title: Plasmon resonances tailored by Fano profiles in silver-based core-shell nanoparticles.
abstract: The optical absorption of bimetallic nanoparticles M-Ag involving silver as an active plasmonic compound has been the subject of very extensive experimental studies, both for a large range of sizes and a large variety of associated metals. Considering the most commonly encountered core-shell segregated configuration M@Ag involving a transition metal M, the spectral response is found to be weakly discriminating with regard to the chemical order and composition and is characterized by a large unstructured plasmon resonance in the 2 eV to 4 eV range. The plasmon band is essentially shaped by the scars made in the absorption continuum of metal M by Fano-like induced resonances and is surprisingly little sensitive to the exact nature of this metal, giving birth to a "quasi universal" optical signature for M@Ag systems. In this paper, we show how this generic behaviour arises from the specific plasmonic response of silver and stress the role of interband transitions of both metals through their coupling with the free electron oscillation modes. This theoretical discussion will be illustrated through selected experimental results.
authors.affiliation: Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Pellarin
authors.affiliation: Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Broyer
authors.affiliation: Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Lermé
authors.affiliation: Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex, France.
authors.forename: Marie-Ange
authors.initials: MA
authors.lastname: Lebeault
authors.affiliation: Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Ramade
authors.affiliation: Institut Lumière Matière, UMR5306 Université Lyon 1-CNRS, Université de Lyon, 69622 Villeurbanne Cedex, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Cottancin