TY - JOUR
T1 - Transition Metal Nanoparticle Oxidation in a Chemically Non-Homogenous Environment Revealed by 2p3d Resonant X-ray Emission
AU - van Schooneveld, M.M.
AU - Suljoti, E.
AU - Campos-Cuerva, C.
AU - Gosselink, R.W.
AU - van der Eerden, A.M.J.
AU - Schlappa, J.
AU - Zhou, K.J.
AU - Monney, C.
AU - Schmitt, T.
AU - de Groot, F.M.F.
PY - 2013
Y1 - 2013
N2 - X-ray absorption spectroscopy (XAS) is often employed in fields such as catalysis
to determine whether transition-metal nanoparticles are oxidized. Here we show 2p3/2 XAS and
2p3d resonant X-ray emission spectroscopy (RXES) data of oleate-coated cobalt nanoparticles
with average diameters of 4.0, 4.2, 5.0, 8.4, and 15.2 nm. Two particle batches were exposed to air
for different periods of time, whereas the others were measured as synthesized. In the colloidal
nanoparticles, the cobalt sites can have different chemical environments (metallic/oxidized/
surface-coordinated), and it is shown that most XAS data cannot distinguish whether the
nanoparticles are oxidized or surface-coated. In contrast, the high-energy resolution RXES
spectra reveal whether more than the first metal layer is oxidized based on the unique energetic
separation of spectral features related to the formal metal (X-ray fluorescence) or to a metal oxide (d-d excitations). This is the
first demonstration of metal 2p3d RXES as a novel surface science tool.
AB - X-ray absorption spectroscopy (XAS) is often employed in fields such as catalysis
to determine whether transition-metal nanoparticles are oxidized. Here we show 2p3/2 XAS and
2p3d resonant X-ray emission spectroscopy (RXES) data of oleate-coated cobalt nanoparticles
with average diameters of 4.0, 4.2, 5.0, 8.4, and 15.2 nm. Two particle batches were exposed to air
for different periods of time, whereas the others were measured as synthesized. In the colloidal
nanoparticles, the cobalt sites can have different chemical environments (metallic/oxidized/
surface-coordinated), and it is shown that most XAS data cannot distinguish whether the
nanoparticles are oxidized or surface-coated. In contrast, the high-energy resolution RXES
spectra reveal whether more than the first metal layer is oxidized based on the unique energetic
separation of spectral features related to the formal metal (X-ray fluorescence) or to a metal oxide (d-d excitations). This is the
first demonstration of metal 2p3d RXES as a novel surface science tool.
U2 - 10.1021/jz4002696
DO - 10.1021/jz4002696
M3 - Article
SN - 1948-7185
VL - 4
SP - 1161
EP - 1166
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
ER -