Nanoshow

Bilder zur Nanotechnologie

Buckyballs

Buckyball

C60-Fullerene at 153 deg.K. C60

crystallizes in a face centered cubic arrangement.

Polymeric fullerene chains in RbC60

C60-Fullerene tetra benzene solvate at 173 deg.K

C60-Fullerene tetrakis(dimethylamino)ethylene,an

itinerant ferromagnet

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.

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.

When the tetrahedral sites are also filled (light blue color), the superconducting A3C60 is produced.

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.

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.

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

Rastertunnelmikroskop

Carbonnanotubes

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.