TY - JOUR
T1 - Electronic and magnetic properties of Ni nanoparticles embedded in various organic semiconductor matrices
AU - Bräuer, Björn
AU - Vaynzof, Yana
AU - Zhao, Wei
AU - Kahn, Antoine
AU - Li, Wen
AU - Zahn, Dietrich R.T.
AU - De Julián Fernández, César
AU - Sangregorio, Claudio
AU - Salvan, Georgeta
PY - 2009/4/9
Y1 - 2009/4/9
N2 - Ni nanoparticles with a size distribution from 2 to 6 nm, embedded in various organic matrices, were fabricated in ultrahigh vacuum. For this purpose metal free and Ni phthalocyanine, fullerene C60, and pentacene were coevaporated with Ni. When coevaporated, Ni and H2Pc react, leading to the formation of NiPc and Ni nanoparticles. The molecular structure of the matrix was found to have negligible effect on the size of the nanoparticles but to influence the magnetic anisotropy of the nanoparticles: Ni nanoparticles formed in the buckyball matrix have a cubic symmetry, while nanoparticles formed in matrices consisting of planar molecules exhibit a uniaxial symmetry. After exposure to atmosphere, photoelectron spectroscopy investigations demonstrate the presence of metallic Ni nanoparticles accompanied by Ni oxide and the existence of a charge transfer from the organic matrix to the particles in all investigated systems. The oxidized Ni nanoparticles exhibit a larger magnetic anisotropy compared to the freshly prepared particles which show superparamagnetic properties above 17 K. Moreover, photoelectron spectroscopy was used to probe the oxidation process of the Ni nanoparticles in different organic matrices. It could thus be shown that a matrix consisting of spherical molecules like C60 prevent the particles much better from oxidation compared to matrices of flat molecules.
AB - Ni nanoparticles with a size distribution from 2 to 6 nm, embedded in various organic matrices, were fabricated in ultrahigh vacuum. For this purpose metal free and Ni phthalocyanine, fullerene C60, and pentacene were coevaporated with Ni. When coevaporated, Ni and H2Pc react, leading to the formation of NiPc and Ni nanoparticles. The molecular structure of the matrix was found to have negligible effect on the size of the nanoparticles but to influence the magnetic anisotropy of the nanoparticles: Ni nanoparticles formed in the buckyball matrix have a cubic symmetry, while nanoparticles formed in matrices consisting of planar molecules exhibit a uniaxial symmetry. After exposure to atmosphere, photoelectron spectroscopy investigations demonstrate the presence of metallic Ni nanoparticles accompanied by Ni oxide and the existence of a charge transfer from the organic matrix to the particles in all investigated systems. The oxidized Ni nanoparticles exhibit a larger magnetic anisotropy compared to the freshly prepared particles which show superparamagnetic properties above 17 K. Moreover, photoelectron spectroscopy was used to probe the oxidation process of the Ni nanoparticles in different organic matrices. It could thus be shown that a matrix consisting of spherical molecules like C60 prevent the particles much better from oxidation compared to matrices of flat molecules.
UR - http://www.scopus.com/inward/record.url?scp=65249097172&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=65249097172&partnerID=8YFLogxK
U2 - 10.1021/jp809777z
DO - 10.1021/jp809777z
M3 - Article
C2 - 19338361
AN - SCOPUS:65249097172
SN - 1520-6106
VL - 113
SP - 4565
EP - 4570
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
IS - 14
ER -