Download Essay code B3

Graphene – The thinnest strongest material in nature
Essay code B3
Carbon is the elementary constituent of life and organic chemistry. It plays huge role in
the existence of life. Carbon is very important because the materials that are made of carbon can
function as conductors, semi-conductors and insulators. Carbon is able to build a strong network
by binding using carbon –carbon bond and the ability of carbon to form strong sp2 covalent
bonding with other elements make possible the exceptional strength observed in crystalline
forms of carbon such as diamond. Nano materials are made by nano technology and are found in
nano scale dimension. There are allotropes of Carbon in nano scale dimensions such as fullerene,
graphene, graphite etc. These were different from other nano materials because of their better
stabilities due to the high activation barrier caused by the structural arrangement. They are
considered very significant because of their unique physical, material and chemical properties.
Nano scale carbon was observed only in zero dimension as fullerene, one dimension as nano tube
and three dimension as graphite and diamond. However recently in 2010, two professors named
Konstantin Novoselov and Andre Geim from University of Manchester from England shared the
Nobel Prize for Physics for extracting the 2 dimensional nano scale carbon known as Graphene
from Graphite. 3D Graphite is a structure formed by stacking many Graphene sheets and is
usually found on lead pencils. Graphene is a one atom thick single layer sheet of sp2 hybridized
carbon atoms. Therefor Graphene is considered to be the thinnest of all materials available. The
professors extracted Graphene from Graphite in 2004 by merely using an adhesive scotch tape.
The unique mechanical, physical, quantum and thermal properties make Graphene one of the
most demanded material on earth now because of its stability even in non-functionalized form
due to its high activation barrier. Graphene is extremely flexible and can be considered as the
building block of other nano scale Carbon forms. Graphene can be rolled to form 1D nano tube
and can be wrapped to form a 0D fullerene and can also be stacked in multiple layers to form 3D
graphite.
The structure of Graphene is that it is a one atom thick sheet of single layer formation of
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 an adhesive tape and a pencil.
However there are higher technologies now available for the synthesis of graphene namely,
micromechanical exfoliation, chemical vapor disposition on the single crystal metals such as
Nickel, chemical synthesis form graphite, reduction of graphene oxide sheets, 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 physical properties of Graphene is very significant because of its better conductivity
and stability. The carbon-carbon bond length in graphene is 0.142 nanometers. Even though
graphene is strong and stable, 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. Due to its
immense stability Graphene can hold materials worth six order of magnitudes higher than what
Copper can hold. The extraordinary chemical and thermal properties of Graphene is 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. The electrons
in graphene also move at a regular speed and it has a very high electron mobility at room
temperature compared to other semiconductors. This is independent of their kinetic energy.
Graphene is a high heat conductor and this helps to prevent the thermal management and heat
dissipation issue of the high speed integrated density chips. Even when graphene is not
functional it is stabilized and therefore it remains highly stable and conductive when it is entered
into other nano material devices. Graphene sheet is thermodynamically unstable if its size is less
than about 20 nm
Graphene is hundred times stronger than steel which means one thin layer of graphene
can hold one elephant. It has been tested that graphene breaks at a strength hundred times
stronger than the strength at which steel breaks. This was done by probing a diamond into a thin
layer of graphene until it broke. 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. AL the photons at different frequency are then
converted to electrons. The tensile strength of graphene is remarkable because of its strongest
bonds among all atoms.
The chemical properties of Graphene is unique because both the sides of the 2D structure
can be exposed to chemical reactions. The carbon atoms ate the tips of graphene sheets have
extra chemical reactivity than compared to other Carbon nano scale materials such as nano tubes.
Carbon can react with Oxygen gas at less than 260 °C and graphene can burn at 350 °C.
Graphene can be considered as the chemically most 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 composites, energy storage devices, include
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 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. 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.