graphene

1. Graphene
The Thinnest material known so far to humanity
Taranpreet singh
(MS12044)

2. What is graphene?
Graphene is the single atom layer of sp2
bonded carbon atoms tightly packed
into 2dimensional (2D) honey comb
lattice, graphene comes from the
graphite one of the allotropic form of
carbon.
even 1mm of graphite consist of 300
million layer of graphene on top of each
other. Graphene is a 2D building
material for carbon materials of all
other dimensionalities. It can be
wrapped up into 0D buckyballs, rolled
into 1D nanotubes or stacked into 3D
graphite.

3. What is so interesting about graphene?
Graphene is a miracle material of 21st century because of its unique
properties and its application found in every field of research where
graphene is offering new and exciting possibilities. And as with
electronics, health sciences, medicine, energy, various fields of science
the potential is mind-boggling. One can imagine with little effort a new
generation of super-strong flak vests, military vehicles and spacecraft
etc. all augmented by the addition of tiny sheets of incredibly light
material.
Graphene is strongest material of world it is stiffer than diamond,
Thinnest material that can be imagine(thin as 100000 time thinner than
human hair) and stretchable (up to 20% elastically)many other
properties that make it the worlds miracle material .

4. Science before graphene came to picture
More than 75 years ago Landau and peierls argued that 2D crystal were
thermodynamically unstable and could not exist.
The argument was latter than supported by mermin strongly supported by
experimental observation that indeed, melting temperature of thin films
rapidly decrease with decreasing thickness and thus the film become
unstable and segregated into parts or decompose at the thickness of dozen
atomic layers. For this reason atomic monolayer have so far been known only
as an integral part of larger 3d structure. Usually grown epitaxially on top of
monocrystal with matching crystal lattice. without 3d base, 2d materials
presumed not to be exist until 2004 when it was falsified by experimental
discovery of graphene.
Referances
• Peierls, R. E. Quelques proprietes typiques des corpses solides. Ann. I. H. Poincare 5, 177–222 (1935).
• Landau, L. D. Zur Theorie der phasenumwandlungen II. Phys. Z. Sowjetunion 11, 26–35
• Mermin, N. D. Crystalline order in two dimensions. Phys. Rev. 176, 250–254 (1968).

5. Isolation of single atomic layer of graphene
Back in year 2004 prof. Andre
geim, prof. kostantin Novoselov at
university of Manchester in uk,
manage to isolate the single
atomic layer of graphene from
graphite using scotch-tape
technique. This experiment of
graphene has completely
revelutionalized the graphene
world for which they awarded
with noble prize in 2010.

6. Synthesis of graphene

7. SYNTHESIS
• TOP DOWN METHODS
1. Mechanical exfoliation of graphite using scotch-tape technique
2. Electrochemical exfoliation
• BOTTOM UP
1. Chemical vapour deposition(CVD)
2. Epitaxial growth of graphene on Sic

8. Mechanical exfoliation

9. ELECTROCHEMICAL EXFOLIATION

10. Chemical vapour deposition
Graphene acquired from cvd process is high quality, on large scale with controllable number of layers, low defects. The CVD
based graphene synthesis process typically involves a thin layer of a transition metal (usually a few hundred nanometers
thick) deposited on a substrate e.g. SiO2. The substrate is then put into a furnace to be heated up to about 1000º C in a
hydrocarbon gas (e.g. methane and hydrogen) environment. The transition metallic layer catalyzes the decomposition of
hydrocarbon gas and the dissociated carbon atoms gradually absorbs into the metal layer or diffuses/remains on the metal
surface depending on the metal. Experimentally, many different transition metal catalysts, (e.g. Ru, Ir, Pd, Ni, Cu) have been
used to synthesize graphene and two distinct growth mechanisms have been proposed (Li, Cai et al. 2009). (I) Precipitated
growth, in which decomposed C atoms dissolve into the catalyst first and then precipitate to the metal surface to form
graphene during the subsequent cooling. This is because the solubility of carbon in the metal decreases with temperature
and the concentration of carbon decrease exponentially from the surface into the bulk. The follow-up cooling process helps
the carbon atoms to segregate to the metal surface to form graphene. (II). Diffusive mechanism, in which the decomposed C
atoms remain or diffuse on the metal surface and then incorporate into graphene directly. Mechanism I corresponds to those
metals that interact strongly with C atoms and has the binary phase of metal carbide (e.g., Ni) and growth mechanism II
corresponds to those which have no metal carbide phase (e.g., Cu). For mechanism I, continuous precipitation of C from the
interior of catalysts normally leads to the non-uniform, multilayer formation of graphene layer as carbon prefers to segregate
at the nickel grain boundaries (Yu, Lian et al. 2008). This problem is alleviated in mechanism II (Li, Cai et al. 2009) and it is
known to be the best for the synthesis of monolayer graphene.

11. EPITAXIAL GROWTH OF GRAPHENE ON SIC

12. Graphene superlatives
• thinnest imaginable and strongest material ever measured
• stiffest known material (stiffer than diamond)
• most stretchable crystal (up to 20% elastically)
• record thermal conductivity (outperforming diamond)
• highest current density at room T (million times of those in copper)
• highest intrinsic mobility (100 times more than in Si)
• conducts electricity in the limit of no electrons
• Good for flexible, wearable devices
• It is transparent: One atom-thick layer sheet absorbs ~2.3% visible light (πα).
• most impermeable (even He atoms cannot squeeze through)

13. Properties of graphene
MORPHOLOGY
The carbon-carbon bond length in
graphene is 0.142 nm.
Mechanical properties
Worlds strongest material
Ultimate tensile strength is
130GPa(0.4 Gpa steel),High
surface to volume ratio, young
modulus (0.5 Tpa)

14. Properties of graphene
Impermeability
Graphene is highly impermeable stopping other material to getting through. It is
useful for detecting and trapping gases.
Chemical properties
Graphene is the only form of carbon (or solid material) in which every atom is
available for chemical reaction from two sides (due to the 2D structure). Atoms at
the edges of a graphene sheet have special chemical reactivity. Graphene has the
highest ratio of edge atoms of any allotrope. Defects within a sheet increase its
chemical reactivity. The onset temperature of reaction between the basal plane of
single-layer graphene and oxygen gas is below 260 °C (530 K). Graphene burns at
very low temperature (e.g., 350 °C (620 K)). Graphene is commonly modified with
oxygen- and nitrogen-containing functional groups and analyzed by infrared
spectroscopy and X-ray photoelectron spectroscopy.

15. Properties of graphene
Optical properties
It is transparent to light(97.7%)and electrons
Electrical properties
high electrical conductivity, high electron mobility, semi metal/zero gap
semiconductor
Thermal Properties
best conductor of heat (better than even copper)

16. APPLICATIONS OF GRAPHENE

17. GRAPHENE APPLICATIONS OVERVIEW
• Composites (Light weight, multifunctional and highly damage tolerant structures)
• Paints and coatings (e.g. barrier, modification of optical/electrical properties of chemical
derivatives of graphene).
• Graphene Photonics (e.g. photomodulators, photodetectors, plasmonics, ultra-fast
lasers, metamaterials).
• Graphene electronics: specialist devices (e.g. high frequency transistors, spintronics) or
in combination with other electronics technologies (e.g. printed electronics).
• Flexible Electronics (e.g. as replacement for indium tin oxide in a range of applications
such as touch screens, solar cells etc.)
• Graphene sensors (e.g. chemical, strain sensors).
• Energy storage (e.g. graphene-based batteries, super-capacitors).

18. GRAPHENE IN TENNIS RACKET

19. GRAPHENE IN ELCECTRONICS

20. GRAPHENE IN SUPERCAPACITOR
• Cairo University graduate Maher
El-Kady wired a small piece of
graphene to an LED and found
that graphene behaved as a
super-capacitor, able to store a
considerable amount of
electricity. Their laser-scribed
graphene is ideal as a super
capacitor partially because of its
enormous surface area, 1520
square meters per gram.

21. Lithium doping turn graphene into
superconductor

22. GRAPHENE IN SOLAR CELLS
Compare to traditional indium tin
oxide solar cell, graphene based
solar cell can be used because it is
flexible, highly conducting, highly
transparent and due to low cost
because carbon is highly
abundant, whereas
traditional(ITO)solar cells are
expansive because indium is very
rare.

23. GRAPHENE IN OPTOELECTRONICS
Graphene can be used as a
material in optoelectronics on a
large commercial scale specifically
touch screen, liquid crystal display,
organic light emitting
diodes(oled), for a material to be
used in optoelectronics it must
transmit light ore than 90% and
should have good conductivity
and graphene have both of these
properties not only that its also
flexible.

24. GRAPHENE IN BODY ARMOR
Layers of carbon one-atom
thick can absorb blows that
would punch through steel.
Recent tests suggest that pure
graphene performs twice as
well as the fabric currently used
in bulletproof vests, making it
an ideal armor for soldiers and
police.

25. GRAPHENE AEROGEL
Chinese material scientist created the
world lightest material, a graphene
aerogel is about 7 time lighter than
air(1.2mg/cm), its 1 cubic centimeter
weighs about 0.16 milligram. Because of
its elasticity and absorbent, it can
absorb 850 time more than its weight,
being good absorbent it can be used in
environmental clean-up, where in the
effected place this graphene aerogel
can be spread and it can then absorb
organic products like oil from water.(it
doesn’t absorb water)*

26. GRAPHENE OXIDE USED FOR REMOVAL OF
HIGH METALS FROM WATER
Single layer graphene oxide with
manganese ferrite magnetic
nanoparticle shows best
absorption properties for efficient
removal of high metal
Pb(II)/As(III)/As(V) from
contaminated water.
ACS Appl. Mater. Interfaces
(2014), 6, 17426−17436

27. GRAPHENE SHEET AS WATER FILTER
Researches of material science at
MIT found that graphene sheet
perforated with hole can be used
in water filteration. Holes with
diameter 1nm are big enough to
let water molecule to pass
through, small enough to stop any
undesired chemical.

28. DNA SEQUENCING THROGH GRAPHENE SHEET
Ultra-thin graphene provides an
extremely precise test platform
for DNA strand sequencing as
the ionic current can recognize
even a single Nucleotide of
Dna. As molecules pass through
the nanoporus holes,
distinguishable ionic current is
measured to interpret the
sequence.