GRAPHENE SYNTHESIS AND ITS APPLICATIONS TERM PAPER PRESENTATION

AMITY SCHOOL OF
ENGINEERING & TECHNOLOGY
TERM PAPER ABSTRACT ON
GRAPHENE
SUBMITTED TO- SUBMITTED BY-
Mrs SHALLY GOYAL AMAN GUPTA
Asst. Professor B.TECH ECE 3 SEM
Dept. Electronics & Communication (2012-2016)

Graphene - What It Is?
In simple terms, graphene is a thin layer of pure carbon; it is a single, tightly packed layer of
carbon atoms that are bonded together in a hexagonal honeycomb lattice. In more complex
terms, it is an allotrope of carbon in the structure of a plane of sp2 bonded atoms with a
molecule bond length of 0.142 nanometres. Layers of graphene stacked on top of each other
form graphite, with an interplanar spacing of 0.335 nanometres.
Figure 1 Figure 2
It is the thinnest compound known to man at one atom thick, the lightest material known
(with 1 square meter coming in at around 0.77 milligrams), the strongest compound
discovered (between 100-300 times stronger than steel and with a tensile stiffness of
150,000,000 psi), the best conductor of heat at room temperature (at (4.84±0.44) × 103 to
(5.30±0.48) × 103 W·m−1·K−1) and also the best conductor of electricity known (studies
have shown electron mobility at values of more than 15,000 cm2·V−1·s−1). Other notable
properties of graphene are its unique levels of light absorption at πα ≈ 2.3% of white light,
and its potential suitability for use in spin transport.

The combination of familiarity, extraordinary properties and surprising ease of isolation
enabled an explosion in graphene research. Andre Geim and Konstantin Novoselov at
the University of Manchester won the Nobel Prize in Physics in 2010 "for ground breaking
experiments regarding the two-dimensional material graphene.
Figure 3
Carbon is the chemical basis for all known life on earth, so therefore graphene could well be
an ecologically friendly, sustainable solution for an almost limitless number of
applications. Since the discovery of graphene, advancements within different scientific
disciplines have exploded, with huge gains being made particularly in electronics and
biotechnology already.
Also, it was previously impossible to grow graphene layers on a large scale using crystalline
epitaxy on anything other than a metallic substrate. This severely limited its use in
electronics as it was difficult, at that time, to separate graphene layers from its metallic
substrate without damaging the graphene.
However, studies in 2012 found that by analysing graphene’s interfacial adhesive energy, it
is possible to effectually separate graphene from the metallic board on which it is grown,
whilst also being able to reuse the board for future applications theoretically an infinite
number of times, therefore reducing the toxic waste previously created by this process.

Furthermore, the quality of the graphene that was separated by using this method was
sufficiently high enough to create molecular electronic devices successfully.
While this research is very highly regarded, the quality of the graphene produced will still be
the limiting factor in technological applications. Once graphene can be produced on very thin
pieces of metal or other arbitrary surfaces (of tens of nanometres thick) then we will start to
see graphene become more widely utilized as production techniques become more simplified
and cost-effective.
Figure 4 Figure 5
Being able to create super capacitors out of graphene will possibly is the largest step in
electronic engineering in a very long time. While the development of electronic components
has been progressing at a very high rate over the last 20 years, power storage solutions such
as batteries and capacitors have been the primary limiting factor due to size, power capacity
and efficiency.
In initial tests carried out, laser-scribed graphene (LSG) supercapacitors (with graphene
being the most electronically conductive material known, at 1738 Siemens per meter
(compared to 100 SI/m for activated carbon)), were shown to offer power density
comparable to that of high-power lithium-ion batteries that are in use today. Not only that,
but also LSG supercapacitors are highly flexible, light, quick to charge, thin and as
previously mentioned, comparably very inexpensive to produce.

Graphene is also being used to boost not only the capacity and charge rate of batteries but
also the longevity. Currently, while such materials as silicone are able to store large amounts
of energy, that potential amount diminishes drastically on every charge or recharge. With
graphene tin oxide being used as an anode in lithium ion batteries for example, batteries can
be made to last much longer between charges (potential capacity has increased by a factor of
10), and with almost no reduction in storage capacity between charges, effectively making
technology such as electronically powered vehicles a much more viable transport solution in
the future.
This means that batteries can be developed to last much longer and at higher capacities than
previously realised. Also, it means that electronic devices may be able to be charged within
seconds, rather than minute or hours and have hugely improved longevity.
Figure 6
Consumers can already purchase graphene-enhanced products to use at home. One company
already produces and offers on the market conductive ink (first developed by researchers at
the University of Cambridge in 2011). This is made by effectively mixing tiny graphene
flakes with ink, enabling you to print electrodes directly onto paper. While this was
previously possible by using organic semi conductive ink, the use of graphene flakes makes
the printed material vastly more conductive and therefore more efficient.

Properties of Graphene
Graphene is, basically, a single atomic layer of graphite; an abundant mineral which is an
allotrope of carbon that is made up of very tightly bonded carbon atoms organised into a
hexagonal lattice. What makes graphene so special is its sp2 hybridisation and very thin
atomic thickness (of 0.345Nm). These properties are what enable graphene to break so many
records in terms of strength, electricity and heat conduction. Now, let’s explore just what
makes graphene so special, what are its intrinsic properties that separate it from other forms
of carbon, and other 2D crystalline compounds?
Fundamental Characteristics
Before monolayer graphene was isolated in 2004, it was theoretically believed that two
dimensional compounds could not exist due to thermal instability when separated. After
suspended graphene sheets were studied by transmission electron microscopy, scientists
believed that they found the reason to be due to slight rippling in graphene. Later research
suggests that it is actually due to the fact that the carbon to carbon bonds in graphene are so
small and strong that they prevent thermal fluctuations from destabilizing it.
Electronic Properties
One of the most useful properties of graphene is that it is a zero-overlap semimetal with very
high electrical conductivity. Carbon atoms have a total of 6 electrons; 2 in the inner shell and
4 in outer shell. The 4 outer shell electrons in an individual carbon atom are available for
chemical bonding, but in graphene, each atom is connected to 3 other carbon atoms, leaving
1 electron freely available for electronic conduction. These highly-mobile electrons are
called pi (π) elec. The electronic properties of graphene are dictated by the bonding and anti-
bonding of these pi orbitals.

Combined research over the last 50 years has proved that at the Dirac point in graphene,
electrons and holes have zero effective mass. This occurs because the energy – movement
relation is linear for low energies near the 6 individual corners of the Brillouin zone. Due to
the zero density of states at the Dirac points, electronic conductivity is actually quite low.
Tests have shown that the electronic mobility of graphene is very high, with previously
reported results above 15,000 cm2·V−1·s−1. It is said that graphene electrons act very much
like photons in their mobility due to their lack of mass. These charge carriers are able to
travel sub-micrometre distances without scattering; a phenomenon known as ballistic
transport. Silicon dioxide as the substrate, for example, mobility is potentially limited to
40,000 cm2·V−1·s−1.
Mechanical Strength
Another of graphene’s stand-out properties is its inherent strength. Due to the strength of its
0.142 Nm-long carbon bonds, graphene is the strongest material ever discovered, with an
ultimate tensile strength of 130,000,000,000 Pascal (or 130 gigapascals), compared to
400,000,000 for A36 structural steel, or 375,700,000 for Aramid (Kevlar).
Figure 7

Not only is graphene extraordinarily strong, it is also very light at 0.77milligrams per square
metre (for comparison purposes, 1 square metre of paper is roughly 1000 times heavier). It is
often said that a single sheet of graphene (being only 1 atom thick), sufficient in size enough
to cover a whole football field, would weigh under 1 single gram.
What makes this particularly special is that graphene also contains elastic properties, being
able to retain its initial size after strain. In 2007, Atomic force microscopic (AFM) tests were
carried out on graphene sheets that were suspended over silicone dioxide cavities. These tests
showed that graphene sheets (thicknesses between 2 and 8 Nm) had spring constants in the
region of 1-5 N/m and a Young’s modulus (different to that of three-dimensional graphite) of
0.5 TPa.
Again, these superlative figures are based on theoretical prospects using graphene that is
unflawed containing no imperfections whatsoever and currently very expensive and difficult
to artificially reproduce, though production techniques are steadily improving, ultimately
reducing costs and complexity.
Optical Properties
Graphene’s ability to absorb a rather large 2.3% of white light is also a unique and
interesting property, especially considering that it is only 1 atom thick. This is due to its
aforementioned electronic properties; the electrons acting like massless charge carriers with
very high mobility.
A few years ago, it was proved that the amount of white light absorbed is based on the Fine
Structure Constant, rather than being dictated by material specifics. Adding another layer of
graphene increases the amount of white light absorbed by approximately the same value
(2.3%). Graphene’s opacity of πα ≈ 2.3% equates to a universal dynamic conductivity value
of G=e2/4ℏ (±2-3%) over the visible frequency range.

Due to these impressive characteristics, it has been observed that once optical intensity
reaches a certain threshold saturable absorption takes place. This is an important
characteristic with regards to the mode-locking of fibre lasers. Due to graphene’s properties
of wavelength-insensitive ultrafast saturable absorption, full-band mode locking has been
achieved using an erbium-doped dissipative soliton fibre laser capable of obtaining
wavelength tuning as large as 30 nm.
Figure 8
In terms of how far along we are to understanding the true properties of graphene, this is just
the tip of the iceberg. Before graphene is heavily integrated into the areas in which we
believe it will excel at, we need to spend a lot more time understanding just what makes it
such an amazing material. Unfortunately, while we have a lot of imagination in coming up
with new ideas for potential applications and uses for graphene, it takes time to fully
appreciate how and what graphene really is in order to develop these ideas into reality. This
is not necessarily a bad thing, however, as it gives us opportunities to stumble over other
previously under-researched or overlooked super-materials, such as the family of 2D
crystalline structures that graphene has born.

Graphene & Graphite - How Do
They Compare??
“The attributes of graphene – transparency, density, electric and thermal conductivity,
elasticity, flexibility, hardness resistance and capacity to generate chemical reactions with
other substances – harbour the potential to unleash a new technological revolution of more
magnificent proportions than that ushered in by electricity in the 19th century and the rise of
the internet in the 1990s.” – LarrainVial
In very basic terms graphene could be described as a single, one atom thick layer of the
commonly found mineral graphite; graphite is essentially made up of hundreds of thousands
of layers of graphene. In actuality, the structural make-up of graphite and graphene, and the
method of how to create one from the other, is slightly different.
Graphite-
Way back when we were at school, it is very likely that you would have come across the
term ‘pencil lead’, referring to the central core of a pencil that is able to produce marks on
paper and other material. In fact, rather than referring to the chemical element and heavy
metal, lead, this central core is most commonly made from graphite mixed with clay.
Figure 9 Figure 10

Graphite is a mineral that occurs in metamorphic rock in different continents of the world,
including Asia, South America and North America. It is formed as a result of the reduction
of sedimentary carbon compounds during metamorphism. Contrary to common belief, the
chemical bonds in graphite are actually stronger than those that make up diamond. However,
what defines the difference in hardness of the two compounds is the lattice structure of the
carbon atoms contained within; diamonds containing three dimensional lattice bonds, and
graphite containing two dimensional lattice bonds. While within each layer of graphite the
carbon atoms contain very strong bonds, the layers are able to slide across each other,
making graphite a softer, more malleable material.
Extensive research over hundreds of years has proved that graphite is an impressive mineral
showing a number of outstanding and superlative properties including its ability to conduct
electricity and heat well, having the highest natural stiffness and strength even in
temperatures exceeding 3600 degrees Celsius, and it is also highly resistant to chemical
attack and self-lubricating. However, while it was first identified over a thousand years ago
and first named in 1789, it has taken a while for industry to realise the full potential of this
amazing material.
Graphite is one of only three naturally occurring allotropes of carbon (the others being
amorphous carbon and diamond). The difference between the three naturally occurring
allotropes is the structure and bonding of the atoms within the allotropes; diamond enjoying
a diamond lattice crystalline structure, graphite having a honeycomb lattice structure, and
amorphous carbon (such as coal or soot) does not have a crystalline structure.
While there are many different forms of carbon, graphite is of an extremely high grade and is
the most stable under standard conditions. Therefore, it is commonly used in
thermochemistry as the standard state for defining the heat formation of compounds made
from carbon. It is found naturally in three different forms: crystalline flake, amorphous and
lump or vein graphite, and depending on its form, is used for a number of different
applications.

As previously touched upon, graphite has a planar, layered structure; each layer being made
up of carbon atoms linked together in a hexagonal lattice. These links, or covalent bonds as
they are more technically known, are extremely strong, and the carbon atoms are separated
by only 0.142 nanometres. The carbon atoms are linked together by very sturdy sp2
hybridised bonds in a single layer of atoms, two dimensionally. Each individual, two
dimensional, one atom thick layer of sp2 bonded carbon atoms in graphite is separated by
0.335nm. Essentially, the crystalline flake form of graphite, as mentioned earlier, is simply
hundreds of thousands of individual layers of linked carbon atoms stacked together.
Graphene-
So, graphene is fundamentally one single layer of graphite; a layer of sp2 bonded carbon
atoms arranged in a honeycomb (hexagonal) lattice. However, graphene offers some
impressive properties that exceed those of graphite as it is isolated from its ‘mother
material’. Graphite is naturally a very brittle compound and cannot be used as a structural
material on its own due to its sheer planes (although it is often used to reinforce steel).
Graphene, on the other hand, is the strongest material ever recorded, more than three
hundred times stronger than A36 structural steel, at 130 gigapascals, and more than forty
times stronger than diamond.
Figure 11 Figure 12

Due to graphite’s planar structure, its thermal, acoustic and electronic properties are highly
anisotropic, meaning that phonons travel much more easily along the planes than they do
when attempting to travel through the planes. Graphene, on the other hand, being a single
layer of atoms and having very high electron mobility, offers fantastic levels of electronic
conduction due to the occurrence of a free pi (π) electron for each carbon atom.
Figure 13
However, for this high level of electronic conductivity to be realised, doping (with electrons
or holes) must occur to overcome the zero density of states which can be observed at the
Dirac points of graphene. The high level of electronic conductivity has been explained to be
due to the occurrence of quasiparticles; electrons that act as if they have no mass, much like
photons, and can travel relatively long distances without scattering (these electrons are hence
known as massless Dirac fermions).

Creating or Isolating Graphene
There are a number of ways in which scientists are able to produce graphene. The first
successful way of producing monolayer and few layer graphene was by mechanical
exfoliation (the adhesive tape technique). However, many research institutions around the
world are currently racing to find the best, most efficient and effective way of producing
high quality graphene on a large scale, which is also cost efficient and scalable.
The most common way for scientists to create monolayer or few layer graphene is by a
method known as chemical vapour deposition (CVD). This is a method that extracts carbon
atoms from a carbon rich source by reduction. The main problem with this method is finding
the most suitable substrate to grow graphene layers on, and also developing an effective way
of removing the graphene layers from the substrate without damaging or modifying the
atomic structure of the graphene.
Figure 14
Other methods for creating graphene are: growth from a solid carbon source (using thermo-
engineering), sonication, cutting open carbon nanotubes, carbon dioxide reduction, and also
graphite oxide reduction. This latter method of using heat (either by atomic force microscope
or laser) to reduce graphite oxide to graphene has received a lot of publicity of late due to the
minimal cost of production. However, the quality of graphene produced currently falls short
of theoretical potential and will inevitably take some time to perfect.

Graphene Applications and Uses
Graphene, the well-publicised and now famous two-dimensional carbon allotrope, is as
versatile a material as any discovered on Earth. Its amazing properties as the lightest and
strongest material, compared with its ability to conduct heat and electricity better than
anything else, mean that it can be integrated into a huge number of applications. Initially this
will mean that graphene is used to help improve the performance and efficiency of current
materials and substances, but in the future it will also be developed in conjunction with other
two-dimensional (2D) crystals to create some even more amazing compounds to suit an even
wider range of applications.
The first time graphene was artificially produced; scientists literally took a piece of graphite
and dissected it layer by layer until only 1 single layer remained. This process is known as
mechanical exfoliation. This resulting monolayer of graphite (known as graphene) is only 1
atom thick and is therefore the thinnest material possible to be created without becoming
unstable when being open to the elements (temperature, air, etc.).
Figure 15
Because graphene is only 1 atom thick, it is possible to create other materials by interjecting
the graphene layers with other compounds effectively using graphene as atomic scaffolding
from which other materials are engineered. These newly created compounds could also be
superlative materials, just like graphene, but with potentially even more applications.

After the development of graphene and the discovery of its exceptional properties, not
surprisingly interest in other two-dimensional crystals increased substantially. These other
2D crystals can be used in combination with other 2D crystals for an almost limitless number
of applications. It improves its efficiency as a superconductor. Or, another example would be
in the case of combining the mineral Molybdenite (MoS2), which can be used as a
semiconductor, with graphene layers when creating NAND flash memory, to develop flash
memory to be much smaller and more flexible than current technology.
The only problem with graphene is that high-quality graphene is a great conductor that does
not have a band gap. Therefore to use graphene in the creation of future nano-electronic
devices, a band gap will need to be engineered into it, which will, in turn, reduce its electron
mobility to that of levels currently seen in strained silicone films. This essentially means that
future research and development needs to be carried out in order for graphene to replace
silicone in electrical systems in the future
In any case, these two examples are just the tip of the iceberg in only one field of research,
whereas graphene is a material that can be utilized in numerous disciplines including, but not
limited to: bioengineering, composite materials, energy technology and nanotechnology.
Biological Engineering
Bioengineering will certainly be a field in which graphene will become a vital part of in the
future; though some obstacles need to be overcome before it can be used. Current
estimations suggest that it will not be until 2030 when we will begin to see graphene widely
used in biological applications as we still need to understand its biocompatibility. However,
the properties that it displays suggest that it could revolutionise this area in a number of
ways. With graphene offering a large surface area, high electrical conductivity, thinness and
strength, it would make a good candidate for the development of fast and efficient bioelectric
sensory devices, with the ability to monitor such things as glucose levels, haemoglobin
levels, cholesterol and even DNA sequencing. It is able to be used as an antibiotic or even
anticancer treatment.

Optical Electronics
One particular area in which we will soon begin to see graphene used on a commercial scale
is that in optoelectronics; specifically touchscreens, liquid crystal displays (LCD) and
organic light emitting diodes (OLEDs). For a material to be able to be used in optoelectronic
applications, it must be able to transmit more than 90% of light and also offer electrical
conductive properties exceeding 1 x 106 Ω1m1 and therefore low electrical
resistance. Graphene is an almost completely transparent material and is able to optically
transmit up to 97.7% of light. It is also highly conductive, as we have previously mentioned
and so it would work very well in optoelectronic applications such as LCD touchscreens.
However, recent tests have shown that graphene is potentially able to match the properties of
ITO, even in current states. While this does not sound like much of an improvement over
ITO, graphene displays additional properties which can enable very clever technology to be
developed in optoelectronics by replacing the ITO with graphene. The fact that high quality
graphene has a very high tensile strength, and is flexible makes it almost inevitable that it
will become utilized in mentioned applications.
Figure 16
In terms of potential real-world electronic applications we can eventually expect to see such
devices as graphene based e-paper with the ability to display interactive and updatable
information and flexible electronic devices including portable computers and televisions.

Ultrafiltration
Another standout property of graphene is that while it allows water to pass through it, it is
almost completely impervious to liquids and gases (even relatively small helium molecules).
This means that graphene could be used as an ultrafiltration medium to act as a barrier
between two substances. The benefit of using graphene is that it is only 1 single atom thick
and can also be developed as a barrier that electronically measures strain and pressures
between the 2 substances (amongst many other variables).
A team of researchers at Columbia University have managed to create monolayer graphene
filters with pore sizes as small as 5nm (currently, advanced nanoporous membranes have
pore sizes of 30-40nm).
Figure 17 Figure 18
While these pore sizes are extremely small, as graphene is so thin, pressure during
ultrafiltration is reduced. Co-currently, graphene is much stronger and less brittle than
aluminium oxide (currently used in sub-100nm filtration applications). What does this mean?
Well, it could mean that graphene is developed to be used in water filtration systems,
desalination systems and efficient and economically more viable biofuel creation.

Composite Materials
Graphene is strong, stiff and very light. Currently, aerospace engineers are incorporating
carbon fibre into the production of aircraft as it is also very strong and light. However,
graphene is much stronger whilst being also much lighter. Ultimately it is expected that
graphene is utilized to create a material that can replace steel in the structure of aircraft,
improving fuel efficiency, range and reducing weight. Due to its electrical conductivity, it
could even be used to coat aircraft surface material to prevent electrical damage resulting
from lightning strikes. In this example, the same graphene coating could also be used to
measure strain rate, notifying the pilot of any changes in the stress levels that the aircraft
wings are under. These characteristics can also help in the development of high strength
requirement applications such as body armour for military personnel and vehicles.
Photovoltaic Cells
Offering very low levels of light absorption (at around 2.7% of white light) whilst also
offering high electron mobility means that graphene can be used as an alternative to silicon
or ITO in the manufacture of photovoltaic cells. Silicon is currently widely used in the
production of photovoltaic cells, but while silicon cells are very expensive to produce,
graphene based cells are potentially much less so. When materials such as silicon turn light
into electricity it produces a photon for every electron produced, meaning that a lot of
potential energy is lost as heat. Recently published research has proved that when graphene
absorbs a photon, it actually generates multiple electrons.
Also, while silicon is able to generate electricity from certain wavelength bands of light,
graphene is able to work on all wavelengths, meaning that graphene has the potential to be as
efficient as, if not more efficient than silicon, ITO or (also widely used) gallium
arsenide. Being flexible and thin means that graphene based photovoltaic cells could be used
in clothing; to help recharge your mobile phone, or even used as retro-fitted photovoltaic
window screens or curtains to help power your home.

Energy Storage
One area of research that is being very highly studied is energy storage. While all areas of
electronics have been advancing over a very fast rate over the last few decades (in reference
to Moore’s law which states that the number of transistors used in electronic circuitry will
double every 2 years), the problem has always been storing the energy in batteries and
capacitors when it is not being used. These energy storage solutions have been developing at
a much slower rate. The problem is this: a battery can potentially hold a lot of energy, but it
can take a long time to charge, a capacitor, on the other hand, can be charged very quickly,
but can’t hold that much energy (comparatively speaking). The solution is to develop energy
storage components such as either a supercapacitors or a battery that is able to provide both
of these positive characteristics without compromise.
Currently, scientists are working on enhancing the capabilities of lithium ion batteries (by
incorporating graphene as an anode) to offer much higher storage capacities with much
better longevity and charge rate. Also, graphene is being studied and developed to be used in
the manufacture of supercapacitors which are able to be charged very quickly, yet also be
able to store a large amount of electricity.
Figure 19 Figure 20
Graphene based micro-supercapacitors will likely be developed for use in low energy
applications such as smart phones and portable computing devices and could potentially be
commercially available within the next 5-10 years. Graphene-enhanced lithium ion batteries
could be used in much higher energy usage applications such as electrically powered
vehicles, or they can be used as lithium ion batteries are now, in smartphones, laptops and
tablet PCs but at significantly lower levels of size and weight.

Graphene Supercapacitors -
What Are They?
Figure 21
Scientists have been struggling to develop energy storage solutions such as batteries and
capacitors that can keep up with the current rate of electronic component evolution for a
number of years. Unfortunately, the situation we are in now is that while we are able to store
a large amount of energy in certain types of batteries, those batteries are very large, very
heavy, and charge and release their energy relatively slowly.
Capacitors, on the other hand, are able to be charged and release energy very quickly, but
can hold much less energy than a battery. Graphene application developments have led to
new possibilities for energy storage, with high charge and discharge rates, which can be
made cheaply. But before we go into specific details, it would be sensible to first outline
basics of energy storage and the potential goals of developing graphene as supercapacitors.
Capacitors and supercapacitors explained

A capacitor is an energy storage medium similar to an electrochemical battery. Most
batteries, while able to store a large amount of energy are relatively inefficient in comparison
to other energy solutions such as fossil fuels. It is often said that a 1kg electrochemical
battery is able to produce much less energy than 1 litre of gasoline; but this kind of
comparison is extremely vague, and should be ignored. In fact, some electrochemical
batteries can be relatively efficient, but that doesn’t get around the primary limiting factor in
batteries replacing fossil fuels.
High capacity batteries take a long time to charge. This is why electrically powered vehicles
have not taken-off as well as we expected twenty or thirty years ago. While you are now able
to travel 250 miles or more on one single charge in a car such as the Tesla Model S, it could
take you over 43 hours to charge the vehicle using a standard 120v wall socket in order to
drive back home. This is not acceptable for many car users. Capacitors, on the other hand,
are able to be charged at a much higher rate, but store somewhat less energy.
Figure 22
Supercapacitors, also known as ultra-capacitors, are able to hold hundreds of times the
amount of electrical charge as standard capacitors, and are therefore suitable as a
replacement for electrochemical batteries in many industrial and commercial applications.
Supercapacitors also work in very low temperatures; a situation that can prevent many types
of electrochemical batteries from working. For these reasons, supercapacitors are already
being used in emergency radios and flashlights, where energy can be produced kinetically
(by winding a handle, for example) and then stored in a supercapacitors for the device to use.

A conventional capacitor is made up of two layers of conductive materials (eventually
becoming positively and negatively charged) separated by an insulator. What dictates the
amount of charge a capacitor can hold is the surface area of the conductors, the distance
between the two conductors and also the dielectric constant of the insulator. Supercapacitors
are slightly different in the fact that they do not contain a solid insulator.
While supercapacitors are able to store much more energy than standard capacitors, they are
limited in their ability to withstand high voltage. Electrolytic capacitors are able to run at
hundreds of volts, but supercapacitors are generally limited to around 5 volts. However, it is
possible to engineer a chain of supercapacitors to run at high voltages as long as the series is
properly designed and controlled.
Graphene-based supercapacitors
Figure 23
Supercapacitors, unfortunately, are currently very expensive to produce, and at present the
scalability of supercapacitors in industry is limiting the application options as energy
efficiency is offset against cost efficiency. This idea of creating graphene monolayers by
using thermo lithography is not necessarily a new one, as scientists from the US were able to
produce graphene nanowires by using thermochemical nanolithography back in 2010;
however, new method avoids the use of atomic force microscope in favour of commercially
available laser device that is already prevalent in many homes around the world.

Why are scientists looking at using graphene instead of the currently more popular activated
carbon? Well, graphene is essentially a form of carbon, and while activated carbon has an
extremely high relative surface area, graphene has substantially more. As we have already
highlighted, one of the limitations to the capacitance of ultra-capacitors is the surface area of
the conductors. If one conductive material in a supercapacitor has a higher relative surface
area than another, it will be better at storing electrostatic charge.
Figure 24
The efficiency of the supercapacitor is the important factor to bear in mind. In the past,
scientists have been able to create supercapacitors that are able to store 150 Farads per gram,
but some have suggested that the theoretical upper limit for graphene-based supercapacitors
is 550 F/g. This is particularly impressive when compared against current technology: a
commercially available capacitor able to store 1 Farad of electrostatic energy at 100 volts
would be about 220mm high and weigh about 2kgs, though current supercapacitor
technology is about the same, in terms of dimensions relative to energy storage values, as a
graphene-based supercapacitor would be.

The future for graphene-based supercapacitors
Due to the lightweight dimensions of graphene based supercapacitors and the minimal cost
of production coupled with graphene’s elastic properties and inherit mechanical strength, we
will almost certainly see technology within the next five to ten years incorporating these
supercapacitors. Also, with increased development in terms of energy storage limits for
supercapacitors in general, graphene-based or hybrid supercapacitors will eventually be
utilized in a number of different applications.
Figure 25 Figure 26
Vehicles that utilize supercapacitors are already prevalent in our society. One Chinese
company is currently manufacturing buses that incorporate supercapacitor energy recovery
systems, such as those used on Formula 1 cars, to store energy when braking and then
converting that energy to power the vehicle until the next stop.
Additionally, we will at some point in the next few years begin to see mobile telephones and
other mobile electronic devices being powered by supercapacitors as not only can they be
charged at a much higher rate than current lithium-ion batteries, but they also have the
potential to last for a vastly greater length of time.

Other current and potential uses for supercapacitors are as power backup supplies for
industry or even our own homes. Businesses can invest in power backup solutions that are
able to store high levels of energy at high voltages, effectively offering full power available
to them, to reduce the risk of having to limit production due to inadequate amounts of power.
Alternatively, if you have a fuel cell vehicle that is able to store a large amount of electrical
energy, then why not use it to help power your home in the event of a power outage?
We can expect that this scenario of using advanced energy storage and recovery solutions
will become much more widely used in the coming years as the efficiency and energy
density of supercapacitors increases, and the manufacturing costs decrease.
While graphene-based supercapacitors are currently a viable solution in the future,
technology needs to be developed to make this into a reality. But rest assured, many
companies around the world are already trialling products using this technology and creating
new ways to help subsidise the use of fossil-fuels and toxic chemicals in our ever-demanding
strive for energy.

Creating Graphene via Chemical
Vapour Deposition
There are different ways in which graphene monolayers can be created or isolated, but by far
the most popular way at this moment in time is by using a process called chemical vapour
deposition. Chemical vapour deposition, or CVD, is a method which can produce relatively
high quality graphene, potentially on a large scale. The CVD process is reasonably
straightforward, although some specialist equipment is necessary, and in order to create good
quality graphene it is important to strictly adhere to guidelines set concerning gas volumes,
pressure, temperature, and time duration.
Figure 27
The CVD Process
Simply put, CVD is a way of depositing gaseous reactants onto a substrate. The way CVD
works is by combining gas molecules in a reaction chamber which is typically set at ambient
temperature. When the combined gases come into contact with the substrate within the
reaction chamber a reaction occurs that create a material film on the substrate surface. The
waste gases are then pumped from the reaction chamber. The temperature of the substrate is
a primary condition that defines the type of reaction that will occur.

During the CVD process, the substrate is usually coated a very small amount, at a very slow
speed, often described in microns of thickness per hour. The solid compound or compounds
is/are vaporized, and then deposited onto a substrate via condensation.
The benefits of using CVD to deposit materials onto a substrate are that the quality of the
resulting materials is usually very high. Other common characteristics of CVD coatings
include imperviousness, high purity, fine grained and increased hardness over other coating
methods. It is a common solution for the deposit of films in the semiconductor industry, as
well as in optoelectronics, due to the low costs involved.
Although there are number of different formats of CVD, most modern processes come under
two headings separated by the chemical vapour deposition operating pressure: LPCVD, and
UHVCVD. LPCVD (low pressure CVD), UHVCVD (ultra-high vacuum CVD).
The disadvantages to using CVD to create material coatings are that the gaseous by-products
of the process are usually very toxic. This is because the precursor gases used must be highly
volatile in order to react with the substrate, but not so volatile that it is difficult to deliver
them to the reaction chamber. During the CVD process, the toxic by-products are removed
from the reaction chamber by gas flow to be disposed of properly.
Fundamental Processes in the Creation of CVD Graphene
CVD graphene is created in two steps, the precursor pyrolysis of a material to form carbon,
and the formation of the carbon structure of graphene using the disassociated carbon atoms.
The first stage, the pyrolysis to disassociated carbon atoms, must be carried out on the
surface of the substrate to prevent the precipitation of carbon clusters during the gas phase.
The problem with this is that the pyrolytic decomposition of precursors requires extreme
levels of heat, and therefore metal catalysts must be used to reduce the reaction temperature.
The second phase of creating the carbon structure out of the disassociated carbon atoms, also
requires a very high level of heat (over 2500 degrees Celsius).

Figure 28
The problem with using catalysts is that you are effectively introducing more compounds
into the reaction chamber, which will have an effect on the reactions inside the chamber. One
example of these effects is the way the carbon atoms dissolve into certain substrates such as
Nickel during the cooling phase.
What all this means is that it is vitally important that the CVD process is very stringently co-
ordinated, and that controls are put in place at every stage of the process to ensure that the
reactions occur effectively, and that quality of graphene produced is of the highest attainable.
Problems Associated with the Creation of CVD Graphene
In order to create monolayer or few layer graphene on a substrate, scientists must first
overcome the biggest issues with the methods that have been observed so far.
The first major problem is that while it is possible to create high quality graphene on a
substrate using CVD, the successful separation or exfoliation of graphene from the substrate
has been a bit of a stumbling block.
The reason for this is primarily because the relationship between graphene and the substrate
it is ‘grown’ on is not yet fully understood, so it is not easy to achieve separation without
damaging the structure of the graphene or affecting the properties of the material. The
techniques on how to achieve this separation differ depending on the type of substrate used.
Often scientists can choose to dissolve the substrate in harmful acids, but this process
commonly affects the quality of graphene produced.

One alternative method that has been researched involves the creation of CVD graphene on a
copper (Cu) substrate (in this example, Cu is used as a catalyst in the reaction). During CVD
a reaction occurs between the copper substrate and the graphene that create a high level of
hydrostatic compression, coupling the graphene to the substrate. It has been shown to be
possible; however, to intercalate a layer of copper oxide between the graphene and the
copper substrate to reduce this pressure and enable the graphene to be removed relatively
easily.
Scientists have also been looking into using (Poly methyl methacrylate) as a support polymer
to facilitate the transfer of graphene onto an alternate substrate. With this method, graphene
is coated with PMMA, and the previous substrate is etched. However, PMMA has been
shown to be the most effective at transferring the graphene without excessive damage.
Current and Potential Solutions
In terms of overcoming these issues, scientists have been developing more complex
techniques and guidelines to follow in order to create the highest quality of graphene
possible. One introductory technique to reducing the effects of these issues is by treating the
substrate before the reaction takes place. A copper substrate can be chemically treated to
enable reduced catalytic activity, increase the Cu grain size and rearrange the surface
morphology in order to facilitate the growth of graphene flakes that contain fewer
imperfections.
This point of treating the substrate prior to deposition is something that will continue to be
researched for a long time, as we slowly learn how to modify the structure of graphene to
suit different applications. For example, in order to enable graphene to be effectively used in
superconductors, doping must be carried out on the material in order to create a band-gap.
This process could potentially be something that is carried out on a substrate before
deposition occurs rather than treating the material after CVD.

Reduced Graphene Oxide - What
Is It? How Is It Created?
Around the world, research institutions are trying to develop ways to revolutionise the
production of graphene sheets of the highest quality. One of the most cost effective ways this
is possible is by the reduction of graphene oxide into rGO (reduced graphene oxide). The
problem with this technique is the quality of graphene sheets produced, which displays
properties currently below the theoretical potential of pristine graphene compared to other
methods such as mechanical exfoliation. However, this doesn't mean that improvements
can’t be made, or that this reduced graphene oxide is effectively unusable.
Figure 29
Graphite Oxide
Graphite oxide is a compound made up of carbon, hydrogen and oxygen molecules. It is
artificially created by treating graphite with strong oxidisers such as sulphuric acid. These
oxidisers work by reacting with the graphite and removing an electron in the chemical
reaction. This reaction is known as a redox (a portmanteau of reduction and oxidisation)
reaction, as the oxidising agent is reduced and the reactant is oxidised.

The most common method for creating graphite oxide in the past has been the Hummers and
Offeman method, in which graphite is treated with a mixture of sulphuric acid, sodium
nitrate and potassium permanganate. However, other methods have been developed recently
that are reported to be more efficient, reaching levels of 90% oxidisation, by using increased
quantities of potassium permanganate, and adding phosphoric acid combined with the
sulphuric acid, instead of adding sodium nitrate.
Graphene oxide is effectively a by-product of this oxidisation as when the oxidising agents
react with graphite, the interplanar spacing between the layers of graphite is increased. The
completely oxidised compound can then be dispersed in a base solution such as water, and
graphene oxide is then produced.
Graphite Oxide to Graphene Oxide
The process of turning graphite oxide into graphene oxide can ultimately be very damaging
to the individual graphene layers, which has further consequences when reducing the
compound further (explanation to follow). The oxidisation process from graphite to graphite
oxide already damages individual graphene platelets, reducing their mean size, so further
damage is undesirable. Graphene oxide contains flakes of monolayer and few layer
graphene, interspersed with water (depending on the base media, the platelet to platelet
interactions can be weakened by surface functionality, leading to improved hydrophilicity).
In order to turn graphite oxide into graphene oxide, a few methods are possible. The most
common techniques are by using sonication, stirring, or a combination of the two. Sonication
can be a very time-efficient way of exfoliating graphite oxide, and it is extremely successful
at exfoliating graphene (almost to levels of full exfoliation), but it can also heavily damage
the graphene flakes, reducing them in surface size from microns to nanometres, and also
produces a wide variety of graphene platelet sizes. Mechanically stirring is a much less
heavy-handed approach, but can take much longer to accomplish.

Graphene Oxide to Reduced Graphene Oxide
Reducing graphene oxide to produce reduced graphene oxide (hitherto referred to as rGO), is
an extremely vital process as it has a large impact on the quality of the rGO produced, and
therefore will determine how close rGO will come, in terms of structure, to pristine
graphene. In large scale operations where scientific engineers need to utilize large quantities
of graphene for industrial applications such as energy storage, rGO is the most obvious
solution, due to the relative ease in creating sufficient quantities of graphene to desired
quality levels.
Figure 30
In the past, scientists have created rGO from GO by:
 Treating GO with hydrazine hydrate and maintaining the solution at 100 for 24 hours
 Exposing GO to hydrogen plasma for a few seconds
 Exposing GO to another form of strong pulse light, such as those produced by xenon
flashtubes
 Heating GO in distilled water at varying degrees for different lengths of time
 Combining GO with an expansion-reduction agent such as urea and then heating the
solution to cause the urea to release reducing gases, followed by cooling
 Directly heating GO to very high levels in a furnace
 Linear sweep voltammetry

The Price of Graphene
Everyone agrees that graphene is an amazing material. Graphene has better electron mobility
than any metal, is one atom thin, is flexible, and all that while being stronger than steel. The
2010 Nobel Prize in physics confirmed the material's potential.
The Quality of the Graphene Affects the Price
The price of graphene is linked to its quality, and not all applications require superb material
quality. For example, graphene oxide powder (oxygen and hydrogen) is inexpensive and has
been used to make a conductive graphene paper, for DNA analysis. Graphene oxide in
solution sells for 99 euros per 250 mL. The electronic properties of graphene oxide at the
moment are not sufficiently good for batteries, flexible touch screens, solar cells, LEDs,
smart windows, and other advanced opto-electronic applications.
Figure 31
Mechanically exfoliated graphene (obtained with the famous “scotch tape” technique)
comes in small, high-quality flakes. Exfoliated graphene has so far shown to hold the best

physical properties. The coverage of mechanically exfoliated graphene, however, is only on
the order of a few small flakes per square centimeter, not nearly enough for applications. In
addition, the price of such graphene can be several thousands of dollars per flake.
CVD graphene, available with high quality from Graphenea, offers sufficient quality for
almost any graphene application. The price of CVD graphene is linked to production volume
and costs of transferring from the copper substrate, on which it is grown, onto another
substrate. Graphenea's industrial scale graphene technology leads to low CVD graphene cost
for bulk orders (see graph). Bulk orders of such graphene can be cheaper than, for example,
silicon carbide, and an important semiconductor. Graphenea has filed a patent for a low cost
industrial scale CVD growth and transfer process.
Technology Reduces the Price of Graphene
In several years, bulk graphene prices may drop below that of silicon, enabling graphene to
enter all markets now dominated by silicon, such as computing, chip manufacturing, sensors,
solar cells, etc. In the meantime, graphene will continue to be used for applications that other
materials simply cannot support. For example, silicon cannot be integrated into future
flexible smartphones, because silicon is brittle and will break upon bending. Graphene offers
a competitive solution.

Figure 32
FUTURE TRENDS IN
GRAPHENE
Flexible Touch Screens-
The outstanding properties of graphene make it attractive for applications in flexible
electronics. Byung Hee Hong, Jong-Hyun Ahn and co-workers have demonstrated roll-to-
roll production and wet chemical doping of mostly monolayer graphene films grown by
chemical vapour deposition onto flexible copper substrates. They also used layer-by-layer
stacking to fabricate a doped four-layer film with properties superior to those of commercial
transparent electrodes such as indium tin oxides. The photograph on the cover shows a
flexible touch-screen device containing graphene electrodes.
LCD “Smart Windows”-

Figure 33
Graphene is flexible, absorbs only 2.3% of light and conducts electricity very well. A layer
of liquid crystals is sandwiched between two flexible electrodes comprised of graphene and
transparent polymer. When there is no applied bias between the electrodes, liquid crystals
scatter light and the smart window is opaque. When a bias is applied, the voltage aligns
them, allowing light to pass through and the smart window turns transparent.
Magnetism and Graphene-
Given the great versatility of graphene’s properties and especially the ability to control many
of its characteristics by external electric field (gate voltage), graphene has a potential to
become an excellent material for spintronics. Our current efforts concentrate on ‘making
graphene magnetic’ by introducing point defects, such as vacancies or adatoms. We have
already demonstrated that vacancies in graphene act as individual magnetic moments and
lead to pronounced paramagnetism.
Graphene for Terahertz Electronics-
Conventional electronic devices are made up of silicon semiconductors, metal contacts,
doped junctions or barrier structures, etc. Each of these components must be added vertically

on top of one another. In contrast, we have recently developed novel concepts of nano-diodes
and transistors that are based on single-layered device architecture.
Figure 34
By using nano-scale electronic channels and tailoring the geometrical symmetry, the new
devices have been demonstrated to have extremely high speed up to 1.5THz (1,500GHz),
making them by far the fastest Nano devices to date The immediate applications include
high-speed electronics for next generation of computations and communications, far-infrared
THz detection and emission, ultra-high sensitive chemical sensors, etc.
Graphene Sensors-
University of Manchester scientists were the first to demonstrate single-atom sensitivity in
graphene Hall-bar devices. The most sensitive electronic detection is achieved by
constructing a Hall-bar with graphene. This transverse Hall resistivity is very sensitive to
changes in carrier concentration.
Figure 35

The binding event between the graphene sensor and analyte leads to the donation or
withdrawal of an electron from the graphene, which changes its electrical conductivity which
can be measured. When a device is fabricated with a graphene sheet suspended in free space
between two electrodes, it has a resonance frequency of vibration proportional to its mass.
3D Printing-
Even on their own, 3D printing technology and the super material graphene have the
potential to bring about the next industrial revolution. So imagine if it were possible to 3D
print objects using graphene? It's pretty mind-boggling.
It’s already possible to make everything from guns to food to human body parts. If graphene
proves workable as a 3D printable material, we could potentially add computers, solar
panels, electronics, even cars and airplanes to the list.

INTRODUCTION
Graphene is a wonder material with many superlatives to its name. It is the thinnest material
in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic
mobility, have the smallest effective mass (it is zero) and can travel micrometer-long
distances without scattering at room temperature. Graphene can sustain current densities 6
orders higher than copper, shows record thermal conductivity and stiffness, is impermeable
to gases and reconciles such conflicting qualities as brittleness and ductility. Electron
transport in graphene is described by a Dirac-like equation, which allows the investigation of
relativistic quantum phenomena in a bench-top experiment. What are other surprises that
graphene keeps in store for us? This review analyses recent trends in graphene research and
applications, and attempts to identify future directions in which the field is likely to develop.
Graphene is a novel material with very unusual properties. To be sure, silicon will reign
supreme in many of the applications in which it is now found. But carbon, silicon's little
brother, has new realms to conquer. And if graphene keeps progressing as fast as it has in the
past two years, it will surely attract the immense weight of investment in research and
development that has so far gone almost exclusively to silicon. If that happens, then little
brother will at first supplement silicon and at last supplant it, as little brothers often.

Acknowledgement
I have taken efforts in this Term Paper. However, it would not have been possible without
the kind support and help of many individuals and organizations. I would like to extend my
sincere thanks to all of them.
I am highly indebted to Dr. Bikram k. bahinipati (HOI, AUMP), Dr. Shally Goyal mam
for their guidance and constant supervision as well as for providing necessary information
regarding the Term Paper & also for their support in completing the Term Paper.
I would like to express my gratitude towards my parents & staff of Amity University,
Gwalior for their kind co-operation and encouragement which help me in completion of this
project.
I would express my special gratitude and thanks to my Mr Pawan Kumar Bansal sir for
giving me such attention and time.
My thanks and appreciations also go to my colleagues and Friends in developing the Term
Paper and people who have willingly helped me out with their abilities.

Bibliography
Books
 Nikhil Koratkar; Graphene in Composite Materials: Synthesis, Characterization
and Applications
 C. N. R. Rao, Ajay K. Sood; Graphene: Synthesis, Properties, and Phenomena.
On-Line Resources
 www.graphene-info.com
 www.google.com
 www.aspbs.com
 www.graphene.manchester.ac.uk
 www.telegraph.co.uk
Research Papers
 A. K. Geim; GRAPHENE: STATUS AND PROSPECTS
Manchester Centre for Mesoscience and Nanotechnology, University of Manchester,
Oxford Road M13 9PL, Manchester UK.
 HUI Pak Ming; An Introduction to Graphene and the 2010 Nobel Physics, Chinese
University of Hong Kong.

Contents
1. Graphene - What It Is?
2. Properties of Graphene
3. Graphene & Graphite - How Do They Compare??
4. Creating or Isolating Graphene
5. Graphene Applications & Uses
6. Composite Materials
7. Graphene Supercapacitors - What Are They?
8. Creating Graphene via Chemical Vapour Deposition.
9. Reduced Graphene Oxide - What Is It? How Is It Created?
10. The Price of Graphene
11. Future Trends in Graphene.

Appendix
FIG. 1 Structure of single layered one atomic graphene material.
FIG. 2 showing top and side view of graphene structure.
FIG. 3 Inventors of magical material “Graphene”.
FIG. 4 Graphene’s conducting property.
FIG. 5 Ultracapacitors made out of graphene.
FIG. 6 Conductive ink a product of graphene.
FIG. 7 Mechanical strength of graphene in comparison to other materials.
FIG. 8 Different fermions made from graphene.
FIG. 9 Graphite materials.
FIG. 10 Structure of graphite.
FIG. 11 Graphene made thin and transparent screen.
FIG. 12 Graphene substrate.
FIG. 13 Zero band gap in graphene.
FIG. 14 Isolation or preparation of graphene.
FIG. 15 Different applications of graphene.
FIG. 16 Use of graphene in OLEDS (organic light emitting diode).
FIG. 17 Water filtration techniques from graphene, separating out Co2.
FIG. 18 Removing Cr from water by passing it through graphene.

FIG. 19 Battery made from graphene.
FIG. 20 Graphene based Super-capacitors.
FIG. 21 Classification of Super-capacitors.
FIG. 22 Capacitor v/s Super-capacitors v/s Battery.
FIG. 23 Super-capacitors better than battery.
FIG. 24 Compressible Super-capacitor made from Graphene.
FIG. 25 Use of graphene super-capacitors in car’s battery.
FIG. 26 Graphene Supercapacitor being used in mobile.
FIG. 27 CVD (chemical vapour techniques) to produce graphene.
FIG. 28 Graphene being prepared from CVD.
FIG. 29 Reduced graphene oxide.
FIG. 30 Reduced graphene oxide produced from graphene oxide.
FIG. 31 Graph showing graphene’s price change.
FIG. 32 Graph showing lowering of graphene’s price with technology.
FIG. 33 Flexible screens made from graphene.
FIG. 34 Graphene being used in Terahertz electronics.
FIG. 35 Sensors made from graphene.

CONCLUSION
Graphene has rapidly changed its status from being an unexpected and sometimes
unwelcome newcomer to a rising star and to a reigning champion. The professional
scepticism that initially dominated the attitude of many researchers (including myself) with
respect to graphene applications is gradually evaporating under the pressure of recent
Developments. Still, it is the wealth of new physics – observed, expected and hoped for –
which is driving the area form the moment.
Research on graphene’s electronic properties is now matured but is unlikely to start fading
any time soon, especially because of the virtually unexplored opportunity to control quantum
transport by strain engineering and various structural modifications. Even after that,
graphene will continue to stand out as a truly unique item in them arsenal of condensed
matter physics. Research on graphene’s non-electronic properties is just gearing up, and this
should bring up new phenomena that can hopefully prove equally fascinating and sustain, if
not expand, the graphene boom.

GRAPHENE SYNTHESIS AND ITS APPLICATIONS TERM PAPER PRESENTATION

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