title: Chemical synthesis and structural characterization of highly disordered N colloidal nanoparticles.
abstract: This work focuses on synthetic methods to produce monodisperse Ni colloidal nanoparticles (NPs), in the 4-16 nm size range, and their structural characterization. Narrow size distribution nanoparticles were obtained by high-temperature reduction of a nickel salt and the production of tunable sizes of the Ni NPs was improved compared to other methods previously described. The as-synthesized nanoparticles exhibited spherical shape and highly disordered structure, as it could be assigned by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). Annealing at high temperature in organic solvent resulted in an increase of nanoparticle atomic ordering; in this case, the XRD pattern showed an fcc-like structure. Complementary data obtained by X-ray absorption spectroscopy confirmed the complex structure of these nanoparticles. Temperature dependence of the magnetic susceptibility of these highly disordered Ni NPs showed the magnetic behavior cannot be described by the conventional superparamagnetic theory, claiming the importance of the internal structure in the magnetic behavior of such nanomaterials.
authors.affiliation: LNLS-Brazilian Synchrotron Light Laboratory, C.P. 6192, Campinas, SP, 13083-970, Brazil.
authors.forename: Herbert
authors.initials: H
authors.lastname: Winnischofer
authors.forename: Tulio C R
authors.initials: TC
authors.lastname: Rocha
authors.forename: Wallace C
authors.initials: WC
authors.lastname: Nunes
authors.forename: Leandro M
authors.initials: LM
authors.lastname: Socolovsky
authors.forename: Marcelo
authors.initials: M
authors.lastname: Knobel
authors.forename: Daniela
authors.initials: D
authors.lastname: Zanchet
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D003460:Crystallization / Q000379:methods*; D046911:Macromolecular Substances / Q000737:chemistry; D008280:Magnetics; D008422:Materials Testing; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods; D009532:Nickel / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties
chemical_list: D003102:Colloids; D046911:Macromolecular Substances; D009532:Nickel