Biomedical Engineering Reference
In-Depth Information
years later, the 2010 Nobel Prize in Physics was awarded jointly to Andre Geim and
Konstantin Novoselov “
for groundbreaking experiments regarding the two-dimensional material
graphene
.”
The origin of all three carbon nanostructures, graphite, fullerene, and CNTs, can be
traced to a single, remarkable species - graphene (Figure 5.3) [31]. Graphene possesses a
unique structure, a chemically stable two-dimensional, one-atom thick membrane that exists
in a three-dimensional world. Each carbon atom in graphene is covalently bonded to three
other carbon atoms. All possess sp
2
hybridization. Apparently, this one-atom thick network
is responsible for the existence of the thinnest known (conceptually and technologically
achievable) material. Interestingly, despite being so thin, graphene has excellent mechanical
characteristic that make this species the strongest material ever measured. Graphene also
possesses many amazing features. It can sustain current densities that are six orders of mag-
nitude higher than that of copper, possesses very high thermal conductivity and stiffness,
and is impermeable to gases [38].
In addition to fullerene and CNTs, graphite can also be considered a derivative of graphene.
When graphene sheets are arranged in three-dimensional stacked layers separated by 0.3 nm, the
structure obtained is called graphite. Since its third dimension (corresponding to just one carbon
layer in graphene) is larger than 100 nm, graphite cannot be considered as a nanomaterial.
Fullerene C
60
(also called Buckminsterfullerene) is considered to form from graphene
formed into a sphere by including pentagons and hexagons into the lattice. Fullerene C
60
represents an important carbon nanostructure that was the first among the three new carbon
allotropes to be discovered. Its discovery created an enormous amount of attention, and
fullerene was initially considered an exceptionally promising material with various potential
applications. Unfortunately, such high hopes have not been entirely fulfilled. Nevertheless,
the fullerene family has some interesting and promising applications. Many of the applica-
tions of fullerenes originate from their unique cage structures. Such structures facilitate their
AFM image
Graphene
C
60
Graphite
Carbon nanotube
Figure 5.3
Graphene is considered as the origin of the three carbon nanostructures graphite,
fullerene and single-wall carbon nanotubes. With kind permission of Springer Science+Business
Media reproduced from Figure 20a [31].
