Graphene

1. Synthesis and Characterization of Graphene
using Liquid Exfoliation Method
Supervisor
Dr. Shumaila Karamat
• Muhammad Ahsan
• Muhammad Subhan
• Basit Ali khan
1

2. Outlines
• Introduction to Graphene
• Properties and Applications
• Synthesis Technique
• Flow Chart
• Results
• Conclusions
2

3. • Graphene is an allotrope of carbon and
2-dimensional material.
• Single sheet of sp2 hybridized carbon
atom in hexagonal arrangement.
• One atom thick layer, bond length
~0.14nm
Introduction to Graphene
3

4. Properties of Graphene
• Transparent, stretchable and flexible.
• Best thermal and electrical conductor.
• Strongest material and extremely light weight .
• Energy storage, sports equipment.
• Construction , electronics.
• Sensors, filtration membranes.
Applications of Graphene
4

5. Motivation
The synthesis of graphene via simplest technique which give
high quality and large amounts.
5

6. Synthesis Technique
Graphene can be prepared using different techniques:
• Mechanical Exfoliation
• Dry Exfoliation
• Chemical Vapor Deposition
• Electrochemical Exfoliation
• Liquid Exfoliation
• To obtain high product purity.
• Provides graphene of very high quality.
• Environment friendly.
6

7. Experimental Procedure
7

8. Preparation of solution
In the first step solution of N-Methyl-1, 2-Pyrrolidone (NMP)
and Graphite powder is made. Solvent in this solution is NMP.
10 g Graphite is dispersed into 100 ml NMP.
𝑺𝒐𝒍𝒖𝒕𝒊𝒐𝒏 = 𝑮𝒓𝒂𝒑𝒉𝒊𝒕𝒆 𝒑𝒐𝒘𝒅𝒆𝒓 + 𝑵𝑴𝑷 (𝒔𝒍𝒐𝒗𝒆𝒏𝒕)
8

9. Sonication
In this step solution was sonicated for
30 hours in probe sonicator. The
purpose of sonication was to break
down the bulk material Graphite into
2D sheets. Sonicator produces
ultrasonic waves that converts bulk
material into 2D sheets. Probe Sonicator
9

10. Centrifugation
After sonication, solution was
centrifuged where liquid solution of
graphene and NMP was extracted from
the graphite powder. Centrifugation
was done at 500 rpm. For
centrifugation an apparatus known as
Ultra centrifuge is used.
Ultra Centrifuge
10

11. Filtration
In this process Vacuum filtration assembly is used
in which filter paper of 0.22 µm is placed. When
solution is filtered some of liquid NMP passes
through the paper and some of it was left behind on
the filter paper with graphene.
Vacuum filtration assembly
Removal of NMP
To separate NMP from graphene, it was placed on filter paper and
then heated at 100ºC temperature. At this temperature NMP
evaporates and graphene was left behind on filter paper.
11

12. Spin Coating
The filtered graphene is mixed with
ethanol. The solution is then
deposited on silicon substrate and
placed on spin coater and turntable
is rotated at the rotation of 5000
RPM for 5 minutes. The required
graphene thin film with uniform
thickness is obtained on the silicon
substrate.
Spin coating process
12

13. Characterization Techniques
• Optical Microscope
• Raman Spectroscopy
13

14. Figure 1:Optical image of Sample 1 at 50x Figure 2:Optical image of Sample 2 at 50x
Optical Microscopy
Microscopic Images
14
Results and Discussions

15. Raman spectroscopy is a spectroscopic technique based on inelastic scattering of
monochromatic light, usually from a laser source. Inelastic scattering means that the frequency
of photons in monochromatic light changes upon interaction with a sample.
1400 1600 1800 2000 2200 2400 2600 2800
-10000
0
10000
20000
30000
40000
50000
Intensity(a.u)
Wavenumber(cm-1
)
D-1373.2
cm
-1
2D-
2762c
m
-1
G-1600cm
-1
Sample 1
1200 1400 1600 1800 2000 2200 2400 2600 2800
0
10000
20000
30000
40000
50000
60000
Intensity(a.u)
Wavenumber(cm-1
)
Sample 2
D-1367
cm
-1
G-1592
cm
-1
2D-274
6
cm
-1
Figure 3:Raman spectrum of sample 1 Figure 4:Raman spectrum of sample 2 15
Raman Spectroscopy

16. The G band is a sharp band which appears at approximate1600 cm-1 in sample
1 and at approximate.1592cm-1 in sample 2 in our graphene spectrum. The G
band is the first-order Raman band of all sp2 hybridized carbon materials
depending on the excitation laser wavelength.
1540 1560 1580 1600 1620 1640 1660
0
2000
4000
6000
8000
10000
12000
14000
Intensity(a.u)
Wavenumber(cm-1
)
G-Peak Sample 1
1540 1560 1580 1600 1620 1640 1660
0
3000
6000
9000
12000
15000
18000
21000
24000
Intensity(a.u)
Wavenumber(cm-1
)
G-Peak
Sample 2
The G-band
Figure 5:Raman spectrum of G-Band for sample 1 Figure 6:Raman spectrum of G-Band for sample 2
16

17. The D band appears at approximate 1373cm-1 in sample 1 and at approximate
1367cm-1 in sample 2 in our graphene spectrum. This D-band is identified as the
disorder band or defect band. The band is typically weak in graphene . If the D-band
is significant, this shows that there are a lot of defects present in the material.
The D-band
1350 1360 1370 1380 1390 1400
800
1000
1200
1400
1600
1800
2000
2200
2400
Intensity
(a.u)
Wavenumber ( cm -1
)
D-Peak
Figure 7:Raman spectrum of D-Band for sample 1 17

18. The 2D band is the second order of the D band. This band is appearing at
approximate 2762cm-1 in sample 1 and at approximate 2746cm-1 in sample 2 in our
graphene spectrum. . This band is always strong in graphene, although when there is
no D band present. It is also used to determine graphene layer thickness.
2680 2700 2720 2740 2760 2780 2800
-2000
-1000
0
1000
2000
3000
Intensity(a.u)
Wavenumber(cm-1
)
2D Peak
Sample 1
2680 2700 2720 2740 2760 2780 2800 2820
-1000
0
1000
2000
3000
4000
5000
6000
7000
8000
Intensity(a,u)
Wavenumber(cm-1
)
2D Peak
Sample 2
The 2D band
Figure 8:Raman spectrum of 2D-Band for sample 1 Figure 9:Raman spectrum of 2D-Band for sample 2
18

19. • Here we synthesize graphene using liquid exfoliation technique. After that
we have performed the Raman spectroscopy of the synthesized graphene
samples.
• The obtained results are in agreement with the formation of multi-layer
graphene. The Raman spectrum shows the FWHM of 2D Band is greater
than 50 cm-1 for both samples which shows that the resulting graphene is
multi-layer graphene.
Conclusion
19

20. Future work
In future we can obtain many applications by making
composites of graphene e.g battery electrodes, sensors etc.
20

21. Thank
You
 21