XPS Characterization of Au (Core)/SiO2 (Shell) Nanoparticles

Ilknur Tunc, Sefik Suzer, Miguel A. Correa-Duarte, and Luis M. Liz-Marzán

J. Phys. Chem. B, 2005, 109, 7597–7600

Core−shell nanoparticles with ca. 15-nm gold core and 6-nm silica shell were prepared and characterized by XPS. The Au/Si atomic ratio determined by XPS is independent of the electron takeoff angle because of the concentric spherical shape of the nanoparticles. The formula given by Wertheim and DiCenzo (Phys. Rev. B 1988, 37, 844) for spherical nanoparticles and the modified one by Yang et. al. (J. Appl. Phys. 2005, 97, 024303) for core−shell nanoparticles are used to correlate the XPS-derived composition with the geometry of the nanoparticles only after significantly modifying either the bulk density of the silica shell or the attenuation length of the photoelectrons.