title: Study of Iron oxide nanoparticles using Mössbauer spectroscopy with a high velocity resolution.
abstract: Iron oxide (magnetite and maghemite) nanoparticles developed for magnetic fluids were studied using Mössbauer spectroscopy with a high velocity resolution at 295 and 90K. The recorded Mössbauer spectra have demonstrated that usual physical models based on octahedral and tetrahedral sites were not suitable for fitting. Alternatively, the Mössbauer spectra were nicely fitted using a large number of magnetic sextets. The obtained results showed that the Mössbauer spectra and the assessed parameters were different for nanoparticles as-prepared and dispersed in the dispersing fluid at 295K. We claim that this finding is mainly due to the interaction of polar molecules with Iron cations at nanoparticle's surface or due to the surface coating using carboxylic-terminated molecules. It is assumed that the large number of spectral components may be related to complexity of the nanoparticle's characteristics and deviations from stoichiometry, including in the latter the influence of the oxidation of magnetite towards maghemite.
authors.affiliation: Department of Physical Techniques and Devices for Quality Control, Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russian Federation; Department of Experimental Physics, Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russian Federation. Electronic address: oshtrakh@gmail.com.
authors.forename: M I
authors.initials: MI
authors.lastname: Oshtrakh
authors.affiliation: Department of Physical Techniques and Devices for Quality Control, Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russian Federation; Department of Experimental Physics, Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russian Federation.
authors.forename: M V
authors.initials: MV
authors.lastname: Ushakov
authors.affiliation: Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Šepelák
authors.affiliation: Department of Physical Techniques and Devices for Quality Control, Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russian Federation; Department of Experimental Physics, Institute of Physics and Technology, Ural Federal University, Ekaterinburg 620002, Russian Federation.
authors.forename: V A
authors.initials: VA
authors.lastname: Semionkin
authors.affiliation: Universidade de Brasília, Instituto de Física, Núcleo de Física Aplicada, Brasília, DF 70910-900, Brazil; Huazhong University of Science and Technology, School of Automation, Wuhan 430074, China.
authors.forename: P C
authors.initials: PC
authors.lastname: Morais
mesh_terms: D005290:Ferric Compounds / Q000737:chemistry*; D058185:Magnetite Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D015204:Spectroscopy, Mossbauer / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; C000499:ferric oxide
keywords: Maghemite nanoparticles; Magnetic fluids; Magnetite nanoparticles; Mössbauer spectroscopy