Experimental evidence of surface-plasmon coupling in anisotropic hollow nanoparticles - art. no. 075501

We report on the investigation of surface-plasmon excitation of anisotropic VS,, hollow nanoparticles in a near-field geometry by means of a scanning transmission electron microscope. The shell thickness influence on the elec tron-energy-loss-spectroscopy spectra is experimentally observed and is ana lyzed within a classical dielectric formalism. As for the isotropic case, w e evidence one symmetric (tangential) and one antisymmetric (radial) mode. We point out the intriguing fact that, for the anisotropic case, one can re late these modes to the interband transition of the in-plane component of t he dielectric tensor and to the bulk-plasmon energy of the out-of-plane com ponent.