Biomedical Engineering Reference
In-Depth Information
component of other important allotropes. h ese carbon sheets can be
stacked to form a 3D graphite or rolled to form nanotubes or fullerenes.
Novoselov reported for the i rst time the synthesis of a single layer of GR
in 2004 [20], this material exhibited high stability and crystallographic
quality with excellent thermal, electrical and mechanical properties, due
to the conjugation [4]. GR has an analogous structure to benzene and
polycyclic aromatic hydrocarbons, so the chemistry of these compounds
is similar; but a determining factor in GR is the formation and/or break-
ing of conjugated C-C bonds in the basal plane and the C-H bonds on the
edges.
Dif erent GR synthesis methods have been reported in literature:
mechanical exfoliation of graphite [5-10], chemical vapor deposition
[10, 11], liquid phase exfoliation from graphite [12], reduction of graphene
oxide, surface segregation [13], and molecular beam epitaxy (MBE) [14].
Mass production of GR is one of the most important drawbacks for their
application, since its number of layers and defects inl uence signii cantly in
the i nal properties of the material.
h e characterization of GR properties is achieved using: scanning probe
microscopy (used to study thickness), atomic force microscopy AFM (used
to measure mechanical properties), and scanning tunneling microscopy
(employed for morphological studies). Raman Spectroscopy has been
recently used to determine the thickness of the sheets obtained by mechan-
ical exfoliation [14].
In general, the main properties of GR are:
•
Mechanical properties
: Surface area (2630 m
2
g
-1
)
,
intrinsic
mobility (200000 cm
2
v
-1
s
-1
), high Young's modulus (1.0
TPa) [15]
• h ermal conductivity: 5000Wm
-1
K
-1
•
Optical properties: GR shows a transmittance of 97.7%
•
Electrical properties: High conductivity ( 10
4
Ω
-1
cm
-1
) [16].
GR can support a current density about six times higher
than that of copper; the electronic characteristics of this
material are mainly due to its topology, because of the size of
the i lms at atomic levels, the electron transport can be bal-
listic at submicrometer distances [5, 17, 18].
GR has become the center of attention of many scientists because all
the properties mentioned above, specially the electric ones. GR has advan-
tages over other nanomaterials as carbon nanotubes, such as its high ther-
mal and electrical conductivity (due to its small thickness) and the large
surface area.
