Optical Properties of Gold NanospheresPublic Deposited
The optical properties of spherical gold nanoparticles are calculated using classical electrodynamics. The wavelength corresponding to maximum extinction shifts to longer wavelengths as the size of the nanoparticle is increased. The influence of higher-order multipoles is evident for large nanoparticles, making the spectra more complex. When the shell thickness of a core/shell particle is decreased, the plasmon resonance shifts to longer wavelengths. This red shift is accompanied by an increase in peak intensity. A model for core/shell nanoparticles is presented to investigate surface coverage effects. This model can be used to interpret the optical properties during the growth process or to examine the effects of shell defects, uneven growth, and surface roughness. The preliminary results for low surface coverage show an increase in extinction as the number of surface particles is increased. The peak position for the array of surface particles matches the resonant wavelength for an isolated spherical nanoparticle with a radius equal to half the shell size, as expected for the uncoupled limit.