Studying The Optical Properties Of Metal-shell Nanoparticles Using DDA Method

In the recent years, researches about the optical properties of metal nanoparticles andsurface-enhanced Raman scattering (SERS) has becoming research hotspots. Metalnanoparticles, which differ from bulk materials and insulation nano materials, have specialphysical mechanism such as small-size effect, quantum size effect, surface effect, andmacroscopic quantum tunneling effect. All this effects lead to the surface plasmonresonance. The peak position of plasmon resonance varies with changes in shape fordifferent metal nanoparticles. We can control the peak position by adjusting the shapeparameters, then getting the specified nanoparticles material with near-field enhancementeffect. Based on these special properties, we can apply materials of metal nanoparticles inmany areas such as single molecule detection, surface-enhanced spectroscopy of chemicaland biological molecules, sensing the dielectric environment.In this paper, we lucubrate the optical properties of the gold ellipsoidal-shell structureby the discrete dipole approximation (DDA) method. We calculate extinction spectra ofgold particles and gold ellipsoid particles and compare the results with experiment. Thedata consistency indicates that DDA is an effective method for studying properties ofmetal nanoparticles.After calculating extinction spectra of gold ellipsoidal-shell nanoparticles withdifferent shape parameters, we give out relationship between absorption peak position andthese shape parameters by fitting formula. The peak attributed by the SPR show redshiftwith shell thickness ration decrease, size increase and the increase in number of layers. Wecan control optical properties of materials by adjusting the structure of metalnanoparticles.At last, we calculate the electric field distribution near metal nanoparticles by DDAmethod, and discuss how the electric field distribution varies with deformation ofnanoparticles.