Stable Surface-Plasmon Resonances in Small Alumina-Embedded Silver Clusters

• Published in: Journal of physical chemistry. C 2023-09, Vol.127 (36), p.17828-17835
• Main Authors: Moreira, Murilo H., Cottancin, Emmanuel, Pellarin, Michel, Boisron, Olivier, Rodrigues, Varlei, Lermé, Jean, Hillenkamp, Matthias
• Format: Article
• Language: English
• Subjects: C: Spectroscopy and Dynamics of Nano, Hybrid, and Low-Dimensional Materials; Physics
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.3c03200

Localized surface-plasmon resonances are ubiquitous for the characterization and in applications of noble metal nanoparticles. Their dependence on the chemical composition, size, shape, and environment has been widely studied for decades, but still many aspects are the subject of controversy. In this article, we experimentally investigate surfactant-free and mass-selected silver nanoparticles embedded in alumina matrices in the size range between several atoms and more than 4 nm diameter, spanning the whole range from large nanoparticles, accurately described by classical Mie theory, down into the range of quantum size effects. Strong and stable resonances are observed for all sizes down to less than 50 atoms, i.e., ∼1 nm diameter, without significant line shift or broadening as a function of size. With the help of semiquantal simulations, we identify all signals as surface-plasmon resonances. The absence of peak shifts is rationalized as being due to the dielectric oxide environment and the constant width of the resonances as a convolution of inhomogeneities in the local environment and inherent broadening due to Landau damping. We discuss our results in comparison with ligand-stabilized nanoclusters and rationalize the different contributions to the Hamiltonian describing the systems.