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> Nanotech forum > Nanotech > Magnetite Nanocrystals
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Magnetite Nanocrystals |
Physya The Cat
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Wed Apr 18 04:02:53 2007
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Magnetite Nanocrystals |
There are bacteria called magnetotactic bacteria that produce perfect magnetite nanocrystals. We now know how to extract these and also how to produce the in vitro.
The sizes range from >2 nm for synthetic and >30 nm for biological magnetite.
There are several interesting aspects here. First is to study the Verwey transition in individual nanocrystal using something like Alexey's templating method.
Second, you could use them as a little magnet for various experiments related to spin manipulation and where you need local fields (say a particle in a squid loop).
Anyway, for more information see here:
http://www3.interscience.wiley.com/cgi-bin/abstract/114096812/ABSTRACT?CRETRY=1&SRETRY=0
and
http://arxiv.org/abs/cond-mat/0703306
I am also making a webpage (hope to fill it soon) at:
http://www.cmpgroup.ameslab.gov/supermaglab/bugs.html
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| Created: Wed Apr 18 16:20:18 2007
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Alexey
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RE: Magnetite Nanocrystals |
PTC says:
"from >2 nm for synthetic and >30 nm for biological magnetite. "
Interesting!
Questions:
-what is "synthetic" magnetite?? is is a piece of magnetic metal produced by bacteria??
-What is Verwey transition?
-Say one more time what is the length and diameter of these nanocrystals.
-Can bacteria grow them over a trench?? |
| Created: Sun Apr 22 02:05:05 2007
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Physya The Cat
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RE: Magnetite Nanocrystals |
Alexey,
Please, read the references I provided. In brief,
- Magnetite is Fe3O4 - most magnetic of iron oxides. Synthetic means produced in a test tube. Bacterial means produced by bacteria when it growth.
- Verwey transition is the most known and studied metal-insulator transition
- bacterial nanocrystals are about 30-50 nm cubes. Synthetic can be much smaller
- no, but they grow them in chains which then could be put across the trench! |
| Created: Sun Apr 22 06:19:09 2007
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Alexey
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RE: Magnetite Nanocrystals |
OK, but when you talk about "synthetic", does it mean that bacteria live in the tube, or bacteria are not involved at all?
Chains is the most interesting stuff. So what holds them in chains? Some glue I suppose?
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| Created: Tue Apr 24 06:18:45 2007
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Physya The Cat
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RE: Magnetite Nanocrystals |
| not involved. synthesis is done with certain protein and other organic stuff. |
| Created: Thu Apr 26 06:47:48 2007
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Alexey
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RE: Magnetite Nanocrystals |
| So do you have these bateria? can we put them on our substrates and grow the wires? How large these bacteria are? |
| Created: Sat Apr 28 00:15:57 2007
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Physya The Cat
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RE: Magnetite Nanocrystals |
| sure, I have them. As for sizes etc - please, read the papers. |
| Created: Sat Apr 28 07:05:57 2007
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Alexey
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RE: Magnetite Nanocrystals |
| what do they eat, these bacteria I mean? |
| Created: Mon Apr 30 01:43:55 2007
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Physya The Cat
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RE: Magnetite Nanocrystals |
Fe3+ and Fe2+, indeed
They live in seas |
| Created: Mon May 7 05:45:55 2007
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Kostia
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Fri May 25 18:59:39 2007
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RE: Magnetite Nanocrystals |
"The sizes range from >2 nm for synthetic ..."
I wonder how the magnetic energy ~(M^2 x volume) is compared to kT? I would expect that for such small creatures (and moments?) at room temepertaures the vector M fluctuates. What for evolution has created such an "unstable" compass ? :) |
| Created: Fri May 25 19:39:42 2007
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RP
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RE: Magnetite Nanocrystals |
| this has been discussed in 60s and lead C.P. Bean to propose "superparamagnetism". The particle stays ferromagnetic, but its moment fluctuates as a whole, so it follows Langevin function with effective moment as large as 10^6 mu_B. |
| Created: Sun Jun 3 20:17:10 2007
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Alexey
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RE: Magnetite Nanocrystals |
ok, you tell us the moment now. But I think the question was about the ration of (mu_B*H)/(k_B*T), where H is the magnetic field of the Earth. If this ratio is much smaller than unity then the magnets will not be oriented and it is not clear how bacteria can make any use of them.
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| Created: Sat Jun 9 18:37:44 2007
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| Pages: 1 2 |
