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2Physics Quote:
"Many of the molecules found by ROSINA DFMS in the coma of comet 67P are compatible with the idea that comets delivered key molecules for prebiotic chemistry throughout the solar system and in particular to the early Earth increasing drastically the concentration of life-related chemicals by impact on a closed water body. The fact that glycine was most probably formed on dust grains in the presolar stage also makes these molecules somehow universal, which means that what happened in the solar system could probably happen elsewhere in the Universe."
-- Kathrin Altwegg and the ROSINA Team

(Read Full Article: "Glycine, an Amino Acid and Other Prebiotic Molecules in Comet 67P/Churyumov-Gerasimenko"

Sunday, June 06, 2010

Magnetic Morphology of Nanoparticles

Kathryn Krycka [photo courtesy: University of Florida]

While attempting to solve one mystery about iron oxide-based nanoparticles, a research team working at the National Institute of Standards and Technology (NIST) stumbled upon another one. But once its implications are understood, their discovery may give nanotechnologists a new and useful tool.

The nanoparticles in question are spheres of magnetite so tiny that a few thousand of them lined up would stretch a hair’s width, and they have potential uses both as the basis of better data storage systems and in biological applications such as hyperthermia treatment for cancer. A key to all these applications is a full understanding of how large numbers of the particles interact magnetically with one another across relatively large distances so that scientists can manipulate them with magnetism.

“It’s been known for a long time that a big chunk of magnetite has greater magnetic ‘moment’—think of it as magnetic strength—than an equivalent mass of nanoparticles,” says Kathryn Krycka, a researcher at the NIST Center for Neutron Research. “No one really knows why, though. We decided to probe the particles with beams of low-energy neutrons, which can tell you a great deal about a material’s internal structure.”

The team applied a magnetic field to nanocrystals composed of 9 nm-wide particles, made by collaborators at Carnegie Mellon University. The field caused the particles to line up like iron filings on a piece of paper held above a bar magnet. But when the team looked closer using the neutron beam, what they saw revealed a level of complexity never seen before.

“When the field is applied, the inner 7 nm-wide ‘core’ orients itself along the field’s north and south poles, just like large iron filings would,” Krycka says. “But the outer 1 nm ‘shell’ of each nanoparticle behaves differently. It also develops a moment, but pointed at right angles to that of the core.”

In a word, bizarre. But potentially useful.

[Image courtesy: NIST] Schematic of a spherical magnetite nanoparticle shows the unexpected variation in magnetic moment between the particle's interior and exterior when subjected to a strong magnetic field. The core's moment (black lines in magenta region) lines up with the field's (light blue arrow), while the exterior's moment (black arrows in green region) forms at right angles to it.

The shells are not physically different than the interiors; without the magnetic field, the distinction vanishes. But once formed, the shells of nearby particles seem to heed one another: A local group of them will have their shells’ moments all lined up one way, but then another group’s shells will point elsewhere. This finding leads Krycka and her team to believe that there is more to be learned about the role that particle interaction has on determining internal, magnetic nanoparticle structure—perhaps something nanotechnologists can harness.

“The effect fundamentally changes how the particles would talk to each other in a data storage setting,” Krycka says. “If we can control it—by varying their temperature, for example, as our findings suggest we can—we might be able to turn the effect on and off, which could be useful in real-world applications.”

The research team included scientists from NIST, Carnegie Mellon University, University of Maryland, Oberlin College and Los Alamos National Laboratory of USA and Paul Scherrer Institute of Switzerland.

K.L. Krycka, R.A. Booth, C. Hogg, Y. Ijiri, J.A. Borchers, W.C. Chen, S.M. Watson, M. Laver, T.R. Gentile, L.R. Dedon, S. Harris, J.J. Rhyne and S.A. Majetich. "Core-shell magnetic morphology of structurally uniform magnetite nanoparticles", Physical Review Letters, 104, 207203 (2010). Abstract.

[We thank NIST for materials used in this report]



At 11:22 PM, Anonymous Anonymous said...

humble question from a"semi-scientist'-
could there be heating shear involved in the perpendicular relationship of the "core and crust" of nanoparticles? -could the heating of shear between core and crust cause a superfluid film of comminication between the core and crust say of superlight quarks and could this heated film cause fluid fissures in the crust of particles if slippage via the film occurred?
-last could a fractal analogy of macro to nano or micro allow some conjecture to larger magnetic induction in the earth's core causing a similat core/crust alignment with possibly fluid fissures in the crust caused easy slippage between crust and core
these questions may be too childish to consider or answer so if this is so , please save me face by not posting this comment/question thank you for your interesting article.


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