Evaluation of effective medium theories for spherical nano-shells

Current effective medium theories for nano-shells are reviewed. A new method for calculating the effective dielectric function of a core-shell nanoparticle is presented and compared with existing theories showing clear advantages in most conditions. It consists of introducing radiating effects in the polariz- ability of the effective sphere, and considering the exact polarizability of the core-shell constructed from the Mie scattering coefficient. This new approach can be considered as an useful tool for designing coated particles with desired plasmonic properties and engineering the effective permittivity of composites with core-shell type inclusions which are used in photocatalysis and solar energy harvesting applications.