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 ((1)H 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. (1)H 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.

Local spin dynamics of iron oxide magnetic nanoparticles dispersed in different solvents with variable size and shape : A (1)H NMR study / M. Basini, T. Orlando, P. Arosio, M.F. Casula, D. Espa, S. Murgia, C. Sangregorio, C. Innocenti, A. Lascialfari. - In: THE JOURNAL OF CHEMICAL PHYSICS. - ISSN 0021-9606. - 146:3(2017 Jan 21). [10.1063/1.4973979]

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

M. Basini
Primo
;
P. Arosio;A. Lascialfari
Ultimo
2017

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 ((1)H 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. (1)H 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.
data-storage; particles; viscosity; law
Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin)
Article (author)
File in questo prodotto:
File Dimensione Formato  
Basini_EtAlii_JournChemPhysics_LocalSpin_2017.pdf

Open Access dal 13/12/2017

Tipologia: Publisher's version/PDF
Dimensione 658.44 kB
Formato Adobe PDF
658.44 kB Adobe PDF Visualizza/Apri
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/470598
Citazioni
  • ???jsp.display-item.citation.pmc??? 0
  • Scopus 12
  • ???jsp.display-item.citation.isi??? 13
social impact