Optical Property-Composition Correlation in Noble Metal Alloy Nanoparticles Studied with EELS

Noble metals are currently the most common building blocks in plasmonics and thus define the available range of optical properties. Their alloying provides a viable strategy to engineer new materials with a tunable range of optical responses. Despite this attractive prospect, the link between composition and optical properties of many noble metal alloys is still not well understood. Here, electron energy-loss spectroscopy is employed to systematically study AuAg and AuPd nanoparticles of varying compositions. The localized surface plasmons, the bulk plasmons, and the permittivity functions of these two sets of alloys are investigated as functions of their composition. In the case of the more widely studied AuAg alloy system, good agreement is found with previous experimental and theoretical studies. The results on the less scrutinized AuPd system provide highly valuable experimental data that complements other experimental investigations and supports the development of theoretical models.