title: An organometallic approach for very small maghemite nanoparticles: synthesis, characterization, and magnetic properties.
abstract: Maghemite (gamma-Fe(2)O(3)) nanoparticles stabilized by long-alkyl-chain amines are synthesized by using an organometallic approach. This method consists of the hydrolysis and oxidation of an organometallic precursor, Fe[N(SiMe(3))(2)](2), in the presence of amine ligands as stabilizing agent in an organic solvent, namely tetrahydrofuran or toluene. Whatever the experimental conditions, particles with a diameter of 2.8 nm are obtained. The use of high-resolution transmission electron microscopy and wide-angle X-ray scattering, together with Mössbauer spectroscopy and SQuId magnetometry, allows a complete characterization of these particles. Herein, we show that their structure is composed of a well-ordered core surrounded by a more disordered shell. The size of the latter varies from 0.65 to 0.50 nm depending on the experimental conditions and is of prime importance for the understanding of the magnetic properties. We demonstrate that the shorter the alkyl chain length of the amine 1) the better the crystallinity of the particle's core and 2) the stronger the interparticle interactions.
authors.affiliation: Laboratoire de Chimie de Coordination, UPR8241 CNRS, 205 route de Narbonne, 31077 Toulouse, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Glaria
authors.forename: Myrtil L
authors.initials: ML
authors.lastname: Kahn
authors.forename: Andrea
authors.initials: A
authors.lastname: Falqui
authors.forename: Pierre
authors.initials: P
authors.lastname: Lecante
authors.forename: Vincent
authors.initials: V
authors.lastname: Collière
authors.forename: Marc
authors.initials: M
authors.lastname: Respaud
authors.forename: Bruno
authors.initials: B
authors.lastname: Chaudret
mesh_terms: D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D013057:Spectrum Analysis; D013696:Temperature