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The plasmonic properties of a concentric nanoshell, or “nanomatryushka”, are investigated. The plasmon resonant modes are analyzed in terms of the plasmon hybridization model, where new resonances occur due to a hybridization of the plasmon modes of the inner metallic shell with those of the outer metallic shell. The plasmon resonant spectra of experimentally realized concentric nanoshells are analyzed in terms of dipolar and higher order multipolar hybridized plasmon modes. A size-dependent asymmetry in the splitting of the hybridized plasmon states is observed, which is related to phase retardation effects due to the nanostructure's finite size.

We report on the dramatic chemical reshaping of metallodielectric nanoparticles upon exposure to cetyltrimethylammonium bromide (CTAB) in aqueous solutions. Metal nanoshells possessing a silica core with a gold shell were observed to undergo a morphological change from their initial shell structure to that of large, elongated gold nanoparticles or toroids. This reaction is dependent on the chemical species available in solution and on the metal shell thickness on the nanostructure. Surprisingly, dissolution of the silica core due to the presence of CTAB was also observed during the reshaping of the nanoshells.