Short time modification of carboxylated multi-wall nanotubes with amino uracil derivative

Article abstract of DOI:10.13005/ojc/300358

In this study, the chemical functionalization of carboxylated multi-walled carbon nanotubes (MWNT-COOH) by Amino uracil derivative via microwave- assisted amidation method have been investigated.The functionalized MWNTs were characterized by Fourier Transform Infrared spectroscopy (FT-IR), Raman spectroscopy, elemental analysis and scanning electron microscopy (SEM). The major advantage of this procedure is reducing the reaction time to the order of minutes and the amidation was completed in one step as compared to two in the conventional approach. The acid chloride formation step was eliminated here.

Full text of DOI:10.13005/ojc/300358

ISSN: 0970-020 X
CODEN: OJCHEG
2014, Vol. 30, No. (3):
Pg. 1379-1383
ORIENTAL JOURNAL OF CHEMISTRY
An International Open Free Access, Peer Reviewed Research Journal
www.orientjchem.org
Short time Modification of Carboxylated Multi-wall
Nanotubes with Amino Uracil Derivative
SHAHAB ZOMORODBAKHSH1*, BEHROOZ MIRZA2 ,
SHIMAYAZDIZADEH1 and EHSAN TAVAHODI1
1Department of Chemistry, Mahshahr Branch, Islamic Azad University, Mahshahr, Iran.
2Department of Chemistry, South Tehran Branch, Islamic Azad University, Tehran, Iran.
*Corresponding author E-mail: zomorodbakhsh@yahoo.com
http://dx.doi.org/10.13005/ojc/300358
(Received: July 10, 2014; Accepted: August 07, 2014)
ABSTRACT
In this study, the chemical functionalization of carboxylated multi-walled carbon nanotubes
(MWNT-COOH) by Amino uracil derivative via microwave- assisted amidation method have
been investigated.The functionalized MWNTs were characterized by Fourier Transform Infrared
spectroscopy (FT-IR), Raman spectroscopy, elemental analysis and scanning electron microscopy
(SEM).The major advantage of this procedure is reducing the reaction time to the order of minutes
and the amidation was completed in one step as compared to two in the conventional approach.
The acid chloride formation step was eliminated here.
Key words: Functionalization, Multi wall nanotubes, Amino uracil.
INTRODUCTION
attention from chemists and scientists owing to
their electronic, mechanical, optical, and chemical
characteristics 4–7. Biomedical applications for
MWNTs are being investigated actively because of
their useful combination of size and physicochemical
properties 8–10. CNTs are usually functionalized to
generate defects on the sidewalls and can provide
sites for the coordination chemistry.functionalization
via conventional methods require additional days
of reaction time. So, regarding the time consuming
process of carbon nanotube functionalization
via conventional methods, we decided to use
microwave radiation for modification of MWNT-
COOH.Functionalization under microwave radiation
is known to be somewhat different, faster and more
Amino uracil derivatives have been
reported to possess diverse biological activities
such as antibacterial, antihypertensive, antiviral,
antitumor effects and integral backbones of several
calcium channel blockers1 . Moreover, several
alkaloids containing the dihydropyrimidine core
unit have been isolated from marine sources, which
also exhibit interesting biological properties 2. Most
notably among these are the batzelladine alkaloids,
which were found to be potent HIV gp-120-CD4
inhibitors3. Thus, syntheses of these heterocyclic
compounds are of much current importance.
Carbon nanotubes have been attracting increasing

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ZOMORODBAKHSH et al., Orient. J. Chem., Vol. 30(3), 1379-1383 (2014)
11-12
efficient than conventional chemical method
.In this paper, we are mainly concerned with the
microwave- assisted chemical functionalization of
MWNTs containing amine groups by modifying the
RESULTS AND DISCUSSION
Raman spectra offer useful information
MWNTs with derivatives of Amino uracil and by this concerning the slightly structural changes of
functionalization, MWNT solubility increased and MWNTs, especially the changes owing to significant
active sites for further reactions are provided.
sidewall modification. As can be seen in Figure 3,
the characteristic peaks of MWNT tangential modes,
namely the D band at around 1339 cm”1 and the G
band at around 1596 cm”1 slightly changed. The
EXPERIMENTAL
All reagents and solvents were obtained frequencies of products are lower than that of MWNT-
from Merck Chemical Inc and MWCNT–COOH (95% COOH, owing to the conjugated effect of uracil
purity, 20–30 nm; Netvino Co. Ltd) were purchased derivative 14-16. We observed an increase in the ratio
and used as received. The FT-IR spectra were of intensities ID/IG, from 0.68 to 1.15 in MWNT- Uracil
recorded using KBr tablets on a Nexus 870 FT-IR derivative.This indicates an increased disorder of the
spectrometer (Thermo Nicolet, Madison, WI). FT- graphitic structure of the modified nanotubes, which
Raman spectra were recorded on 960 ES, 1064 shows that the nanotubes were covalently modified.
Thermo Nicolet. SEM measurement was carried
out on the XL30 electron microscope (Philips,
Fig.4 shows the FT-IR spectrum of the
Amsterdam, Netherlands) for study the morphology modified MWNTs.In spectrum A, the band at around
of the MWCNTs. Elemental analyses of carbon, 1527 cm-1 corresponds to the stretching mode of the
hydrogen, nitrogen and sulphur were performed C =C double bond that forms the framework of the
using a Series ™™ 2400(Perkin Elmer, Waltham, carbon nano tube Sidewall 17. The peaks at 1704,
MA) .
3304 cm-1 and 1071 cm-1 apparently corresponds to
the stretching modes of the carboxylic acid groups.
In spectrum B The carbonyl peak shift to 1646-1695
Preparation derivatives of Amino uracil
We have found that the microwave assisted cm-1 (as compared with 1704 cm-1 in spectrum A) is
of reaction urea (1 mmol) with cyano acetic acid a result of amid (C =O)NH linkage formation and the
(1 mmol) under solvent-free conditions results peaks at 3304 (OH) is removed.
in rapid formation of the corresponding Amino
uracil (Figure1).The products were easily obtained
Moredirectevidenceforthefunctionalization
by addition of water to the reaction mixture and of MWNTs comes from the SEM images. Figure5
recrystalization of crude products from ethanol.13
indicates that the MWNT–COOH has a smooth
surface.The changes in morphology are remarkable.
6-amino uracil, was obtained in 78% yield, as white It seems that the diameters of MWNT– Amino uracil
powder, m.p>200 °C. IR: 3420, 3345 (N-H), 1660 derivative are slightly increased in comparison with
(C=O), 1619, 1528 (C=C),
MWNT–COOH. The structure in MWNT– Amino
uracil derivative is quite different from those of the
starting MWNT–COOH, in which the tube surface is
Preparation of MWNT- Amino uracil derivative
50 mg of the MWNT-COOH were mixed with relatively smooth and clean, as shown in Figure 5.18
150 mg Amino uracil derivative and then sonicated
in 20 ml of DMF for 30 minutes. Subsequently, the
mixture was loaded into an extraction vessel and
exposed to 300 W microwave irradiation for 30 min
in several step mode.Then the reaction mixture was
allowed to cool down and the mixture was filtered
and washed thoroughly with ethyl alcohol and THF.
Thus, the black solid was vacuum dried at room
temperature for 6 hours.Corresponding chemical
reaction is illustrated by Figure 2.
Table 1: Elemental analysis of A; carboxylated
multi-walled carbon nanotube (MWNT-
COOH) and B; modified multiwalled carbon
nanotube ( MWNT- Amino uracil derivative)
Sample
%C
%H
%N
%S
A
B
96.4
82.5
0.04
0.3
0
2.7
0
0

ZOMORODBAKHSH et al., Orient. J. Chem., Vol. 30(3), 1379-1383 (2014)
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O
O
HN
acetic anhydride
+
COOH
NC
H2N
NH2
NaOH, MW
10 min
O
N
NH2
H
Fig. 1: Microwave assisted Synthesis of Amino uracil
Fig. 2:
Fig. 3:Raman spectroscopy of A; carboxylated multi-walled carbon nanotube
(MWNT-COOH) and B; modified multi-walled carbon nanotube ( MWNT- Amino uracil derivative)

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Fig. 4: Fourier transform spectra of A; carboxylated multi-walled carbon nanotube
(MWNT-COOH) and B; modified multi-walled carbon nanotube ( MWNT- Amino uracil derivative)
Fig. 5: Scanning electron microscopy images of A carboxylated
multiwalled carbon nanotubes and B MWCNT- Amino uracil derivative
Fig. 6:The images of MWNT-COOH and MWNT- Amino
uracil in deionized water (1mg/6ml) after standing for 1 month

ZOMORODBAKHSH et al., Orient. J. Chem., Vol. 30(3), 1379-1383 (2014)
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Elemental analyses of the MWNT-COOH
(A) and MWNT- Amino uracil derivative (B) are
shown in Table 1. Apart from the carbon values,
the atomic percentages of hydrogen, nitrogen and
sulphur of B (as compared with A) indicated that A
is functionalized with Amino uracil derivative.
CONCLUSIONS
Many potential applications of carbon
nanotubes often need them to be prior purified and
functionalized. We have introduced Amino uracil
derivative derivatives onto the surface of nanotubes
under microwave radiation. The functionalized
MWNTs was confirmed by Raman spectroscopy,
FT-IR spectroscopy, elemental analysis and SEM
images. The results show successful functional
groups and by this functionalization, MWNT solubility
increased and active sites for further reactions are
provided.
A dispersion test gives a fair idea whether
the modification on the carbon nanotubes has been
achieved or not. Figure 6 presents a photograph
of two vials containing MWNTCOOH and MWNT-
Amino uracil dispersed in deionized water. As can
be seen from Figure 6, MWNT-COOH are insoluble
in deionized water while the modified CNTs can
be directly dispersedin deionized water (without
sonication) homogeneously and no precipitation was
found even after it was sealed for 1 month at room
temperature.
ACKNOWLEDGEMENTS
We gratefully acknowledge the financial
support from the Research Council of Islamic Azad
University Mahshahr Branch.
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