Smallest Bimetallic CoPt3Superparamagnetic Nanoparticles.
We present for the first time a nonaqueous sol-gel route to produce ultrasmall (<2 nm) magnetic bimetallic CoPt3nanoparticles (NPs). The one-pot procedure is carried out at low temperature (180 °C) using benzyl alcohol, acting as both reducing agent and solvent. The highly monodisperse CoPt3NPs were investigated with innovative advanced X-ray methods (whole powder pattern modeling), HR-STEM, XPS, and SQUID magnetometry. XPS showed Co was mostly in metallic form, but with a very small amount of CoO on the NP surface. The spherical NPs had an ultrasmall diameter of 1.6 nm and could self-assemble in aligned linear chains, or nanobelts, of single NPs. They are superparamagnetic, with blocking temperature of ∼20 K and coercivity at 10 K of 27.9 kA m-1(∼350 Oe). However, there is evidence of a second magnetic phase (probably CoO) in the ZFC magnetization curve, which enhances their magnetization values, without significantly affecting their superparamagnetism.
School of Chemistry-College of Engineering and Physical Sciences, University of Birmingham Edgbaston , Birmingham B15 2TT, United Kingdom.
Mohamed
M
Karmaoui
Department of Physics/CICECO - Aveiro Institute of Materials, University of Aveiro , Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
J S
JS
Amaral
Laboratorio de Microscopías Avanzadas, Instituto de Nanociencia de Aragón, Universidad de Zaragoza , 50018 Zaragoza, Spain.
Luc
L
Lajaunie
Department F4, Jozef Stefan Institute , Jamova cesta 39, Ljubljana 1000, Slovenia.|Jozef Stefan international Postgraduate School , Jamova cesta 39, Ljubljana 1000, Slovenia.
Harinarayanan
H
Puliyalil
Department of Materials and Ceramic Engineering/CICECO - Aveiro Institute of Materials, University of Aveiro , Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
David M
DM
Tobaldi
Department of Materials and Ceramic Engineering/CICECO - Aveiro Institute of Materials, University of Aveiro , Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.|Department of Materials, Imperial College London , London SW7 2AZ, United Kingdom.
Robert C
RC
Pullar
Department of Materials and Ceramic Engineering/CICECO - Aveiro Institute of Materials, University of Aveiro , Campus Universitário de Santiago, 3810-193 Aveiro, Portugal.
João A
JA
Labrincha
Laboratorio de Microscopías Avanzadas, Instituto de Nanociencia de Aragón, Universidad de Zaragoza , 50018 Zaragoza, Spain.|ARAID Foundation , 50018 Zaragoza, Spain.
Raul
R
Arenal
Department F4, Jozef Stefan Institute , Jamova cesta 39, Ljubljana 1000, Slovenia.|Jozef Stefan international Postgraduate School , Jamova cesta 39, Ljubljana 1000, Slovenia.
Uroš
U
Cvelbar