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

Abstract

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.

Characterization of core/shell nanoparticle thin films for gas analytical applications

“…[8,11] Angle-resolved XPS data justify the achievement of spherical core/shell nanoparticles as the expected identical Sn/Si intensity ratio was found for all applied electron emission angles, which is a direct verification of the core/shell structure. [12] Additionally, XPS is suited to measure the thickness of nanoscaled thin films. The description of the detailed underlying formalism based on a modified Lambert-Beer equation and least square fitting recently has been the subject of a series of comprehensive studies.…”

Spectroscopy and Femtosecond Dynamics of Type‐II CdTe/CdSe Core–Shell Quantum Dots

“…The peak intensity ratio for elements of the core versus shell as a function of the electron takeoff angle may serve as a valuable tool to extract geometrical information about the nanoparticles. [13] Note that, if QDs were composed of an alloy, the relative peak intensities for Se versus Te would be independent of the electron takeoff angle. Furthermore, empirically, the ratio of the peak area for Te (3d 5/2 ) versus Se (3d) is estimated to be 6.82 and 6.68 for X-ray sources at 90 o and 54.7 o , respectively.…”

Synchrotron radiation x-ray photoelectron spectroscopy of Si nanocrystals grown onto Al2O3∕Si surfaces

“…The considerable structural constraints inside oxide shells were shown by a recent study of 6 nm thick silica shells on 15 nm gold nanocrystals, suggesting a two-fold reduction in density. 12 In this letter, we investigate by SRXPS chemically oxidized Si NCs, highlighting the main differences in the Si 2p core-level spectra between planar and NCs oxidation.…”