Research On Sers Of Go Composite Substrate Based On Light Field And Processing Structure Conterol

Surface-enhanced Raman scattering?SERS?as a non-contact,highly sensitive,zero-damage,repeatable detection and analysis technique,has been widely studied in recent years.Combined with advanced femtosecond laser micro-nano processing technology and high-precision microfluidic chip detection technology,SERS technology has great application potential in biomedicine,environmental monitoring and sensing detection.However,how to achieve ultra-high SERS enhancement factor and high performance SERS substrate is the most critical issue in the field of SERS research.Based on the vector light field regulating and the femtosecond laser direct writing technology,this paper studies the physical mechanism of the interaction between light field polarization and GO/AuNRs to enhance the electromagnetic field.On the other hand,the chemical enhancement of GO/AuNPs composite substrate is achieved by laser etching.The specific research contents is as follows:Firstly,the GO/AuNRs composite substrate is constructed,and the SERS effect is studied by changing the polarization state of the incident light based on FDTD Solutions simulation software.The SERS enhancement factor of GO/single-AuNR composite substrate excited by the radially polarized light is up to 10⁸,which is six and ten orders of magnitude stronger than that achieved by the linearly polarized light and azimuthally polarized light under the same conditions.This enhancement mechanism is mainly attributed to the unique axially symmetric polarization distribution of the radially polarized light field,which is more conducive to the coherent resonance of the surface electromagnetic field.Furthermore,the effects of different thicknesses of GO,the number,shape and arrangement of gold nanorods on the properties of SERS with the radially polarization illumination are discussed in detail.The result show that the SERS enhancement factor reaches 10¹³ when the thickness of GO is 3nm and one end of the gold nanorod is cut to the cone of 40 degree and the tip radius is 1nm.The enhancement mechanism is mainly due to the generation of super-resolution surface plasma hot-spots at the tip end contacted with GO.Furthermore,the SERS performance of GO/AuNRs composite substrate excited by the tightly focused vector light is proposed to study.A super resolution longitudinal field parallel to the axis of the gold nanorod is generated since tightly focusing of the radially polarized light,the SERS enhancement factor of the GO/single-AuNR excited by it is 2.3 × 10¹²,under the same conditions,only a hollow azimuthal field is obtained after tight focusing of azimuthally polarized light,and the SERS enhancement factor is 36.The SERS effect increases with the number of gold nanorods,but the existence of GO and the shape of gold nanorod have little effect on the SERS performance.The physical mechanisms for this performance improvement is due to the super-resolution longitudinal field produced by the tight focus of the radially polarized light.Finally,we fabricated SERS substrates with excellent performance by etching micro-nano structure on GO film-base materials based on femtosecond laser direct writing technology in the experimental.The grid structure is processed on the composite substrate by controlling the nano-displacement platform and the polarization state of the laser,and the characterization is performed using a SEM,optical microscope,UV-vis and Raman spectrometer.The result show that the Raman intensity of the radially polarized light processing GO substrate is higher than that of the azimuthally polarized light processing,and the Raman intensity of processed GO/AuNPs is stronger than that of pure GO,this is mainly due to the hybridization of sp² and sp³ in the partially reduced GO during processing to enhance the electromagnetic field.