The optical properties of plasmonic nanoparticles are well understood nowadays. Scattering and absorption cross sections of nanoparticles can be calculated by solving Maxwell equations either analytically for spheres (Mie theory) or numerically for arbitrary shapes. Simulations match well with experimental results. However, agreement between experimental spectra and simulations based on the dielectric function of the metal and surrounding medium breaks down when the nanoparticle surface is chemically modified. In this case, the plasmon is stronger damped than expected from electrodynamic simulations. This type of plasmon energy loss has been termed chemical interface damping. Here, we investigate how exactly chemical interface damping depends on a) the size and shape of the nanostructure and b) on the chemical nature of the surface adsorbate. In both cases, we carefully observed the plasmon damping of single gold nanorods during adsorption of thiol molecules and either varied the particle dimension or adsorbates. We found that the chemical interface damping depends on the surface-to-volume ratio of the gold nanostructure and that the nature of the gold sulfur bond is important for the chemical interface damping. Our results give new insight into the mechanism of chemical interface damping. Understanding this mechanism will help to understand in future, how the plasmon energy is converted at the nanoparticle surface guiding applications like photocatalysis.

Plasmon damping at the nanoparticle surface

255th National Meeting (2018)

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