Study On The Fabrication And Performance Of MIM SERS Substrates Based On Nanosphere Lithography

Surface-enhanced Raman scattering(SERS)has been widely used in surface science,analytical science and biomedicine due to its high sensitivity,high resolution and water environmental friendliness.SERS substrate is the core of SERS technology.In order to enhance its practicability,SERS substrate should have performances of high stability,excellent sensitivity,low cost,good reproducibility and uniformity.SERS substrates prepared by nanosphere lithography(NSL)technology own many advantages,such as low cost,simple preparation process,large area and high repeatability.In recent years,the preparation of SERS substrates has become the focus of research.In this thesis,two kinds of SERS substrates based on the metal-insulator-metal(MIM)structure were prepared by using the NSL technology.A set of simple preparation technology was proposed,and the SERS enhancement performance was explored.The research contents of this thesis are as follows:1.Preparation of Ag-AgFON substrate and study on its SERS performance.Combined nanosphere self-assembly with vacuum evaperation technology,the substrate of Ag film-Ag film over nanosphere(referred to as Ag-AgFON)with MIM structure was obtained.As the SERS substrate,the SERS enhancement performance was explored through experiments.R6G was selected as probe molecule to measure the Raman enhancement factor of the substrate,and the result was up to 10~7.The relative standard deviation(RSD)value of the substrate was less than 20%,which indicates that the SERS substrate obtained based on NSL has the advantages of large area,high sensitivity and good homogeneity.Meanwhile,the electromagnetic field distribution of SERS substrate with different thickness of silver film was calculated and analyzed by using simulation software FDTD Solutions.The results are basically consistent with the experimental results,which provided a reference for further improvement of SERS substrate.2.Preparation of Ag-Au/AgFON substrates and their SERS performance.Compared with Au,Ag has higher Raman activity,but its stability and oxidation resistance are insufficient.We combined the characteristics of the two materials and continued to deposite different thickness of gold film on surface of the optimized Ag-AgFON structure,to form the Ag-Au/AgFON substrates.Still using R6G as the probe molecule,the Raman enhancement factor of 10~8was obtained,which is about twice of Ag-AgFON structure,and the RSD value in large area of the substrate is less than 8%.The Raman signals of the two kinds of substrates were measured every 30 days under the same storage conditions.After60 days,the stability of the two substrates was compared.It was found that the Raman signals of the Ag-Au/AgFON and Ag-AgFON substrates decreased by 50%and 94%respectively(compared with the measured Raman signals of the newly prepared substrates).This shows that the SERS substrates obtained based on NSL technology has the advantages of large area,low cost,simple preparation,high uniformity and high sensitivity,as well as good stability.In addition,the simulation results of FDTD Solutions are basically consistent with the experimental results.In this study,only the most commonly R6G was used as the probe molecule to study the enhancement performance of Ag-AgFON and Ag-Au/AgFON substrates with large area,low cost,high precision and high stability.Based on this work,our research group is cooperating with a research group in the Second College of West China Attached to Sichuan University to carry out further research work,applying this substrate to detect biomedical viral protein molecules.The substrates can also be applied in biomedical sensing and measurement,food safety,environmental monitoring and many other fields.