Synchrotron
Radiation X‑ray Photoelectron Spectroscopy
as a Tool To Resolve the Dimensions of Spherical Core/Shell Nanoparticles
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Abstract
In this work we demonstrate the potential
of synchrotron X-ray
photoelectron spectroscopy (XPS) to provide quantitative information
on the intrinsic dimensions of core–shell nanoparticles. The
methodology is based on the simulation of depth profiling curves,
using simplified quantitative models earlier proposed in the literature.
Three model systems consisting of X@Fe<sub>2</sub>O<sub>3</sub> (with
X = Au, Pt, and Rh) metal–iron oxide core–shell nanoparticles,
formed via oxidation of size-selected 5 nm bimetallic FeX nanoparticles
inside the spectrometer, were measured in situ by near ambient pressure
XPS. We show that when the shell layer is composed of a unique component,
the experimental depth profiling curve can be simulated by the quantitative
calculations and reveal the core and the shell thickness of the nanoparticles.
On the contrary, a significant offset between the experimental and
the theoretical depth profiling curves implies intermixing between
the core and the shell layers. In this case the theoretical model
has been modified to represent the more complex particle morphology.
Transmission electron microscopy results are in good agreement with
the XPS findings, confirming the validity of the model to predict
the nanoparticle dimensions