Dependence of the optical properties of metal nanoparticles on the eternal dielectric medium: effects of the particle size, shape, and structure

The influence of the size, shape and structure of gold and silver nanoparticles on the dielectric environment dependence of their extinction and integral scattering spectra has been studied. Calculations were carried out for spheres and nanoshells (Mie theory), randomly oriented bispheres, spheroids and s-cylinders with hemispherical ends (T-matrix method). The sensitivity of plasmon resonance (PR) tuning to variations of the refractive index was studied (n=1.3-1.7) for the particles with different equivolume size. In the case of nanoshells, the metal layer thickness was also varied. For nanoparticles with equivolume diameter 15 nm, the maximal PR shifts is observed in case of bispheres and decreases in the order: nanoshells, s-cylinders (spheroids), spheres. For the particles with diameter 60 nm, the maximal PR shifts is observed in case of nanoshells and decreases in the order: bispheres, s-cylinders (spheroids), spheres. Other things being equal, the PR of silver nanoparticles is more sensitive to the dielectric surroundings as compared to the gold counterparts.