title: Magnetic Cu-Ni (core-shell) nanoparticles in a one-pot reaction under microwave irradiation.
abstract: We successfully prepared face-centered cubic (fcc) Cu-Ni (core-shell) nanoparticles by intramolecular reduction of formate complexes of Cu(2+) and Ni(2+) with long-chain amine ligands in a one-pot reaction within an extremely short time realized only under microwave irradiation. Observation by an HAADF-STEM technique showed that the nanostructure in one particle consisted of a Ni-rich shell and a Cu-rich core. Cu(4)Ni(6) nanoparticles with an average size of 11.7 nm were comprised of a Cu core with a diameter of ca. 6.0 nm, a Ni shell ca. 1.6 nm thick and a 0.9 nm thick interlayer of mixed Cu-Ni alloy between the Cu core and the Ni shell. Both the oxidation characteristics and the magnetic properties were dramatically affected by the molar ratios of Cu : Ni in the Cu-Ni nanoparticles. The magnetization of Cu(3)Ni(7) and Cu(4)Ni(6) comprised of a diamagnetic Cu-rich core, ferromagnetic Ni-rich shell and antiferromagnetic NiO-rich layer on the particle surface showed an exchange bias (209 and 143 Oe, respectively).
authors.affiliation: Graduate School of Engineering, Osaka University, 2-1 Yamada-oka Suita, Osaka 565-0871, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Yamauchi
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Tsukahara
authors.forename: Takao
authors.initials: T
authors.lastname: Sakata
authors.forename: Hirotaro
authors.initials: H
authors.lastname: Mori
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yanagida
authors.forename: Tomoji
authors.initials: T
authors.lastname: Kawai
authors.forename: Yuji
authors.initials: Y
authors.lastname: Wada
mesh_terms: D000588:Amines; D056831:Coordination Complexes / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D005561:Formates / Q000737:chemistry; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D008872:Microwaves; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size
chemical_list: D000588:Amines; D056831:Coordination Complexes; D005561:Formates; C030544:formic acid; D003300:Copper; D009532:Nickel