title: Unintended phosphorus doping of nickel nanoparticles during synthesis with TOP: a discovery through structural analysis.
abstract: We report the discovery of unintentional phosphorus (P) doping when tri-n-octylphosphine (TOP) ligands are used in Ni nanoparticle synthesis, which is the most common method for monodisperse Ni nanoparticle synthesis. The nanoparticles appear pure face-centered cubic (fcc) Ni in X-ray diffraction despite the surprisingly high level (5 atomic %) of P. We find that the P doping follows a direct relationship with increased reaction time and temperature and that the P doping can be estimated with the degree of lattice expansion shown from a peak shift in the XRD spectrum. Through EXAFS modeling and density-functional (DFT) calculations of defect formation energies we find that the P atoms are preferentially located on the fcc lattice as substitutional dopants with oxidation state of zero. Magnetic and catalytic properties are shown to be greatly affected by this doping; DFT calculations show magnetization losses in the Ni system, as well as in Fe and Co systems. These findings are likely relevant for other metal syntheses that employ phosphine ligands.
authors: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, United States.
authors: Liane M
authors: LM
authors: Moreau
authors: Don-Hyung
authors: DH
authors: Ha
authors: Clive R
authors: CR
authors: Bealing
authors: Haitao
authors: H
authors: Zhang
authors: Richard G
authors: RG
authors: Hennig
authors: Richard D
authors: RD
authors: Robinson
mesh_terms: D003198:Computer Simulation; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D008956:Models, Chemical; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010316:Particle Size; D010720:Phosphines / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry*
chemical_list: D010720:Phosphines; D010758:Phosphorus; D009532:Nickel; C044646:phosphine