Preparation of double-walled carbon nanotubes from fullerene ...

CARBON 48 (2010) 1312– 1320
available at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/carbon
Letters to the Editor
Preparation of double-walled carbon nanotubes from fullerene
waste soot by arc-discharge
Jieshan Qiu a,b, *, Gang Chen a , Zhentao Li a , Zongbin Zhao a
a Carbon Research Laboratory, Center for Nano Material and Science, State Key Lab of Fine Chemicals, School of Chemical Engineering,
Dalian University of Technology, 158 Zhongshan Road, P.O. Box 49, Dalian 116012, China
b Key Laboratory for Micro/Nano Technology and System of Liaoning Province, Dalian University of Technology, Dalian 116023, China
ARTICLE
INFO
ABSTRACT
Article history:
Received 19 July 2007
Accepted 25 January 2009
Available online 3 February 2009
Fullerene waste soot (FWS) was used as raw material to fabricate double-walled carbon
nanotubes (DWCNTs) by arc-discharge in a mixture of Ar and H 2 (2:1, v/v) at 300 Torr.
The results of transmission electron microscope and Raman spectroscopy indicate that
the high quality FWS-derived DWCNTs can be synthesized by arc-discharge method.
Ó 2009 Published by Elsevier Ltd.
Double-walled carbon nanotubes (DWCNTs) with unique
properties that are different from single-walled carbon nanotubes
(SWCNTs) and multi-walled carbon nanotubes
(MWCNTs) have drawn much attention in the past several
years. Up to now, a number of approaches for making
DWCNTs have been explored, including coalescence of C 60 inside
SWCNTs at high temperature, catalytic decomposition of
hydrocarbons and arc-discharge of different carbon electrodes
[1–4]. Of the techniques available now, the arc-discharge
is widely used because of its simplicity and
reliability for producing high quality DWCNTs. Hutchison
et al. [4] first reported the synthesis of DWCNTs from graphite
electrodes by arc-discharge. Following Hutchison’s work,
more efforts have been made to optimize the synthesis conditions
of DWCNTs by arc-discharge. For example, Saito et al. [5]
found that several parameters, such as element sulfur in the
graphite anode, hydrogen gas and iron-group metal catalysts,
are indispensable for the selective production of DWCNTs. We
have found that the yields of DWCNTs can be improved
greatly with chloride as catalyst [6]. In addition to graphite,
coal, MWCNTs and carbon black have also been tested for
making DWCNTs [7–9]. In the present work, we report for
the first time the efficient synthesis of high quality DWCNTs
from fullerene waste soot (FWS) which was a main by-product
in the production of fullerenes by arc-discharge or by
flames [10], and can be produced with a capacity more than
tens of tons per year [11].
The procedure for producing DWCNTs from FWS by arcdischarge
is described below. For a typical run, 150 g FWS
(Frontier Carbon Corp.) was soaked in an aqueous solution
of FeCl 2 (200 ml, 1 M) under stirring to make slurry, then an
aqueous solution of NaOH (200 ml, 2 M) was slowly added to
the slurry under continued stirring, which resulted in a mixture.
After filtration and drying, the mixture was further
mixed with coal tar in a weight ratio of 5:2 to get a paste.
The paste was pressed into a stainless steel tube to form
green FWS-derived rods with a diameter of ca. 10 mm. Then,
the green FWS-derived rods were carbonized at 1173 K for
2 h in flowing N 2 , leading to FWS-derived carbon rods that
were used as anodes for making DWCNTs in a modified arcdischarge
setup [7]. The cathode was made of high-purity
graphite rod that remained unchanged before and after the
arcing discharge. The arc-discharge was conducted at a current
of 85–110 A and voltage of 30–40 V in a mixture of Ar
* Corresponding author: Fax: +86 411 8899 3991.
E-mail address: jqiu@dlut.edu.cn (J. Qiu).
0008-6223/$ - see front matter Ó 2009 Published by Elsevier Ltd.
doi:10.1016/j.carbon.2009.01.036

CARBON 48 (2010) 1312– 1320 1313
and H 2 (2:1, v/v) at 300 Torr, and the gap between the electrodes
was kept at ca. 2 mm during the arcing discharge. For
each run, when FWS-derived anode with length of 3–4 cm
was consumed, about 100–150 mg of DWCNTs film-like sticky
deposite on the wire cage can be obtained.
The as-obtained DWCNTs were examined using scanning
electron microscope (SEM, JSM-6301F), transmission electron
microscopy (TEM and HRTEM, Philips Tecnai G 2 20) and Raman
spectroscopy (JY LabRam HR800 at 632.8 nm).
The typical X-ray diffraction (XRD, Rigaku D/MAX 2400, Cu
Ka, 40 kV and 100 mA) profile of FWS-derived anode is shown
in Fig. 1. The catalyst in the anode is Fe nanoparticles with
diameters of ca. 40 nm that is estimated by Scherrer equation.
From SEM image shown in Fig. 2a, lots of long filament-like
material can be found in the as-obtained DWCNTs. These filaments
entangle into nets with some catalyst nanoparticles
Intensity (a.u.)
•
• Fe
•
10 20 30 40 50 60 70 80
2 Theta
Fig. 1 – XRD profile of anode prepared from FWS.
on the surface, as shown in Fig. 2b. Further HRTEM examination
reveals that the filaments are DWCNT bundles, as shown
in Fig. 2c and d, and the formation of bundles is believed to be
due to the van der Waals interaction between individual
nanotubes [8]. On average, the interlayer spacing between
the inner and outer walls of the DWCNTs is ca. 0.4 nm, which
is bigger than the interlayer spacing of MWCNTs and graphite.
This may be due to the large repulsive force of the adjacent
tube walls in DWCNTs [7]. It has been found that
amorphous carbons on the DWCNT bundles (see Fig. 2c and
d) and most catalyst particles (see Fig. 2b) can be easily removed
from the as-synthesized DWCNT samples through a
purification process [6], resulting in high-purity DWCNT bundles,
as evidenced in Fig. 2e.
Raman spectroscopy is a powerful tool that is capable of
yielding more detailed information about DWCNT’s structure
[7]. Fig. 3a shows a typical Raman spectrum of the as-prepared
DWCNTs. For the as-prepared DWCNTs, the intensity
ratio of G-band at 1593 cm 1 and D-band around 1323 cm 1 ,
i.e., I G /I D is over 30, indicating that the DWCNT product contain
little amorphous carbon and have well-developed graphitic
structures.
DWCNT is made of two coaxial SWCNTs. Because of this,
the G-band of DWCNTs would be associated with vibration
along the circumferential direction in the lower frequency
range (G outer
and G inner
), and is also related to vibration along
the direction of the nanotube axis in the higher frequency region
(G + ) [8]. The G-band of the as-made DWCNTs shown in
Fig. 3b can be fitted with Lorentzian peaks at 1594 cm 1 (G + ),
1572 cm 1 (G outer
), and the broad peak around 1540 (G inner
)
which are present due to existence of metallic tubes in the
product, or due to the overlap of peaks of tubes with different
Fig. 2 – (a) SEM image of raw product; (b) Low magnification TEM image of raw product; (c) and (d) HRTEM images of raw
DWCNTs; (e) TEM image of the purified DWCNTs.

1314 CARBON 48 (2010) 1312– 1320
a
1593.1
b
1594
Intensity (a.u.)
1323.2
Intensity (a.u.)
1540
1572
0 500 1000 1500 2000
Raman shift (cm -1 )
1500 1600 1700
Raman shift (cm -1 )
c
e
Intensity (a.u.)
a
d
c
b
f
g
h
i j
50 100 150 200 250
Raman shift (cm -1 )
Fig. 3 – (a) Raman spectrum of raw product synthesized from FWS-derived anode; (b) G-band of Raman spectrum; (c) RBM
band of Raman spectrum.
diameters [12]. The radial breathing modes (RBM) of DWCNTs
can also be seen clearly at low frequency region, as shown in
Fig. 3c. Assuming the influence of van der Waals interactions
Table 1 – Raman shift of RBM, and corresponding diameter
of DWCNTs.
Raman shifts
(cm 1 )
Diameter
(nm)
Raman shifts
(cm 1 )
Diameter
(nm)
a = 89.0 2.88 f = 169.8 1.44
b = 110.9 2.27 g = 188.9 1.28
c = 116.0 2.17 h = 199.1 1.21
d = 127.6 1.96 i = 214.3 1.12
e = 144.2 1.71 j = 220.7 1.08
in DWCNTs is similar to the behavior of SWCNTs within bundles,
the DWCNT diameters can be calculated using a formula
of x r = 238/d 0.93 [12], of which the results are shown in Table 1.
The biggest calculated value of diameter is much smaller
than that observed in HRTEM images due to the very weak Raman
cross-sections induced by the larger nanotubes. The
diameters of DWCNTs directly measured using HRTEM are
shown in Fig. 4, which are the statistical results based on
the measurement of 125 nanotubes. Obviously, the HRTEM
measurement results are in good agreement with the Raman
results.
Up to now, little is known about the formation mechanism
of FWS-based DWCNTs. Nevertheless, besides the very important
role of Fe catalyst [4,5], the formation and growth of
FWS-based DWCNTs must be related to the properties and
30
30
Number
20
10
Number
20
10
0
1 2 3 4 5
Inner diameter (nm)
0
2 3 4 5
Outer diameter (nm)
Fig. 4 – Histograms of DWCNT diameters measured from 125 DWCNTs.

CARBON 48 (2010) 1312– 1320 1315
structure of FWS-derived anodes, which is evidenced by the
fact that no DWCNTs are obtained under identical arcing conditions
when high-purity graphite powder was used instead
of FWS powders. Previous study suggested that FWS may be
seen as icospiral graphitic giant molecules or spheroidal graphitic
microparticles with pentagonal configurations [13–15],
and the structure may remain curly after carbonization
[16,17]. With all of these information in mind, it is easy for
one to envision that some special Cn species formed in the
arcing discharge of FWS-derived carbon rods would act as
the basic building blocks for the construction of DWCNTs
[18]. To confirm and clarify this speculation, more detailed
work would be necessary, in which the effect of composition
and structures of the FWS-anodes needs to be addressed. The
work is now in progress.
In summary, high quality DWCNTs were synthesized by
arc-discharge using FWS as raw material. The present work
provides an alternative way for direct synthesis of high quality
DWCNTs, and opens a new cost-effective approach to utilization
of FWS.
Acknowledgements
The work was supported by the National Natural Science
foundation of China (Nos. 50472082, 20836002, 20725619).
REFERENCES
[1] Bandow S, Takizawa M, Hirahara K, Yudasaka M, Iijima S.
Raman scattering study of double-wall carbon nanotubes
derived from the chains of fullerenes in single-wall carbon
nanotubes. Chem Phys Lett 2001;337(1–3):48–54.
[2] Ren WC, Li F, Chen J, Bai S, Cheng HM. Morphology, diameter
distribution and Raman scattering measurements of double
walled carbon nanotubes synthesized by catalytic
decomposition of methane. Chem Phys Lett 2002;359(3–4):
196–202.
[3] Zhu HW, Xu CL, Wei BQ, Wu DH. A new method for
synthesizing double-walled carbon nanotubes. Carbon
2002;40(11):2023–5.
[4] Hutchison JL, Kiselev NA, Krinichnaya EP, Krestinin AV, Loutfy
RO, Morawsky AP, et al. Double-walled carbon nanotubes
fabricated by a hydrogen arc discharge method. Carbon
2001;39(5):761–70.
[5] Saito Y, Nakahira T, Uemura S. Growth conditions of doublewalled
carbon nanotubes in arc discharge. J Phys Chem B
2003;107(4):931–4.
[6] Qiu HX, Shi ZJ, Guan LH, You LP, Gao M, Zhang SL, et al. Highefficient
synthesis of double-walled carbon nanotubes by arc
discharge method using chloride as a promoter. Carbon
2006;44(3):516–21.
[7] Qiu JS, Wang ZY, Zhao ZB, Wang TH. Synthesis of doublewalled
carbon nanotubes from coal in hydrogen-free
atmosphere. Fuel 2007;86(1–2):282–6.
[8] Li LX, Li F, Liu C, Cheng HM. Synthesis and characterization of
double-walled carbon nanotubes from multi-walled carbon
nanotubes by hydrogen-arc discharge. Carbon
2005;43(3):623–9.
[9] Chen ZG, Li F, Ren WC, Cong HT, Liu C, Lu GQ, et al. Doublewalled
carbon nanotubes synthesized using carbon black as
the dot carbon source. Nanotechnology 2006;17:3100–4.
[10] Howard JB, Mckinnon JT, Makarovsky Y, Lafleur AL, Johnson
ME. Fullerenes C 60 and C 70 in flames. Nature 1991;352:
139–41.
[11] Murayama H, Tomonoh S, Alford JM, Karpuk ME. Fullerene
production in tons and more: from science to industry. In:
Abstracts, 6th Biennial International Workshop Fullerenes
and Atomic Clusters IWFAC’2003, vol. 35. St. Petersburg
(Russia): Ioffe Physico-Technical Institute and St. Petersburg
Nuclear Physics Institute of the Russian Academy of
Sciences; 2003.
[12] Osswald S, Flahaut E, Gogotsi Y. In situ Raman spectroscopy
study of oxidation of double- and single-wall carbon
nanotubes. Chem Mater 2006;18(6):1525–33.
[13] Zhang QL, O’Brien SC, Heath JR, Liu Y, Curl RF, Kroto HW,
et al. Reactivity of large carbon clusters: spheroidal carbon
shells and their possible relevance to the formation and
morphology of soot. J Phys Chem 1986;90(4):525–8.
[14] Kroto HW, Allaf AW, Balm SP. C 60 : buckminsterfullerene.
Chem Rev 1991;91(6):1213–35.
[15] Kroto HW. Fullerene cage clusters. J Chem Soc Faraday Trans
1990;86(13):2465–8.
[16] Harris PJF, Tsang SC, Claridge JB, Green MLH. High-resolution
electron microscopy studies of a microporous carbon
produced by arc-evaporation. J Chem Soc Faraday Trans
1994;90(18):2799–802.
[17] Harris PJF. New perspectives on the structure of graphitic
carbons. Crit Rev Solid State Mater Sci 2005;30:235–53.
[18] Kataura H, Kumazawa Y, Maniwa Y, Ohtsuka Y, Sen R, Suzuki
S, et al. Diameter control of single-walled carbon nanotubes.
Carbon 2000;38(12):1691–7.