O A RIGINAL RTICLES

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Journal of Applied Sciences Research, 9(3): 1277-1281, 2013
ISSN 1819-544X
This is a refereed journal and all articles are professionally screened and reviewed
ORIGINAL ARTICLES
Rectangular Graphene Synthesis by CVD Method
1,2
Md.Naushad Ali, 1Md. Daud Ali, 1Farough Ali
1
2
Bottom Up Technologies,Pipra, MB Dih,MahagmaGodda ,Jharkhand PIN:814154
RedexNanolab, India
ABSTRACT
Inspired by the recent concentric interest towards the graphene, this study is concerned to optimize the large
scale synthesis with specific shape of this exciting nanomaterial. Few layered graphene of uniquerectangular
shaped were synthesized by chemical vapor deposition (CVD) method using a catalyst of specific combination.
The produced graphene was characterized by various techniques to know the aspect ratio, number of layers and
purity. This study is suggestive to extend work for easy scale up production method of themost potent emerging
nanomaterial.
Key words: Graphene, CVD, Catalyst, TEM, Raman, EDX, Electronics
Introduction
Graphene is a single atom thin two dimensional lattice of carbon atoms which has been attracting intense
research efforts owing to its superior electronic, mechanical, and thermal properties (Novoselov, K.S., et al.,
2005; Zhang, Y., et al., 2005; Lee, C., et al., 2008; Baladin, A.A., et al., 2008). Graphene exhibits interesting
electronic transport properties such as high carrier nobilities and the half-integer quantum Hall effect
((Novoselov, K.S., et al., 2005; Zhang, Y., et al., 2005) and displays a high Young’s modulus (Lee, C., et al.,
2008).
Graphene embodies a range of unique properties leading an exciting electronic character, described as a
zero-gap semiconductor (Castro Neto, A.H. et al. 2009), unparalleled strength (breaking strength ~40 N/m,
Young’s modulus ~1.0TPa) (Lee, C., et al. et al., 2008), and record thermal conductivity (Balandin, A.A. et al.
2008). Charge carriers, described as massless Dirac fermions, exhibit ballistic movement across submicron
distances approaching relativistic speeds, with intrinsic carrier mobilities up to 200,000 cm2 V–1 s–1 (Geim,
A.K., K.S. Novoselov, 2007; Novoselov, K.S. et al. 2005; Hwang, E.H. et al. 2007).
Chemical vapor deposition (CVD) is an attractive approach to graphene synthesis due to its capability of
producing large area deposition and the lack of intense mechanical and/or chemical treatments. It is believed
that carbon is then adsorbed and absorbed into the metal surface at high temperatures, where it is then
precipitated out in the lowest free energy state (graphene) during the cool down to room temperature (Reina, A.
et al. 2009; Kim, K.S. et al. 2009; Arco, L.G.D. et al. 2009; Chae, S.J. et al. 2009; Reina, A. et al. 2009; Li, X.
et al. 2009).
2. Experimental:
Initially, the catalyst of specific combination of transition metals was prepared through conventional wet
chemistry involvement. More specifically 5g Iron nitrate (III) nonahydrate [Fe (NO3)3.9H2O] and 5g Cobalt (II)
nitrate hexahydrate[ Co (NO3)2.6H2O ] were mixed in 50 ml ethanol. The solution was added in to 190 gm
Magnesium Oxide [MgO] in 500 ml ethanol with stirring. These chemicals were procured from Sigma Aldrich.
The mixture was viscous and in order to facilitate the mixing process 50 ml ethanol is again added. It was then
stirred for another two hours .The resultant mixture was again left for two hours on probe sonication. The
catalyst mixture was then kept in the oven at 130°C for overnight. The dried light greenish cake was grinded to
obtain powder.
Graphene samples were grown in a quartz boat ( 100 mm X 25 mm ) centrally placed inside the quartz tube
( 800 mm length and 74 mm inner diameter ) furnace system using CVD ( Catalytic chemical vapor deposition )
method using methane and argon gas (Li, X.S. et al, 2009).
The grinded powder of the mixed catalyst was taken as thin layer on the quartz boat inside the quartz boat.
The set up was connected to gas inlet and outlet. The tube was evacuated by running vacuum pump. Argon gas
Correspondence Author: Md.Naushad Ali-(Managing Director), Postal address: Bottom UpTechnologies, M. Pipra, MB
Dih, MahagmaGodda, Jharkhand, India PIN: 814154
E-mail: [email protected]; Contact number:+91.9608326752
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J. Appl. Sci. Res., 9(3): 1277-1281, 2013
was in flowed at the rate of 200 ml/minute while temperature kept on rising at the rate of 10°C/min. Once the
furnace temperature reaches the niche temperature (1050 °C) methane gas was purged into the CVD reactor tube
along with argon gas. The flow rate of the methane gas (500 ml /minute along with 200 ml/minute of argon) was
maintained for a period of time corresponding to the amount of catalyst loaded in the CVD reactor. The methane
gas purged inside the CVD reactor was reduced to the pure carbon form, i.e., Graphene, by the alkaline and
transition metal catalyst.
Followed by the completion of reaction the flow of methane gas into the tube was stopped and then the
system was cooled under argon gas atmosphere. Fast cooling is achieved by continued argon gas flow at 500
ml/minute for another 2 hours. The nanomaterial thus formed were purified by one-step Hydrochloric acid (HCl
)(35%) demineralization process. Further repeated washing with DM (demineralized) water and ethanol were
performed using shear stirring. The Graphene cake was finally dried in an oven at 120°C for 12 hours and then
grinded into fine powder using mortar and pestle. Thus ultrafine powder of very fine grayish-black, randomly
aggregated powder was obtained. On characterization it revealed that product was few layered thin rectangular
Graphene sheet. The percentage yield calculated was found to be 69%.
Figure 1A:TEM image
Figure1B: TEM image
Figure 1C HRTEM image
Figure 1D TEM image
Fig. 1: TEM images
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J. Appl. Sci. Res., 9(3): 1277-1281, 2013
Result And Discussion
The structural analysis and characterization of the Graphene were performed using the transmission
electron microscopy (TEM) and Raman spectroscopy. The transmission electron microscopy (TEM) studies
were carried out to determine the exact size of as-manufactured Graphene rectangular structure using Philips,
TECHNAI FE 12 microscope (TEM) at an accelerating voltage of 120 kV. Figure1A, 1B, 1D and Figure 1D
show the (TEM) images. Figure 2 shows a typical Raman spectrum of Graphene thus formed in the present
study. The three intense peaks were observed as the D band at 1350 cm-1, the G band at 1580 cm-1 and the 2D
band at 2650 cm-1. The elemental analysis of the Graphene rectangular structure thus synthesized shows the
carbon content of 91.67 atomic percentages in table 1.
Fig. 2: Raman Spectra of Graphene
Table 1: Elemental analysis
Element
CK
Mg K
Co K
Weight %
84.41
14.45
2.14
Atomic %
91.67
7.85
0.48
Graphene deposition was uniformly formed few layered as defect free flakes. The uniform layer can be
caused due to a surface adsorption growth mechanism. The nucleation caused during the growth process due to
presence of metallic entities in catalyst.
TEM images are clearly exhibiting the uniformity and morphology without any defects at surface. HRTEM
(High resolution TEM) is explaining the growth pattern. At the same time some impurities are seen in EDX
spectra depicted in figure 3, which are remaining during the purification process. EDX spectra (Quantization
method, Cliff Lorimer thin ratio section Number of iterations = 1) are revealing the purity level of the obtained
product. Further purification steps can give absolute pure product.
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J. Appl. Sci. Res., 9(3): 1277-1281, 2013
Fig. 3: EDEX of Graphene
The results obtained from Raman spectroscopy are in favor of uniform growth of the graphene sheet. The
spectrum has large symmetrical G and 2D peaks indicating the presence of few layered graphene (Malard, L.M.
et al., 2009).
There are many reports regarding the synthesis of graphene sheet but synthesis of rectangular graphene has
been rare. The rectangular graphene seeks many electronic applications because of its unique electronic
properties (Nikolaev, A.V.,; Barone, V., et al., 2001). Thus, this work is unique in regard to controlled synthesis
of this particular structure of graphene.
Conclusion:
Few layered graphene flakes of rectangular structure obtained, have average particle size of 45nM, and
thickness of less than 6nM. The catalyst combination in these experiments is capable of giving uniform
rectangular Graphene sheet with high purity and defect free surface by CVD method at the current parameter.
Further study is suggestive to scale up the synthesis method taking current study in consideration. A facile and
scalable production method of specific shaped graphene is reported herein.
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