Magnetic La sub(1-x)Sr sub(x)MnO sub(3) nanoparticles as contrast agents for MRI: the parameters affecting super(1)H transverse relaxation

Magnetic nanoparticles of the La sub(1-x)Sr sub(x)MnO sub(3) perovskite phase (x = 0.20-0.45) were synthesized by a sol-gel method followed by thermal and mechanical treatments. The particles were coated with a uniform silica shell, and differential centrifugation yielded a product with high colloid...

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Bibliographic Details
Published in:Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology 2015-01, Vol.17 (1), p.1-11
Main Authors: Veverka, P, Kaman, O, Kacenka, M, Herynek, V, Veverka, M, Santava, E, Lukes, I, Jirak, Z
Format: Article
Language:English
Subjects:
Coating
Colloids
Contrast agents
Magnetic cores
Nanoparticles
Shells
Silicon dioxide
Strontium
X-ray diffraction
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Summary:Magnetic nanoparticles of the La sub(1-x)Sr sub(x)MnO sub(3) perovskite phase (x = 0.20-0.45) were synthesized by a sol-gel method followed by thermal and mechanical treatments. The particles were coated with a uniform silica shell, and differential centrifugation yielded a product with high colloidal stability in water. X-ray powder diffraction (XRD) data showed that the mechanical processing did not affect the lattice parameters of the magnetic cores but only reduced their mean size d sub(XRD). The magnetic properties of the bare particles were mainly controlled by the chemical composition and were also affected by the size of the particles. Subsequent silica coating led to an effective decrease in magnetization. Relaxometry measurements were focused primarily on colloids using magnetic cores of the same size (d sub(XRD) approximately 20 nm) and different compositions, and coated with a shell measuring approximately 20 nm in thickness. The exceedingly high transverse relaxivities [r sub(2)(20 degree C) = 290-430 s super(-1) mmol super(-1) L at B sub(0) = 0.5 T] of the samples exhibited pronounced temperature dependence and correlated very well with the magnetic data. Additional samples differing in the size of the cores and silica shell thickness were prepared as well to analyze the effect of the particles on super(1)H transverse relaxation. The results suggest that the dominant regime of transverse relaxation is the static dephasing regime.
ISSN:1388-0764
1572-896X
DOI:10.1007/s11051-014-2848-6