Linear optical response of metallic nanoshells in different dielectric media

Metal nanoshells, which consist of nanometer-scale dielectric cores surrounded by thin metallic shells, have been designed and studied for their linear optical responses. The plasmon resonance of metal nanoshells displays geometric tunability controlled by the ratio of shell thickness either to the core radius or to the total radius of the particle. Using Mie theory the surface plasmon resonance (SPR) of metallic nanoshells (Au, Ag, Cu) is studied for different geometries and physical environments. Considering a final radius of about 20 nm, the SPR peak position can be tuned from 510 nm (2.43 eV) to 660 nm (1.88 eV) for Au, from 360 nm (3.44 eV) to 560 nm (2.21 eV) for Ag, and from 553 nm (2.24 eV) to 655 nm (1.89 eV) for Cu, just by varying the ratio t/RShell and the environments inside and outside. With the decrease of the t/RShell ratio the SPR peak position gets redshifted exponentially and the shift is higher for a higher refractive index surroundings. The plasmon linewidth strongly depends on the surface scattering process and its FWHM increases with the reduction of shell thickness.