Nanoshow - PowerPoint PPT Presentation

Title: Nanoshow


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Nanoshow

• Bilder zur Nanotechnologie

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Buckyballs
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Buckyball
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C60-Fullerene at 153 deg.K. C60 crystallizes in
a face centered cubic arrangement.
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Polymeric fullerene chains in RbC60
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C60-Fullerene tetra benzene solvate at 173 deg.K
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C60-Fullerene tetrakis(dimethylamino)ethylene,an
itinerant ferromagnet
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C60 molecules form a face-centered-cubic (fcc)
solid. Here the buckyballs are represented by
spheres, and the size of the spheres
approximately corresponds the size of the C60
molecules, 10 Angstrom. There is plenty of empty
space between the fullerene molecules. A little
exploration reveals that, for each C60, there are
three available sites where other atoms could go.
One of these sites is called the "octahedral
site", and the other two are the "tetrahedral"
sites.
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When the octahedral sites are filled with alkali
ions the A1C60 is obtained. ("A" stands for
potassium, rubidium or cesium.) In this picture
the blue spheres indicate the alkali metals.
Interestingly, when this material is cooled below
room temperature, the structure changes, as the
buckyballs bind into long polymer chains, as
illustrated in the title picture of the buckyball
page. These chains form along the face diagonals
of the cube, as seen here. There is still more
empty space between the bucky balls. Those are
the "tetrahedral" sites, where more alkali metal
could go.
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When the tetrahedral sites are also filled (light
blue color), the superconducting A3C60 is
produced.
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Here is another way of looking at the same A3C60
structure. (How to get this look? See the simple
explanation.) This time the larger space in the
octahedral sites is even more visible.
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When the fullerene molecules are rearranged, even
more alkali metal ion can be stuffed in,
producing A4C60. The name of this structure is
"body centered tetragonal" or bcc.
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Finally, a little more pushing and pulling of the
buckyballs puts them into a "body centered
cubic", or bcc structure. In this structure,
there is enough space for six alkali metals for
each fullerenes this is A6C60
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Rastertunnelmikroskop
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Carbonnanotubes
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Nanobased memory element

• The associated MPEG movie shows the functionality
  of a nanotube-based memory element. The outer
  capsule is a short segment of a (10,10) carbon
  nanotube, with a diameter of 1.4 nanometers,
  terminated at both ends by perfect fullerene
  caps. The capsule is large enough to hold a C60
  buckyball molecule inside. The buckyball carries
  a net charge if it contains an alkali atom in the
  hollow cage. The C60 molecule can be shifted from
  one end to the other by applying an electric
  field between the ends of the capsule. The two
  energy minima of this system, with the buckyball
  bonded to either end of the capsule, can be
  associated with bit 0 and bit 1. The simulation
  has been performed by Young-Kyun Kwon.
• This structure has been patented as a
  non-volatile memory element and awarded U.S.
  Patent Number 6,473,351.