novel conducting lithium ferrite/chitosan nanocomposite: synthesis, characterization, magnetic and...
TRANSCRIPT
Accepted Manuscript
Novel Conducting Lithium Ferrite/Chitosan Nanocomposite: Synthesis,Characterization, Magnetic and Dielectric Properties
Manish Srivastava, Jay Singh, Rajneesh K. Mishra, Manish K. Singh, Animesh K.Ojha, Madhu Yashpal, Srivastava Sudhanshu
PII: S1567-1739(14)00130-8
DOI: 10.1016/j.cap.2014.04.013
Reference: CAP 3626
To appear in: Current Applied Physics
Received Date: 20 October 2013
Revised Date: 12 March 2014
Accepted Date: 22 April 2014
Please cite this article as: M. Srivastava, J. Singh, R.K. Mishra, M.K. Singh, A.K. Ojha, M. Yashpal, S.Sudhanshu, Novel Conducting Lithium Ferrite/Chitosan Nanocomposite: Synthesis, Characterization,Magnetic and Dielectric Properties, Current Applied Physics (2014), doi: 10.1016/j.cap.2014.04.013.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service toour customers we are providing this early version of the manuscript. The manuscript will undergocopyediting, typesetting, and review of the resulting proof before it is published in its final form. Pleasenote that during the production process errors may be discovered which could affect the content, and alllegal disclaimers that apply to the journal pertain.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
Novel Conducting Lithium Ferrite/Chitosan Nanocomposite: Synthesis, Characterization, Magnetic and Dielectric Properties Manish Srivastava1, 2 *, Jay Singh3, Rajneesh K. Mishra4, Manish K. Singh5, Animesh K. Ojha4,
Madhu Yashpal6, Srivastava Sudhanshu7
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
1
Novel Conducting Lithium Ferrite/Chitosan Nanocomposite:
Synthesis, Characterization, Magnetic and Dielectric Properties
Manish Srivastava1, 2 *, Jay Singh3, Rajneesh K. Mishra4, Manish K. Singh5,
Animesh K. Ojha4, Madhu Yashpal6, Srivastava Sudhanshu7
1Department of Physics, School of Vocational Studies and Applied Sciences, Gautam Buddha
University, Gautam Buddha Nagar, 201308 India.
2 Department of Biotechnology, Delhi Technological University, Shahbad Daulatpur, Main
Bawana Road, Delhi 110042, India.
3Department of Applied Chemistry & Polymer Technology, Delhi Technological University,
Shahbad Daulatpur, Main Bawana Road, Delhi 110042, India
4Department of Physics, Motilal Nehru National Institute of Technology, Allahabad,
Allahabad 211004, India
5Department of Physics, The LNM Institute of Information Technology
Jaipur-302031, India.
6Electron Microscope Facility Department of Anatomy Institute of Medical Sciences,
Banaras Hindu University,Varanasi 221005, India
7Department of Physics and Electronics, Dr. R. M. L. Avadh University, Faizabad (UP)-
224001, India
___________________________________________________________________________ *Corresponding author. Mobile. +91 7503757601, E-mail addresses:
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
2
Abstract A study on Lithium ferrite/chitosan nanocomposite (LFCN), easily moldable into arbitrary
shapes, as the conducting polymer and ferromagnetic characteristics is presented. The
composite material is produced in the presence of Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4
nanoparticle by ex-situ polymerizations process. Various characterizations techniques have
been used to explore the characteristic of the synthesized products. The frequency dependent
dielectric properties and electrical conductivity of all the samples have been measured
through complex impedance plot in the frequency range of 1 kHz -6 MHz at room
temperature. It was observed that in case of (LFCN), fluctuation in value of (ε´) and (ε˝) is
ceased over the frequency range of 4Mz which can be attributed to the steady storage and
dissipation of energy in the nanocomposite system. Moreover, it is also observed that
electrical conductivity of (LFCN) increases with frequency and its value was found to be
(0.032-0.048) (ohm-cm)-1 in frequency range of 1 kHz -6 MHz. Due to its low cost, a simple
synthesis process and high flexibility, the proposed LFCN may find applications in various
types of electronic components.
Key words: Polymer-matrix composites (PMCs), nanocomposites, magnetic properties,
Electrical properties
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
3
1. Introduction
The research on nanomaterials is gaining tremendous attraction to the scientific world
and stirred the spirit of research for the development of new materials for their pioneering
and superior applications in different areas [1]. In spite of extensive innovation, there remains
a need of improvement to match the ever growing demand for multifunctional materials. In
this contest nanocomposites are a versatile class of the materials and they exhibit interesting
and technologically important properties which are not possessed by their individual
components. Nanocomposites are one of the core types of engineering materials. In case of
nanocomposite materials more than one solid phase is present and out of which at least one of
the phases is in the nanometer size range. These phases are immiscible and separated by
interface boundaries [2]. Thus, nanocomposites materials provide a vast field of possibilities
to produce a special class of materials to the researchers. Mechanical [3], magnetic [4],
electric [5], dielectric [6] and other physical properties can be improved by the association of
two or more than two phases.
Polymer based magnetic composite, as a representative of the multifunctional
composites, are also receiving a great attention to the world wide scientists because of their
peculiar structure and properties. These materials have a wide range of applications [7].
Recently, a number of studies on various types of polymer based magnetic nanocomposites
have been reported. In a more recent study, magnetite-chitosan containing carbon paste has
been used as a glucose biosensor [8]. Magnetic-chitosan nanocomposites were investigated
for the hyperthermia application [9]. Hasio-Yen Lee et al. have synthesized core–shell
polyaniline–polystyrene sulfonate@Fe3O4 nanoparticles which can be used as conducting as
well as magnetic nanocomposites [10]. Polymer-magnetic nanocomposites have been used in
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
4
microwave applications [11-13] and LiNi0.8Co0.2O2/PANI composites as the electrode
materials [14].
Thus, the combination of inorganic (ferrites) and organic (polymers) components at
the nano-sized provides potential applications in many fields such as separation processes,
optoelectronics, catalysts, sensors, biotechnology, medical diagnosis, and therapy [15].
Among the various types of ferrites, the high saturation magnetization, square hysteresis
loop, high Curie temperature, high resistivity, and low-cost properties have made lithium
ferrites as the potential candidate for microwave applications such as; circulators, isolators,
phase shifters, etc [16-17].
In addition, chitosan is the alkaline deacetylated product of chitin and it is derived
from chitin by deacetylation. It is a linear polysaccharide consisting of β-(1,4) linked d-
glucosamine residues and N-acetyl-glucosamine groups [15-18]. It has several advantageous
characteristics such as: biocompatibility [19], biodegradability, hydrophilicity, non-toxicity,
and non-antigenicity as well as bioadherence and cell affinity [20-22]. Due to the presence of
both, hydroxyl and amine groups in its structure chitosan can be chemically modified and it
can also be used as novel separation media [23]. Chitosan has been widely used as
antimicrobials, biomedical materials, cosmetics, food packaging, additives, separators,
sewage disposers, agricultural materials [24-29]. The combination of nanoparticles with
chitosan has been found to be a useful biopolymer for the immobilization of biomolecules for
biosensor and food packaging applications and it is due to its excellent film-forming ability,
high permeability, mechanical strength, nontoxicity, low cost and easy availability [21, 27].
Furthermore, several applications of chitosan are based on its ability to coordinate with
metals ions strongly. Since H+ ions are strongly bonded in chitosan structure, it normally
exhibits a low electrical conductivity. If, somehow one can increase the electrical
conductivity of chitosan then it may further be used in some technological based applications
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
5
such as: high energy densities in batteries and fuel cells. It has been observed that chitosan
can also be used as a polymer matrix for ionic conduction and it is because of the fact that
each nitrogen and oxygen atoms in chitosan has a lone pair electron where complexation can
occur and therefore chitosan meets an important requirement for acting as a polymer host for
the solvation of salts [5].
Numerous studies on variety of multifunctional nanomaterials have been
reported. Nevertheless, it still remains a challenge to develop a new, low-cost,
environmentally friendly, simple, and versatile approach for synthesis of special types of
multifunctional nanomaterials. A literature survey shows that till date, though several studies
on the multifunctional nanomaterials have been reported, a very few studies on lithium
ferrite/chitosan [28] based multifunctional nanocomposites have been done. Moreover, most
of the studies on conducting polymers are based on; polyaniline (PANI), polythiophene
(PTh), polyacetylene (PA), polyaniline (PANI), polypyrrole (PPy), polythiophene (PTh),
poly(para-phenylene) (PPP), poly(phenylenevinylene) (PPV), polyfuran(PF), [10, 30-37]
polymers only. In view of above mention facts and different applications of polymer based
nanocomposites it was thought worthwhile to synthesize and study the physical properties of
(LFCN). In this work, as the extension of our previous work we report a study on (LFCN) as
the conducting polymer with ferromagnetic characteristics which can be easily tuned into
arbitrary shapes, and try to explore its possible application as the multifunctional
nanocomposite [38].
Experimental:
2.1 Synthesis of Li0.5Cr0.1Fe2.4O4, Li0.5Co0.1Fe2.4O4 and (LFCN)
Chromium and cobalt doped lithium ferrites nanoparticles having compositional formula
Li 0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4 are synthesized by sol-gel process according to our
earlier study [38]. The (LFCN) are synthesized through following steps: 1g of chitosan
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
6
powders was added into a 100mL of 0.1M acetic acid and the mixture was stirred to form a
1% (W/V) clear solution of chitosan. Then, the above synthesized homogeneous solution was
filtered through a synthetic cloth to remove any un-dissolved materials and degassed by
keeping the solution into vacuum oven for 3h to remove the trapped air bubbles. Further, the
calculated amount of Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4 nanoparticles were dispersed in
(2 ml) of glycolic acid, used as the surfactant with vigorous ultra-sonication to prepare two
different solutions and their after 10 ml clear solution of chitosan is mixed in the above
prepared two solutions (i.e. solution of lithium ferrites nanoparticle with glycolic acid) with
magnetic stirring for 6h. The resulting viscous solutions are dried at 80 ˚C for 6h to obtain the
final product for further characterization. A step wise schematic synthesis process is also
shown in Fig. 1 (i). The LFCN synthesized by using the Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4
nanoparticles are symbolised as Cr-LFCN and Co-LFCN, respectively.
22 Preparation of lithium ferrites/chitosan film
To prepare (LFCN) film the final solution of (lithium ferrites nanoparticels + glycolic
acid + chitosan) are poured into the glass plate in a dust free environment. After that, these
blend films are dried in vacuum for 48 h at 50 ˚C in order to remove any residues of water
and acetic acid. This (LFCN) film is washed with 1% (w/v) NaOH solution to neutralize
acetic acid, and then deionized water to remove any unbound particles. A schematic synthesis
process of (LFCN) film is also shown in Fig. 1 (ii).
2.3 Characterizations
The phase identification of synthesized products is carried out by powder X-ray
diffraction (XRD) XPERT-PRO (PW3050/60), Cu-Kα radiation (λ = 1.54060 Å). Fourier
transforms infrared (FT-IR) spectra of the samples are recorded in the range of 400–4000
cm−1 using Perkin Elmer spectrophotometer. Diffuse reflectance (DRS) measurements of the
synthesized samples are recorded in the range of 300–1100 nm using Hitachi 330 UV-Vis
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
7
spectrometer. The exothermic reaction and the weight loss of LFCN are investigated through
thermo gravimetric analysis/differential thermal analysis (TGA/ DTA) model (PERKIN
ELMER TGA-7). The structural morphology of the synthesized nanoparticles is investigated
with a scanning electron microscope (SEM) FEI Quanta-200 MK2 series and transmission
electron microscope (TEM) technique. Dielectric measurements are also done by making
pellets of fine powder of Li0.5Cr0.1Fe2.4O4, Li 0.5Co0.1Fe2.4O4 and their composites by
introducing a hydraulic pressure of ~15 MPa. Diameter and their thickness were kept 12 mm
and 3 mm, respectively. The flat faces of the prepared pellets are polished and then coated
with a thin layer of silver paste for making good electrical contacts. The ac measurements
(impedance and phase angle) on the pellets were carried out in the frequency range of (1MHz
- 6 MHz) at room temperature by using the Precision Impedance Analyzer (Agilent
Technologies; Model: 4294A). The magnetic properties are measured at room temperature by
means of vibrating sample magnetometer (VSM) (ADE-DMS, model EV-7USA).
2. Results and Discussion: 3.1 XRD
Fig. 2 (i) shows the X-ray diffraction patterns of Cr and Co doped lithium ferrite
samples, respectively. The XRD patterns of both the sample are almost similar and the
diffraction peaks are very intense, which indicates that the synthesized nanoparticles are well
crystalline in nature. All peaks are indexed to the standard patterns reported to file
no: (JCPDS- 49-0266) for cubic Li0.5Fe2.5O4 structure having the space group P4132/(213).
The absence of peak related to any other phases in the XRD patterns verify the formation of
single phase, Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4. It can be seen from the XRD patterns that
main diffraction planes are (210), (220), (311), (400), (511), (440) and (620), where (311)
plane has maximum intensity [39-40]. The cubic lattice parameter for both the samples is
calculated to be nearly 8.33 Å and these values are comparable to the ordered phase of
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
8
lithium ferrite [41]. The average crystallite size is calculated from the XRD line broadening
using the Scherrer relationship:
D = 0.9 λ /β cos θ (1)
where D is the crystallite size in Å, β is the full width at half maximum of the peak and λ is
the wavelength of X-rays [38]. The average crystallite sizes of the samples are calculated to
be ~45 nm. X-ray diffraction patterns of (LFCN) and pure chitosan are shown in Fig. 2 (ii).
The XRD pattern of chitosan exhibits one broad peak at ~ 20˚ thereby indicating
amorphous/long range disorder features of the polymer [18]. It can be observed from XRD
pattern of (Cr-LFCN & Co-LFCN) there is a noticeable decrease in the intensity of the peak
in comparison to pure Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4, which is mainly due to the
introduction of amorphous feature of chitosan polymer in the nanocomposite system.
Additionally, it was observed that the XRD peaks of Cr-LFCN shifted towards smaller angles
compared to that of Co-LFCN. This phenomenon is attributed to slightly bigger crystallite
size in case of Cr-LFCN compared to that of Co-LFCN as calculated through Scherrer
relationship.
3.2 FT-IR
In order to confirm presence of impurities in Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4, the
FT-IR spectra were recorded in the range of 450-4000 cm-1. FT-IR spectra of Li0.5Cr0.1Fe2.4O4
and Li0.5Co0.1Fe2.4O4 are shown in Fig. 2 (iii). The presence of two bands in 400–1000 cm-1
range in both the spectra is attributed to the metal-oxygen bond in the tetrahedral and
octahedral voids [40, 42].
The infrared spectra of pure chitosan and LFCN are shown in Fig. 2(iv). In case of
pure chitosan, a band at ~3422 cm−1 corresponds to O–H stretching overlapping with N–H
stretching vibration. The bands ~2921 and ~2867 cm−1 are assigned to C–H stretching,
whereas; a band at ~2364 cm−1 is attributed to O=C=O asymmetric stretching of
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
9
atmoshpheric CO2. The band at ~ 1653 cm−1 corresponds to the combination of (amide II
band, C–O stretch of acetyl) and the band at ~1592 cm−1 is assigned to the combination of
(amide II and N–H stretch). The band at ~1375 cm−1 is assigned to asymmetric C–H bending
of CH2 group and ~1071 cm−1 (skeletal vibration involving the bridge C–O stretch) of
glucosamine residue [42]. The FT-IR spectra of (LFCN) exhibit band features almost similar
to the FT-IR spectrum of chitosan with a small variation in the intensity of bands. However,
presence of vibrational band ~1750 cm-1 in LFCN may be attributed to presence of C=O
functional group of acetic acid which was used during the synthesis of LFCN.
3.3 TEM/SEM
TEM/SEM micrographs are used to investigate the size and surface morphology of the
synthesized products as shown in Fig. 3(i-iii). Fig. 3 (i, a-c) shows the TEM and HR-TEM
micrographs of Co-doped lithium ferrites nanoparticles. TEM image shows that the particles
are quasi spherical in shape with some agglomeration, which may be due to the presence of
magnetic dipole interaction/sample preparation during the TEM investigation. The average
size of the particles is calculated to be ~65 nm [39].
Fig. 3 (ii, a-b) shows the SEM micrographs of Cr and Co doped lithium ferrites
nanoparticles. It can be seen that Cr doped lithium ferrites nanoparticles show micro size
porous type morphology, whereas; SEM micrograph of Co- doped lithium ferrites
nanoparticles exhibit thin sheet type morphology [39]. SEM micrographs of Cr-LFCN are
shown in Fig. 3 (iii, a-b). It can be seen that lithium-ferrites nanoparticles are encapsulated in
chitosan, moreover the surface of the Cr-LFCN) becomes irregular or coarse because of the
wrapping of chitosan cross-linking networks stacked together, which exhibits micro-grain
and snow white type morphology.
3.4 UV-Vis
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
10
In case of powder samples, diffuse reflectance measurement is a more appropriate
approach for the determination of absorption edge and energies of optical band gap. The DR
spectra of synthesized products are recorded in the spectral range 300-1100 nm and shown in
Fig.4 (i-v). Energy band gap is calculated by plotting the graph between
[hνln{(Rmax-Rmin)/(R-Rmin)}]2 vs. hν and extrapolation of the linear part yields the direct
energy band gap [inset of Fig.4 (i-v)]. The calculated values of energy band gap of the
synthesized products along with pure chitosan are summarized in the Table 1.
The calculations show that Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4 have semiconducting
features, however, the pure chitosan has a large energy band gap of (~4.80 eV). Further, the
(LFCN) also exhibits the semiconducting features by reducing the large energy band gap
compared to pure chitosan sample. It has also been observed that the energy band gap varies
with the variation in lattice parameter and particles size as well. Thus, the variation in energy
band gap for the Cr and Co doped lithium ferrites can be explained on the basis of above facts
[43].
3.5 Magnetic properties
Magnetic properties of Li0.5Cr0.1Fe2.4O4 and Li0.5Co0.1Fe2.4O4 nanoparticles and their
composites were investigated by measuring the hysteresis loop at room temperature using
VSM technique. The obtained hysteresis loops of the nanoparticles and LFCN are shown in
Fig. 5 (i & ii), respectively. The value of magnetic parameters such as: saturation
magnetization (Ms), remnant magnetization (Mr) and coercivity (Hc) obtained from the VSM
measurements are presented in Table 2. It can be seen that the value of Ms for
Li 0.5Cr0.1Fe2.4O4 nanoparticle is lower than that of Li0.5Co0.1Fe2.4O4 nanoparticles because of
the lower magnetic moment of the Cr compared to the Co doped nanocparticle. In addition,
the Ms value of (LFCN) are very low compared to its values for Li0.5Cr0.1Fe2.4O4 and
Li 0.5Co0.1Fe2.4O4 nanoparticles. This is necessary due to the diamagnetic nature of chitosan.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
11
The presences of hysteresis loop in the M-H curve reveal the ferromagnetic feature of the
synthesized product [44]. It was also observed that the ratio of magnetic parameter such as:
Ms, Mr, and Hc [see table 2] in case of lithium ferrites nanoparticle to (LFCN) are nearly
same for Cr-LFCN and Co-LFCN.
The as synthesized (LFCN) are also used to prepare different shape of
nanocomposites. We also observed that it is easy to prepare tunable shapes of
nanocomposites. Fig. 6 shows the different shapes such as: disk, sphere and capsule type
structure of the nanocomposites and their magnetic response was also checked.
3.6 TGA/DTA
As we know that the synthesized nanocomposites are considered to be use for
technological applications, the information about the thermal stability and degradation
mechanisms are particularly important. In order to study the thermal stability of the
synthesized nanocomposites, TGA/DTA analysis was carried out. Fig. 7 (i & ii) shows the
TGA/DTA curves of pure chitosan and Cr-LFCN, respectively in the temperature range
(50 -1200 ˚C). The weight loss in the case of (LFCN) can be observed mainly through three
steps. The first step in the temperature range of (50-230 ◦C) is accompanied with loss of
absorbed water and ammonia. The second step, the higher temperature (230–410 ◦C) is
associated with the decomposition of chitosan. The third step, in the temperature range of
(499–682 ◦C), may be associated with the degradation of organic components. It can be seen
from the TGA curves [Fig. 7 (ii)], the rate of weight loss in the case of pure chitosan is much
faster while the rate of weight loss in case of Cr-LFCN is slower than that of pure chitosan.
On the basis of TGA/DTA analysis, we may say that the interaction between chitosan and
lithium ferrite nanoparticles is quite possible. It is believed that lithium ferrite nanoparticles
act as the obstacle, which restrict the thermal motion of the chitosan polymer chains,
and hamper the easy degradation of chitosan in the nanocomposite system [45-46]. The
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
12
content of Li0.5(Co/Cr)0.1Fe2.4O4 nanoparticle in LFCN calculated from TGA/DTA analysis
was found to be ~ 40 wt%.
3.7 Dielectric Properties
It is well known that the electromagnetic absorption behavior of a material depends on
the dielectric properties which are related to the complex permittivity (ε׳ & ε ״) and
permeability (µ). The complex dielectric constant is represented by the following equation
[47-51]:
ε* = ε’- i ε” (2)
where 22 "'
''
MM
M
+=ε (3)
22 "'
""
MM
M
+=ε (4)
The real part of dielectric constant represented by Equation (3) depict the storage of energy in
the system (amount of polarization occurring in the material) whereas, the imaginary part of
dielectric constant Equation (4) specify the dissipation of energy in the system. The variation
of dielectric constants as a function of frequency for synthesized samples is shown in
Fig. 8 (i & ii). Fig. 8 (i) & (ii) represents the real and imaginary part, respectively. It can be
noticed that the dielectric constant for all the samples presents a relatively high value at low
frequency range and it decreases with increasing frequency. It can be realized; as the
frequency of the applied field increases the dipoles in the system cannot reorient themselves
fast enough to respond to applied electric field which reduces the dielectric constant at higher
frequency whereas at low frequency dipoles in the system can reorient themselves
accordingly. Moreover, it is also observed that the dielectric constant (ε׳) of (LFCN) is
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
13
greatly influenced and was found to be lower than pure that of Cr and Co doped lithium
ferrites nanoparticles. The lower value of (ε׳) in case of (LFCN) can be attributed to the well
conducting grains (lithium ferrites) separated by poor conducting grain boundaries (chitosan),
which results a lower charge holding capacity of the material at higher frequency [49, 51]. In
addition, the presence of insulating chitosan in (LFCN) resulting the formation of more
interface and heterogeneous system, due to which some space charge accumulates at the
interface which may contributes towards the higher microwave absorption properties of the
composites system. It is also conferring that the (ε´) and (ε˝) both depend on the polarizability
of the material, which in turn depend on the dipole density and their orientation in the system.
It can also be seen [Fig. 8 (i & ii)] that in case of (LFCN) fluctuation in value of (ε´) and (ε˝)
is ceased over the frequency range of 4MHz which can be attributed to the steady storage and
dissipation of energy in the (LFCN) system.
Frequency dependent tangent losses for the synthesized products are shown in
Fig. 8 (iii).
tanδ = ε” /ε’ (5)
It is observed that the tangent loss decreases with increase in frequency for all the samples
and becomes almost constant over the frequency (4MHz). Decrease in tangent loss may be
due to the space charge polarization. It can also be seen [Fig. 8(iii)] that tanδ in the case of
Cr and Co doped lithium ferrite exhibit two loss peaks around the frequency 1.5 MHz and 4.3
MHz. This is ascribed as the hopping frequency of metal ions matches with the frequency of
applied field. For designing of super-capacitors to achieve high energy density it is necessary
to choose materials having low tangent loss/dielectric loss at higher frequency [47]. We also
observed a constant value of tangent loss over the frequency range of 4 MHz in all samples.
Tangent loss was also found to be higher in case of Co-LFCN with compare to pure Co-
doped lithium ferrite below the frequency of 4 MHz.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
14
The modulus spectroscopy is a prominent and suitable tool to understand the
phenomenon such as; apparent conductivity and relaxation processes. It provides an insight
into the electrical processes characterized by the smallest capacitance of the material. The
complex electrical modulus (M*) spectroscopy is described by the following relation [47].
"'* iMMM += (6)
where M’ and M” are the real and imaginary part of modulus spectroscopy respectively and
described as [52].
'2' 0ZfCM π= (7)
"2" 0ZfCM π= (8)
where f, Z’, Z”, C0 are the frequency, real, imaginary part of impedance and vacuum
capacitance, respectively. The vacuum capacitance (C0) of the sample holder between the
electrodes having an air gap in place of sample and it is defined by the following relation
[53].
=t
AC 00 ε (9)
Here 0ε is the permittivity of the free space ( cmF /1085.8 14−× ), ‘A’ and ‘t’ are the cross-
sectional area and thickness of the sample, respectively. Fig.9 (i & ii) represents the cole–cole
plot (M’ vs. M”) of Co and Cr doped Li ferrite and their composites with chitosan,
respectively. It can be seen from the graphs that all the curves display a distorted arc
moreover these curves do not form semicircles corresponding to the ideal Debye model [51].
The existences of a suppressed semicircle reflect the absence of intermediate dipolar effect
mode.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
15
Fig. 9 (iii) & (iv) represent the frequency dependence of electrical conductivity of
lithium-ferrite nanoparticles and their composites with chitosan. The AC electrical
conductivity of the material may be represented by the following equation [54].
σac= ωεoε’tanδ (10)
where ω (= 2πf) is the angular frequency.
It is observed that the conductivity of (LFCN) is lower than that of pure lithium ferrite
nanparticles because of insulating nature of the chitosan. The conductivity of the lithium-
ferrites nanparticles increases with frequency [Fig.9 (iii)] and at frequency ~2.25MHz and
~4.72MHz a valley can be also observed where the conductivity of the samples slowly
decreases and then increases. This phenomenon may be associated to the grain boundaries
defects. The AC conductivity in the case of (LFCN) also varies similar to the case of pure
lithium-ferrites nanoparticles. It can be seen from equation (4) the conductivity of the
materials also depend on the dielectric loss. The dielectric loss is decreased by increasing the
frequency [Fig. 8 (iii)] and consequently the conductivity of the material increases. This may
be attributed to the bound charge carriers trapped in the sample or due to a gradual decrease
in series resistance with increasing frequency [55-58]. Moreover, an increase in frequency
may enhance the electron hopping frequency which in turns increases the conductivity of the
material. Thus, the synthesized (LFCN) can be used as conducting polymer nanocomposite.
3. Conclusion
In summary, (LFCN) are synthesized by ex-situ polymerization process and characterized
by several techniques. FT-IR, XRD and TGA analysis confirmed that lithium ferrites
nanoparticles are successfully incorporated into the chitosan polymer matrix. We also,
propose a simple method to prepare (LFCN) nanocomposite film. DR spectroscopic
measurements show that Cr and Co doped lithium ferrites nanoparticle and their composites
are semiconducting in nature with optical energy band gap lies in range of (2.0 - 2.3 eV). The
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
16
synthesized product is found to be ferromagnetic in nature. The thermal stability of the LFCN
is found to improve as compared to stability of pure chitosan. The dielectric measurements
revealed that in case of (LFCN), the fluctuation in value of (ε´) and (ε˝) is ceased over the
frequency range of 4MHz which can be attributed to the steady storage and dissipation of
energy in the nanocomposite systems and thus the LFCN can also be used as the conducting
polymer nanocomposite. Due to its low cost and high flexibility, the proposed LFCN may
find applications in various types of electronic components.
Acknowledgments:
MS is thankful to MNNIT, Allahabad for granting the senior research fellowship.
J.S. acknowledges the Department of Science & Technology, Govt of India for awarding the
DST-INSPIRE Fellowship [IFA-13 CH-105] 2013 and DST Young Scientist award
(CS-393/2012). AKO is thankful to the Alexander von Humboldt Stiftung for the award of a
research fellowship.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
17
References: [1] T. Hanemann, D.V. Szabó, Materials 3 (2010) 3468 - 3517.
[2] J. Stabik, A. Dybowska, J. Pluszyñski, M. Szczepanik, L. Suchoñ, Archives of Materials
science and Engineering. 41 (2010) 13 - 20.
[3] Y. Whulanza, E. Battini, L. Vannozzi, M. Vomero, A. Ahluwalia, G. Vozzi, J. Nanosci.
Nanotechnol. 13 (2013) 188 – 197.
[4] I. Ali, A. Shakoor, M. U. Islam, M. Saeed, M. N. Ashiq, M.S. Awan, Curr Appl Phys. 13
(2013) 1090 – 1095.
[5] M. A. Rehim, A. Youssef, E. Hassan, N. Khatab, G. Turky, Synth. Met. 160 (2010)
1774–1779.
[6] H. Yang, Y. Lin, J. Zhu, F. Wang, Curr Appl Phys. 10 (2010) 1148-1151.
[7] L. Kong, X. Lu, E. Jin, S. Jiang, X. Bian, W. Zhang, C. Wang. J. Solid State Chem.182
(2009) 2081-2087.
[8] A. L. Kavitha, H. Gurumallesh Prabu, S. Ananda Babu, and S. K. Suja,
J. Nanosci. Nanotechnol. 13, (2013) 98-104.
[9] L. Luo, Q. Li, Y. Xu, Y. Ding, X. Wang, D. Deng, Y. Xu, Sensors and Actuators B, 145
(2010) 293-298.
[10] J. H. Parka, K. H. Ima, S. H. Leea, D. H. Kima, D. Y. Leea, Y. K. Leea, K. M. Kim, K.
N. Kim, J. Magn. Magn. Mater. 293 (2005) 328 - 333.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
18
[11] H. Y. Lee, S. P. Rwei, L. Wang, P. H. Chen, Mater. Chem. Phys. 112 (2008) 805 – 809.
[12] T. H. Hsieh, K. S. Ho, X. Bi, C. H. Huang, Y. Z. Wang, Y. K. Han, Z. L. Chen, C. H.
Hsu, P. H. Li, Y. C. Changd, Synth. Met. 160 (2010) 1609- 1616.
[13] P. Martins, C. M. Costa, M. Benelmekki, M. S. Lanceros, J. Nanosci. Nanotechnol. 12
(2012) 6845 – 6849.
[14] Y. Mosqueda, E. P. Cappe, J. Arana, E. Longo, A. Ries, M. Cilense, P. A. P. Nascente, J.
Solid State Chem 179 (2006) 308 – 314.
[15] Z. Jia, W. Yujun, L. Yangcheng, M. Jingyu, L. Guangsheng, React. Funct. Polym. 66
(2006) 1552 – 1558.
[16] Y. P. Fu, Y. D. Yao, C. S. Hsu, J. Alloys Compd. 421 (2006) 136 - 140.
[17] V. Verma, R. K. Kotnala, V. Pandey, P. C. Kothari, L. Radhapiyari, B. S. Matheru, J.
Alloys Compd. 466 (2008) 404 – 407.
[18] J. Singh, P. K. Dutta, Int. J. Biological Macromolec. 45 (2009) 384 – 392.
[19] G. Molinaro, J. C. Leroux, J. Damas, A. Adam, Biomaterials 23 (2002) 2717 – 2722.
[20] H. Gong, Y. Zhong, J. Li, Y. Gong, N. Zhao, X. Zhang, J. Biom. Mater. Res. 52 (2000)
285 - 295.
[21] J. Singh, P. Kalita, M. K. Singh, B. D. Malhotra, Appl. Phy. Lett. 98, (2011) 123702-
123704.
[22] P. K. Dutta, M. N. V. Ravikumar, J. Dutta, J.M.S. Polym. Rev. C 42, (2002) 307 – 354.
[23] J. E. Santos, E. R. Dockal, E. T. G. Cavalheiro, Carbohydr. Polym. 60, (2005) 277 – 282.
[24] H. K. No, S. P. Meyers, W. Prinyawiwatkul, Z. Xu, J. Food Sci. 72 (2007) 87 – 100.
[25] D. Brito, S. P. C. Filho, Polym. Degrad. Stab. 84 (2004) 353 – 361.
[26] P. K. Dutta, S. Tripathi, G. K. Mehrotra, Dutta J, Food Chem. 114 (2009) 1173 – 1182.
[27] J. Singh, M. Srivastava, J. Dutta, P. K. Dutta, Int. J. Biol Macromol 48 (2011) 170 – 176.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
19
[28] K. Hayashi, W. Sakamoto, T. Yogo, J. Mater. Res., 22 (2007) 974 - 981.
[29] R. Qin, F. Li, W. Jiang. M. Chen, Mater. Chem. Phys. 122 (2010) 498 - 501.
[30] D. Yuping, W. Guangli, L. Xiaogang, J. Zhijiang, L. Shunhua, L. Weiping, Solid State
Sci. 12 (2010) 1374 - 1381.
[31] X. Lu, W. Zhang, C. Wang, T. C. Wen, Y. Wei, Prog. Polym. Sci. 36 (2011) 671 - 712.
[32] T. H. Ting, R. P. Yu, Y. N. Jau, Mater. Chem. Phys. 126 (2011) 364 - 368.
[33] P. B. Bhargav, V. M. Mohan, A.K. Sharma, V. V. R. N. Rao, Curr Appl Phys. 9 (2009)
165-171.
[34] A. Uygun, O. Turkoglu, S. Sen, E. Ersoy, A. G. Yavuz, G. G. Batir, Curr Appl Phys. 9
(2009) 866-871.
[35] R. Patil, A. S. Roy, K. R. Anilkumar, K. M. Jadhav, S. Ekhelikar, Compos Part B: Eng
43 (2012) 3406 – 3411.
[36] G. G. kumar, A. R. Kim, K. S. Nahm, D. J. Yoo, Curr Appl Phys. 11 (2011) 896-902.
[37] V. Balan, M. I. Popa, L. Verestiuc, A.P. Chiriac, I. Neamtu, L.E. Nita, M.T. Nistor,
Compos Part B: Eng, 43 (2012) 926 - 932.
[38] M. Srivastava, A. K. Ojha, S. Chaubey, P. K. Sharma, A. C. Pandey, Mater Sci Eng B
175 (2010) 14 – 21.
[39] M. Srivastava, N. Vyas, A K. Ojha, Vib Spectros. 56 (2011) 19 – 25.
[40] C. Sun, K. Sun, Solid State Commun, 141 (2007) 258 – 261.
[41] Y. P. Fu, S. B. Wen, C. C. Yen, Cerm Int. 35 (2009) 943 – 947.
[42] S. A. Mazen, S. F. Mansour, E. Dhahri, H. M. Zaki, T. A. Elmosalami, J. Alloys Compd.
470 (2009) 294 – 300.
[43] M. Naeem, S. K. Hasanain, A. Mumtaz, J. Phys.: Condens. Matter. 20 (2008) 025210.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
20
[44] M. Srivastava, S. Layek, J. Singh, A. K. Das, H. C. Verma, A. K. Ojha, N. H. Kim, J. H.
Lee, J. Alloys Compd. 591 (2014) 174-180.
[45] R. M. Khafagy, J. Alloys Compd. 509 (2011) 9849 – 9857.
[46] X. Ding, D. Han, Z. Wang, X. Xu, L. Niu, Q. Zhang, J Colloid. Interf. Sci. 320 (2008)
341- 345.
[47] G. Sui, B. Li, G. Bratzel, L. Baker, W. H. Zhong, X. P. Yang, Soft Matter 5 (2009) 3593
– 3598.
[48] S. M. Abbas, M. Chandra, A. Verma, R. Chatterjee, T. C. Goel, Composites: Part A 37
(2006) 2148 – 2154.
[49] L. A. Ramajo, A. A. Cristóbal, P. M. Botta, J. M. P. López, M. M. Reboredo, M. S.
Castro, Composites: Part A 40 (2009) 388 - 393.
[50] C. R. Indulal, R. Raveendran, Indian J. Pure & Appl. Phys 48 (2010) 121 - 126.
[51] L. Ai, J. Jiang, L. Li, J Mater Sci: Mater Electron 21 (2010) 206 - 210.
[52] N. Frickel, M. Gottlieb, A M. Schmidt, Polymer 52 (2011) 1781 – 1787.
[53] K. L. Gordon, J. H. Kang, C. Park, P. T. Lillehei, J. S. Harrison, J Appl Polym Sci 125
(2012) 2977 – 2985.
[54] A. B. Selcuk, S. B. Ocak, O. F. Yuksel, Nucl. Instr. Meth. Phys. Res. A 594 (2008) 395
– 399.
[55] H. M. Chenari, M. M. Golzan, H. Sedghi, A. Hassanzadeh, M. Talebian, Current Appl.
Phys. 11 (2011) 1071 - 1076.
[56] A. Tataroglu, S. Altındal, M. M. Bulbul, Microelectron Eng. 81 (2005) 140 – 149.
[57] I. M. Afandiyeva, I. Dokme, S. Altındal, M. M. Bulbul, A. Tataroglu, Microelectron
Eng. 85 (2008) 247 – 252.
[58] M. Srivastava, J. Singh, M. Yashpal, Animesh K. Ojha, J. Nanosci. Nanotechnol 12
(2012) 6248-6257.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
21
[59] A.A.A. Darwish, E.F.M. El-Zaidia, M.M. El-Nahass, T.A. Hanafy, A.A. Al-Zubaidi, J.
Alloys Compd., 589, (2014) 393-398.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
1
Figure and Table captions
Table 1 Optical energy band gap of the samples.
Table 2 Magnetic properties of the samples
Fig. 1 Schematic diagram represents a synthesis method of the lithium ferrites
nanoparticles and LFCN.
Fig. 2 XRD pattern of (i) Cr, Co doped lithium ferrites nanoparticles and Li0.5Fe2.5O4
(JCPDS-490266) (ii) Cr-LFCN & Co-LFCN (iii) FT-IR spectra of Cr and Co doped
lithium ferrites nanoparticles (iv) chitosan, Cr-LFCN and Co-LFCN.
Fig. 3 TEM micrograph of (i, a) Co doped lithium ferrites nanoparticles and (i, b-c)
HR-TEM micrograph (ii, a) SEM micrograph of Cr doped (ii, b) SEM
micrograph of Co doped lithium ferrites nanoparticles (iv, a-b) SEM micrograph
of Cr-LFCN.
Fig. 4 DR UV-Vis absorption spectra of (i) Cr doped lithium ferrites nanoparticles
(ii) Co doped lithium ferrites nanoparticles (iii) pure chitosan (iv) Cr-LFCN
(v) Co-LFCN, [inset show Tauch plot].
Fig. 5 M-H curve of (i) Cr and Co doped lithium ferrites nanoparticles (ii) Cr-LFCN and
Co-LFCN.
Fig. 6 Photographs of (i) Cr and Co doped lithium ferrites nanoparticles samples
(ii) Cr-LFCN (iii) Co-LFCN (iv) LFCN prepared in different shapes
(v-vii) magnetic response of different shapes of nanocomposites.
Fig. 7 TGA/DTA curve of (i) chitosan (ii) Cr-LFCN.
Fig. 8 Graph (i) real part of dielectric constant vs frequency (ii) imaginary part of
dielectric constant vs frequency (iii) Tangent loss vs frequency for synthesized
products.
Fig. 9 Graph (i) M’ vs M” for Cr and Co doped lithium ferrites nanoparticles (ii) M’ vs
M” for Cr-LFCN and Co-LFCN (iii) Ac conductivity vs frequency for Cr and Co
doped lithium ferrites nanoparticles (iv) Ac conductivity vs frequency for
Cr-LFCN and Co-LFCN.
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
2
12
3
45 6
7
8
91 1
0
2
3
45 6
7
8
911
O
O C H
3
O O
O
O H
O H
H
H H
H H
H H
H H
O H
O H
N H
N H 2
0.8 0.2
0.01M
OH---CH2---COOH
70%
25%
1:2.5
aq. ammonia solution
viscous gel
magnetic stirrer
calcination
NH3+
NH3+
NH3+
NH3+
NH3+
NH3+
1
2
3
45 6
7
8
9
1 10
2
3
45 6
7
8
91 1
magnetic stirrer
1% (w/v) chitosan solution
OH-CH2-COOH (2ml)2.5g nanoparticles
stirrer 6h
ChitosanGlycolic acid
Nanoparticles
Nanocomposite
Chitosan
Surfactant
+OH-CH2-COO
--
glycolic acid
(Li0.5Co0.1Fe2.4O4)(Li0.5Cr0.1Fe2.4O4)
Heat 70-80 oC
Drying at 80 oC for 6h
700 oC for 8h
12
3
45 6
7
8
91 1
0
2
3
45 6
7
8
911
O
O C H
3
O O
O
O H
O H
H
H H
H H
H H
H H
O H
O H
N H
N H 2
0.8 0.2
0.01M
OH---CH2---COOH
70%
25%
1:2.5
aq. ammonia solution
viscous gel
magnetic stirrer
calcination
NH3+
NH3+
NH3+
NH3+
NH3+
NH3+
1
2
3
45 6
7
8
9
1 10
2
3
45 6
7
8
91 1
magnetic stirrer
1% (w/v) chitosan solution
OH-CH2-COOH (2ml)2.5g nanoparticles
stirrer 6h
ChitosanGlycolic acid
Nanoparticles
Nanocomposite
Chitosan
Surfactant
+OH-CH2-COO
--
glycolic acid
(Li0.5Co0.1Fe2.4O4)(Li0.5Cr0.1Fe2.4O4)
Heat 70-80 oC
Drying at 80 oC for 6h
700 oC for 8h
Solvent evaporation
Film casting
Glass plate
1% chitosan solution30mg lithium ferrite
nanoparticles
Vacuum drying at 50 0C
Peel out
Solvent evaporation
Film casting
Glass plate
1% chitosan solution30mg lithium ferrite
nanoparticles
Vacuum drying at 50 0C
Peel out
Solvent evaporation
Film casting
Glass plate
1% chitosan solution30mg lithium ferrite
nanoparticles
Vacuum drying at 50 0C
Peel out
Srivastava et al.
Fig.1
(i)
(ii)
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
3
Srivastava et al. Fig.2
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
4
Srivastava et al. Fig.3
(i) c b a
5 µm 5 µm
5 µm 2 µm
(ii) a b
b a (iii)
(i) c b a
5 µm 5 µm
5 µm 2 µm
(ii) a b
b a (iii)
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
5
Srivastava et al. Fig.4
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
6
Srivastava et al. Fig.5
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
7
Srivastava et al. Fig.6
(i) (ii) (iii)
(iv)
(v) (iv) (iv)
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
8
Srivastava et al. Fig.7
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
9
Srivastava et al. Fig. 8
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
10
Srivastava et al. Fig.9
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
11
Table 1
Sample Code Optical band gap (eV)
Li0.5Cr0.1Fe2.4O4 (A)
2.18
Li0.5Co0.1Fe2.4O4 (B)
2.21
Chitosan (X) 4.81
Cr-LFCN (C)
2.55
Co-LFCN (D) 2.49
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
12
Table 2
Sample (code) Ms (emu/gm)
Ratio of Ms in case of pure
lithium ferrites nanoparticle to
LFCN
Mr (emu/gm)
Ratio of Mr in case of pure
lithium ferrites nanoparticle to
LFCN
Hc (Oe)
Ratio of Hc in case of pure
lithium ferrites nanoparticle to
LFCN
Li0.5Cr0.1Fe2.4O4
(A)
31.90 A/B
11.86
7.7 A/B
12.78
90.5 A/B
1.07 Cr-LFCN (B)
2.688
0.6022
84.32
Li0.5Co0.1Fe2.4O4 (C)
47.2
C/D
11.83
18.8 C/D
12.52
265 C/D
0.97
Co-LFCN
(D)
3.989 1.502
265.90
MANUSCRIP
T
ACCEPTED
ACCEPTED MANUSCRIPT
Highlight
� Novel conducting lithium ferrite/chitosan nanocomposites (LFCN) have been
synthesized.
� Nanocomposites are easily moldable into arbitrary shapes.
� Synthesized nanocomposite exhibits the characteristics of conducting polymer and
ferromagnetism.
� Due to low cost and high flexibility, the proposed LFCN may find applications in various
types of electronic components.