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C.J. Powell, W.S.M. Werner, H. Kalbe, A. Shard, D. Castner:
"Comparisons of Analytical Approaches for Determining Shell Thicknesses of Core−Shell Nanoparticles by X‑ray Photoelectron Spectroscopy";
The Journal of Physical Chemistry C, 122 (2018), 4073 - 4082.

We assessed two approaches for determining shell thicknesses of core−shell nanoparticles (NPs)
by X-ray photoelectron spectroscopy (XPS). These assessments were based on simulations of photoelectron peak
intensities for Au-core/C-shell, C-core/Au-shell, Cu-core/Al-shell, and Al-core/Cu-shell NPs with a wide range of
core diameters and shell thicknesses. First, we demonstrated the validity of an empirical equation developed by
Shard for determinations of shell thicknesses. Values of shell thicknesses from the Shard equation typically agreed
with actual shell thicknesses to better than 10%. Second, we investigated the magnitudes of elastic-scattering effects on
photoelectron peak intensities by performing a similar series of simulations with elastic scattering switched off in our simulation
software. Our ratios of the C-shell 1s intensity to the Au-core 4f7/2 intensity with elastic scattering switched off were qualitatively
similar to those obtained by Torelli et al. from a model that neglected elastic scattering. With elastic scattering switched on, the C
1s/Au 4f7/2 intensity ratios generally changed by less than 10%, thereby justifying the neglect of elastic scattering in XPS models
that are applied to organic ligands on Au-core NPs. Nevertheless, elastic-scattering effects on peak-intensity ratios were generally
much stronger for C-core/Au-shell, Al-core/Cu-shell, and Cu-core/Al-shell NPs, and there were second-order dependences on
core diameter and shell thickness.