5.3 Nanostructures Related to Compounds with Layered Structures 91
tives of benzene. Therefore, graphene is often termed as infinitely extended
two-dimensional aromatic compound.
Certainly, like in any other crystal, graphene is also prone to lattice defects.
Among other possibilities, it is possible that a pentagon or a heptagon replaces
a hexagon. In particular, the formation of pentagons is most important, as this
defect enables the formation of three-dimensional objects, the fullerenes. Figure
5.12 demonstrates the bulging of the structure around a pentagon. This phenomenon makes the formation of three-dimensional structures, such as fullerenes,
possible. If graphene can be called a two-dimensional aromatic compound, fullerenes are three-dimensional aromatics.
Combining a larger number of structures, as shown in Figure 5.12, leads to
spherical shapes, polyhedra, consisting of pentagons and hexagons. Euler was the
first to predict the existence of such polyhedra.
The most common fullerene, and the first one identified by Kroto and coworkers
[8], consists of 60 carbon atoms, C 60 . This molecule is set up of twelve pentagons
and twenty hexagons. The next larger fullerene consists of 70 carbon atoms, C 70 .
Figure 5.13 displays these two fullerenes.
Besides C 60 and C 70 , many other fullerenes exist. Furthermore, fullerenes can
form nested particles, “fullerene in an fullerene”, like a “Russian Doll”. These
nested fullerenes are called onion crystals. Besides C 60 , the most important further
fullerenes are C 70 , C 76 , C 78 und C 84 . As C 60 looks like a soccer ball, C 60 is often called
a “soccer ball molecule”. Fullerene molecules are quite stable; however, like in
graphene, each carbon atom has only three neighbors. Therefore, there are free
valences, which may be used for functionalization, for example, it is possible to
attach metal atoms or other molecules at the surface. In view of applications, this
is of great importance.
Figure 5.12 Effect of a pentagon in a hexagonal structure. Closing of the structure is possible
only by bulging. This is the elementary requirement for the formation of three-dimensional
structures, such as fullerenes.
tives of benzene. Therefore, graphene is often termed as infinitely extended
two-dimensional aromatic compound.
Certainly, like in any other crystal, graphene is also prone to lattice defects.
Among other possibilities, it is possible that a pentagon or a heptagon replaces
a hexagon. In particular, the formation of pentagons is most important, as this
defect enables the formation of three-dimensional objects, the fullerenes. Figure
5.12 demonstrates the bulging of the structure around a pentagon. This phenomenon makes the formation of three-dimensional structures, such as fullerenes,
possible. If graphene can be called a two-dimensional aromatic compound, fullerenes are three-dimensional aromatics.
Combining a larger number of structures, as shown in Figure 5.12, leads to
spherical shapes, polyhedra, consisting of pentagons and hexagons. Euler was the
first to predict the existence of such polyhedra.
The most common fullerene, and the first one identified by Kroto and coworkers
[8], consists of 60 carbon atoms, C 60 . This molecule is set up of twelve pentagons
and twenty hexagons. The next larger fullerene consists of 70 carbon atoms, C 70 .
Figure 5.13 displays these two fullerenes.
Besides C 60 and C 70 , many other fullerenes exist. Furthermore, fullerenes can
form nested particles, “fullerene in an fullerene”, like a “Russian Doll”. These
nested fullerenes are called onion crystals. Besides C 60 , the most important further
fullerenes are C 70 , C 76 , C 78 und C 84 . As C 60 looks like a soccer ball, C 60 is often called
a “soccer ball molecule”. Fullerene molecules are quite stable; however, like in
graphene, each carbon atom has only three neighbors. Therefore, there are free
valences, which may be used for functionalization, for example, it is possible to
attach metal atoms or other molecules at the surface. In view of applications, this
is of great importance.
Figure 5.12 Effect of a pentagon in a hexagonal structure. Closing of the structure is possible
only by bulging. This is the elementary requirement for the formation of three-dimensional
structures, such as fullerenes.