Spectroscopic Characterization and Molecular Dynamics Simulation
31
1.2 Graphene Nanoplatelets (GnPs)
Environmental pollution caused by burning fossil fuels, motor vehicles powered by
gasoline, emissions released from manufacturing industries, are a growing global concern because of the associated negative impact on human and animal health, and on the
Earth’s climate system. Graphene and its derivatives, such as graphene oxide (GrO), are
suitable candidates for gas sensing applications due to their high surface area, excellent
thermal conductivity and stability, and high mechanical rigidity [7]. In addition, functionalization of graphene further improves the adsorption of gas molecules on its surface,
which in turn improves the sensing capabilities, such as quick response to adsorbed gas
molecules even at low concentrations (~ parts per million level) and shorter recovery
time [8]. These unique characteristics can overcome the major shortcomings of the metal
oxide semiconductor-based sensors, which have low selectivity for target gas molecules,
high operating temperatures and high-power consumption [9]. Graphene nanoplatelets
(GnPs) are a new type of nanoparticle that can be regarded as derivatives of graphene
and graphite, since they are manufactured by exfoliating graphite and composed of a few
layers of graphene. In addition, GnPs can be produced on a large scale gives it an edge
over graphene [10] for numerous applications (e.g. gas sensing, flexible electronics and
energy storage). The chemical reactivity of the carbon atoms localized at the edges of
GnPs makes it feasible to functionalize GnPs at the edges, as shown in Fig. 2. GnPs have
the same honeycomb structure as two-dimensional (2D) graphene. The carbon atoms
are arranged in a hexagonal shape with an atomic distance of 1.42 Å. Each carbon atom
is connected to three other neighboring carbon atoms via three (σ ) sigma bonds and one
π -bond. The three σ covalent bonds are formed by the hybridization of 2 s and 2p atomic
orbitals of neighboring carbon atoms to form sp 2 orbitals, while the p z orbital forms the
π -bond. GnPs are like graphite in terms of their interlayer distance of approximately
3.35 Å, which has been obtained using the XRD technique. Each of these nanoplatelets
consists of small stacks of platelet-shaped graphene sheets that typically have a thickness
in the range ~ 0.34–100 nm [11].
Fig. 2. Diagram showing functional groups (ammonia, carboxyl, hydroxyl and fluorocarbon)
attached to the edges of four graphene layers with an interlayer distance of 3.35 Å.
In this section, we report the characterization of pristine and functionalized GnPs
(incorporating individually carboxyl, fluorocarbon, nitrogen, oxygen, ammonia and
argon) by utilizing Raman spectroscopy, SEM and XRD characterization techniques.
31
1.2 Graphene Nanoplatelets (GnPs)
Environmental pollution caused by burning fossil fuels, motor vehicles powered by
gasoline, emissions released from manufacturing industries, are a growing global concern because of the associated negative impact on human and animal health, and on the
Earth’s climate system. Graphene and its derivatives, such as graphene oxide (GrO), are
suitable candidates for gas sensing applications due to their high surface area, excellent
thermal conductivity and stability, and high mechanical rigidity [7]. In addition, functionalization of graphene further improves the adsorption of gas molecules on its surface,
which in turn improves the sensing capabilities, such as quick response to adsorbed gas
molecules even at low concentrations (~ parts per million level) and shorter recovery
time [8]. These unique characteristics can overcome the major shortcomings of the metal
oxide semiconductor-based sensors, which have low selectivity for target gas molecules,
high operating temperatures and high-power consumption [9]. Graphene nanoplatelets
(GnPs) are a new type of nanoparticle that can be regarded as derivatives of graphene
and graphite, since they are manufactured by exfoliating graphite and composed of a few
layers of graphene. In addition, GnPs can be produced on a large scale gives it an edge
over graphene [10] for numerous applications (e.g. gas sensing, flexible electronics and
energy storage). The chemical reactivity of the carbon atoms localized at the edges of
GnPs makes it feasible to functionalize GnPs at the edges, as shown in Fig. 2. GnPs have
the same honeycomb structure as two-dimensional (2D) graphene. The carbon atoms
are arranged in a hexagonal shape with an atomic distance of 1.42 Å. Each carbon atom
is connected to three other neighboring carbon atoms via three (σ ) sigma bonds and one
π -bond. The three σ covalent bonds are formed by the hybridization of 2 s and 2p atomic
orbitals of neighboring carbon atoms to form sp 2 orbitals, while the p z orbital forms the
π -bond. GnPs are like graphite in terms of their interlayer distance of approximately
3.35 Å, which has been obtained using the XRD technique. Each of these nanoplatelets
consists of small stacks of platelet-shaped graphene sheets that typically have a thickness
in the range ~ 0.34–100 nm [11].
Fig. 2. Diagram showing functional groups (ammonia, carboxyl, hydroxyl and fluorocarbon)
attached to the edges of four graphene layers with an interlayer distance of 3.35 Å.
In this section, we report the characterization of pristine and functionalized GnPs
(incorporating individually carboxyl, fluorocarbon, nitrogen, oxygen, ammonia and
argon) by utilizing Raman spectroscopy, SEM and XRD characterization techniques.