Preparation of cyclodextrin-modified multi-walled carbon nanotubes through acylamide bond and its application in capturing b-naphthol from wastewater

Article abstract of DOI:10.14233/ajchem.2013.oh86

Multi-walled carbon nanotubes (MWNTs) were covalently modified with water-soluble b-cyclodextrin (b-CD) through acylamide bond. The products cyclodextrin modified multi-walled carbon nanotubes [MWNTs-CO-NH-(CH ₂)₂-NH-CD] were charact

Full text of DOI:10.14233/ajchem.2013.oh86

Asian Journal of Chemistry; Vol. 25, No. 10 (2013), 5762-5764
http://dx.doi.org/10.14233/ajchem.2013.OH86
Preparation of Cyclodextrin-Modified Multi-Walled Carbon Nanotubes Through
Acylamide Bond and Its Application in Capturing β-Naphthol from Wastewater†
1
3
2,*
1
1
XIAO-JIE SONG , FAN YANG , XIAN-WEN WEI , XIAN-BIAO WANG and CHEN-GUANG SHE
1
2
3
School of Materials and Chemical Engineering, Anhui University of Architecture, Hefei 230601 P.R. China
College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241000, P.R. China
Department of Chemistry, Anhui Medical University, Hefei 230032, P.R. China
*
Corresponding author: E-mail: xwwei@mail.ahnu.edu.cn
AJC-13328
Multi-walled carbon nanotubes (MWNTs) were covalently modified with water-soluble β-cyclodextrin (β-CD) through acylamide bond.
1
The products cyclodextrin modified multi-walled carbon nanotubes [MWNTs-CO-NH-(CH
FT-IR spectroscopy and thermogravimetric analysis. The solubility of MWNTs-CO-NH-(CH
precipitates were observed after 18 months. The fluorescence spectra proved that the MWNTs-CO-NH-(CH
probe can be used in the molecular recognition of β-naphthol (β-NOH) and the effective association constant (Ka) was calculated 1.27×10
from fluorescence spectra. By centrifugated, the β-naphthol could be separated from MWNTs-CO-NH-(CH -NH-CD, collected and
reused circularly. The results showed that the MWNTs-CO-NH-(CH -NH-CD can be used to capture the aromatic pollutant such as
2
)
2
-NH-CD] were characterized by H NMR,
-NH-CD in water was 336.4 mg/L and no
-NH-CD as a spectral
2 2
)
2 2
)
4
2 2
)
2 2
)
β-naphthol from wastewater. This study widened the application of nanosupramolecule materials.
Key Words: Carbon nanotubes, β-Cyclodextrin, Acylamide bond, Molecular recognition, β-Naphthol.
INTRODUCTION
Since the discovery of carbon nanotubes in 1991 , they
have attracted more and more attention in physical, chemical
EXPERIMENTAL
1
Modification of MWNTs with β-cyclodextrin: 2.02 g
MWNTs were added into a mixed solution of 25 mL nitric
acid and 75 mL sulfuric acid. The mixture was ultrasonicated
for 20 min at 50 ºC. The acid-treated MWNTs were collected
by filtration, washed with deionized water for several times
until neutral and dried at 70 ºC overnight.
2,3
and material science fields due to their unique characteristic
such as high electrical conductivity, chemical stability and high
4
mechanical strength and modulus . For practical applications,
the aggregation of pristine carbon nanotubes which greatly
decreases the efficiency of carbon nanotubes usage should be
The MWNTs-COOH and 20 mL thionyl chloride were
mixed in a flask and refluxed for 24 h at 70 ºC with stirring.
The acyl chloride functionalized MWNTs (MWNTs-COCl)
was collected by filtration, washed with anhydrous tetrahy-
drofuran for several times and dried in vacuum oven. The aim
of this process was the introduction of acyl chloride groups
on the surface of MWNTs.
5
,6
overcome . Therefore, the chemical modifications on the
surface of carbon nanotubes with small hydrophilic molecules
open the door for solving the above-mentioned problem and
the different strategies of chemical modification of carbon
7
nanotubes can be further referred in a recent review . Because
of good solubility in water, β-cyclodextrin (ß-CD) was chosen
to be introduced on the surface of multi-walled carbon
nanotubes to enhance the solubility of multi-walled carbon
nanotubes.
β-CDOTs were synthesized in alkalescence solution as
9
reported . H NMR (300 MHz, D O) δ : 3.42-3.82 (8H, m),
1
2
4.49-4.96 (2H, m), 7.43-7.46 (1H, d, J = 8.10 Hz), 7.12- 7.14
(1H, d, J = 7.82 Hz). 2.0 g β-CDOTs, 0.025 g KI and ethylene-
diamine were added into 5 mL NMP in turn. This solution was
stirred at 70 ºC for 8 h in dark. The light yellow solution was
cooled down to room temperature and diluted with ethanol,
In this study, the aim was to modify the multi-walled
carbon nanotubes with β-cyclodextrin through acylamide
8
bond . This compound was tried to be used in capturing
aromatic pollutant in wastewater such as β-naphthol.
†
Presented to the 6th China-Korea International Conference on Multi-functional Materials and Application, 22-24 November 2012, Daejeon, Korea

Vol. 25, No. 10 (2013)
Preparation of Cyclodextrin-Modified Multi-Walled Carbon Nanotubes Through Acylamide Bond 5763
-
1
then resultant precipitate was collected by filtration, washed
successivelywithethanolanddiethyletheranddriedunder vacuum.
In curve a, the broad peak at 3431 cm was assigned
-1
to the -OH stretching vibration, the peak at 1631 cm was
assigned to the C=O stretching vibration. These characteristic
peaks illustrated that carboxyl groups were introduced on
MWNTs.
8
-NH-CD was obtained as reported .
The product NH (CH
2
2
)
2
NH (CH
2
2
)
2
-NH-CD was dissolved into 20 mL DMF. The
MWNTs-COCl was dispersed into this solution with aid of
ultrasonic agitation. The mixture was stirred under Ar atmos-
phere at ambient temperature for 24 h. The β-cyclodextrin
The spectra of β-cyclodextrin and MWNTs-CO-NH-
(CH
rance of peaks at 1703 cm , 1618 cm , 1107 cm in spectrum
of MWNTs-CO-NH-(CH -NH-CD. The peak at 1703 corres-
2 2
) -NH-CD were quite alike, the difference was the appea-
-1
-1
-1
modified MWNTs (MWNTs-CO-NH-(CH
2 2
) -NH-CD) was
collected by filtration, washed with DMF, dried in vaccum at
2 2
)
1
ambient temperature. H NMR (300 MHz, D
1H, m), 1.92 (4H, s), 2.58-2.68 (1H, m), 3.25-3.74 (5H, m),
.44-4.83 (1H, m).
2
O) δ : 0.92-1.21
ponded to the stretching vibration of C=O groups and the subtle
shift was due to the link of amino groups. The peak at 1107 was
assigned to the C-N stretching vibration; the peak at 1618 was
corresponding to the N-H stretching vibration.All these charac-
teristic peaks showed that the β-cyclodextrin was introduced
on the surface of MWNTs through acylamide bond.
(
4
Thermogravimetric analysis: Fig. 2 demonstrated the
thermogravimetric analysis results of β-cyclodextrin and
2 2
MWNTs-CO-NH-(CH ) -NH-CD. The experiment carried out
in nitrogen atmosphere with a heating rate 10 ºC/min. The
weight loss was due to the decomposition of β-cyclodextrin
in curve a. In curve b, the initial weight loss should be evapo-
ration of water, the main weight loss region was from 180 to
Scheme-I: Synthesis of β-cyclodextrin modified MWNTs through acylamide
bond
Preparation of complex of β-naphthol and MWNTs-
3
40 ºC and the weight almost kept constant after 340 ºC. This
was mainly attributed to the decomposition of β-cyclodextrin
in MWNTs-CO-NH-(CH -NH-CD.
-6
CO-NH-(CH
NOH) was prepared. A certain amount of new MWNTs-CO-
NH-(CH -NH-CD was added into it, the mixture was stirred
for 2 h to form the complex for study.
2 2
) -NH-CD: 2 × 10 mol/L solution of β-naphthol
(
2 2
)
2 2
)
100
RESULTS AND DISCUSSION
Fourier transform infrared spectroscopy: In curve b
a
8
0
-1
(
Fig. 1), the broad peak at 3417 cm was assigned to the -OH
-1
stretching vibration, the peak at 2927 cm was assigned to
-CH
60
-
1
b
2
- stretching vibration, the peak at 1645 cm was assigned
-
1
to C=O stretching vibration, the peak at 1160 cm was assigned
4
0
0
0
-1
to C-O-C asymmetric vibration and the peaks at 1027 cm and
-1
1080 cm were corresponding to C-O/C-C stretching vibration.
These peaks were the characteristic adsorption peaks of β-
cyclodextrin and these characteristic peaks all appeared in
2
2 2
spectrum of MWNTs-CO-NH-(CH ) -NH-CD (curve c).
0
100
200
300
400
500
600
700
800
900
o
Temperature ( C)
Fig. 2. TGA curves of (a) recrystallized β-cyclodextrin (b) MWNTs-CO-
NH-(CH -NH-CD
a
1
631
2 2
)
b
3431
Fluorescence spectra: Fig. 3 shows the fluorescence
-
6
spectra of β-naphthol (2 × 10 mol/L) in the presence of
different concentration of MWNTs-CO-NH-(CH -NH-CD
at ambient temperature. The trends of curve showed that with
the increase of concentration of MWNTs-CO-NH-(CH -NH-
1
645
2
926
2 2
)
1160
3
417
2 2
)
c
1080
027
CD, the fluorescence intensity decreased constantly. These
results indicated that the reduction of fluorescence intensity
was due to the introduction of β-naphthol into cyclodextrin
cavities and the formation of inclusion complex between β-
1
1
618
1107
1
703
naphthol and MWNTs-CO-NH-(CH
Effective association constant (K
from the following equation (1). I
2 2
) -NH-CD.
a
) could be calculated
4000
3500
3000
2500
2000
1500
1000
500
0
was the fluorescence
-6
-
1
intensity of single β-NOH (2 × 10 mol/L), I was the fluore-
Wavenumber (cm )
Fig. 1. FT-IR spectra of (a) MWNTs-COOH (b) β-cyclodextrin and (c)
MWNTs-CO-NH-(CH -NH-CD
-6
scence intensity of β-NOH (2 × 10 mol/L) in presence of
different concentration of MWNTs-CO-NH-(CH -NH-CD.
2
)
2
2 2
)

5
764 Song et al.
Asian J. Chem.
1
1
300
200
Conclusion
1
1
1
400
200
000
MWNTs were successfully modified with water-soluble
β-CD through acylamide bond. The synthesis of MWNTs-
4
3
1
100
CO-NH-(CH
2
)
2
-NH-CD was characterized by FTIR spectra,
TGA and H NMR, the solubility of MWNTs-CO-NH-(CH
NH-CD in water was about 336.4 mg/L. The MWNTs-CO-
NH-(CH -NH-CD powder was dispersed in water well and
1
000
2
1
2 2
) -
1
900
8
6
4
2
00
00
00
00
0
8
00
2 2
)
0
.00004 0.00005 0.00006 0.00007 0.00008 0.00009 0.00010
Ligand
no precipitates were observed. This dispersion situation was
last for 18 months. The β-naphthol can be included into
cyclodextrin cavities of MWNTs-CO-NH-(CH ) -NH-CD to
2
2
form inclusion complex. The result was proved by fluorescence
spectra. By centrifugated, the β-naphthol could be separated
2 2
from MWNTs-CO-NH-(CH ) -NH-CD, recovered and used
2
80
300
320
340
360
380
400
420
440
460
circularly easily. This study may widen the application of
water-soluble MWNTs-based nanosupramolecules and capture
the aromatic pollutant such as β-naphthol from wastewater.
(
nm)
Fig. 3. Fluorescence spectra of β-NOH (2 × 10 mol/L) in the presence of
different concentration of MWNTs-CO-NH-(CH -NH-CD. The
excitation wavelength was 235 nm.(From curve 4 to curve 1, the
-6
2 2
)
ACKNOWLEDGEMENTS
-4
2 2
concentration of MWNTs-CO-NH-(CH ) -NH-CD were 1 × 10 , 8
-5
10 , 6 × 10 , 4 × 10 respectively)
-5
-5
×
This work was supported by National Natural Science
Foundation (No. 21071005) and National Natural Science
Foundation for Young Scholars (No. 21001002).
Y = 1-{[(1/K) + x + S-([(1/K)+ x + S]⋅
/2
1
(1)
0
1
[
(1/K)+ x + S]- 4xS)]/(2S)}
REFERENCES
S = [NOH], K = K
a
, x = [MWNTs-CO-NH-(CH
2
)
2
-NH-CD-
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×
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As displayed in Fig. 4, the β-naphthol molecules were
introduced into cavities of cyclodextrin moieties to form
complex. When β-naphthol molecules were included into the
cavities of cyclodextrin moieties, the hydorphibic interaction
were formed between β-naphthol and cyclodextrin. The
molecular recognition of β-naphthol was attributed to
cyclodextrin linked up with MWNTs, which may widen the
application of nanosupramolecule materials and can be used
to capture the aromatic pollutant such as β-naphthol from
wastewater. Then, by centrifugated, the β-naphthol could be
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2 2
separated from MWNTs-CO-NH-(CH ) -NH-CD, recovered
11
and used circularly .
(
a)
(b)
Fig. 4. (a) The interaction of β-naphthol with β-CD; (b) The schematic
interaction of MWNTs-CO-NH-(CH -NH-CD with β-naphthol
2 2
)