Study On The Extinction Characteristics Of Composite Metal Nanoparticles

With the continuous development of science and technology,nanomaterials have become the focus of research in the field of new materials research.In recent years,metal nanomaterials have unique and novel properties in physics and chemistry due to their special structure,which has attracted great attention in the fields of drug medicine,communication detection,air transportation and other fields.In the field of photonics,noble metal nanostructures can generate localized surface plasmon resonance?LSPR?on the surface of the particles by excitation of incident light,and LSPR is greatly affected by the composition,morphology and external environment of the nanoparticles.The paper based on the classical electromagnetic theory and surface plasmon hybrid theory of metal nanoparticle LSPR characteristics,the finite element method?FEM?method is used to analyze the effects of various parameters such as material composition,shape size and polarization angle of incident light on the LSPR characteristics of the three-layer concentric nanoshells,the symmetry breaking in Ag-TiO₂-Au multilayer nanoshells,the dual symmetry breaking in Ag-TiO₂-Au multilayer nanocups.The research results provide a theoretical basis for the design of new nanostructure sensors.The numerical results indicate that the LSPR resonance wavelengths of typical three-layer nanoshells structure and the symmetry breaking in Ag-TiO₂-Au multilayer nanoshells structure are red shifted with the increase of the refractive index of the surrounding medium,however,the extinction intensity changes of each mode are slightly different;Compared with the same size two-layer metal nanoshells,the three-layer concentric nanoshells has more plasmon resonance modes,and the formant tuning range on the extinction spectrum becomes larger;By changing the distance between the center of the core,the center of the interlayer,and the center of the shell along the x-axis and the y-axis,he symmetry breaking multilayer nanoshells can obtain a richer resonance peaks than the concentric nanoshells,and the extinction spectrum is further expanded in the near-infrared region around 800 nm.It is found that the extinction properties of the dual symmetry breaking in Ag-TiO₂-Au multilayer nanocups are sensitve to the orientation of the nanocups with respect to polarization state of incident light.It can produce two kinds of surface plasmon resonance modes in the transverse direction?the polarization direction of the incident light is perpendicular to the axis of symmetry?and the axial direction?the polarization direction of the incident light is parallel to the axis of symmetry?,In the transverse extinction spectrum,the resonance peak wavelength of the anti-symmetric coupled mode can be tuned to the vicinity of 1100 nm in the near-infrared region,and the resonant wavelength also red shifted with the increase of the refractive index of the surrounding medium.