2. GRAPHENE
Graphene is an allotrope of carbon in the form of a two-dimensional,
atomic-scale, hexagonal lattice in which one atom forms each vertex.
It is the basic structural element of other allotropes,
including graphite, charcoal, carbon nanotubes and fullerenes.
It can also be considered as an indefinitely large aromatic molecule,
the limiting case of the family of flat polycyclic aromatic
hydrocarbons.
3. Andre Geim and Konstantin
Novoselov at the University of
Manchester won the Nobel Prize in
Physics in 2010 "for groundbreaking
experiments regarding the two-
dimensional material graphene.
The global market for graphene is
reported to have reached $9 million
by 2014 with most sales in the
semiconductor, electronics, battery
energy and composites industries.
4. STRUCTURE….
Graphene is a crystalline allotrope of carbon with 2-
dimensional properties. Its carbon atoms are densely packed in
a regular atomic-scale chicken wire (hexagonal) pattern.
Each atom has four bonds, one σ bond with each of its three
neighbors and one π-bond that is oriented out of plane. The
atoms are about 1.42 Å apart.
Graphene's stability is due to its tightly packed carbon atoms
and an sp2 orbital hybridization – a combination of orbitals
px and py that constitute the σ-bond.
The atomic structure of isolated, single-layer graphene was
studied by transmission electron microscopy (TEM) on sheets
of graphene suspended between bars of a metallic grid.[
5. ELECTRONIC SPECTRUM..
• Graphene is a zero-gap semiconductor,
because its conduction and valence
bands meet at the Dirac points.
• Electrons propagating through
graphene's honeycomb lattice effectively
lose their mass, producing quasi-
particles that are described by a 2D
analogue of the Dirac equation
6.
7. THE STORY OF GRAPHENE..
• If you've ever drawn with a pencil, you've probably made graphene.
The world's thinnest material is set to revolutionize almost every part
of everyday life.
• Although scientists knew one atom thick, two-dimensional crystal
graphene existed, no-one had worked out how to extract it from
graphite. That was until it was isolated in 2004 by two Russian-born
researchers at The University of Manchester, Andre Geim and
Konstantin Novoselov.
8. THE EARLY YEARS….
• Graphene, millions of ultra-thin layers that stack together to form
graphite commonly found in pencils, was first studied as long ago as
1947.
• That electric current would be carried by effectively massless charge
carriers in graphene was pointed out theoretically in 1984, and the
name 'graphene' was first mentioned in 1987.
10. HOME OF GRAPHENE…
Andre and Konstantin adopted a method that researchers in
surface science were using – using simple Sellotape to peel away
layers of graphite to expose a clean surface for study under the
microscope. Once used, the tape was simply being thrown away.
Yet no-one had noticed the material on the tape was thinner than
the material produced by polishing. They had made graphene, yet
had not realised it.
11. FROM NANOMATERIAL TO GLOBAL
EXPLOSION
• Konstantin continued to explore how thin the graphite flakes on the tape
could be made. He peeled the layers so thinly that what was left was one-
atom thick graphene.
• Groups around the world sent students and postdocs to The University of
Manchester to learn how to make the material and much work was done to
explore the unusual electronic properties of graphene.
• Andre and Konstantin continued to publish academic papers describing how
it could potentially be used in a huge number of diverse applications.
12. TYPES OF GRAPHENE….
Few-layer graphene (FLG) or multi-layer graphene (MLG) – a 2D,sheet-like material, either
as a free-standing flake or substrate-bound coating, consisting of a small number (between two
and about 10) of well-defined, countable, stacked graphene layers of extended lateral dimension.
Graphene oxide (GO) – chemically modified graphene prepared by oxidation and exfoliation.
Graphene oxide is a monolayer material with a high oxygen content.
Reduced graphene oxide (rGO) – graphene oxide (as above) that has been reductively
processed by chemical, thermal, microwave, photo-chemical, photo-thermal or microbial/bacterial
methods to reduce its oxygen content.
Graphite oxide – this precursor to GO is a bulk solid made by oxidation of graphite through
processes that functionalize the basal planes and increase the interlayer spacing.
13. THE MANUFACTURING PROCESS..
1. Chemical Vapour Deposition,
where a gas containing carbon
(such as Methane) is broken down
and reassembled on a hot metallic
surface into a sheet of graphene.
2. Solution Exfoliation, where
graphite is blasted into small
fragments of graphene using
ultrasonic energy.
14. Graphene batteries and supercapacitors to
power our world
• The potential of graphene for batteries becomes more apparent each day,
with headlines touting new graphene electrodes and battery materials.
• Adding some boron atoms to the graphene structure result in an ultrathin
efficient flexible anode for lithium ion batteries & helps the lithium ions of
the battery stick better to the graphene anode, which was a problem earlier.
• Graphene anodes result in faster battery charging and discharging compared
to conventional anodes.
15. Already some years ago,
engineers
at Northwestern
University have shown
that graphene anodes
hold energy better than
graphite anodes, with
10x faster charging.
Finally, graphene is not only
being used for the electrodes
of batteries, but for the active
material itself. Graphene
makes such a good battery
material that the devices are
called "supercapacitors", i.e.
batteries which hold
enormous power and charge
within a few seconds.
UCLA researchers caused
shock waves when they
showed a graphene mixture
that can be coated onto the
surface of a regular DVD. An
ordinary DVD burner is then
used to inscribe millions of
supercapacitor circuits into
the graphene layer. The layer
can later be simply peeled off
and transferred anywhere
where a super powered
battery is desired.
16. • A new battery under development promises
to store twice as much and power an electric
vehicle for more than 300 miles .
• Battery that can store more than twice the
Wh/kg of a Li ion battery, and has already
shown that it can do 1,500 charge cycles
without deterioration – probably more.
Lithium sulphur graphene - a battery
breakthrough?
17. APPLICATION OF GRAPHENE..
• Medicine: Graphene could pave the way for a step change in the
treatment of cancer and conditions such as Parkinson's.
• Water purification and treatment in developing countries, and even provide
more efficient desalination plants.
• In aircraft technology and cars.
• Graphene detects: It could create sensors that can detect even minute
traces of gases or dangerous chemicals
