Sharp spectral variations of the ultrafast transient light extinction by bimetallic nanoparticles in the near‐UV

AUTHORS

• Otomalo Tadele Orbula
• Di Mario Lorenzo
• Hamon Cyrille
• Constantin Doru
• Do Khanh-Van
• O'Keeffe Patrick
• Catone Daniele
• Paladini Alessandra
• Palpant Bruno

KEYWORDS

Bimetallic nanoparticles

Nanocuboids

Plasmonics

High-order plasmon modes

Transient absorption

Document type

Journal articles

Résumé

Noble metal nanoparticles exhibit localized plasmon resonance modes that span the visible and near-infrared spectral ranges and have many applications. Modifying the size, shape, and composition of the nanoparticles changes the number of modes and their properties. The characteristics of these modes are transiently affected when illuminating the nano-objects with ultrashort laser pulses. Here, we synthesize core-shell gold-silver nanocuboids and measure their spectral signature in the stationary and ultrafast transient regimes. Their dipolar transverse mode vanishes with increasing Ag-shell thickness, while higher-order modes grow in the near-ultraviolet range where no plasmon resonance can be generated with single noble metal nanoparticles. These higher-energy modes are associated with sharp spectral variations of the ultrafast transient light extinction by the bimetallic nanocuboids. By carrying out a theoretical investigation, we break down the different contributions to this response and

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