Surface Plasmon Resonance Characteristics Of Three-dimensional Silver Nanoring Structures

Under the action of specific excitation light,the free electrons on the surface of the noble metal nanoparticles interact with the incident light to generate the plasmonics.At this time,unique optical response can be observed.This unique phenomenon is related to the material,morphology,size,surrounding media and the nature of the excitation light,which makes the optical properties of the noble metal nanoparticles have a strong maneuverability,and bring the nano-materials into the surface enhanced raman scattering(SERS),surface enhanced fluorescence(SEF),solar cells,medical imaging and biosensing applications.In recent years,the rapid development of micro-nano processing technology,the production and regulation of precious metal nanostructures is no longer a problem,combining with the gradual maturity of theoretical research,for the study of precious metal micro-nanostructure system has become a more popular research field and become a new frontier discipline,that is,surface plasmonics.The current research of nanostructures is mainly focused on the simplification of two-dimensional nanostructures,however the common three-dimensional nanostructures in experiments are usually not symmetrical,and usually are polymer-coupled.As for three-dimensional nanostructure,the observed optical response is richer than the two-dimensional nanostructures and the mechanism will be more complex.Therefore,the next research direction of surface plasmonic will base on the three-dimensional nano-asymmetric structure.In this paper,we ananlysis three-dimensional nanostructure and adjust its asymmetric degree,to conduct the theoretical study and explore the coupling mechanism of three dimensional nano-polymer structure.This paper is divided into two parts:the first part is the design and study the surface plasmon resonance characteristics of three dimensional crossing-ring-dimer(3D-CR-dimer);the second part is the design and research the surface resonance characteristics of three dimensional crossing-ring-trimer(3D-CR-trimer).Part 1:Surface plasmon resonance properties of three dimensional crossing-ring-dimer(3D-CR-dimer).The finite element method(FEM)is used to systematically describe the hybridization of 3D-CR-dimer coupling properties.The coupling pattern between individuals is generated and controlled by three geometric parameters of the nanostructure.We observed that the two completely different coupling modes can be achieved by simply adjusting the distance between individual rings,in this process,the bright and dark modes exchange their locations.In addition,we found that the 3D-CR-dimer structure is very sensitive to the dielectric constant of the surrounding environment,which indicates that the nanostructure has a broad application prospects.The research content of this paper can provide a theoretical reference for the design and analysis of three-dimensional plasma nanostructures.Part 2:Resonance characteristics of surface plasmon resonance of three dimensional crossing-ring-trimer(3D-CR-trimer).The optical response of three dimensional crossing-ring-trimer(3D-CR-trimer)in different directions of polarized light is introduced in detail.It is found that when the incident light is polarized in the x direction,the surface plasmon resonance characteristic of the trimer is similar to that of the dimer,and when the excitation light is polarized in the y direction,a similarity to dolmen coupling characteristics,the spectrum shows a strong coupling under the Fano line type.By changing the thickness of horizontal ring,the Fano line type is more pronounced,and the vertical parallel nanorings can activate the higher order coupling in trimer system.The above discloses that the 3D-CR-trimer has a higher degree of modulation of the optical properties than the dimer nanostructure described in Chapter 4,and the resulting Fano line type shows that it can achieve the weak coupling,moderate coupling,strong coupling between the three different coupling strength adjustment,thereby enhancing its application in different areas of the possibility.