Imaging of magnetic colloids under the influence of magnetic field by cryogenic transmission electron microscopy
DSpace at IIT Bombay
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Title |
Imaging of magnetic colloids under the influence of magnetic field by cryogenic transmission electron microscopy
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Creator |
WU, J
ASLAM, M DRAVID, VP |
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Subject |
cobalt nanoparticle rings
dipolar chains flux-closure zero-field nanocrystals |
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Description |
The application of superparamagnetic nanoparticles for in vivo magnetic resonance imaging (MRI) under external ac magnetic field has attracted considerable research efforts in recent years. However, it is unclear how superparamagnetic nanostructures arrange themselves in fluidic environment under external magnetic field. Here, we report direct visualization of the effect of applied magnetic field to the ferrofluids (about 6 nm superparamagnetic magnetite (Fe(3)O(4)) nanoparticle "colloidal" suspension) using the cryogenic transmission electron microscopy (cryo-TEM). While long dipole chains (up to millimeter range) of the magnetite along the magnetic lines are found in samples dried inside the magnetic field, only short dipole chains (within tens of nanometer scale) with random orientations are observed in the wet sample observed by cryo-TEM. In the wet sample, aggregations of medium-length dipole chains (up to hundreds of nanometer) can be observed at the areas where the nanoparticles are "solidified" when phase separation occurs. In situ formation of flux-closure rings is observed at the edge where vitreous ice sublimes due to high-energy electron radiation that leaves magnetite nanoparticles isolated in the vacuum. Such observations may help elucidate the nature of magnetic field-induced assembly in fluidic environment as in the physiological aqueous conditions in MRI and related applications. (C) 2008
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Publisher |
AMER INST PHYSICS
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Date |
2011-07-16T07:23:21Z
2011-12-26T12:49:39Z 2011-12-27T05:35:12Z 2011-07-16T07:23:21Z 2011-12-26T12:49:39Z 2011-12-27T05:35:12Z 2008 |
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Type |
Article
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Identifier |
APPLIED PHYSICS LETTERS, 93(8), -
0003-6951 http://dx.doi.org/10.1063/1.2976751 http://dspace.library.iitb.ac.in/xmlui/handle/10054/4361 http://hdl.handle.net/10054/4361 |
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Language |
en
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