A Theoretical Research On The Surface Plasmon Resonance In Noble Metal Nanoparticles Array

The Surface Plasmon Resonance(SPR) phenomenon happens when the nanoparticles are exposed to incident light. With lots of researches, It's found that the SPR phenomenon is relevant with the particles' shape, size and media they're in, etc. The optical property of the surface Plasmon Resonance has invoked a great deal of interest for many researchers because of its importance and the wide potential application.So far, lots of approximate methods are also developed to simulation the optical response of nano-materials, the all made for guide the performance and predict its results. There are many frequently-used simulation methods, like Finite Element Method(FEM), T-matrix method, Finite Difference Time Domain(FDTD), Discrete Dipole Approximation(DDA), etc. Every method has its unique merit and demerit. The proper method is chosen to get the more efficiency and credible results for different structure. As such, DDA method is used to simulate the optical response of different structures to discuss its absorption spectra, extinction spectra and scattering spectra with wave range.In this thesis, the DDSCAT 7.3 software is used to simulate the optical response of ultrafine Au nanoparticles and Ag nanoparticles with a diameter of 4 nm, 5nm, 7nm, a border-to-border interparticle distances of 2nm, 3nm, 4nm and incident angles of 0°,15 °, 30°,45°,60°,75°,90°, respectively. Meanwhile, the medium surrounding the metal spheres is the vacuum environment and it's fixed at 1.46extn(28) for all the calculations. It can be assembled in three kinds of structures, including zero dimension(0D), one dimension(1D) and two dimension(2D) nanostructures. Specifically, the single nanoparticle, 1D cycle chain structure composed of one kind(Ag or Au) of NPs and two kinds of NPs, a planar(2D) hexagonal periodic array composed of one kind(Ag or Au) of NPs and two kinds of NPs. Different incident direction, different NPs radius and interparticle spacing and different composition ratio are taken into account. The absorption spectrums, extinction spectrums and scattered spectrums of every structures are get by the calculation, And the absorption spectrums are compared and some meaningful conclusions are reached. There are follows:1) In all cases, the absorption spectrums are blueshifted for increasing incident.2) In 1D cycle chain structures, the absorption spectrums are blueshifted for increasing interparticle distances and redshifted for increasing particle size.3) In 2D hexagonal periodic array composed of two kinds of NPs with different proportions, it has four cases,(a) Ag : Au(28)1: 2,(b) Ag : Au(28)2 :1,(c) Ag : Au(28)1: 3,(d)Ag : Au(28)3 :1, the absorption efficiency is larger for increasing the dominant NPs and smaller for increasing incident.