Graphene – The thinnest strongest material in nature
Essay code B3
Carbon is the elementary constituent of life and organic chemistry. It plays a huge role in
the existence of life. Carbon is very important because materials made of carbon can function as
conductors, semi-conductors and insulators. Carbon is able to build a strong network by forming
carbon–carbon bonds. The ability of carbon to form strong hybridized sp2 covalent bonds with
other elements leads to the exceptional strength observed in crystalline forms of carbon such as
diamond. The unique strength and bonding properties of carbon has lead to increased interest in
its applications at the nanoscale.
Fullerene, graphene, and graphite are a few of the most important allotropes of carbon
that exist in nanoscale dimensions, and all three have unique physical, material, and chemical
properties. Fullerene, graphene, and graphite are all highly stable molecules due to the high
activation barrier caused by the structural arrangement. The three types of carbon can be
achieved by restricting different dimensions. In zero dimensions a carbon network of fullerene
forms. By confinining carbon to only one dimension, nanotubes will form. In three dimensions,
graphite and diamond are observed. Until recently, it was unclear how carbon existed in two
dimensions.
In 2010, two professors named Konstantin Novoselov and Andre Geim from the
University of Manchester from England shared the Nobel Prize for Physics for extracting the 2
dimensional nano scale carbon known as Graphene from Graphite. The professors extracted
Graphene from Graphite in 2004 by merely using an adhesive scotch tape. 3D Graphite is a
structure formed by stacking many Graphene sheets and was used to replace lead in pencils.
Graphene is a one atom thick single layer sheet of sp2 hybridized carbon atoms. Therefore,
Graphene is considered to be the thinnest of all materials available. The carbon-carbon bond
length in graphene is 0.142 nanometers. The stacking of graphene to from graphite is held
together by weak Vander Waals forces and therefore graphite is the softest material available on
Earth. Additionally, grapheme is extremely conductive, stable, and strong. The unique
mechanical, physical, quantum and thermal properties make Graphene one of the most demanded
materials on Earth.
Graphene is stable even in its non-functionalized form due to its high activation barrier.
Graphene is extremely flexible and can be considered as the building block of other nanoscale
carbon forms. Graphene can be rolled to form 1D nanotubes and can be wrapped to form a 0D
fullerene and can also be stacked in multiple layers to form 3D graphite. Graphene is a one atom
thick sheet of single layer sp2 hybridized carbon atoms. Electron diffraction patterns from the
studying of structure of Graphene using Transmission Electron Microscopy indicates Graphene
has a honeycomb lattice in hexagonal array, and when graphene is bombarded with a carbon
atom, it can rearrange itself to become a hexagonal molecule. The properties of Graphene 2D is
in many ways different from that of 3D graphite.
The synthesis of graphene was first made possible by using adhesive tape and a pencil.
However, there are more sophisticated technologies now available for the synthesis of grapheme.
New synthesis mechanisms include micromechanical exfoliation, chemical vapor disposition on
the single crystal metals such as Nickel, chemical synthesis form graphite, reduction of graphene
oxide sheets, and chemical exfoliation. The micromechanical cleavage of graphene is done by
peeling of a highly oriented pyrolitic graphite using scotch tape and sticking it onto a silicon
substrate. This is referred to as a top-down approach. The reduction of Graphene oxide to
obtain graphene is possible by removal of functional groups by chemical reduction to make it
highly hydrophilic. The reducing agents that are used are hydroquinone, dimethyl hydrazine,
hydrazine hydrate. Other types of reduction include electrostatic reduction, thermo reduction
and photo catalytic reduction.
The extraordinary chemical and thermal properties of Graphene are due to several
factors. It is a chemically inert molecule. In the delocalized orbitals, electrons are free to move
and therefore suffer very little energy dissipation, and there is no energy gap. Graphene has very
high electron mobility at room temperature compared to other semiconductors. This is
independent of the electron’s kinetic energy. Graphene is a high heat conductor and has been
used in high speed integrated density chips for thermal management and heat dissipation.
Graphene’s has many unique physical properties including heightened strength,
conductance, and flexibility, and a unique absorbance pattern. Graphene is hundred times
stronger than steel which means one thin layer of graphene can hold one elephant. It is
obversved that graphene breaks at a force a hundred times greater than the force at which steel
breaks. The force was measured by probing a diamond into a thin layer of graphene until it
broke. The tensile strength of graphene is remarkable because of its strongest bonds among all
atoms. Graphene is very stretchable because it can stretch up to 20 percent of its length and is
also transparent in color and conducts electricity better than copper. There is no band gap in
graphene, and therefore it is used in photovoltaic cells because every energy frequency can be
absorbed by Graphene. All the photons at different frequencies are thus converted to electrons.
The chemical properties of Graphene are unique because both the sides of the 2D
structure can be exposed to the surroundings and there can engage in chemical reactions. The
carbon atoms at the tips of graphene sheets have extra chemical reactivity compared to other
carbon nanoscale materials such as nanotubes. Graphene can be considered as the most
chemically reactive form of carbon because of its honeycomb lattice like hexagonal arrangement
of carbon atoms. The structural analysis of Graphene is often done using NMR and IR
spectroscopy by modifying it with functional groups. The thermal properties of Graphene
include conductivity at room temperature measured at 4.84±0.44) × 103 to (5.30±0.48) ×
103 W·m−1·K−1. The isotope of Carbon 12C has a better conductivity than the 50:50 isotope ratio.
Even though graphene can be rolled into a nano tube, it is less stable at this structure. The
mechanical strength of Graphene was illustrated using 1 square meter graphene will support a
4kg cat and will weigh only up to one of cat’s whiskers. The spring constant value of graphene
was 1-5 N/m and the stiffness was 0.5 TPa,
The major uses and applications of graphene include as composites, energy storage
devices, terahertz imaging, sensors, transistors, membranes, batteries, thin coating for solar cells,
digital and LCD displays. Due to its high tensile strength and because of the fact that graphene
would not crack upon bending, graphene can be used to replace indium tin oxide which is used
for the transparent layer of computers and phones. Graphene can be used in the new super
capacitors which store very large amounts of power. This is because of its extraordinary high
surface area to volume ratio. The transistors that are made from carbon can be faster than the
silicon chips used today because of its high electrical conductivity. Due to all the unique
properties mentioned above graphene can be used in digital displays such as phone and
computer, flexible electronic devices and composite materials. Because graphene is a good
semiconductor and metal, it can be used to replace silicon chips and thus impact highly defined
applications such as high sped computer chips and biochemical sensors. The thousand times
better conductivity shown by graphene compared to Copper means it can replace copper in future
computer chips.
One of the major uses of graphene is to minimize over heating by efficient thermal
management of high speed high integration density chips because of its high heat conducting
property. (You already said this.) The increasing power densities of chips create a major issue of
inefficient heat removal. It can be properly managed to remove heat efficiently and spread the
heat out in future integrated circuit chips. Solar cells must be efficiently removed of heat in order
to function properly and generate heat. The high electron mobility at room temperature will help
ballistic conduction possible by having high nano electric devices such as ballistic transistors.
The interconnection between chips is possible due to the high electron mobility of graphene. The
high spring constant and stiffness value of graphene would help if used in applications such
pressure sensors and resonators.
Carbon can be functionalized in chemical and biological manner to produce opportunities in
variety of fields. The covalent modification can be altered to produce change in properties
because of its strong delicate thin layer. One of the methods to change graphene functionally
without changing its inherent properties is by using bio recognition molecules. This is possible
by attaching avidin – biotin, peptides, Nucleic acids, proteins, aptamers, small molecules,
bacteria by physical adsorption or chemical conjugation. Also to introduce catalytic properties,
graphene can be functionalized into hybrids such nano particle. Thus by synthesizing these
hybrids, Graphene is thus used as bio sensors. For example an inorganic - - graphene hybrid
such as gold graphene has been showing exceptional properties better than individual
constituents. This is synthesized by spontaneous reduction of gold ions and layer by layer filling
of alternate graphene and gold. In the field of medicine, graphene has improved PCR results by
reducing the number of cycles to 65% and increasing the yield of DNA product due to its high
thermal conductivity. Graphene is also being used as frequency multiplier when an incoming
frequency was used to produce multiple outgoing same frequencies. Graphene quantum dots can
be used in applications such as electronics, opt electrics and electro magnetics. Graphene is an
excellent source of microbial detection due to its small atomic thickness and large surface area.
The potential applications of graphene are also highly remarkable. Because of it high
flexibility, graphene can be expected to lead to building of new types of cell phones which can
be rolled into thin layers behind the ear, HD televisions with thickness of a wallpaper, electronic
devices which the users can fold and wrap into a tiny square. Improved results in desalination
has also been tested using graphene to yield better results. Graphene could be practically used for
single molecule gas detection because it is a good sensor due to its 2D structure and exposure to
chemical reaction on both sides. This makes it easier to sense adsorbent molecules.