Journal of Materials Science and Chemical Engineering, 2014, 2, 31-37
Published Online January 2014 (http://www.scirp.org/journal/msce)
http://dx.doi.org/10.4236/msce.2014.21006
OPEN ACCESS MSCE
Carbon Nanofibers Containing Ag/TiO2 Composites as a
Preliminary Stage for CDI Technology
Khalil Abdelrazek Khalil1,2*, Hamoud Eltaleb3, Hany S. Abdo1,2, Salem S. Al-Deyab3, H. Fouad4
1Mechanical Engineering Department, College of Engineering King Saud University, Riyadh, Saudi Arabia
2Mechanical Design and Materials Department, Faculty of Energy Engineering, Aswan University, Aswan, Egypt
3Department of chemistry, Petrochemical research chair, King Saud University, Riyadh, Riyadh, Saudi Arabia
4Biomedical Engineering Dept., Faculty of Engineering, Helwan University, Ain Helwan, Egypt
Received November 2013
ABSTRACT
Silver/titanium dioxide composite nanoparticles imbedded in polyacrylonitrile (PAN) nanofibers and converted
into carbon nanofibers by stabilization and calcination was obtained and tested for capacitive deionization tech-
nology. First, the silver ions were converted to metallic silver nanoparticles, through reduction of silver nitrate
with dilute solution of PAN. Second, the TiO2 precursor (Titanium Isopropoxide) was added to the solution to
form Ag/TiO2 composites imbedded in the PAN polymer solution. Last step involves electrospinning of viscous
PAN solution containing silver/TiO2 nanoparticles, thus obtaining PAN nanofibers containing silver/TiO2
nanoparticles. Scanning electron microscopy (SEM) revealed that the diameter of the nanofibers ranged between
50 and 300 nm. Transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) showed sil-
ver/TiO2 nanoparticles dispersed on the surface of the carbon nanofibers. The obtained fiber was fully charac-
terized by measuring and comparing the FTIR spectra and thermogravimetric analysis (TGA) diagrams of PAN
nanofiber with and without imbedded nanoparticles, in order to show the effect of silver/TiO2 nanoparticles on
the electrospun fiber properties.
KEYWORDS
Polyacrylonitrile (PAN) Nanofibers; Carbon Nanofibers; Electrospinning; Silver/TiO2 Nanoparticles
1. Introduction
Polyacrylonitrile (PAN) and preferably its copolymers
are the most common precursors for the production of
carbon nanofibers as well as activated carbon nanofibers
and fabrics. They are established as the primary precur-
sor used in commercial carbon fiber production. The
production of Polyacrylonitrile based carbon nanofibers
has grown significantly [1].
Adding metal nanoparticles to polymer nanofiber ma-
trix (metal-polymer nanocomposites) has attracted a
great attention due to synergic combinations of the
unique optical, electrical, and catalytic properties of
metal nanoparticles and excellent specific surface area of
polymer nanofibers [2-9]. The incorporation of Ag
and/or TiO2 nanoparticles into polyacrylonitrile (PAN)
fibers exhibits excellent catalytic activity, surface-en-
hanced Raman scattering activity, electrical conductivity,
and antimicrobial activity [3,6,7]. D. Lee et al. [10] re-
ported that Silver (Ag) nanoparticles were prepared in
polyacrylonitrile nanofibrous film by a sol-gel derived
electrospinning and subsequent chemical reduction for
30 min in hydrazine hydroxide (N2H5OH) aqueous solut-
ion. The Ag/PAN nanocomposite film was characterized
by XRD, TEM and UV absorption spectrophotometer. N.
Pimpha et al. [11] reported that Titanium dioxide nano-
fibers were fabricated by electrospinning technique. The
titania solutions were obtained from adding various types
of Ti precursor (Ti (OBu)4, Ti (OiPr)4, and Ti(OPr)4 to an
ethanol solution containing polyvinyl pyrrolidone (PVP).
A photocatalytic activity testing shows that the electros-
pun nanofibers had stronger efficiency to remove NOx. J.
Bai et al. [12] reported a novel composite nanofibers
consisting of Ag nanoparticles and polyacrylonitrile
(PAN) were fabricated successfully and we treated at low
temperatures. T. Amna et al. [13] reported a biological
evaluation of antimicrobial activity using Zn-doped tita-
nia nanofibers, which prepared by the electrospinning of
a sol-gel. The bacterial cells following the treatment with
*Corresponding author.

K. A. KHALIL ET AL.
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32
nanofibers solutions. M. A. Kanjwal et al. [14] investi-
gated the influence of the silver content and the mor-
phology of nanofibers on the photocatalytic activity of
silver-grafted titanium dioxide. Titanium dioxide con-
taining different weight percentages of silver was pre-
pared in nanofibrous and nanoparticulate forms. Sil-
ver-grafted titanium dioxide nanofibers were synthesized
by the electro spinning process. The prepared nanostruc-
tures were utilized as a photocatalyst to degrade two dyes.
The obtained results endorse the use of this composite in
a nanofibrous form. Y. Li et al. reported a Ag-TiO2 na no-
particles were prepared by a miniemulsion method using
Ti (O B un) 4 and Ag(NO3) as starting materials. The results
show that Ag doping showed a controlling effect on the
transformation of titania from anatase to rutile. The spe-
cific surface area increased with the Ag-doped amount to
reach a maximum (86.3 m2·g−1) at Ag/Ti molar ratio of
0.8% and then decreased with further increase of the
Ag-doped amount. The applications of nanoparticulate in
waste water treatment, for example; Ag (I) and silver
compounds have been used as antimicrobial compounds
for coliform found in waste water. Nanoscale silver par-
ticles are typically 1 - 40 nanometers (nm) with an aver-
age particle size of 2 - 10 micron range with a specific
surface area of approximately 1 m2·g−1. Applications for
silver nanocrystals include as an anti-microbial, anti-
biotic and anti-fungal agent when incorporated in coat-
ings, nanofibers, first aid bandages, plastics, soap and
textiles, in treatment of certain viruses, in self cleaning
fabrics, as conductive filler and in nanowire and certain
catalyst applications. It has been reported that Ag
nanoparticles were active biocides against Gram-positive
Gram-negative bacteria [15]. H. Bai et al. [16] reported a
novel kind of multifunctional membrane was fabricated
via integrating the advantages of conventional polymer
membrane as supporting layer like hierarchically struc-
tured TiO2/ZnO nanomaterial as functional layer. This
novel membrane possesses the common advantages of
polymer membrane and multifunctional properties of the
hierarchical TiO2 nanofibers/ZnO nanorod materials,
which demonstrated to be able to produce clean water at
a constant high flux with no membrane fouling problem
and energy saving manner.
In this paper, polyacrylonitrile solution containing
Ag/TiO2 was directly electrospun to obtain nanofibers
films containing Ag Ag/TiO2, and the Ag/TiO2 of rsuling
composite nanofibers were reduced to Ag/TiO2 nnoparti-
cles. Then, we treated PAN/Ag/TiO2 composite nanofi-
bers at different temperatures. The PAN/ Ag/TiO2 nano-
composite film was characterized by scanning eletron
microscopy (SEM), X-ray diffraction (XRD) paterns and
surface-enhanced Raman scattering (SERS) spectros-
copy.
2. Experimental Work
PANNF film was prepared by electrospinning. PAN (7
wt.%) was dissolved in DMF, and stirred until homoge-
nous at room temperature. 0.03 gm AgNO3 was dis-
solved in 70 ml DMF with stirring at 30 min (UV/vis
spectrometer used to obtain the optimum weight per-
centage and the time of reduction for AgNO3), then 0.01
gm of polyethylene glycol was added as stabilizer and
reduction agent. This solution was stirred for 30 min be-
fore analyze using UV spectra. 0.5 ml of acetic acid and
2 ml of titanium is opropoxide were added into 20 ml
DMF. The solution was stirred for 15 min, then 5 wt%
PAN was added to the solution. The two solutions were
mixed together by adding the first (TIP/PAN) to the sec-
ond one (Ag/PAN) gradually with continuous stirring
until homogenous. The solution containing silver and
titanium isopropoxide salt with PAN were stirred for 24
h at room temperature. After that, the solution obtained
was added into a plastic syringe, the internal diameter of
plastic was 20 cm, the pinhead was connected to a
(20-kV) high-voltage, and aluminum foil served as
counter electrode. TCD was (21 cm), the feed rate of the
solution was adjusted to (0.1 ml/h) through a syringe
pump. The electrospinning was performed at room tem-
perature. The nanofibers were stabilized in an air atmos-
phere at 270˚C for 2 h (at a heating rate of 2˚C/min) and
followed by carbonization at 1000˚C for 1 h (at a heating
rate of 4.5˚C/min) under an inert nitrogen atmosphere to
yield carbonized. The resulting carbon nanofibres were
cooled down to room temperature in an inert gas atmos-
phere before they were taken out of the furnace. Full-
stained ultra-thin sections were examined using the field
e mission transmission electron microscope (JEOL-JEM-
2100F, Japan). Thermal properties of electrospinning
nanofibers were examined using thermogravimetric anal-
ysis (TGA) carried on TA-Q500 System of TA; samples
of 5 - 10 mg were heated in the temperature range 30˚C -
800˚C at a scanning rate of 10˚C·mi n−1 under nitrogen
atmosphere, and by using TG-DTA: NETZSCH Ger-
many(Model: STA 449 F3). The bonding configurations
of the samples of carbon nanofibers were recorded by
Four ie r -transformer infrared (FT-IR) Spectra using
TENSOR 27. Tube furnace (Model: T2F-16/610, carbo-
lite-England) was used in treatment nanofibers to convert
them into carbon nanofibers. Thermoanalytical technique
in which the difference in the amount of heat required to
increase the temperature of sample and reference is
measured as a function of temperature. (DSC Q 20-TA
National scientific company USA). Counter ions are
stored in the electrical double layers which form at the
solution interface inside the porous electrodes, with the
ions of cations stored in the negatively charged electrode,
and anions stored in the positively charged electrode
(anode). Plimmer test unit.

K. A. KHALIL ET AL.
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33
3. Results and Discussions
Titanium dioxide (TiO2) has been the focus of numerous
studies in recent years, because of its photocatalytic ef-
fects which decompose organic chemicals and kill bacte-
ria [17]. Most of the work carried out focused on the use
of TiO2 powders suspended in the water as a catalyst [18].
It has been applied to a variety of environmental prob-
lems in addition to water and air purification [19]. Poly-
mers are a common material used in the fabrication of
the membranes. However, it is readily contaminated by
proteins and other impurities during water and wastewa-
ter treatment, which leads to a sharp drop in the mem-
brane flux [20]. Chemical modification methods could be
employed to improve the hydrophilicity of the membrane,
but the main chain of polymer molecule would be
changed and the advantages of the polymer membrane
may be decreased [21,22]. Usually, physical modification
method such as mixing was used, and the mixture mate-
rials were macromolecules [23-25]. When TiO2 nano p ar-
ticles are dispersed in the polymer membranes, the addi-
tion of nanoparticles not only improves the hydrophilic-
ity of polymer membranes but also mitigates the bio-
fouling problem of polymer membrane and membrane
bioreactor (MBR) systems [26,27] and the microbial
biofouling of RO membranes [28]. In addition, the TiO2/
polymer membrane could significantly increase the de-
gradation rate of the phenyl urea herbicide known as iso-
proturon.
One -dimensional (1D) Ag/TiO2-carbon composite
nanofibers were fabricated via electrospinning of a ho-
mogenous mixture of PAN and AgNO3/TIP salt precur-
sors at different ratios followed by heat treatments. The
1D nanostructures of the composite material were char-
acterized by field-emission scanning electron microscopy
(FE-SEM), powder X-ray diffraction (XRD). Figure 1
shows the SEM image of the PAN/Ag/TiO2 nanofibers
web prepared by the electrospinning method in the form
of the thin mat. It is seen that the fibers are dispersed
randomly but densely covering the whole substrate face.
The diameters of the PAN/Ag/TiO2 nanofiber diameters
lie in the region between 200 and 500 nm. Surprisingly,
the PAN/Ag/TiO2 web embodied a relatively high degree
of adhesion to the substrate. The optimized annealing
ramp carried out under nitrogen atmosphere yielded
transformation of PAN/Ag/TiO2 nanofibers to the desired
carbon Ag/TiO2 nanofibrous form without losing their
web structure.
The energy dispersive spectrum (EDS) collected on
the PAN/Ag/TiO2 NPs sample (whose microstructure is
illustrated in Fig ure 1 distinctly identifies Ag, Ti as the
elemental component in the fiber and is shown in Figure
2. The other peaks belonging to carbon are generated
from the PAN. Elementary analysis of PAN /Ag/TiO2
Figure 1. SEM image 0.02 gm of AgNO3 with 1ml TIP/PAN Nanofibers.

K. A. KHALIL ET AL.
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Figure 2. EDS analysis of nanofibers confirms the presence of Ti and Ag in PAN matrix.
NPs nanocomposite was carried out by using SEM-EDS.
The results show that carbon and Ag/TiO2 were the prin-
cipal element of PAN/Ag/TiO2 NPs nanocomposite. EDS
analysis thus provides direct evidence that Ag/TiO2 ions
embedded in the PAN/ silver/TiO2 nanocomposite. It is
indicated that silver/TiO2 nanoparticles were well loaded
without any chemical and structural modifications into
PAN polymer matrix to form an organic-inorganic nano-
composite. The energy dispersive spectrum (EDS) col-
lected on the PAN/Ag/TiO2 NPs sample distinctly identi-
fies Ag/TiO2 as the elemental component in the fiber and
is shown in Figure 3. The other peaks belonging to car-
bon are generated from the PAN. Elementary analysis of
PAN/Ag/T iO2 NPs nanocomposite was carried out by
using SEM-EDS. The results show that Ag and TiO2
were the principal element of PAN/Ag/TiO2 NPs nano-
composite. EDS analysis thus provides direct evidence
that Ag and TiO2 ions embedded in the PAN/Ag/TiO2
nanocomposite. It is indicated that silver and TiO2 nano-
particles were well loaded without any chemical and
structural modifications into PAN polymer matrix to
form an organic-inorganic nanocomposite. Figure 4
shows the X-ray diffraction pattern of a bundle of PAN/
Ag/TiO2 electrospun nanofibers. The nanofibers exhib-
ited two equatorial peaks with a diffuse meridian peak
and four sharp peaks. The primary equatorial (1010) peak
at 2θ = 16.88˚ corresponds to a spacing of d = 5.25 A˚
while the weaker reflection (1120) at 2θ = 29.5˚ corre-
sponds to a spacing of d = 3.05 A˚ (note Miller indices
(hkil) are used for identification of planes in hexagonal
crystals). The TiO2 peaks were observed at 2θ = 38˚, 45˚,
65˚, 78˚ as shown in the XRD in Fig ure 4.
Generally PAN begins to degrade when heated near its
melting point. The degradation reaction of PAN is so
exothermic that it tends to obscure its melting endotherm
in ordinary DSC traces. Therefore, the melting endo-
therm is normally not observed in PAN. In this study,
DSC and DTA were conducted in N2 atmosphere as
shown in Figure 5.
Figure 3. EDS analysis mapping of nanofiber confirms the
presence Ti vs C in PAN matrix.
Figure 4. XRD of PAN/Ag/TiO2 nano f ibers .
TEM analysis is used to investigate the crystal stru-
cture. Figure 6 shows the TEM of the obtained Ag/TiO2
doped nanofibers. As shown in these figures, there are
some black dots in both formulations which can be con-
sidered as the TiO2 nanoparticles as these dots have dif-
ferent crystal structures compared to the carbon ma-
trices. Both formulations have good crystallinity as shown
in Figure 6.

K. A. KHALIL ET AL.
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The SEM images of PAN/TiO2 electrospun nanofibers
after stabilization at 270˚C for 2 h in air share similar
characters of smooth and uniform surfaces with occa-
sional bead-like structures indicating the presence of at-
tached metal oxides (Figure 7). There is no significant
difference in the diameters of nanofibers with the previ-
ous nanofibers. As could be seen, the long duration and
high temperature of the stabilization process spoil the
fiber morphology.
The stabilized PAN/ TiO2/Ag nanofiber was subse-
quently carbonized at a relatively low temperature of
1000˚C in an inert (high purity nitrogen gas) environ-
ment with the heating rate set at 4.5˚C/min as shown in
Figures 8. All of the carbonized PAN nanofiber bundles
were held at the respective final temperatures for 1.5 h to
allow the carbonization to complete. The average diame-
ters of the 1000˚C carbonized PAN nanofibers were re-
duced to 250 nm and 220 nm, respectively. During car-
bonization, a variety of gases (e.g., H2O, N2, HCN, and
others) were evolved and the carbon content increased to
90 wt.% or higher; the process therefore led to the reduc-
tion of fiber diameter and the formation of three-dime n -
sional carbonaceous structures.
4. Conclusion
The results showed that, electrically conducting carbon
nanofiber (CNF) mats were produced by using polyacry-
lonitrile (PAN) via electrospinning. The CNF showed
high capacitance and energy/power density values due to
the formation of ultra-micropores and the introduction of
high surface area. Furthermore, this project reports on
research conducted on Capacitive Deionization as an
alternative to the more conventional membrane desalina-
tion technologies like reverse osmosis and electrodialsis.
The simultaneous one-pot synthesis of P AN/ Ag /Ti O2
Figure 5. DSC of Ag/TiO2 composite PAN nanofibers.
Figure 6. TEM results for Ti/PAN nanofibers.

K. A. KHALIL ET AL.
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Figure 7. SEM image stabilizations of PAN/Ag/TiO2 Nanofibers at 270 C.
Figure 8. SEM image carbonization of PAN/Ag/TiO2 Nanofibers at 1000˚C.
composites has several advantages in terms of controlling
particle size and fiber diameter. In addition, the FTIR
spectroscopy, thermal gravimetry analysis (TGA) proved
the presence of silver and titanium dioxide nanoparticles
in the PAN fiber. The SEM micrographs clarified that
there are random orientation for nanofiber. N,N Di-
methylformamide (DMF) was used as both the solvent
for PAN and reducing agent for Ag ions. Furthermore,
this project reports on research conducted on Capacitive
Deionization as an alternative to the more conventional
membrane desalination technologies like reverse osmosis
and electrodialysis.
Acknow l edgements
This work was financially supported by the National Plan
for Science & Technology (NPST), King Saud Univer-
sity Project No. 11-NAN1460-02.
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