Evaluating the Internal Structure of Core-Shell Nanoparticles Using X-ray Photoelectron Intensities and Simulated Spectra.
The functionality of a new version of the National Institute of Standards and Technology database Simulation of Electron Spectra for Surface Analysis (SESSA) has been extended by implementing a new geometry engine. The engine enables users to simulate Auger-electron spectra and X-ray photoelectron spectra for different predefined morphologies (planar, islands, spheres, multi-layer core-shell particles). We compared shell thicknesses of core-shell nanoparticles derived from core-shell XPS peak intensities using Shard's method, which allows one to estimate shell thicknesses of core-shell nanoparticles, and a series of SESSA simulations for a wide range of nanoparticle dimensions. We obtained very good agreement of the shell thicknesses for cases where elastic scattering within the shell can be neglected, a result that is in accordance with the underlying assumptions of the Shard model. If elastic-scattering effects are important, there can be thickness uncertainties of up to 25 %. Experimental spectra of functionalized gold nanoparticles obtained by Techaneet al. were analyzed with SESSA 2.0 both with respect to the relevant peak intensities as well as the spectral shape. Good agreement between experiment and theory was found for both cases. These results show that the single-sphere model for core-shell nanoparticles is valid when just using peak intensities, but more detailed modeling is needed to describe the inelastic background.
Technische Universität Wien, Institut für Angewandte Physik, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria.
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M
Chudzicki
Technische Universität Wien, Institut für Angewandte Physik, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria.
W S M
WS
Werner
National ESCA and Surface Analysis Center for Biomedical Problems, Departments of Chemical Engineering and Bioengineering, University of Washington, Seattle, Washington 98195-1653, USA.
A G
AG
Shard
Technische Universität Wien, Institut für Angewandte Physik, Wiedner Hauptstraße 8-10, A-1040 Vienna, Austria.
Y-C
YC
Wang
National ESCA and Surface Analysis Center for Biomedical Problems, Departments of Chemical Engineering and Bioengineering, University of Washington, Seattle, Washington 98195-1653, USA.
D G
DG
Castner
Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370, USA.
C J
CJ
Powell