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2013-12-01 - Colloque/Présentation - poster - Anglais - 1 page(s)

Henrard Daniel , Gossuin Yves , "Magnetic properties and NMR relaxation of different-sized iron oxide nanoparticles" in 12ème YBMRS, Blankenberge, Belgique, 2013

  • Codes CREF : Résonance magnétique nucléaire (biophysique) (DI131B), Physique du spin (genre RMN) (DI1234), Biophysique (DI3113)
  • Unités de recherche UMONS : Physique biomédicale (M104)
  • Instituts UMONS : Institut de Recherche en Science et Ingénierie des Matériaux (Matériaux)
  • Centres UMONS : Physique des matériaux (CRPM)

Abstract(s) :

(Anglais) ron oxide nanoparticles are of great interest in nanomedicine. They are used in Magnetic Resonance Imaging (MRI) as negative contrast agent. In this work, we explored magnetic properties and Nuclear Magnetic Resonance (NMR) relaxation of different-sized magnetite nanoparticles (Fe3O4). First, by using Vibrating Sample Magnetometry (VSM), we performed Zero-Field-Cooling (ZFC) and Field-Cooling (FC) curves. Samples were cooled to very low temperature under zero magnetic field (for the ZFC) or under 10 mT (for the FC). At 2 K, the magnetic field was fixed at 10 mT for both curves and magnetization measurements were made for increasing temperatures. The average blocking temperature of the iron oxide crystals was determined as the maximum of the ZFC[1]. Then, we carried out, at different temperatures, magnetization measurements in function of the magnetic field. Best Langevin fits[2] to data yielded the average nanoparticles radius and a standard deviation estimation of the lognormal size distribution. Based on the average blocking temperature and the average radius, we calculated the uniaxial magnetic anisotropy constant KA. Finally, we performed relaxometric measurements using low resolution relaxometry and Fast Field Cycling (FFC) relaxometry. T1 and T2 were determined at two Larmor frequencies, 28,8 MHz and 38,7 MHz corresponding respectively to 0,68 T and 0,91 T. All the relaxometric measurements were made at 37°C. The longitudinal relaxation rate R1 was obtained by a saturation-recovery sequence (SR) and the transverse relaxation rate R2 by a Carr Purcell Meiboom Gill sequence (CPMG). Solutions with different concentrations were prepared for each sample. The relaxivities r1 and r2 were calculated as the straight line slope linking R1 and R2 relaxation rates to the concentration. The obtained results are compared to the prediction of well established relaxation theories[2][3]. [1] M. Lévy, F. Gazeau, J-C Bacri, C. Wilhelm and M. Devaud, Physical Review B 2011, 84, 075480 [2] Y. Gossuin, P. Gillis, A. Hocq, Q. L. Vuong, and A. Roch, Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology 2009, Volume 1, issue 3, p. 299-310 [3] Q. L. Vuong, J-F. Berret, J. Fresnais, Y. Gossuin and O. Sandre, Advanced Healthcare Materials 2012, 1,4: 502-2012