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  Local spin dynamics of iron oxide magnetic nanoparticles dispersed in different solvents with variable size and shape: A H-1 NMR study.

Basini, M., Orlando, T., Arosio, P., Casula, M. F., Espa, D., Murgia, S., et al. (2017). Local spin dynamics of iron oxide magnetic nanoparticles dispersed in different solvents with variable size and shape: A H-1 NMR study. The Journal of Chemical Physics, 146(3): 034703. doi:10.1063/1.4973979.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-002C-E679-E Version Permalink: http://hdl.handle.net/11858/00-001M-0000-002E-9C37-1
Genre: Journal Article

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 Creators:
Basini, M., Author
Orlando, T.1, Author              
Arosio, P., Author
Casula, M. F., Author
Espa, D., Author
Murgia, S., Author
Sangregorio, C., Author
Innocenti, C., Author
Lascialfari, A., Author
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1Research Group of Electron Paramagnetic Resonance, MPI for Biophysical Chemistry, Max Planck Society, ou_578606              

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 Abstract: Colloidal magnetic nanoparticles (MNPs) based on a nearly monodisperse iron oxide core and capped by oleic acid have been used as model systems for investigating the superparamagnetic spin dynamics by means of magnetometry measurements and nuclear magnetic resonance (1H NMR) relaxometry. The key magnetic properties (saturation magnetization, coercive field, and frequency dependent “blocking” temperature) of MNPs with different core size (3.5 nm, 8.5 nm, and 17.5 nm), shape (spherical and cubic), and dispersant (hexane and water-based formulation) have been determined. 1H NMR dispersion profiles obtained by measuring the r1 (longitudinal) and r2 (transverse) nuclear relaxivities in the frequency range 0.01–60 MHz confirmed that in all samples the physical mechanisms that drive the nuclear relaxation are the Néel reversal at low temperature and the Curie relaxation at high frequency. The magnetization reversal time at room temperature extracted from the fitting of NMR data falls in the typical range of superparamagnetic systems (10−9-10−10 s). Furthermore, from the distance of minimum approach we could conclude that water molecules do not arrive in close vicinity of the magnetic core. Our findings contribute to elucidate the local spin dynamics mechanisms in colloidal superparamagnetic nanoparticles which are useful in biomedical application as, e.g., contrast agents for magnetic resonance imaging.

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Language(s): eng - English
 Dates: 2017-01
 Publication Status: Published online
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 Rev. Method: Peer
 Identifiers: DOI: 10.1063/1.4973979
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Title: The Journal of Chemical Physics
Source Genre: Journal
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Pages: 10 Volume / Issue: 146 (3) Sequence Number: 034703 Start / End Page: - Identifier: -