title: Galvanically replaced hollow Au-Ag nanospheres: study of their surface plasmon resonance.
abstract: We synthesized hollow Au-Ag nanospheres (NSs) by employing a galvanic replacement reaction between HAuCl4 and Ag NSs. Uniform Ag NSs with controllable sizes were synthesized as sacrificial templates by a seed-mediated strategy. The atomic ratio of Au to Ag in Au-Ag NSs was tunable by controlling the reagent concentration. UV-vis extinction spectra acquired from well-dispersed colloidal NS solutions were used to investigate the optical properties of the solutions. In addition to a common dipole mode exhibited on most transition metal nanoparticles, we observed a quadrupole plasmon resonance mode when the diameters of the Ag and Au-Ag NSs were larger than 100 nm. The quadrupole and dipole peaks both shifted to longer wavelengths with increased Au content in Au-Ag NSs. The experimental observation of optical properties of hollow Au-Ag NSs was compared with the theoretical simulation using DDA calculation, showing a good agreement.
authors.affiliation: Department of Chemistry and ‡Department of Energy Science, SKKU Advanced Institute of Nanotechnology, Sungkyunkwan University , Suwon 440-746, South Korea.
authors.forename: Yoonjung
authors.initials: Y
authors.lastname: Choi
authors.forename: Soonchang
authors.initials: S
authors.lastname: Hong
authors.forename: Lichun
authors.initials: L
authors.lastname: Liu
authors.forename: Seong Kyu
authors.initials: SK
authors.lastname: Kim
authors.forename: Sungho
authors.initials: S
authors.lastname: Park