Research On Surface-enhanced Raman Substrates Based On Metasurface Structures

Raman scattering spectroscopy enables molecules to have "fingerprints" and has attracted special research interest in the field of molecular sensing and biology.Compared with traditional Raman spectroscopy,surface-enhanced Raman scattering spectroscopy has higher detection sensitivity,and it has gained rapid attention in the study of biomolecules adsorbing on metal surfaces.Part of the enhancement mechanism of surface-enhanced Raman scattering spectra can be attributed to the large local electromagnetic fields generated by the resonant surface plasmons,which can be excited by specific wavelengths of light on different shaped metal particles or tightly packed groups of particles.The key to the resulting overall enhancement depends on the morphology of the particles or aggregated nanostructures.The application of surface-enhanced Raman scattering spectroscopy is inseparable from surface-enhanced Raman substrate.The surface-enhanced Raman substrates can be roughly divided into metal materials and semiconductor materials.Metal materials have been widely studied and used.Metal materials have the advantages of structural stability,reusable,simple processing and so on.In this thesis,gold is used as surface reinforced Raman substrate material.Surface enhancement The enhancement effect of Raman substrate depends not only on the material of the substrate,but also on the surface shape of the substrate.Based on the research of gold micron column array metasurface structure and gold micron cone array metasurface structure,gold nano hollow circular array metasurface structure is used to prepare surface reinforced Raman substrates.The main research contents of this thesis are as follows:1.The optical properties of gold nanocrystalline hollow cylindrical array metasurface structure and gold nanocrystalline hollow circular array metasurface structure were analyzed by FDTD Solutions simulation software.By adjusting the shape,size,material,quantity and other factors,the metasurface structure with good enhancement effect is designed for Raman spectroscopy detection.2.The designed metasurface structure of the hollow cylindrical array of gold nanoparticles was prepared into samples.The near-field optical properties of the samples were analyzed by near-field scanning optical microscope,and the absorption spectra of the surface enhanced Raman substrates in air,water and anhydrous ethanol were measured by optical fiber spectrometer.3.Rhodamine 6G solution of different concentrations was used to test the sensitivity and enhancement factor of micro analytes detection when the sample was used as surface reinforced Raman substrate,and the advantages and weaknesses of the sample used as surface reinforced Raman substrate were analyzed according to the results of Raman test.According to the simulation results of FDTD Solutions simulation software,the gold material and appropriate size were selected for fabrication.By analyzing the nearfield optical properties of the samples,it is proved that the samples have the local electric field enhancement and the high efficiency near-field energy focusing ability.The results of Raman test show that the gold nanocrystalline hollow circular array metasurface structure has a high sensitivity of Raman spectrum detection.The results show that it is feasible to use the metasurface structure of gold nanocrystalline array as surface reinforced Raman substrate,and it has a higher enhancement factor than the gold micron column structure.