Synthesis of multi core-shell nanocomposite of O -multi

Open Science Journal of Modern Physics 2014; 1(5): 37-43

Published online January 20, 2015 (http://www.openscienceonline.com/journal/osjmp)

Synthesis of multi core-shell nanocomposite of MnFe2O4-multi-walled carbon nanotube based polypyrrole and investigation radar absorbing properties

S. Hossein Hosseini1, *

, N. Arjmand2, M. Shirazi Madani

2

1Department of Chemistry, Faculty of Science, Islamshahr Branch, Islamic Azad University, Tehran, Iran

2Department of Chemistry, Faculty of Technical and Engineering, Saveh Branch, Islamic Azad University, Saveh, Iran

Email address

[email protected] (S. H. Hosseini)

To cite this article S. Hossein Hosseini, N. Arjmand, M. Shirazi Madani. Synthesis of Multi Core-Shell Nanocomposite of MnFe2O4-Multi-Walled Carbon

Nanotube Based Polypyrrole and Investigation Radar Absorbing Properties. Open Science Journal of Modern Physics.

Vol. 1, No. 5, 2014, pp. 37-43.

Abstract

The synthesis of multi-walled carbon nanotube of polypyrrole (PPy) composites that functionalized by MnFe2O4

nanoparticles (MWCNTS/MnFe2O4/PPy) were reported. The novel procedure relies on a two-step synthesis method. The

prime step includes synthesis of mono-dispersed MnFe2O4 nanoparticles (NPS) nested on the surface of carboxylated

MWNTS. The second step deals with the newly formed nanocomposite decorated by a PPy layer via in situ polymerization

with multi core-shell structure. SEM and TEM images indicated that the obtained samples have the morphologies of

nanotubes. Further to this the TEM images and selected area electronic diffractions showed that MnFe2O4 NPs and

MWCNT were embedded in PPy. The molecular structure and composition of MWCNTS/MnFe2O4/PPy nanocomposites

were characterized by fourier transform infrared spectra (FTIR) and UV-Vis spectra. The results of XRD confirmed the

formation of MWCNT/MnFe2O4/PPy nanocomposites and hence confirmed ordered structure of NPs. As a multifunctional

material, some physical properties of MWCNT/MnFe2O4/PPy nanocomposites were also investigated. As prepared

conducting ferromagnetic polymer nanocomposites have electrical conductivity of the order of 0.5 S/cm and saturation

magnetization (Ms) value of 0.06 emu/g. Microwave absorbing properties of the nanocomposite were investigated by using

vector network analyzers in the frequency range of 8–16 GHz. The values of the minimum reflection loss were -30 dB in the

frequency of 11.6 GHz for MWCNT/MnFe2O4/PPy core/shell nanocomposite with a thickness of 1.5 mm and 60wt%

MWCNTs/MnFe2O4 as core. These include; electrical conductivity by means of using four probe method and magnetic

property via VSM and AFM techniques.

Keywords

Multi-Walled Carbon Nanotube, MnFe2O4, Polypyrrole, Nanocomposite, Radar Absorbing Materials

1. Introduction

Carbon nanotubes (CNTs) are high aspect ratio allotropes

of carbon. They have unique physical and chemical

characteristics. CNTs walls are not reactive, however, their

fullerene-like tips are known to be rather reactive. In this

view, end functionalization of CNTs is often used to

relatively generate functional groups (e.g., COOH, OH, or

C=O). Like in fullerenes reactivity is activated by curvature

effects. Curvature in nanotubes is much smaller than in

conventional fullerenes. This is owing to the facts that: (a)

the tube diameters are generally larger and, (b) they are

curved in one direction only. Generally nanomaterials enjoy

exceptional properties [1] which make them appropriate for

38 S. Hossein Hosseini et al.: Synthesis of Multi Core-Shell Nanocomposite of MnFe2O4-Multi-Walled Carbon Nanotube Based

Polypyrrole and Investigation Radar Absorbing Properties

many novel applications. Herein, CNTs have very interesting

physicochemical properties such as: ordered structure with

high aspect ratio, Ultra light weight, high mechanical

strength, high electrical conductivity, high thermal

conductivity, metallic or semi-metallic behavior and high

surface area. The combinations of these characteristics make

CNT a unique material with the potential for diverse

applications. A wide range of applications has been

envisaged for CNTs ranging from sensors for the detection of

genetic or other molecular abnormalities, to substrates

cellular growth for tissue regeneration and the use of CNT as

substrates for neuronal growth [2], delivery systems [3] and

radar absorbing materials [4].

Radar absorbing materials can be classified in two broad

categories, either dielectric or magnetic absorbers [5].

Dielectric absorbers depend on the ohmic loss of energy that

can be achieved by loading loss fillers like carbon, graphite,

conducting polymers or metal particles/powder into a

polymeric matrix. Among the dielectric properties can be

cited the dielectric constant and the loss tangent. Magnetic

absorbers depend on the magnetic hysteresis effect, which is

obtained when particles like ferrites are filled into a

polymeric matrix [6,7].

Xu, introduced phenylamine groups (–C6H4–NH2) the

monomers of polyaniline on the surface of MWNTs

(designated as p-MWNTs) by using an effective chemical

route and HCl doped PANI was chemically grafted onto

phenylamine groups containing MWNTs by in situ oxidation

polymerization [8]. Lee and coworkers reported a new

strategy for the synthesis of hybrid nanocomposites

consisting of MWCNTs functionalized with PANI

(MWCNTs-f-PANI) and noble metal (Au and Ag)

nanoparticles. The synthesized hybrid composites possessed

high conductivity [9]. In the other work, Zhang showed that a

microwave hydrothermal strategy has been employed to

functionalize acid-treated CNTs with a thorn like

organometallic, the methyl orange–iron (III) chloride (MO–

FeCl3) complex. This complex could serve as both

morphology guiding agent and oxidant, thereby polypyrrole

nanoparticles could be attached directionally on CNTs by the

polymerization of pyrrole in the absence of extra oxidants

[10]. In the preceding works, we have synthesized some of

conducting and magnetic nanocomposites and investigated

the corresponding applications [11-14].

In this paper, we reported a facile method to prepare

MWCNTs/MnFe2O4 NPs/PPy composite nanotubes in two

steps. The first step deals with the synthesis of nearly mono

dispersed MnFe2O4 NPs on the surface of MWCNTs by in

situ method to achieve fine morphology without MnFe2O4

NPs aggregates even at a high weight ratio of MnFe2O4 NPs.

The second step includes decorating the nanocomposites with

PPy via in situ polymerization with multi core-shell structure.

TEM images showed that the MWCNTs/MnFe2O4 NPs

nanotubes were coated with a thin PPy layer.

2. Experimental

2.1. Materials

Functionalized MWCNT (diameters: 10-20 nm, purity:

95%) used in this work were purchased from neutrino. port.

Co, (China). Other reagents were analytical grade and used

without further purification including FeCl3.6H2O,

MnCl2.2H2O, NaOH and pyrrole (Py) monomer that was

distilled under reduced pressure and stored below 0°C before

use. Dodecylbenzenesulfonic acid (DBSA) was of industrial

grade.

2.2. In Situ Synthesis of MWCNTs/MnFe2O4

Nanotubes

50 mg of functionalized MWCNTS were dissolved in 30

ml aqueous alcohol by ultrasonic irradiation for 30 min. Then

added 150 ml of NaOH aqueous solution and mixture was

sonicated for 30 min. The sample was filtered, washed with

enough distilled water and dried. The obtained powder mixed

with 50 ml (0.5 M) of FeCl3.6H2O and 50 ml (0.25 M)

MnCl2.2H2O and sonicated in an ultrasonic bath for 30 min.

The mixture was stirred vigorously for 1 h using a

mechanical stirrer (2000 rpm). Subsequently 200 ml (1M) of

the NaOH aqueous solution syringed rapidly into reaction

container while continue stirring for 2 h. The whole process

proceeded under N2 atmosphere. The reaction mixture was

then centrifuged, washed with distilled water and dried at

50°C for 24 h.

2.3. Synthesis of MWCNTS/MnFe2O4/PPy

Nanocomposite

300 mg of MWCN/MnFe2O4nanocomposite were

dissolved in 15 ml of NaOH (0.5 M) aqueous solution and

pH value was adjusted to 8-9 by adding distilled water and it

was stirred homogeneously for 30 min. Then 1.62 g

FeCl3.6H2O dissolved in 20 ml of distilled water and added

to the reaction mixture. Subsequently 0.2 ml of the Py

monomer and 0.5 ml DBSA was syringed into reaction

container. The reaction mixture was stirred at room

temperature using magnetic stirrer for 24 h. Finally mixture

was filtered, washed with distilled water and dried at room

temperature.

3. Results and Discussion

This work describes a novel route for preparing novel

MWCNTs/MnFe2O4 and MWCNTs/MnFe2O4/PPy

conducting magnetic core shell nanoparticles (Figures 1 and

2), by pursuing a combination of two step procedure

including; single step co-precipitation method and in-situ

polymerization. Morphology, conductivity, X-ray diffraction

(XRD) characterizations, magnetic and microwave

absorption properties of nanocomposites were investigated in

this communication.

Open Science Journal of Modern Physics 2014; 1(5): 37-43 39

Figure 1. Schematic for route synthesis of MWCNTs/MnFe2O4

Figure 2. Schematic for route synthesis of MWCNTs/MnFe2O4/PPy nanotube

3.1. XRD Patterns of MWCNTs/MnFe2O4

The XRD pattern of the as-prepared MWCNTs/MnFe2O4

is shown in Figure 3. The analysis of the results indicates that

the product is composed of a single phase: cubic MnFe2O4

(JCPDS card no 00-002-0896) and MWCNTs (JCPDS card

no 049-1719). The diffractions 2θ =32.94, 35.50, 45.20,

55.50, 64.21, 66.11° and 2θ =23.18, 38.60

° could be ascribed

to the reflections of MnFe2O4 and MWCNTs, respectively.

The other peaks related to Fe2O3. The XRD peak with a

maximum at 2θ =32.94° may be ascribed to the diffraction

peak of MnFe2O4. The average size of the MnFe2O4

crystalline calculated using the scherrer’s formula is about

38.18 nm.

Figure 3. The XRD pattern of MWCNTs/ MnFe2O4

3.2. Analysis of the Magnetic Properties

MWCNTs/MnFe2O4/PPy

a

b



c

Figure 4. The VSM curve of a) MnFe2O4, b) MWCNTs/MnFe2O4 and c)

MWCNTs/MnFe2O4/PPy

The magnetic properties of the MWCNTs/MnFe2O4/PPy

nanocomposites were investigated by vibrating sample

magnetometer (VSM). Figure 4(a-c) show clear saturation

between -10≤H≤10 kOe, magnetization curves measured at

room temperature for 4a) MnFe2O4, 4b) MWCNTs/MnFe2O4

and 4c) MWCNTs/MnFe2O4/PPy. Figure 4a shows clear

saturation magnetization (Ms) about 60emu/g. The values of

remnant magnetization (Mr) and the coercivity field (Hc) for

MnFe2O4 nanocomposite were reported approximately

18emu/g and 140Oe, respectively. The lack of hysteresis

loops indicates that the super paramagnetic nature of the

MWCNTs/MnFe2O4 NPs is specified by a MS=1.6 emu/g and

Mr is 0.6 emu/g and HC is 65Oe, Figure 4b. This indicates

that the MWCNTs core and MnFe2O4 first shell contact

intimately. Ms, Mr and Hc decreased by increasing MWCNT.

Figure 4c shows clear magnetic properties of

MWCNTs/MnFe2O4/PPy nanocomposite. In this Figure, Ms,

Mr and Hc for the MWCNTs/MnFe2O4/PPy nanocomposite

were measured 0.06, 0.005 emu/g and 200 Oe. The changes

in Ms and the Hc can be attributed to the existence of

MnFe2O4 NPs on the surface of MWCNTs, which can be

resulted in the polar interaction at the interface of two phases.

The magnetization curve of the sample shows weak

ferromagnetic behavior, with slender hysteresis. Magnetic

properties of nanocomposites containing magnetite or ferrite

particles are believed to be highly dependent on the sample

shape, crystallinity, and the value of magnetic particles, so

that they can be adjusted to obtain optimum magnetic

property.

3.3. FTIR Spectra

Figure5(a-c) shows the characteristic peaks of a) MnFe2O4,

b) MWCNTs/MnFe2O4 and c) MWCNTs/MnFe2O4/PPy

nanocomposites. In spectrum (Figure5a), the IR bands at

578.13 and 400 cm-1

were assigned to stretching vibrations of

the Mn-O and Fe-O bonds, respectively. The OH stretching,

carbonyl stretching vibration, C-C-O and Mn-O stretching in

modified MWCNTs/MnFe2O4 were attributed at 3430, 1639,

1124 and 577 cm-1

, respectively. It was showed in Figure 5b.

In this spectrum, the peak at 570.22 cm-1

is attributed to

stretching vibration of the Mn-O bond. It can be seen that one

absorption peak is corresponding to the characteristic peak at

the end of the nanotube’s rings (707 cm

-1) resembling the =C-

H out-of-plane deformation vibration. In Figure 5c shows the

characteristic peaks of MWCNTs/MnFe2O4/PPy

nanocomposites. The strong peaks at 580 and 1037 cm-1

typical signal could be attributed to Mn-O and C-N

vibrational stretching. Peaks at 1161 and 1292 cm-1

are

attributed to the C-H in-plane vibration, whereas peak 668

cm-1

is attributed to the C-H out-plane bend. The peaks at

1541 and 1400 cm-1

are attributed to the characteristic C=C

stretching of the pyrrole ring. The MWCNTs/MnFe2O4/PPy

can be clearly showed the characteristic peaks for Mn,

MWCNTs and PPy. The peaks of vibrational stretching for

C=O, C-H and N-H groups were showed at1653, 2918 and

3428 cm-1

. The =C-H out-of-plane deformation vibration for

the nanotube’s rings shows in 815 cm

-1, too.

a


b

c

Figure 5. FTIR spectra of a) MnFe2O4, b) MWCNTs/MnFe2O4 and c) MWCNTs/MnFe2O4/PPy nanocomposite

3.4. Morphology of MWCNTs/MnFe2O4 and

MWCNTs/MnFe2O4/PPy

The SEM images of resulting MWCNTs,

MWCNTs/MnFe2O4 and MWCNTs/MnFe2O4/PPy are

referred in Figure 6(a-c). A typical nanostructure MWCNTs

that is a spaghetti-like morphology is depicted in Figure 6a.

This figure represents a typical SEM image of pure

MWCNTs with an average diameter of 30-50 nm. Figure 6b

exhibits the surface morphology of the MnFe2O4/MWCNTs

core-shell nanocomposite in which the MWCNTs outer

surfaces are decorated by MnFe2O4. From Figure 6c the

nanofiber size of MWCNTs/MnFe2O4/PPy is determined in

the range 50-700 nm with rod morphology.

a



b

c

Figure 6. SEM images of (a) pure MWCNTs, (b) MWCNTs/MnFe2O4, and (c)

MWCNTs/MnFe2O4

3.5. Conductivity

Electrically conductivity of samples at room temperature

was measured by four probe method. When the PPy was re-

doped by DBSA, the conductivity was improved from 10 to

45 S/cm, suggesting that doping H+ increased conductivity of

PPy. The conductivity of MWCNT was decreased from 88 to

5 S/cm by addition of MnFe2O4. Then electrical

conductivities were increased by addition of PPy as final

shell in nanocomposites. The conductivities of

MWCNTs/MnFe2O4/PPy nanocomposites are 0.5, 0.04 and

0.0034 S/cm for 20, 40 and 60 wt% MWCNTs/MnFe2O4 as

core, respectively.

3.6. Investigation of Radar Absorbing

Properties

Nanocomposites were prepared by in situ polymerization

of PPy with MnFe2O4/MWCNTs as multi core-shell structure.

Then, the mixture was pasted on metal plate with the area of

40mm×40mm as the test plate by dip coating method. The

radar absorbing properties of the nanocomposite with the

coating thickness of 1.5 mm were investigated by using a HP

8720B vector network analyzer and standard horn antennas

in anechoic chamber in the frequency range of 8–16 GHz.

For the confirmation of microwave absorption capability

of MWCNTs/MnFe2O4/PPy nanocomposites, the reflection

loss (RL) was measured in 8–16 GHz, which is revealed in

Figure 7. This Figure shows the microwave absorption

behavior of the MWCNTs/MnFe2O4/PPy nanocomposite in

different weight ratios. For MWCNTs/MnFe2O4/PPy

nanocomposites, the RL values were obtained less than -25

dB in the frequency of 10.8 GHz, -30 dB in the frequency of

11.6 GHz and -20 dB in the frequency of 14 GHz for 20, 40

and 60wt% MWCNTs/MnFe2O4 as core, respectively. The

MWCNTs/MnFe2O4/PPy nanocomposites (weight ratio: 40%)

exhibits good absorption property at 1.5 mm. The minimum

RL value reaches -30 dB at 11.6 GHz. In the other weight

ratios (20 and 60 wt%).

Figure 7. Reflection loss of frequency of MWCNTs/MnFe2O4/PPy

nanocomposites for a) 20, b) 40 and c) 60wt% MWCNTs/MnFe2O4 as core.

4. Conclusions

In summary, we have described a facile chemical approach

to synthesize magnetic and conductive multi core-shell

nanocomposite of MnFe2O4/MWCNTs with PPy.

The conducting MWCNTs/MnFe2O4 nanocomposite can

be fabricated by in situ polymerization of pyrrole. SEM

images confirmed the core-shell nanostructure and the

attachment of MnFe2O4 NPs on the surface of MWCNTs.

FTIR and XRD spectra were used to characterize the

molecular structure of nanocomposite. The magnetization

measurements proved that the samples are conductive and

have a super paramagnetic behavior. The results may be used

for super capacitors and actuators. For

MnFe2O4/MWCNTs/PPy multi core–shell nanocomposite

with the coating thickness of 1.5 mm, the minimum RL

values less than -30 dB were obtained in the frequency of X-

band. The introduction of PPy improved the absorbing

properties, which was due to the dielectric loss of PPy. Such

strong absorption is attributed to better electromagnetic

matching due to the existence of PPy and the special

core/shell structure. Therefore, the prepared composites have

potential applications in EMI shielding.

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Synthesis of multi core-shell nanocomposite of O -multi