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BITS PILANI K.K BIRLA GOA CAMPUS

PREPARATION OF GRAPHENE 

FINAL REPORT

J Lakshmi Saradhi Reddy

2012A1PS426G

Submitted in partial fulfillment of Lab Project (Jan 2015-May 2015)

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INDEX

SerialNo.

Topic Page No.

1. Introduction :Graphene 2

2. Properties of Graphene 4

3. Graphene and its Applications in various

fields

6

4. Existing methods for preparation of Graphene 7

5. Hummers Method 8

6 Bibliography 12

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GRAPHENE 

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 honey-comb lattice. In more complex terms, it is an allotrope of carbon in the struc-

ture of a plane of sp2 bonded atoms with a molecule bond length of 0.142 na-

nometres. Layers of grapheme stacked on top of each other form graphite,

with an interplanar spacing of 0.335 nanometres.It is the thinnest compound

known to man at one atom thick, the lightest material known the strongest

compound discovered (between 100-300 times stronger than steel), the best

conductor of heat at room temperature and also the best conductor of electrici-

ty known Other notable properties are its unique levels of light absorption ofwhite light, and its potential suitability for use in spin transport. Graphene's

stability is due to its tightly packed carbon atoms and an sp2orbital hybridiza-

tion –  a combination of orbitals s, px and py that constitute the σ-bond. The fi-

nal pz electron makes up the π- bond. The π-bonds hybridize together to form

the π- band and π∗ -bands. These bands are responsible for most of graphene's

notable electronic properties, via the half-filled band that permits free-moving

electrons.

Individual layer of Graphite - Graphene 

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Graphene layer placed on top of each other- Graphite

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GRAPHENE & Its Properties

Electronic Properties

One of the most useful properties of graphene is that it is a zero-overlap se-

mimetal (with both holes and electrons as charge carriers) with very high elec-

trical conductivity. Carbon atoms have a total of 6 electrons; 2 in the inner

shell and 4 in the outer shell. The 4 outer shell electrons in an individual car-

 bon atom are available for chemical bonding, but in graphene, each atom is

connected to 3 other carbon atoms on the two dimensional plane, leaving 1

electron freely available in the third dimension for electronic conduction.

These highly-mobile electrons are called pi (π) electrons and are located a boveand below the graphene sheet. These pi orbitals overlap and help to enhance

the carbon to carbon bonds in graphene. Fundamentally, the electronic proper-

ties of graphene are dictated by the bonding and anti-bonding (the valance and

conduction bands) of these pi orbitals. 

Tests have shown that the electronic mobility of graphene is very high

Mechanical Strength

Another of graphene’sstand-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. 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. Graphene also con-

tains 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 (with thicknesses of between 2 and 8 Nm) had spring con-

stants 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

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 based on theoretical prospects using graphene that is unflawed containing no

imperfections whatsoever and currently very expensive and difficult to artifi-

cially reproduce, though production techniques are steadily improving, ulti-

mately reducing costs and complexity.

Thermal conductivity

Thermal transport in graphene is an active area of research, which has at-

tracted attention because of the potential for thermal management applications.

Early measurements of the thermal conductivity  of suspended graphene re-

 ported an exceptionally large thermal conductivity of approximately

5,300 W

m

−1

K 

−1

, compared with the thermal conductivity of pyrolyticgra- phite of approximately 2,000 Wm

−1K 

−1  at room but measured range of

thermal conductivities between 1,500 –  2,500 Wm−1K 

−1 for suspended sin-

gle layer graphene.Potential for this high conductivity can be seen by consi-

dering graphite, a 3D version of graphene that has basal planethermal conduc-

tivity of over a 1000 Wm−1K 

−1 (comparable to diamond). In graphite, the

c-axis (out of plane) thermal conductivity is over a factor of ~100 smaller due

to the weak binding forces between basal planes as well as the larger lattice

spacing. In addition, the ballistic thermal conductance of graphene is shown togive the lower limit of the ballistic thermal conductances, per unit circumfe-

rence, length of carbon nanotubes.

Chemical

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. Gra-

 phene has the highest ratio of edge atoms of any allotrope. Defects within asheet increase its chemical reactivity. The onset temperature of reaction be-

tween the basal plane of single-layer graphene and oxygen gas is below

260 °C. Graphene burns at very low temperature (e.g., 350 °C ).Graphene is

commonly modified with oxygen- and nitrogen-containing functional groups

and analyzed by infrared spectroscopy and X-ray photoelectron spectroscopy.

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Optical Properties 

Graphene's unique optical properties produce an unexpectedly high opacity for

an atomic monolayer in vacuum

Uses Of Graphene in various fields 

Graphene is used in areas including electronics,  biological engineering, filtra-

tion, lightweight/strong composite materials, photovoltaics and energy storage.

Graphene is often produced as a powder and as a dispersion in a polymer ma-

trix. This dispersion is supposedly suitable for advanced composites,paints andcoatings, lubricants, oils and functional fluids, capacitors and batteries, ther-

mal management applications, display materials and packaging, inks and 3D-

 printers’ materials, and barriers and films. 

ELECTRONIC NANODEVICES

  Field Effect Transistors

  Transparent conductive films

ENERGY STORAGE DEVICES

  Li- ion batteries

  Ultra capacitors

  Fuel cell and solar cells

SENSORS

  Electrochemical Sensors

  Biosensors

BIOMEDICAL ENGINEERING

  Gene Delivery

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  Drug Delivery

  Tissue Engineering

  Cancer Therapy

Preparation Methods 

  Reduction of graphite oxide

  Shearing

  Solvent/surfactant-aided

  Epitaxy

 

Silicon carbide  

Solar Exfoliation 

  Liquid Phase Exfoliation

  Microwave Assisted Oxidation 

  Electro Chemical Method

The method we followed in lab is chemical reduction of Graphite oxide pre-

 pared via Hummers method. Graphene oxide produced was chemically re-duced used a reducing agent like Hydrazine Hydrate or Sodium Borohydride

to obtain Graphene.

We used Sodium Borohydride for reduction because it is relatively less ha-

zardous and harmful to use when compared to Hydrazine Hydrate

Hummers MethodFor Hummers’ method, the following chemicals required:

1. 2.5 grams graphite

2. 1.25 grams of sodium nitrate

3. Concentrate sulphuric acid

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4.  7.5grams of potassium permanganate

5. 30% H2O2 solution (2.5 ml)

6. 

Hydrazine hydrate/ Sodium Borohydride(NABH4) - 2 grams7. Ice bath and distilled water

Apparatus Required

  2 500ml beaker

  4 100ml beaker

  1 litre beaker

  spatula

  stirrer rod

Preparation of Graphene oxide

1. 2.5 g of graphite powder and 1.25 g of sodium nitrate were mixed in a

 beaker.

2. Concentrated sulfuric acid (165 ml) was added to the mixture and un-

iformly stirred in an ice bath (0 C).

3. While maintaining vigorous stirring, 7.5 g of potassium permanganate

was slowly added at a carefully controlled rate to keep the temperature

 below 20 C.

4. The suspension was then stirred for 2 h in an ice bath.

5. After heating the solution at 35 C and stirring it for 30 min, 75 ml of dis-

tilled water was slowly added to the suspension, resulting in an exother-

mic reaction that heated up the suspension to 95 C.

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6. Temperature was controlled at 95 C for 30 min under stirring to com-

 plete the reaction, after which the solution was diluted with 200 ml of

distilled water.

7. The solution was treated with a 30% H2O2 solution (2.5 ml) to reduce

residual permanganate into soluble manganese ions until the gas evolu-

tion ceased.

8. The cooled mixture was filtered, resulting in a yellow-brown filter cake

and then washed with a 37% HCl solution to remove residues, followed

 by several washings with distilled water

Finally GO was obtained by centrifugation, and the precipitate was dried at 60

C for24 h.

The Graphene oxide obtained was dispersed in a beaker distilled water and so-

nicated it for 24 h.

The solution will be homogenous and add 2 g of Sodium Borohydride by heat-

ing the mixture up to 100 C for another 24 h to evaporate water.

The final solution is centrifuged to separate graphene and water , dried in an

oven at 80 C.

Weight of the graphene prepared is 1.8 g.

It is tested in die swelling characcerstics using 1 wt% polymer and got satis-

factory results

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Graphen oxide befor drying

Graphene oxide after drying

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Graphene obtained after reduction

BIBLIOGRAPHY1. Production methods of graphene and resulting material properties

UrszulaKosidlo, Marta Arias Ruiz de LarramendiFriedemann Tonner,

Hye Jin Park, CarstenGlanz, VieraSkakalov, Siegmar Roth, IvicaKolaric 

2. 

Improved Synthesis of Graphene Oxide,Daniela C. Marcano,† Dmitry

V. Kosynkin,† Jacob M. Berlin, Alexander Sinitskii, Zhengzong Sun,

Alexander Slesarev, Lawrence B. Alemany, Wei Lu, and James M.

Tour* 

3. 

Recent advances in applications of graphene,TapanK.Das and Smita-

Prusty 

4. Graphene Applications and Uses – 

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 Nanotechnolo-

gyhttps://www.google.co.in/search?q=Graphene+applications&biw=127

6&bih=715&source=lnms&sa=X&ei=c1JEVdhqzra5BKT6gIgL&ved=0

CAUQ_AUoAA&dpr=1#

5. Wikipedia Graphen produc-tion,http://en.wikipedia.org/wiki/Graphene#Production_techniques 

6. 

GrapheneSythesisvs Voltage in a dry cell , scientific report, DanAvilla