Fabrication Of SERS Nanostructures For Evanescent Field Excitation

Surface-enhanced Raman Scattering(SERS)is a high-sensitivity surface detection technology,that can perform more accurate and more rapid specific detection of molecules which basing on scattering spectra,after the interaction between the incident light and scattering light from the molecule.It can be applied to cancer detection,drug analysis,plus environmental pollution and explosives detection,the detection range is very wide,so it is particularly favored by people.Surface enhanced Raman scattering(SERS)is based on the localized surface plasmon resonance of metal nanoparticles to achieve the enhancement of Raman spectrum,for the surface Raman scattering effect,the molecular scattering spectrum is particularly low,to achieve the identification of molecules to be detected,we must achieve the enhancement of Raman spectrum,the only effective way to make the metal nano array structure substrate.For metal materials,when the structure size is limited to 100 nm,under the illumination of incident light,the free electrons on the metal surface will produce directional movement,resulting in the collective oscillation of the outer electrons of the metal nanoparticles,forming a huge local field near the metal particles.When the frequency of the incoming light matches the oscillation frequency of the metal electrons,the local area near the metal surface will be formed an enhanced region.When the Raman molecule to be detected is placed in the enhanced region,the Raman signal will be greatly enhanced.SERS is the only technology to detect single molecule and determine its chemical structure.On the basis of current research,we usually use precious metals such as gold,silver and copper for metal materials.In this paper,we want to use the electron beam lithography machine to etch the gold cylinder array structure with the area of 25 um × 25 um on the silicon wafer.Therefore,we need to determine the parameters of the gold cylinder array structure first-the radius r of the gold cylinder structure,the distance d between adjacent gold cylinders,they are processed by femtosecond laser in the Key Laboratory of the College of Optoelectronic Engineering of Shenzhen University,electron beam lithography machine in the optoelectronic center of Shenzhen University and vacuum multicavity coater.Then Cy5 dye produced by Shanghai Yuanye biological Co.Ltd is used as the dye to be tested,placed on the metal nano array structure,the Raman spectrum of Cy5 reagent was measured.The Raman spectrum of Cy5 reagent was compared with the standard spectrum before and after,It was confirmed that the local field strength produced by the metal nano particles can enhance the Raman spectrum of the components.Finally,the metal nano array structure was fabricated on the surface of the optical waveguide,the evanescent field of the waveguide is used as the excitation source to study the enhancement effect of Cy5 fluorescent dye.