NMR and Spin Relaxation in Systems with Magnetic Nanoparticles
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0984-MM07-19
NMR and Spin Relaxation in Systems with Magnetic Nanoparticles T. Weaver1, N. Noginova1, M. King1, A. B. Bourlinos2 , E. P. Giannelis3, and V. A. Atsarkin4 1 Center for Materials Research, NSU, Norfok, VA, 23504 2 Institute of Materials Science, NCSR Demokritos, Athens, Greece 3 Cornell University, Ithaca, NY, 14853 4 Institute of Radio Engineering & Electronics RAS, Moscow, Russian Federation
Abstract. To better understand the effects of magnetic nanoparticles to nuclear spectra and spin relaxation in different systems, we have studied H NMR spectra and spin dynamics of the host system in liquid and solid suspensions of γ-Fe O nanoparticles. Significant line broadening of H NMR spectra and growing relaxation rates were observed with increased concentration of nanoparticles in the liquid systems, with the relation T /T depending on the particular host. Solid systems demonstrate inhomogeneous broadening of the spectra and practically no dependence of T upon the nanoparticle concentration. We explain the experimental results taking into account predomination of diffusion as a source of the relaxation, and estimate effective parameters of relaxation in the systems in study. 1
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Introduction. Magnetic nanoparticles, in recent years, have been used to improve technological development for many disciplines including chemical engineering and medicine [1,2]. Superparamagnetic iron oxide nanoparticles (SPIO), especially γ-Fe O (maghemite) and Fe O (magnetite) have been promising for different applications, particularly in the medical field as contrast agents for MRI spectroscopy, magnetic carriers for drug delivery, and “hypothermia” treatment of cancer [2]. Presently, theory is well developed for the dynamics of the host nuclei when in the presence of a paramagnetic ion. However, the relatively large objects such as superparamagnetic nanoparticles can have their own specifics. The descriptions of their effects are based on the classic “outer sphere” model [3,4] taking into account magnetic anisotropy and high magnetization of the SPIO [4]. It was shown that this model adequately describes the spin relaxation in liquids with magnetic nanoparticles in moderate fields. More studies of NMR and spin relaxation are needed to get information about SPIO effects to spin-spin, spinlattice relaxation and NMR in different types of the systems including both liquid and solid systems. NMR and spin relaxation studies of the systems with maghemite nanoparticles can reveal further complexities in the colloidal suspensions of SPIO systems, like larger grain aggregates, not estimated by the existing model. In our work we study the effects of the surface modified maghemite nanoparticles in both liquid and solid systems in the dependence on the temperature and concentration of SPIO and discuss the applicability of the existing model. 2
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Experimental
The experimental samples were prepared using the solvent-free ferrofluid containing surface functionalized maghemite (γ-Fe O ) nanoparticles of d~5 nm diam
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