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This journal is © The Royal Society of Chemistry [year] [journal], [year], [vol], 00–00 |1

Mechanically robust biocomposite films of chitosan grafted carbon

nanotubes via [2+1] cycloaddition of nitrene

Santosh Kumar Yadav,*ab Sibdas Singha Mahapatra,

c Mukesh Kumar Yadav

d and Pradip Kumar Dutta*

e

Received (in XXX, XXX) XthXXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX

DOI: 10.1039/b000000x 5

Chitosan functionalized multiwalled carbon nanotubes (CS-MWCNTs) are prepared using [2+1]

cycloaddition of nitrenes to the π electron system of carbon nanotube and followed by amidation reaction

with chitosan. Analysis of transmission electron microscopy (TEM) micrographs suggests more than 14

nm grafting on MWCNTs by chitosan, and the covalent linkage of chitosan with MWCNTs is confirmed

from FT-IR, Raman spectra, XPS and energy dispersive X-ray spectroscopy (EDS) elemental mapping. 10

The calculated grafting density by using thermogravimetric analysis was 1.8 chitosan chains per 1000

MWCNT C’s. The effectiveness of the biofunctionalized CS-MWCNTs as a reinforcing filler (3 wt%) in

a chitosan polymer matrix was verified by the dramatic enhancement of the mechanical properties (tensile

strength of the composite is significantly increased to 81.3 MPa from 36.5 MPa of the pure chitosan, the

highest modulus was up to 4.4 GPa for the composite with 3 wt% CS-MWCNTs) with high elongation-at-15

break. The interfacial bonding between CS-MWCNTs in chitosan matrix plays a crucial role in the

enhancement of physical performances of MWCNTs-based composites.

Introduction

The inherent extraordinary physico-chemical, very high electrical 20

conductivity, high flexibility, large aspect ratio, excellent thermal

stability and extremely high mechanical properties have

bequeathed carbon nanotubes (CNTs) a unique role in the area of

material science.1-4 However the potential applications of

multiwall carbon nanotubes (MWCNTs) are gainsaid by 25

following issues: chemical inertness of the graphitic network,

poor dispersion, and interfacial bonding and so on.

A prerequisite for functionalization of MWCNTs is to efficiently

disperse the individual nanotubes and establish a strong chemical

affinity or adherence of the nanotubes (covalent or non-covalent) 30

with the surrounding matrix. In this regards, diverse strategies

designed to functionalize CNTs continuously emerge, such as end

and defect-chemistry, endohedral functionalization, ionic

chemistry, covalent functionalization, and noncovalent

functionalization.5,6 Controlled CNTs functionalization 35

ameliorates their processibility, providing the retention of their

characteristic properties. The serious break of CNTs is inevitable

during the covalent functionalization of CNTs, affecting their

electronic properties.7,8

Researchers are continuing to search for uncomplicated and better 40

inexpensive routes for CNTs functionalization in order to

enhance their dispersibility and processibility.9, 10 The

functionalization of CNTs using cycloaddition reactions plays a

significant role in this area and covers a wide range of addition

reactions such as 1,3-dipolar cycloaddtion, Huisgen [3+2] 45

cycloaddition, [4+2] Diels–Alder reaction, and the [2+1]

cycloaddition reaction, etc. The [2+1] cycloaddition of nitrenes is

a significant addition reaction and is successfully exploited to

functionalize CNTs, fullerene and graphene in very simple

conditions exhibiting its eminent efficiency.11,12-16 It is a novel 50

and controlled approach because it does not cause serious harm to

CNTs as it occurs in acid functionalization and it helps to

introduce various functional groups onto the CNTs surface in

single step CNTs functionalization.17, 18

Chitosan (CS), a naturally occurring linear cationic 55

polysaccharide, has found widespread bio applications in sensors,

medicine, metal chelating agents, water treatment, separation

membranes, food packaging, tissue engineering, drug delivery,

adhesives, and textiles, tissue engineering, and as a

pharmaceutical ingredient, because of its good biocompatibility, 60

biodegradability, low immunogenicity, and antibacterial property.

However, the applications of chitosan may be limited by its poor

mechanical properties and the loss of structural integrity.19-23

Many attempts have been made to improve the mechanical

properties of chitosan by fabrication of nanocomposites with 65

CNTs. Wang et al.24 reported the fabrication of chitosan

MWCNTs composites by a simple solution-evaporation

method. They achieved the 74.3 MPa tensile strength and 2.15

GPa modulus by incorporation of 2 wt% of CNTs. Liu et al.25

also prepared the Poly(styrene sulfonic acid) modified MWCNTs 70

and chitosan composite, suggested that the chemical linkages

between chitosan and CNTs form in the nanocomposites causing

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Fig. 1 Synthesis of carbon nanotubes biofunctionalized with

chitosan by nitrene reaction and a chitosan grafting reaction via

the amide bond formation between the amine group of chitosan

and carboxylic group of chemically functionalized CNTs. 5

more effective stress transfer through the interface, resulted the

dispersion and high mechanical properties with 1.5 wt%

modified MWCNTs. The fracture strength and tensile modulus of

the nanocomposite was increased to 30.4 MPa and 2.8 GPa 10

respectively. Based on these considerations, we have fabricated a

mechanically strong chitosan composite film by introducing

chitosan grafted MWCNTs (CS-MWCNTs) in to pure chitosan

matrix. The CS-MWCNTs was prepared by the chemical

functionalized MWCNTs using nitrene chemistry, and then 15

covalently grafting chitosan to the outer walls of MWCNTs. The

mechanical properties and antimicrobial activity of the composite

film were dramatically improved, because of the strong

interfacial bonds between the homogeneously dispersed chitosan-

functionalized MWCNTs and the chitosan matrix. We expect that 20

this tough, antimicrobially active film will be useful in the food

industry and for biomedical device.

Result and discussion

Functionalization of MWCNTs

In one-step reaction, carboxyl functional group was introduced 25

onto MWCNTs to obtain the f-MWCNTs by simple process as

pristine CNTs and functional azides (4-(2-azidoethoxy)-4-

oxobutanoic acid) in N-methyl-2-pyrrolidone (NMP) at 160 °C

for 24 hours (Fig. 1). This ecofriendly functionalization method

provides an ideal alternative process for biological and composite 30

application, which is more facile and effective compared to more

complicated methods based on acid treatment. The FTIR spectra

for pure MWCNTs and functionalized f-MWCNTs indicated the

[2+1] cycloaddition of nitrene reactions between 4-(2-

azidoethoxy)-4-oxobutanoic acid and MWCNTs was successful. 35

The characteristic carbonyl peak at 1720 cm-1, indicating new

functional group has introduced on the outer walls of MWCNTs

(Fig. 2 (a)).12

In addition, comparing the FTIR spectra for f-MWCNTs and CS-

MWCNTs indicated the amidation reaction between chitosan and 40

the functionalized MWCNTs was completed. The characteristic

secondary amide peak (N–H bending) shifted from 1580 to 1610

cm-1, indicating new amide bonds between the MWCNTs and the

chitosan polymer.26 Further, in order to identify the formation of

covalent bonds between azide containing molecule and the outer 45

Fig. 2 Characterization of modified MWCNTs. (a) FTIR spectra,

and (b) Raman spectra of functionalized MWCNTs by nitrene

chemistry and chitosan decorated MWCNTs. Pure MWCNTs is

shown for comparison. 50

Fig. 3 (a) Wide-scan XPS spectra, and (b) N 1s spectra of the

funactionalized MWCNTs and chitosan decorated MWCNTs.

55

tubes of the MWCNTs, Raman spectra of the pure MWCNTs, f-

MWCNTs, and the chitosan-grafted MWCNTs (CS-MWCNTs)

were recorded ( Fig 2(b)). Raman spectroscopy can detect slight

changes in the structure of carbon nanomaterials, making it a very

valuable and powerful tool for characterizing carbon nanotubes 60

before and after chemical reactions.5

The D-band peak at 1325 cm-1 is attributed to the disordered

graphite structure or sp3-hybridized carbons of the nanotubes, and

the high frequency G-band peak at 1580 cm-1 represent to a

splitting of the E2g stretching mode of graphite, which reflects 65

the structural intensity of the sp2-hybridized carbon atoms. The

relatively increased R value (ID/IG), which is the intensity of the

D band at 1325 cm-1 G divided by the intensity of the G band at

1580 cm-1) of the functionalized carbon nanotubes (Fig. 2(b))

indicates the effective generation of structural defects on the outer 70

walls of the nanotubes.27 Further there was no change in the

defects side on the covalent grafting of the chitosan on the outer

walls of the MWCNTs. XPS clearly supports the

functionalization of organic molecule on the surface of CNTs via

[2+1] cycloaddition reaction. The wide-scan X-ray photoelectron 75

spectra (XPS) of the surface of the pristine MWCNTs shows two

strong peaks at 285.0 eV (C 1s) and 531.6 (O 1s), (Fig. 3 (a)).

However in the case of f-MWCNTs one extra peak was observed

at 400 eV (N 1s) for the nitrogen, indicates that nitogenous

groups were introduced to the MWCNTs via covalent 80

functionalization. 12, 28 The expanded N 1s region of f-MWCNTs

and CS-MWCNTs displayed one peak at 400 eV (Fig. 3(b)). N 1s

binding energies for amides and amines are expected between

399.5 and 400.5 eV,29 and Liao et al.30 assigned the peak at 399.8

eV to amide nitrogen. Thus, both the energy and the 85

comparatively broad peak supported the conversion of a part of

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Fig. 4 TEM images of functionalized MWCNTs (a) and chitosan

decorated MWCNTs (b, c, d). It can be seen that MWCNTs are

evenly wrapped with chitosan chains, providing strong evidence 5

of well functionalized chitosan on the surface of the MWCNTs.

amino groups into amide.31 The fine structure and morphology of

the pristine MWCNTs, f-MWCNTs and chitosan grafted

MWCNTs were further evaluated by TEM measurements. The 10

TEM image of pure MWCNTs and f-MWCNTs shows that the

surface of the sample is relatively smooth, clean, and

distinguishable from that of the chitosan grafted MWCNTs (Fig.

4). In the case of chitosan grafted MWCNTs, it can be seen that

MWCNTs are evenly wrapped with chitosan chains, providing 15

strong evidence of well functionalized chitosan on the surface of

the MWCNTs. Due to the chitosan grafted on the MWCNTs,

overall tube diameter dimensions of CS-MWCNTs are increased

to 30 to 40 nm, while their tube lengths remain almost constant.

The surface of MWCNTs is covered with the chitosan layer 20

homogeneously, which suggests a uniform grafting of chitosan

polymer chains around the surface of carbon nanotubes.32

Beside the TEM measurement, the surface analysis of the

chitosan grafted MWCNTs is also carried out by the scanning

SEM image together with an energy dispersive X-ray 25

spectroscopy (EDS) elemental mapping. The EDS elemental

mapping can be performed to address the element composition

variation in the area of a SEM image (Fig. 5).

In addition, comparing the extent of functionalization was

quantitatively determined by thermogravimetric analysis (Fig. 6). 30

The weight loss of pristine MWCNTs was less than 1.0 wt% at

600 °C, which might arise from decomposition of impurities,

suggesting that the thermal stability as well as the purity of the

nanotubes was high. Interestingly, the mass loss from the f-

MWCNTs sample at 600 °C is used to estimate the amount of 35

functional group that is covalently introduced to the MWCNTs

surface. A mass loss of about 16.0 wt%, due to functional group

decomposition, was observed for f-MWCNTs.

40

Fig. 5 The surface analysis of the chitosan grafted MWCNTs is

carried out by the scanning SEM image together with an energy

dispersive X-ray spectroscopy (EDS) elemental mapping. The

EDS mapping images of dark green (nitrogen) underpin the fact

that chitosan were uniformly grafted onto MWCNTs. 45

Fig. 6 Thermogravimetric analysis of the modified carbon 50

nanotubes. The grafting density of chitosan on the surface of

MWCNTs was evaluated using the TGA spectra.

We have calculated the grafted chain density, by using

thermogravimetric analysis to measure the average mass of 55

grafted polymer per nanotube.33,34

Calculation for CS-MWCNT’s (42% w/w Chitosan) based on 1 g

sample CS- MWCNT’s.35 60

�������� 1�� ������ �0.42��

1�� ������

�1����

5000�� 8.4 � 10��������

���������������

1�� ����� �0.58�������

1�� ������

�1�����������

12.01���������

4.7 � 10���������������

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Fig. 7 (a) Stress-strain curves, and (b) tensile modulus of composite films with different amounts of the biofunctionalized carbon

nanotubes. Approximately 3 and 2 fold increase in the modulus and tensile strength of the composite film were achieved by incorporating 5

3 wt% of CS-MWCNTs.

�� �!"#�$�#�"!% 8.4 � 10��������

4.7 � 10���������������

0.0018����/���

1.8��' "#�(��1000������′�

The calculated grafting density was 1.8 chitosan chains per 1000 10

MWCNT C’s.

Mechanical and antimicrobial properties of biocomposites films

The homogeneity of composites and the stronger interfacial 15

interaction between nanofillers and the polymer matrix should

have a significant effect on the mechanical properties.36, 37 To

examine the effect of the covalent bonding density between

MWCNTs and chitosan on the mechanical properties of

polymers, several chitosan composite films containing different 20

chitosan grafted MWCNTs contents were prepared by a solution

casting method. The typical stress-strain curves are shown in Fig.

7 (a). The Young’s modulus and tensile strength are plotted in

Fig. 7(b) as a function of CS-MWCNTs content. It can be seen

that the addition of CS-MWCNTs significantly improves the 25

tensile properties of chitosan matrix, and the mechanical

properties increase with the increase of CS-MWCNTs loading. It

is clear that the incorporation of CS-MWCNTs show dramatic

reinforcement effects for chitosan matrix because all the

nanocomposites have a higher modulus and greater strength than 30

neat chitosan (Table 1).38

This strengthening effect increases with increasing filler loading.

Interestingly, all the nanocomposites show good stretchability as

evidenced by the elongation at break. The addition of CS-

MWCNTs significantly increases the modulus of the composites 35

as well as ultimate stress and ductility. It is striking to note that,

at the addition of 3 wt% CS-MWCNTs, the tensile strength of the

composite is significantly increased to 81.3 MPa from 36.5 MPa

of the pure chitosan, while the strain at break is also increased to 40

25.2% from 28.8% of the pure chitosan film. Such superior

mechanical properties can certainly be attributed to the strong

interfacial adhesion and good compatibility between the CS-

MWCNTs and the chitosan matrix, resulting in effective load

transfer from the matrix to CS-MWCNTs.39 The dramatic impact 45

of CS-MWCNTs on the modulus of the chitosan is shown in Fig.

7(b) and Table 1. The modulus increases with increasing CS-

MWCNTs loading with a wt% of 3 wt%. The highest modulus

was up to 4.4 GPa for the composite with 3 wt% CS-MWCNTs,

which is higher than that of the pure chitosan (1.4 GPa).38,40 50

It has been demonstrated that chitosan functionalization provides

a large number of functional groups on the outer walls of carbon

nanotubes, which can be very compatible with the pure chitosan

matrix, resulting in higher load transfer efficiency in comparison

with pure MWCNTs. Such a result indicates that the interfacial 55

bonding between carbon nanotubes and the polymeric matrix

plays a crucial role in the load transfer effect of composites.41, 42

In this study, the toxicity of pure chitosan and CS-MWCNTs to

E. Coli was evaluated. Planktonic cell growth experiments with

CS-MWCNTs demonstrated a significant inhibitory effect. 60

The bacterial growth was prevented at a sample concentration of

500 µg/mL (Fig. 8). Furthermore, significantly decreased bacteria

colonies were detected in samples, which contained CS-

MWCNTs and CS-MWCNT-3 composites. The decrease in

optical density demonstrates that the chitosan grafted MWCNTs 65

as well as composites possessed significant antimicrobial activity

against E. Coli (Fig. 8), which was greater than that of pure

chitosan. There are various proposed mechanisms of CNTs

cytotoxicity, including production of and cell interaction with

reactive oxygen species, direct cell surface oxidation, and 70

physical perturbation of the cell wall. Functionalization of CNTs

can alter the physicochemical properties of MWCNTs

significantly enough to change MWCNTs antibacterial properties

in E. Coli. The mode of death is the interaction of the CNTs with

the bacterial cell membranes 75

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Table 1 Mechanical properties of pure chitosan and CS-MWCTs filled chitosan composites, respectively

Sample CS-MWCNTs (wt%) Breaking stress [MPa] Elongation-at-break [%] Modulus [GPa]

Pure chitosan 0 36.5 ± 2.2 25.2 ± 2.3 1.4 ± 0.10

Chitosan/CS-MWCNT-1 1 61.5 ± 3.8 31.4 ± 3.1 2.1 ± 0.12

Chitosan/CS-MWCNT-2 2 71.8 ± 3.7 31.0 ± 2.9 2.8 ± 0.16

Chitosan/CS-MWCNT-3 3 81.3 ± 4.4 28.8 ± 2.6 4.4 ± 0.19

5

Fig. 8 Optical density growth (OD) curves of bacteria during 18 h

for pure chitosan, and CS-MWCNTs. The inset shows the

evaluation of the antibacterial activity of pure chitosan, CS-

MWCNTs and composite (Chitosan/CS-MWCNT-3). 10

causing significant membrane damage. This is thought to be due

to the high solubility of CS-MWCNTs and presence of chitosan

polymer chain on the MWCNTs, which have a greater chance of

contracting with the bacteria.43-45 15

Conclusions

This paper reports the fabrication of high-performance

biopolymer composite of chitosan functionalized CS-MWCNTs

and chitosan by a simple solution casting method. Chitosan 20

functionalized multiwalled carbon nanotubes (CS-MWCNTs) are

prepared using the [2+1] cycloaddition of nitrenes to the π

electron system and amide linkage. The results of FTIR, EDX,

TGA, TEM and Raman spectra indicate that the chitosan chain

have been successfully grafted on the MWCNTs. We calculate 25

the grafted chain density, by using thermogravimetric analysis to

measure the average mass of grafted polymer per nanotube. The

calculated grafting density was 1.8 chitosan chains per 1000

MWCNT C’s. The interfacial bonding between MWCNTs and

matrix plays a crucial role in the enhancement of the mechanical 30

properties of the bio composite film. The breaking stress and

Young’s modulus of the composite film were substantially higher 35

than pure chitosan, and having high elongation-at-break even

though CS-MWCNTs are incorporated. The bio composite film

exhibited higher cytotoxicity against E. Coli than did pure

chitosan. Furthermore, the high mechanical strength, and

antimicrobial properties of bio composite films mean they are 40

promising materials for various applications, such as separation

membranes, food packaging, biosensors, and scaffolds for tissue

engineering.

Experimental section

Starting materials 45

The chitosan powder (95% degree of deacetylation) for the

grafting on f-MWCNTs was obtained from Qingdao Yunzhou

Biochemistry (China), average molecular weight was about

~5000 g/mol. High molecular weight chitosan for the film

preparation (85% deacetylated, Sigma Aldrich, USA) was 50

purified according to a literature procedure.46, 47 MWCNTs used

in this study were purchased from Iljin Nano Tech, Seoul, Korea.

Their diameter and average length were about 10-20 nm and 20

µm, respectively. N-(3-dimethylaminopropyl)-N-ethyl

carbodiimide hydrochloride (EDC·HCl, 99%), 2-(N-55

morpholino)ethanesulfonic acid (MES, 99%), and N-

hydroxysuccinimide (NHS, 97%) were purchased from Sigma

Aldrich and used without further purification.

Biofunctionalization of multiwalled carbon nanotubes by chitosan grafting 60

Chitosan was grafted on the outer walls of the carbon nanotubes

by combination of the [2+1] cycloaddition and amidation

reaction. Firstly, the carboxylic acid group functioanalized

MWCNTs was prepared via the [2+1] cycloaddition reaction and

subsequently, chitosan were grafted via amidation reaction in the 65

presence of EDC and NHS.

The functionalized MWCNTs were prepared via following

protocol. At first, 4-(2-azidoethoxy)-4-oxobutanoic acid was

synthesized according to a literature procedure.12 In a typical

experiment, pristine MWCNTs (200 mg) and N-methyl-2-70

pyrrolidinone (NMP, 100 mL) were placed in a 250 mL two-

necked flask fitted with a condenser and magnetic stirrer bar. The

mixture was treated with an ultrasonic bath for 2 h and then

placed on oil bath. After the mixture was bubbled with nitrogen

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for 15 min, 4-(2-azidoethoxy)-4-oxobutanoic acid (2 g, mol) was

added via syringe. The reaction mixture was then heated and

maintained around 160 °C in a nitrogen atmosphere under

constant stirring for 24 h. After cooling down to room

temperature, the product was purified by precipitation into 5

acetone. The resulting product were redispersed in acetone with

the help of an ultrasonic bath and then separated by

centrifugation. This centrifugation was repeated until the upper

layer was nearly colorless. The separated solid was sequentially

redispersed in water and purified by at least several centrifugation 10

cycles. The sample was dried under vacuum at 60 °C overnight to

obtain the functionalized MWCNTs.

Finally, the MWCNTs was grafted with chitosan by the

amidation of the functionalized MWCNTs with chitosan in the

presence of EDC and NHS. A homogeneous colloidal suspension 15

of chitosan (1 g) and functionalized MWCNTs (0.2 g) in MES

buffer (100 mL, 0.1 M, pH adjusted to 5) was obtained by using

an ultrasonic bath for 1 h. EDC (1.208 g, 6.8 mmol) and NHS

(1.564 g, 13.6 mmol) were added into the flask over 20 min under

argon. The reaction mixture was sonicated for 1 h and stirred for 20

another 16 h at ambient temperature. After the reaction was

complete, the product was filtered over a 0.2 µm nylon

microporous membrane and was washed thoroughly with acetic

acid solution (0.1 M) to remove unreacted chitosan. The product

was redispersed and dialyzed against distilled water for one week 25

at 4 °C. The final product was dried at 60 °C overnight.

Fabrication of biofunctionalized CS-MWCNTs reinforced chitosan film

The biocomposite films were fabricated by adding, 1.0, 2.0, and

3.0 wt% of the biofunctionalized MWCNTs to a pure chitosan 30

polymer matrix (Table 1). Biofunctionalized CS-MWCNTs

solution in water (10 mL) was dispersed ultrasonically for 30 min

at 4oC. Then, chitosan (100 mg) was completely dissolved in 5

mL of aqueous acetic acid solution (1% acetic acid) in a vial at

room temperature for 1 day. The both solutions were combined 35

and stirrer at room 90 oC for 1 h followed by sonication for 1h to

ensure a homogeneous dispersion of CS-MWCNTs in the

chitosan solution. Finally, the solution was transferred to a Petri

dish and left to stand at 60 oC for 2 days. The obtained material

was completely black composite film of 500 nm in thickness. 40

Characterization and measurement

The chitosan grafted MWCNTs were characterized by Fourier

transform infrared spectra (FT-IR 300E, Jasco). X-ray

photoelectron spectroscopy (XPS, ESCSA 2000) was used to

investigate the surface composition of the carbon nanotubes. 45

Raman spectroscopy (LabRam HR Ar-ion laser 514 nm, Jobin-

Yvon) was used to confirm the fictionalization of multiwalled

carbon nanotubes. The mechanical properties of the composite

films were measured at an elongation rate of 5 mm/min at room

temperature using a tensile testing machine (4468, Instron, USA) 50

for a dog-bone type dumbbell specimen. The dimensions of the

specimens were 60 (length) x 10 (width) x 10 (narrow portion

length) x 3 (narrow portion width) x 0.50 (thickness) mm. our

used measurement conditions was: gauge length = 25 mm;

crosshead speed = 10 mm/min; load cell = 2.5 kN. At least three 55

samples were tested and the average of each property

measurement was used.

Determination of antimicrobial activity

The antimicrobial activity of chitosan and CS-MWCNTs was

evaluated by growing the Escherichia coli (E. Coli) with and 60

without compound. The effect of chitosan and CS-MWCNTs on

bacterial growth was detected by measuring the optical density

(OD) at 600 nm. A fresh colony of E. Coli grown overnight on

agar plate was scraped and grown in LuriaBertani (LB) broth for

24 h at 37 oC. After 24 hours the cell suspension was diluted 65

1:100 in fresh LB broth medium and inoculated in tubes

containing chiostan and CS-MWCNTs compound. The

compounds were mixed by vortexing and incubated at 37 oC. The

control sample was without chitosan and CS-MWCNTs

compounds supplement. The growth of bacteria was measured 70

after 4 hours time interval. All the experiments were performed in

triplicate and the average was calculated. The cell suspension

with and without chiostan and CS-MWCNTs was inoculated for

24 hours and spread 10 µl on LB agar plates and incubated at 37 oC for 24 hours. The differences in the bacterial colonies were 75

noted after 24 hours. 3, 43

Notes and references

aCenter for Materials Architecturing, Korea Institute of Science and

Technology (KIST), Seoul 136-791, Korea.; Tel: +65-94276950; E-mail:

santoshkonkuk@gmail.com 80

bPresent Address, School of Chemical and Biomedical Engineering,

Nanyang Technological University, Singapore 637722, Singapore. cDepartment of Chemical Engineering and Chemical Technology,

Imperial College London SW7 2AZ, UK. dDongguk University Medical Center, Dongguk University Ilsan Hospital, 85

Goyang 410-773, Korea. eDepartment of Chemistry, Motilal Nehru National Institute of

Technology, Allahabad 211004, India.; Tel: +91-532-227127; E-mail:

pkd_437@yahoo.com

90

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Table of Contents 5

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Mechanically robust biocomposite films of chitosan grafted MWCNTs prepared using [2+1] cycloaddition of nitrenes,

followed by amidation reaction with chitosan.

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