CHEMICAL ENGINEERING DEPARTMENT

Date: 21/11/2014

GRAPHENE

Seminar By- Hitesh D. Parmar

GRAPHENE

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Sr. No. Title Slide No.

1. Introduction 4

2. History 6

3. Structure 8

4. Production 10

5. Chemical Properties 13

6. Electronic Properties 15

7. Mechanical Properties 17

8. Thermal Properties 19

9. Optical Properties 20

10. Applications 21

11. References 33

CONTENTS

3.

Introduction

• Graphene can be described as a one atom thick layer of graphite.

• It is two dimensional crystal.

• Sp2 hybridized carbon atoms are densely packed in atomic scale.

• It is the basic structural element of other allotropes of carbon

What is Graphene?

4.

5.

History• Firstly in 1859 Benjamin Bordie was introduced highly lamellar

structure.

• In 1916 structure of graphite solved by V. Kohlschutter & P. Haenni.

• Theory was explored in 1947 by P. Wallace.

• First patents pertaining to the production of graphene was filled in 2002 entitled, “Nano-scaled Graphene Plates”.

• Two years later, in 2004 Andre Geim and Kostya Novoselov at University of Manchester extracted single-atom-thick crystallites from bulk graphite.

• Geim and Novoselov received several awards for their pioneering research on graphene, specially in 2010 by Nobel Prize in Physics.

6.

Inventor of Graphene

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Structure• It is two dimensional network of carbon atom

• These carbon atoms are bounded within the plane by strong bonds into a honeycomb array comprised of six membered rings.

• Stacking of this layers on top of each other 3-dimensional graphite crystal is formed.

• It is basic structural element of all carbon allotropes.

• It is an sp2 orbital hybridization with 3σ and 1π bond

• Atomic thickness is about 0.345nm

• Stability

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9.

Production• Micromechanical cleavage

• Epitaxial growth on silicon carbide substrate

• Chemical reduction of graphene oxide

• Exfoliated Graphene

• Epitaxial growth on metal substrate

• Pyrolysis of Sodium Ethoxide.

• From Nanotubes

• CO2 reduction method

• From Graphite by Sonification10

1. Micromechanical Cleavage:• Simplest Method• Graphite rubbed across flat surface• Low Yield Process

2. Epitaxial Growth on SiC Substrate: • Heating process• Opposite to Mechanically exfoliated• Expensive

3. Chemically Exfoliation of Graphene by Graphite:• Attached oxygen-rich functional groups• Immersed in water• Deposit Graphene oxide• Reduced it to Graphene

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Scotch Tape Method

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Chemical properties

• Chemically the most reactive form of carbon,

• Only form of carbon in which each single atom is in exposure for chemical reaction from two sides (2D structure)

• Carbon atoms at the edge of graphene sheets and various types of defects within the sheets increases the reactivity.

• Highest ratio of edgy carbon.

• Burns at very low temperature i.e. 350 ºC.

• One atom thick sheet is 100 times more reactive than thicker sheet.

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Defects in Graphene sheets

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Electronic properties

• It is zero-overlap semimetal with very high electrical conductivity

• Electrons are able to flow through graphene more easily than through even copper

• Electrons travel through graphene as if they carry no mass, as fast as just one hundredth that of speed of light.

• High charge carrier mobility, for which values of 2,00,000 cm2/V.s

• Resistivity is 10-6 Ω.

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Mechanical properties• Strongest material ever discovered

• Tensile strength 130GPa compared to A36 structural steel with 400MPa.

• Harder than diamond and about 200 times harder than steel.

• Very light - 0.77mg/m2 i.e 1m2 paper is 1000 times heavier

• It is stretchable up to 20% of its initial length.

• AFM test shows that graphene sheets with atomic thickness 2-8 nm had spring constant 1-5N/m and Young’s modulus 0.5 – 1TPa

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Thermal Properties• It is perfect thermal conductor.

• Its thermal conductivity is much higher than all other carbon structure at room temperature i.e. 5000 W/mK

• Graphite shows thermal conductivity about 5 times smaller i.e. 1000 W/mK

• Graphene based electronic device even on a substrate thermal conductivity reaches 600 W/mK

• The Ballistic thermal conductivity of graphene is isotropic.

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Optical Properties• Despite it is one atom thick it is still visible to naked eye.

• Due to its unique electronic properties, it absorbs a high 2.3% of light that passes through it.

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Photograph of graphene in transmitted light. This one atom thick crustal can be seen to naked eye because it absorbs approx 2.6% of green light and 2.3% of red light

Applications• In Paint industry: As it protects and conducts it means it can be used in

advanced paints to reduce corrosion and to increase energy efficiency

• In Aircraft techniques and vehicles Due to light weight, high tensile strength and hardness it

can be used in aircraft and cars.

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• Biomedical

• Graphene could soon be used to analysis DNA at record breaking pace

• Sending molecules through tiny slit in graphene sheet

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• Integrated Circuits

• Due to high carrier mobility and low noise, allow to used as channel in a field effect transistor

•Processor using 100GHz transistor on 51mm graphene sheet

•Graphene based integrated circuit handled frequencies upto 10GHz

•Transistor printed on flexible plastic that operate at 25GHz

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• Optical Electronics

• High Electrical conductivity and high transparency make it candidate for transparent conducting electrode

• Its medical strength and flexibility are advantageous compared to indium-tin-oxide, which is brittle

•So it would be work very well in optoelectronic

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• Solar cells

•The transparent, conductive and ultrathin graphene films are fabricated from exfoliated graphene oxide, followed by thermal reduction

•The obtained films exhibits high conductivity and transparency of more than 70% over 2000-3000 nm

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• Energy Storage Devices

• Due to extremely high surface area to mass ratio of graphene, it is used in conductive plates of superconductors

• It could be used to produce super capacitor with greater energy storage density.

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• Potable water by desalination:

• Arrange thin monolayer graphene sheet in cross with each other

• It allows only water molecule through to it and remain salt behind it.

• It depends upon the pressure and size of the pore also

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A) By arrangement of sheets

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• New Method – CDI (Capacitive deionization technology)

• No secondary pollution and cost effective

• Energy efficient

• Uses graphene like nanoflakes as electrode

B) By CDI

• Alcohol distillation:

• Arrange Graphene oxide sheets in such a way that between them there is room for exactly one layer of water molecule.

• if another molecule tries to escape, Graphene capillaries either shrinks or clogged with water

•It blocks Helium gas also

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• Sensor:

• Able to the detection of low concentration, toxic, and explosive chemical vapors and gases.

•Sensors capable of detecting chemical vapor concentration part per billion. •CMG film attached with oxygen functional group on it.

• reduced chemically or thermally and provide knob with which to tune the sensor response.

•These devices are then exposed to pulses of chemical vapors and resulting change in material is measured.

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CMG Film

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Some other Applications:-

• Graphene Nano ribbons

• IR detectors

• Piezoelectric materials

• Composite materials

• Liquid cells for Electron Microscopy

• Optical Modulators

• Thermal Management materials.

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References

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• The uniqueness of physical and chemical natures of graphene: their coherence and conflicts E.F. Sheka Peoples’ Friendship University of Russia, 117198 Moscow, Russia

• A.K. Geim, K.S. Novoselov, $e rise of graphene. Nature Materials 6, 183-191 (2007).

• M.J. Allen, V.C. Tung, R.B. Kaner, Honeycomb carbon: a review of graphene. Chem. Rev. 1, 132-145 (2010)

• Elimelech, M.; Phillip, W. A. Science 2011, 333, 712−717.

• Spiegler, K.; El-Sayed, Y. Desalination 2001, 134, 109−128.

• Alexiadis, A.; Kassinos, S. Chem. Rev. 2008, 108, 5014−5034.

• S. Stankovich et al., “Synthesis of Graphene-based Nanosheets Via Chemical Reduction of Exfoliated Graphite Oxide,” Carbon 45(7), 1558–1565 (2007).

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• S. Anthony, Graphene: the perfect water f!lter. ExtremeTech (2012). Available at http://www.extremetech.com/extreme/115909-graphene-theperfect-water-!lter (January 2012).

• K.S. Novoselov et al., “Electric Field Effect in Atomically ThinCarbon Films,” Science 306(5696), 666–669 (2004).

• S. Stankovich et al., “Synthesis of Graphene-based Nanosheets via Chemical Reduction of Exfoliated Graphite Oxide,” Carbon 45(7), 1558–1565 (2007).

• J.T. Robinson et al., “Reduced Graphene Oxide Molecular Sensors,” Nano Letters 8(10), 3137–3140 (2008); J.T. Robinson et al., “Wafer-scale Reduced Graphene Oxide Films for Nanomechanical Devices,” Nano Letters 8(10), 3441–3445 (2008).

• Blankenburg, S.; Bieri, M.; Fasel, R.; Muellen, K.; Pignedoli, C. A.; Passerone, D. Small 2010, 6, 2266−2271.

• Wallace, P. R. The band theory of graphite. Phys. Rev. 71, 622-634 (1947).

• Fradkin, E. Critical behavior of disordered degenerate semiconductors, Phys. Rev. B 33, 3263-3268 (1986).

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• Novoselov, K. S. et al. Electric field effect in atomically thin carbon films. Science 306, 666-669 (2004).

• Novoselov, K. S. et al. Two-dimensional atomic crystals. Proc. Natl Acad. Sci. USA 102, 10451-10453 (2005).

• Novoselov, K. S. et al. Two-dimensional gas of massless Dirac fermions in graphene. Nature 438, 197-200 (2005).

• Zhang, Y., Tan, J.W., Stormer, H.L., Kim, P. Experimental observation of the quantum Hall effect and Berry's phase in graphene. Nature 438, 201-204 (2005).

•Haldane, F. D. M. Model for a quantum Hall effect without Landau levels: Condensed-matter realization of the ‘parity anomaly’. Phys. Rev. Lett. 61, 2015-2018 (1988).

• McClure, J.W. Diamagnetism of graphite. Phys. Rev. 104, 666-671 (1956).

•Slonczewski, J.C., Weiss, P.R. Band structure of graphite. Phys. Rev. 109, 272-279 (1958).

•Semenoff, G.W. Condensed-matter simulation of a three-dimensional anomaly. Phys. Rev. Lett. 53, 2449-2452 (1984).

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Thank You

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