Collective excitations in concentric metallic nanoshells

Invention of nanoshells made of a silica core coated with an ultra-thin metallic layer [1] has opened a floodgate of many applications in medical and other fields. Most of these applications are triggered by the fact that the nanoshells have unusual electronic and optical properties which can be controlled by controlling the inner and outer radii of the nanoshell. Employing a classical hydrodynamic model, we have obtained a general expression for the resonant frequencies (plasmons) of the electrons for N concentric nanoshells. Results obtained using this theory will be compared with previous calculations for two concentric nanoshells [2] and possible applications of the new results will be discussed. 1. S.J. Oldenburg, \textit{et al}., Chem. Phys. Letts. \textbf{288}, 243 (1998). 2. E. Prodan, \textit{et al}.., Science \textbf{302}, 419 (2003).