Preparation And Analysis Of The Au-SiO₂ Multi-layer Nanospheres As High SERS Resolution Substrate

Recent years, with the development of nanotechnology, precious metalnano materials due to good physical and special optical properties areattracting more and more scientists' attention. And the surface modificationof nanoparticles has become a research hotspot in the field of materialsscience. Au nano-particle size and shape are important factors to determinetheir performance, so the different structural and dimensions goldpreparation, assembly, surface modification have become the dominantdirection of nano-material study.In this paper, using the MATALAB and COMSOL finite elementmodeling software simulated the Au-SiO₂ multi-layer nanoparticles' opticalproperties and analysis the absorption spectrum and red-shiftedphenomenon in near infrared region. Simulation results show the coreradius, thickness of layers and number of layers determine NPs properties.In this paper, five-layer structure of Au-SiO₂ (Au core) was simulated bychanging the core size and shell thickness to analysis the optical properties.The results show that in the same shell thickness and number of layerscircumstances, with the core radius increasing, the red-shift effect in thenear infrared region increased, and the scattering density reduced; thestructure of other conditions remained unchanged, as the increasing ofSiO₂ shell thickness increases, the structure has a significant red-shift andscattering density reduced too; Similarly, changing the Au shell thicknesswill be a similar phenomenon. The results show that the core-shellstructure of nanoparticles determines its optical properties. In addition, thepaper also analysis the Au @ SiO₂ core-shell structure (SiO₂ core) opticalproperties. In the thesis, the preparation of Au NPs is the reduction of HAuCl4using citrate, and SiO₂ NPs were synthesised by w/o microemulsion. thesurface amination of SiO₂ used by APTES was to prepare Au@SiO₂core-shell structure NPs. the synthesised Au nano-spheres and SiO₂nanospheres have size-controlled dimension, uniform morphology andexcellent distribution. For the control of Au film growth, a novel method isstudied. Frstly, surface amination of sio2 used by APTES; Fecondly, SiO₂NPs modified by APTES were added into Au-ehanol solution withvigorous stirring, condensing and collecting SiO₂@Au NPs. Finally, theparticles were immersed in the boiled NaBH4 solution and adding someHAuCl4 to grow the Au film.By measuring the structural analysis using UV-vis, Au shell thicknessis higher,and the absorption peak stronger red-shift the more obvious in theresonance wavelength, which verify the simulation results.