Bimetallic Ag–Au nanoparticles: Extracting meaningful optical constants from the surface-plasmon extinction spectrum

摘要: We report an approach for extracting the optical constants of bimetallic Ag–Au nanoparticles from measured surface-plasmon (SP) extinction spectra. The dielectric function metal is expressed as analytic wavelength in which interband (and all other non-Drude) contributions to are represented by a sum Lorentz functions. This expression then used fit experimental spectra appropriate functions based on Mie theory. Three (plus Drude term) were found be sufficient reproduce Ag and Au [P. B. Johnson R. W. Christy, Phys. Rev. B 6, 4370 (1972)] over entire 0.6–6.5 eV range reported. With this type, excellent multiparameter spectrum colloidal was obtained. Extinction series (Ag)Au hydrosols, prepared reducing gold precursor presence previously synthesized silver seed particles with mol...