Preparation of NiZn-ferrite nanofibers by electrospinning for DNA separation

Article abstract of DOI:10.1016/j.jmmm.2009.02.044

We present the synthesis, magnetic and UV spectrometry of NiZn-ferrite nanofiber. The single phase of spinel ferrite was obtained at 600 °C. The NiZn-ferrite fibers fabricated by an electrospinning process were formed as a polygonal grain growth with firi

Full text of DOI:10.1016/j.jmmm.2009.02.044

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Journal of Magnetism and Magnetic Materials 321 (2009) 1389–1392
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials
journal homepage: www.elsevier.com/locate/jmmm
Preparation of NiZn-ferrite nanofibers by electrospinning for DNA separation
a,
Ã
a
b
b
a
Joong-Hee Nam , Yong-Hui Joo , Ji-Ho Lee , Jeong Ho Chang , Jeong Ho Cho ,
a
a
Myoung Pyo Chun , Byung Ik Kim
a
Advanced Materials & Components Laboratory, Korea Institute of Ceramic Engineering and Technology, 233-5, Gasan-dong, Geumcheon-gu, Seoul 153-801, Republic of Korea
Eco-Biomaterials Laboratory, Korea Institute of Ceramic Engineering and Technology, Seoul 153-801, Republic of Korea
b
a r t i c l e i n f o
a b s t r a c t
Available online 20 February 2009
We present the synthesis, magnetic and UV spectrometry of NiZn-ferrite nanofiber. The single phase of
spinel ferrite was obtained at 600 1C. The NiZn-ferrite fibers fabricated by an electrospinning process
were formed as a polygonal grain growth with firing temperature in fiber matrix. It appeared that the
Keywords:
Ceramic nanofiber
Electrospinning
NiZn ferrite
S
saturation magnetization (M ) of NiZn-ferrite nanofiber was dependent on Ni/Zn molar ratio which is
similar to that of the inverse spinel ferrites. The NiZn-ferrite fibers showed good DNA adsorption
efficiency that can be modified and utilized for DNA separation with magnetic nanofiber as a novel
material in clinical applications.
DNA separation
&
2009 Elsevier B.V. All rights reserved.
Although electrospinning techniques have been generally used
for the fabrication of polymer nanofibers, they are now also used
for the preparation of ceramic nanofibers including composite
materials [1–7]. The possibility of extending this process to
ceramic materials has started in nanostructure research for new
applications. One reason for this increasing interest in electro-
spinning stems from the fact that it is a relatively inexpensive
technique to make nanofibers. With the expansion of electrospin-
ning from polymers to composites and to ceramics, applications
expand to the preparation of nanostructured materials. Their
typical properties of having a high surface-to-volume ratio make
them useful for potential applications such as nanoelectronic
devices, sensors, solar cells, photonics, and multiferroic materials
collapsing into droplets before it evaporates, the surface tension
of the solution must be low. Morphological change of electrospun
fibers before calcinating can be strongly dependent upon the
distance between nozzle needle and collector in various applied
electrical field, flow rate, and ambient environment like tempera-
ture and humidity. The increase of needle-to-collector distance or
decrease in the electrical field may result in reduced bead density,
regardless of the polymer solution concentration [12].
The chemical synthesis of spinel ferrite-based particulates may
represent an important step towards the engineering of typical
magnetic carriers. Bio-separation is a crucial phenomenon for the
success of several biological processes. Magnetic separation of
cells or bio-molecules is more effectively done by adsorption/
desorption from the modified particles of spinel iron oxides. The
synthesis parameters on the morphological and magnetic proper-
ties of spinel iron oxide are strongly dependent on the reaction
conditions. A novel technology for DNA separation using the new
magnetic materials can be promising for enhancing the efficiency
of the bio-separation process. Classical methods for DNA/RNA
isolation are either column-based techniques or include precipi-
tation and centrifugation steps having the disadvantage of being
time consuming, difficult to automate or not useful for down-
scaling to small sample volumes [13].
[
6], molecular sieves [8], high-temperature insulation [9], cata-
lysis [10], biomedical separation, and microwave absorbers.
Recently, a few popular processes to produce ceramic nanofi-
ber and inorganic-polymer composite fiber as well as polymer
fiber have been reported [11]. In general, ceramic nanofibers
are prepared by the electrospinning of ceramic precursors in the
presence of polymers followed by calcination. Careful preparation
of the precursors is essential to electrospun ceramic systems.
Several parameters such as solvent volatility, viscosity, surface
tension, conductivity, and applied voltage need to be controlled.
Electrospinning methods usually adopt the cone-jet principle
to manufacture ultra-thin fibers. For this purpose, the electro-
spinning solution must have a high polymer concentration,
high enough to cause entanglement with low viscosity to allow
motion induced by the electric field. To prevent the solvent from
Effective cell separation is a primary and most important
process for many clinical immunological applications using the
magnetic oxide compounds. The selection of magnetic particles
based on shape, size, and microstructures will significantly affect
the final result of separation. Work presented here describes a
new challenging process for efficient and direct DNA separation
with functionalized NiZn-ferrite fibers.
Ã
Magnetic separation is an emerging technology that uses
magnetism for the efficient separation of micrometer-sized
Corresponding author. Tel.: +82 2 3282 2443; fax: +82 2 32827759.
E-mail address: jnam@kicet.re.kr (J.-H. Nam).
0304-8853/$ - see front matter & 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jmmm.2009.02.044

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magnetic carriers from chemical or biological suspensions.
Magnetic separation has many advantages compared to other
techniques used for bio-separation or purification and is generally
done with iron oxide nanoparticles as magnetic carriers. Now,
to make magnetic ceramic nanofibers might be another way of
gaining a large surface area and appropriate nanostructure for the
application of DNA separation.
2
0
0
100
8
0
0
-
-
20
40
6
The spinel ferrite MFe
2
O
4
(M ¼ Ni, Zn) nanofibers were
synthesized by an electrospinnng process in this study. Raw
materials used were iron (III) chloride (FeCl
3
), nickel acetate
40
.
-60
-80
tetrahydrate (C
4
H
6
O
4
Ni 4H
2
O) and zinc acetate dehydrate
.
(C H O Zn 4H O). The aqueous metal salt/polymer solution was
4 6 4 2
20
prepared with polyvinyl pyrrolidone (PVP) in DMF (N,N-dimethyl-
formamide) and metal salts under stirring at room temperature.
The applied electric field and spurting rate for spinning conditions
were 10 kV, 2 ml/h, respectively. The obtained fibers were calcined
at 600 1C for 3 h and annealed at 900 1C in air. By tuning the
viscosity of batch solution before electrospinning, we were able
to control the microstructure of NiZn-ferrite fiber in the range
200
400
600
800
o
Temperature ( C)
Fig. 2. Thermal analysis (TG–DTA) curves of metal salts/PVP solution.
7
0–200 nm at 770 cp. The multiple individual grain size in a ferrite
fiber was about 10–15 nm. The properties of those NiZn-ferrite
fibers as magnetic carrier were determined from X-ray diffraction,
electron microscopy, thermal analysis, and magnetic measure-
ment. The DNA adsorption efficiency yields compared to magne-
tite nanoparticle showed about 50% for UV-light wavelength,
which can be modified and utilized for DNA separation with
magnetic nanofiber in clinical applications.
(
311)
: (Ni,Zn)Fe
: FeOCl
2
O4
Prior to electrospinning, the viscosities of batch solutions
were measured with the viscometer. The crystalline phases were
idendified by X-ray diffraction (XRD); and the morphology of
the NiZn-ferrite nanofiber were observed by FE-SEM. Reaction
processes during the calcinations were studied by thermal
analysis (TG–DTA) in the temperature range of 20–900 1C to
determine calcination temperatures. Magnetic measurements
were carried out at room temperature using VSM.
(220)
(440)
(
511)
(
400)
(
422)
Fig. 1 shows the results of microstructure of electrospun
polymer and viscosity with polymer (PVP) content to optimize the
experimental conditions of raw materials for fabrication of NiZn-
ferrite fiber. The morphology and diameter of electrospun fibers
are dependent on a number of processing parameters that include
the type of polymer in solution, the operational conditions of
electrospinning unit [14]. As shown in Fig. 1a–d, we can obtain the
various electrospun PVP fibers prepared with PVP content and the
1
0
20
30
40
50
60
70
80
2
θ
2 4
Fig. 3. XRD patterns of NiZn-ferrite (Ni0.4Zn0.6Fe O ) nanofibers fabricated at
various firing temperatures. (a) As electrospun, (b) calcined at 400 1C, (c) calcined
at 600 1C, and (d) calcined at 600 1C and annealed at 900 1C, respectively.
1
1
1
1
600
400
200
000
8
6
4
00
00
00
2
00
0
0
5
10
15
20
Concentration of polymer (wt %)
Fig. 1. Various electrospinning conditions for PVP fiber made from (a) 5 wt% (27 cP), (b) 10% (180 cP), (c) 15% (770 cP), (d) 20% (1,515 cP) of the polymer, and (e) the viscosity
ꢀ1
at 2.3 cm shear rate increases with higher PVP concentration.

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J.-H. Nam et al. / Journal of Magnetism and Magnetic Materials 321 (2009) 1389–1392
1391
fiber diameter. The formation of beads in electrospun fibers in
Fig. 1a and b can be affected by the solution properties as
viscosity, surface tension, and the density of net charges carried
by the liquid jet [15]. It can be clearly presented that the viscosity
of solution was dramatically increased at a proper concentration
of polymer. The batch solution of sol precursor was affected the
viscosity which was resulted in change of ferrite fiber diameter.
The viscosity for high performance of fiber by electrospinning was
out of metal salts (Fe-chloride, Ni-acetate, Zn-acetate). An
exothermic DTA peak at about 550 1C indicates the onset in
crystallization of spinel structure of NiZn-ferrite fiber. The XRD
patterns of NiZn-ferrite fibers are presented in Fig. 3. The
unreacted FeOCl phase appeared at 400 1C (Fig. 3b). NiZn-ferrite
fibers, thus, can be obtained at over 600 1C with single phase of
spinel structure with good crystallinity. The molar ratio (Ni:Zn)
2 4
of NiZn ferrite was selected as 0.4:0.6 (Ni0.4Zn0.6Fe O ) due to its
ꢀ
1
obtained in the range 300–700 cP at a shear rate of 2.3 s . In
order to obtain a normal electrospun fiber (Fig. 1c and d), the PVP
content should be over 15% in batch solution.
high saturation magnetization (Fig. 4). NiZn-ferrite fibers obtained
at various calcination temperatures show ferromagnetic behavior
S
[16]. It also appeared that the saturation magnetization (M ) of
Fig. 2 shows the characteristic thermal analysis (TGA and DTA)
curves of the batch solution of metal salts with PVP. Between 200
and 300 1C, weight loss and an exothermic DTA peak in TGA were
observed because of the decomposition of PVP which yields to an
increasing viscosity. A further weight loss in TGA and exothermic
DTA peaks at around 500–600 1C is consistent with the burning-
NiZn-ferrite nanofiber was dependent on the Ni/Zn molar ratio as
is typically found in inverse spinel ferrites [17].
2 4
The NiZn-ferrite (Ni0.4Zn0.6Fe O ) fibers fabricated by electro-
spinning process were also characterized by scanning electron
microscope. Fig. 5 shows the microstructures of NiZn-ferrite
2 4
(Ni0.4Zn0.6Fe O ) nanofibers calcined at various calcination tem-
peratures. SEM images of NiZn-ferrite nanofiber in Fig. 5a–c
shows the multiple grains as a polygonal grain growth with firing
temperature in matrix. The bubble-shaped individual grain in
NiZn-ferrite fiber (Fig. 5a) was identified as an unreacted phase of
FeOCl by EDS analysis (Fig. 5d). At 600 1C, no residual chloride
of PVP was detected anymore (Fig. 5e) and pure NiZn-ferrite fiber
obtained with a continuous structure.
Magnetic separation is an emerging technology that uses
magnetism for the efficient separation of nano-sized para-
and ferromagnetic particulate media from chemical or biological
suspensions [18]. The basic technology of using magnetic
separation techniques to purify biological compounds (nucleic
acids, proteins, etc.) and cells is interesting due to advantages over
other techniques used for the same processes. The efficiency of
magnetic separation is well suited for large-scale purification
o
7
6
5
4
3
0
0
0
0
0
4
6
9
00 C
o
00 C
o
00 C
4
3
2
1
0
using small particles of 0.05–0.1 mm in diameter. The increasing
application of magnetic carriers in biochemical or molecular
biology processing has many advantages compared to other
nonmagnetic separation.
Table 1 shows the variation of UV-light absorbance with
adsorption time measured by UV/VIS spectrophotometer for char-
0.2
0.4
0.6
0.8
1.0
Ni contents, x
S x 2 4
Fig. 4. Saturation magnetization (M ) of Ni Zn1ꢀxFe O nanofibers with Ni content
at various firing temperature.
2 4
acterization of DNA separation using NiZn-ferrite (Ni0.4Zn0.6Fe O )
2
nd phase
FeOCl)
10nm
(
≤
~10nm
≥200nm
c:\edax32\genesis\genmaps.spc 03-Apr-2008 13:57:40
LSecs : 44
c:\edax32\genesis\genmaps.spc 06-oct-2008 17:43:04
2.1
LSecs : 97
2
.5
.0
.5
.0
1
1
.7
.2
2
1
1
o
Zn
Fe
0
0
0
.8
.4
.0
Zn
Fe
0
0
.5
.0
CI
Fe
Ni
Ni
Pt
Zn
Ni
1
.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00
Energy - keV
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.0
Energy - keV
2 4
Fig. 5. SEM images of various NiZn-ferrite (Ni0.4Zn0.6Fe O ) nanofibers (a) calcined at 400 1C, (b) calcined at 600 1C, and (c) calcined at 600 1C and annealed at 900 1C. The
EDS analysis peaks of some of the nanofibers are shown in (d) calcined at 400 1C and (e) calcined at 600 1C.

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Table 1
Characterization of DNA separation using NiZn ferrite (Ni0.4Zn0.6Fe
in a next step to make this method a successful DNA separation
with functionalized magnetic nanofibers that can be utilized in
clinical diagnoses and biomolecular recognition.
2 4
O ) nanofibers.
Adsorption time (h)
UV-light absorbance
DNA only
NiZn ferrite fiber added
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0.53
0.53
0.59
0.31
0.28
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