Characteristics Of Local Surface Plasmon Resonance Of Graphene-Metal Composite Nanoparticles

Local surface plasmon resonance?LSPR?as an important branch of nanotechnology has increasingly drawn much attention of researchers.LSPR properties of metal nanoparticles have been widely investigated.However,LSPR properties of graphene and metal nanocomposite are still in the initial stage.This paper explores the ways of graphene and metal,graphene and metal composite structure.The effects of materials,shape,size and the refractive index of the ambient medium on the extinction properties have been studied,and the internal relationship has been revealed.The intrinsic links between the establishment of nano-composite structure design and performance optimization are built,providing theoretical guidance for the design of novel nano-photonics composites.It is found that graphene with single atom layer has significant influence on the extinction performances of metal core-shell structure.Resonance wavelengths of Au-Ag-Graphene core-shells move towards longer wavelength direction with the external refractive index increasing.The wavelength moves from 390 nm to 790 nm and the variation of the redshift is up to 400 nm.The graphene shell in Au-Ag-Graphene three-layered core-shell field enhancement plays a dominant role.The charges are mainly distributed at both ends of the graphene shells,instead of uniformly distributed around the nanometer nuclear shell.A new type of multilayer graphene metal three layer core-shell structure is proposed in this work.It is found that the Graphene atom number,core-shell ratio and external refractive index structure parameter have significant influences on LSPR spectra.The simulation results show that when the middle Au core and Ag layer radius are 40 nm and 45 nm,respectively,the resonance wavelength increases with the graphene layer thickness and refractive index increasing for the multi-atomic layer graphene-Au-Ag nanoshell.When the refractive idex of the ambient medium varies from 1.25 to 2.05,the mode of resonance redshifts from 540 nm to 740 nm,the redshift range is about 200 nm.In addition,the mode of ??? blueshifts and the mode of ??? redshifts with the refraction index increasing.Two kinds of Ag/Au/ multilayered graphene and Ag/SiO₂/multilayered graphene nano-array structure are designed.The simulation results show that the intermediate layer material and thickness have great effects on the extinction spectra of the composite nano-array.When the substrate thickness ratio is 1:1,the extinction strength of double metal substrate is stronger than those of the metal base compound.For the same external medium under the same conditions,the resonance peak offset of Ag/SiO₂ based composite structure is large thanthat of Ag/Au bimetal based composite structure.It is also found that the extinction spectra of the nano array redshift for the overall refractive index.Dipole resonance peaks redshift from 460 nm to 800 nm and quadrupole resonance peaks redshift from 420 nm to 690 nm,exhibiting a large redshift.