracted widespread attention because of its strong stability and high sensitivity.However,the enhancement of Raman signals is highly dependent on the structure of the SERS substrate.How to prepare a SERS substrate with high stability and repeatability has been a hot topic in the research of SERS signal amplification.In this thesis,by studying the preparation method of core-shell nanomaterials,a simple and convenient method for synthesizing Raman substrate materials with good repeatability and excellent stability is studied.The main research contents include the following three aspects:1.Research on 3D-FDTD simulation of physical enhancement mechanism of nanomaterials.Since most of the enhancement factors of the SERS signal come from physical enhancement,the effect of the surface morphology of the nanomaterials on the distribution of enhanced hot spots of the electromagnetic field was studied by simulation,and the influence of hot spot distribution of electromagnetic field enhancement on Raman signal in the presence of monomer and dimer.FDTD was used to theoretically study the electromagnetic field enhancement hot spot distribution of flower silver nanoparticles with different aggregation levels,and then the flower silver nanoparticles were used to experimentally detect the SERS signal of the antihypertensive drug glezetide.Finally,the detection concentration values of the three samples were obtained,and then compared with the actual concentrations.The results showed that even if there was some material interference,the error was less than 15%.2.Study on Synthesis of Ag@ZrO₂Substrate Material and Its SERS Effect.It mainly describes a method of preparing Ag@ZrO₂core shell nanoparticle materials by using traditional seed growth methods.The core-shell ratio was adjusted by adding different volumes of zirconium propoxide,and then image characterization was performed by TEM,SEM.In order to further understand the distribution of physical enhancement hotspots,we use FDTD for electromagnetic field simulation to theoretically explain physical enhancement.By testing the probe molecule R6G,the test results show higher sensitivity,with a LOD of 10^-8M（4.79 ug/L）,and then the principal component analysis algorithm（PCA）was used to obtain a goodness of fit of 97.4%.In order to verify the stability of the core-shell structure nanoparticles,the material particles were etched at different times in a strong acid and strong alkali solution environment,and then Raman tests were performed.The results show that Ag@ZrO₂substrate material still has good SERS signal stability and enhancement effect in harsh environments.3.Synthesis of SiO₂@Ag@ZrO₂substrate material and its SERS effect.First of all,we used the common St（?）ber method for synthesizing silicon dioxide.Next,the silica ball was subjected to an amination modification test,and then the surface was covered with a layer of Ag nanoparticles,and finally the outer surface was coated with a layer of zirconia film,namely,a SiO₂@Ag@ZrO₂substrate material.The prepared nanoparticles were subjected to surface characterization tests and nanoparticle size distribution to obtain a substrate material with good uniformity.After testing R6G,it was found that the modified silica had good SERS enhancement effect and stability after silver coating.Finally,R6G was tested using SiO₂@Ag@ZrO₂substrate material.The results show that there was still a weak signal when the concentration is 10^-8M,so the composite core-shell structure SiO₂@Ag@ZrO₂nanoparticles have better SERS sensitivity and detection limit.