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Functionalized fullerenes are divided into two classes: exohedral fullerenes with substituents outside the cage and endohedral fullerenes with trapped molecules inside the cage. This article covers the chemistry of these so-called "buckyballs," while the chemistry of carbon nanotubes is covered in carbon nanotube chemistry .
There are two major families of fullerenes, with fairly distinct properties and applications: the closed buckyballs and the open-ended cylindrical carbon nanotubes. [27] However, hybrid structures exist between those two classes, such as carbon nanobuds — nanotubes capped by hemispherical meshes or larger "buckybuds".
Alternatively, endohedral hydrogen fullerenes can be produced by opening and closing a fullerene by organic chemistry methods. A recent example of endohedral fullerenes includes single molecules of water encapsulated in C 60. [10] Noble gas endofullerenes are predicted to exhibit unusual polarizability.
The iron compounds produced on the largest scale in industry are iron(II) sulfate (FeSO 4 ·7H 2 O) and iron(III) chloride (FeCl 3). The former is one of the most readily available sources of iron(II), but is less stable to aerial oxidation than Mohr's salt ((NH 4) 2 Fe(SO 4) 2 ·6H 2 O). Iron(II) compounds tend to be oxidized to iron(III ...
These endohedral fullerenes are usually synthesized by doping in the metal atoms in an arc reactor or by laser evaporation. These methods gives low yields of endohedral fullerenes, and a better method involves the opening of the cage, packing in the atoms or molecules, and closing the opening using certain organic reactions. This method ...
Ferritin is a hollow sphere that has an outer diameter close to 12 nm and an inner diameter of 7-8 nm. The inner chamber of ferritin uptakes or binds iron in its ferrous state and stores iron in its ferric or trivalent state. There are many examples of highly symmetrical macromolecular cage motifs known as protein cages in biological systems.
An area of controversy and frequent experimentation regarding the storage of hydrogen by adsorption in carbon nanotubes is the efficiency by which this process occurs. The effectiveness of hydrogen storage is integral to its use as a primary fuel source since hydrogen only contains about one fourth the energy per unit volume as gasoline.
Scheme 2. Endohedral hydrogen fullerene mechanism. From X-ray crystallography it is determined that the shape of the orifice in the sulfur compound is roughly a circle. Inserting hydrogen in this compound is an easy step taking place with 100% efficiency. Zipping up the orifice is a reversal of the steps required to open the cage.