Journal of Biomaterials and Nanobiotechnology, 2010, 1, 50-60
doi:10.4236/jbnb.2010.11007 Published Online October 2010 (http://www.SciRP.org/journal/jbnb)
Synthesis and Characterization of Novel Hybrid
Poly(methyl methacrylate)/Iron Nanowires for
Potential Hyperthemia Therapy
Huey-Wen Liou1, Hong-Ming Lin1*, Yeu-Kuang Hwu2, Wen-Chang Chen3, Wei-Jen Liou1, Li-Chung
Lai4, Wei-Syuan Lin1, Wen-An Chiou4
1Department of Materials Engineering, Tatung University, DeHui St., Taipei, Taiwan; 2Institute of Physics, Academia Sinica,
Academia Rd., Nankang, Taipei, Taiwan; 3Department of Chemical and Materials Engineering, National Yunlin University of
Science and Technology, University Road, Section, Douliou, Yunlin, Taiwan; 4NISP Lab, Jeong H. Kim Engineering Building,
NanoCenter, University of Maryland, College Park, U.S.A.
Received July 22nd, 2010; revised August 14th, 2010; accepted September 30th, 2010.
ABSTRACT
Externally applied magnetic fields have been used in this study to fabricate bamboo-like iron nanowires with or without
a layer of Poly(methyl methacrylate) (PMMA). The hybrid PMMA/Fe nanowires were synthesized via hard X-ray
synchrotron radiation polymerization with various treatment parameters. The results of XRD show that an oxide layer
formed on the surface of the iron nanowires. The Fe2O3 and Fe3O4 phases coexist in the iron nanowires without X-ray
irradiation. After X-ray irradiation, the Fe 2O3 phase transform ed into Fe3O4, which stabilized th e iron nanowires. The
results of XAS proved this phase transformation. TGA analysis confirmed the thermal properties and solid contents in
these specimens. Their ferromagnetic behaviors were examined by magnetic hysteresis measurement, which indicated
that the magnetic and structural properties of the nanowires can be manipulated by irradiation treatment. This may
lead to a novel synthesis for iron nan owires that can be used in high thermal efficiency hyperthermia therapy.
Keywords: Iron Nanowires, Poly(methyl methacrylate), Hybrid, X-Ray Irradiation, XAS, Magnetic Materials
1. Introduction
Recently, several research groups have carried out inves-
tigations of the magnetic properties of metal wires. They
used different methods to prepare nanowires and mi-
crowires. Menon et al. [1], Bandyopadhyay et al. [2] and
Zheng et al. [3] fabricated Fe, Co and Ni nanowires, re-
spectively, using electrodeposition into nanoporous an-
odic alumina templates. Pan et al. synthesized NiCo mi-
crowires using a hydrothermal method [4]. A template-
free method that combines chemical reduction and a ma-
gnetic field is applied to prepare Ni nanowires [5]. The
latter method only needs one step in its preparation and
no thermal treatment.
Herein, iron nanowires have been prepared by an ex-
ternally applied magnetic field. Hybrid Poly(methyl
methacrylate) (PMMA)/iron nanowires are synthesized
by combining iron nanowires with radiation polymeriza-
tion of PMMA. Hard X-ray synchrotron radiation can be
used to initiate polymerization of PMMA and success-
fully produces PMMA beads [6]. This method has two
essential characteristics. First, it requires only one step
for the preparation of Fe nanowires with a polymerized
PMMA coating by hard X-ray synchrotron radiation.
Second, the PMMA/iron nanowires can be successfully
synthesized without adding emulsifier. Compared with
the usual chemical methods of preparing organic/inor-
ganic hybrid materials, the method presented here is a
quick, simple and ‘green’ process, which may reduce
environmental pollution and increase broad, practical
applications. Hybrid PMMA/Fe nanowires are intention-
ally designed to manipulate their magnetic properties for
application in magnetic hyperthermia. The needle-sharp
nanowires enhance friction heating while an alternative
magnetic field is applied that increases the heating effi-
ciency in hyperthermia therapy.
In this study, hybrid PMMA/Fe nanowires are investi-
gated by X-ray diffraction (XRD), scanning electron mi-
croscopy (SEM), high resolution transmission electron
microscopy (HRTEM), X-ray absorption spectroscopy

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
51
Nanowires for Potential Hyperthemia Therapy
(XAS), thermogravimetry (TGA), and vibrating sample
magnetometry (VSM). An XAS spectrum, which is ba-
sically the measured X-ray absorption coefficient as a
function of the incoming photon energy, is generally di-
vided by the role of multiple scattering photoelectrons
into two different regions: X-ray Absorption Near-Edge
Structure (XANES) and Extended X-ray Absorption Fine
Structure (EXAFS). XANES, also referred as NEXAS
(Near Edge X-ray Absorption Fine Structure), can be
used to investigate the electronic structure of specific
elements, and EXAFS is used mainly to investigate the
local atomic structure concerning the type and number of
elements as well as the nearest neighbor bond length [7].
In this study, the oxidation states of iron will be exam-
ined by XAS to reveal the effects of X-ray irradiation on
the formation of iron oxides in iron nanowires.
2. Experimental
Methyl methacrylate monomer (MMA, Fluka Chemical
Reagent Co.) was purified by reduced pressure distilla-
tion to remove the inhibitor before polymerization. Ferric
chloride hexahydrate (FeCl3·6H2O) and sodium boro-
hydride (NaBH4) were obtained from Sigma-Aldrich, Inc.
Polyvinylpyrrolidone (PVP, K-30, average molecular
weight: ca. 40,000 g/mol) was obtained from Tokyo Ka-
sei Kogyo Chemical Reagent Co. Nitric acid (reagent
ACS 99.5%), methanol and ethyl alcohol were bought
from Wako Pure Chemical Industries. All solutions were
prepared with deionized water (> 18 MΩ).
2.1. Preparation of Iron Wires and PMMA/Iron
Nanowires
Five specimens of iron nanowires and PMMA/Fe nano-
wires with various parameters were prepared in this stu-
dy. The first specimen was fabricated using the standard
synthesis procedure for magnetic wires. Iron nanowires,
denoted as specimen (I), were prepared using an exter-
nally applied magnetic field with an intensity of 0.3 T.
Normally, Fe nanowires are produced in a 0.7 M aqueous
solution of FeCl3·6H2O at room temperature in a high
purity nitrogen atmosphere with an externally applied
magnetic field after adding 0.8 M NaBH4 aqueous solu-
tion. After synthesis, this notated specimen I is washed
with anhydrous ethanol and dried in air. The chemical
reaction mechanism (Equation 1) is shown as follows:
23
243
216)(62
1862
HNaClOHBFe
OHNaBHFeCl



 (1)
The second specimen is the same as specimen I after it
undergoes hard X-ray synchrotron radiation for 10 min
and is notated as specimen (II). The irradiation is carried
out at the National Synchrotron Radiation Research
Center (NSRRC) in Taiwan, with the hard X-ray beam
line (BL01A). This NSRRC synchrotron light provides a
300 mA, 1.5 GeV electron beam to generate a photon
source for scientific research. The hard X-ray beam line
is a semi-white-light beam line. The photon flux is 1 
1012 photons/sec, and the radiation is incident onto the
sample with a beam footprint of 18.6  9.3 mm2. The
distribution range of photon energy is between 10 and 15
keV, and the dose rate is 5.1 ± 0.9 kGy/s. After exposure,
the specimen was washed with anhydrous ethanol and
then dried.
For the third specimen, a 0.7 M solution of iron ion
was prepared by dissolving FeCl3·6H2O in methanol and
then mixing it with PVP and MMA monomer in a high
purity nitrogen atmosphere. Then, a 0.8 M NaBH4 aque-
ous solution was dropped into the previously prepared
solution to synthesize iron nanowires in an externally
applied magnetic field. After forming the iron nanowires,
the sample was exposed to hard X-ray synchrotron radia-
tion for 10 min. The obtained PMMA/Fe nanowires are
denoted as specimen (III).
For the fourth specimen, a 0.7 M FeCl3·6H2O metha-
nol solution was mixed with PVP and MMA monomers
in a high purity nitrogen atmosphere and then exposed to
hard X-rays for 10 min to polymerize before a 0.8M
NaBH4 aqueous solution was added under an externally
applied magnetic field. The obtained sample underwent
polymerization once again by hard X-ray exposure for
another 10 min.
For the fifth specimen, PMMA polymer was synthe-
sized before iron nanowires formation. MMA stock solu-
tion was prepared by dissolving PVP (5 vol.%) in
methanol (35 vol.%) with de-ionized water (45 vol.%)
and mixing it with MMA monomer (15 vol.%). The
stock solution was stirred in high purity nitrogen gas to
eliminate oxygen. In addition, the stock solution of iron
precursor was prepared in deionized water with concen-
trations of 0.7 M FeCl3·6H2O. Ten milliliter quantities of
MMA stock solution were prepared in sealed bottles,
ready for irradiation-induced polymerization for 10 min.
After that, we prepared the volume ratios of iron stock
solution to PMMA emulsion solution at 1:1. Next, 0.8 M
NaBH4 was added to the mixture solution for self-as-
sembled hybrid PMMA/Fe nanowires under high-purity
nitrogen gas atmosphere and a magnetic field. These are
called specimen (V). The obtained sample was separated
from the solution and washed with anhydrous ethanol
and deionized water and then dried in air. Fe nanowires
(I, II) and PMMA/Fe nanowires (III, IV, and V) were
then dispersed on a carbon adhesive tape and observed
by SEM. The structural properties of these specimens

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
52
Nanowires for Potential Hyperthemia Therapy
were analyzed with an X-ray diffractometer. TEM obser-
vation further confirmed the specimen’s morphology.
The magnetic hysteresis properties of all specimens were
also analyzed by a VSM analyzer; other correlation
characteristics are discussed as well.
2.2. Material Properties
The Fe nanowires and Fe nanowires coated with PMMA
were characterized by X-ray diffraction, SEM, TEM,
TGA analysis and VSM. Powder X-ray diffraction (XRD)
patterns of Fe nanowires were obtained by employing
NSRRC 17A1 W20 X-ray Powder Diffraction. An SEM
HITACHI-S4700 was used to observe the morphology
and shape of the Fe nanowires and hybrid PMMA/Fe
nanowire materials. High resolution transmission
electron microscopy (HRTEM, JEOL JEM-2100F) was
used to characterize the morphology of the Fe nanowires
and hybrid PMMA/Fe nanowires. The source of
synchrotron radiation at the National Synchrotron
Radiation Research Center (NSRRC) in Taiwan was used
to study the X-ray absorption spectroscopy (XAS) of iron
nanowires in the NSRRC 16A and 20A beam line. The
fluorescence EXAFS technique was used in this study to
detect the X-rays emitted as a result of filling the core
hold created by optical absorption.
The magnetic property measurements were carried out
with a VSM (Lake Shore 7407, USA) with a maximum
magnetic field of 2 T. Thermal degradation was
examined with a thermal analyzer (model SDT 2960
Simultaneous DSC-TGA, TA, Germany). Each sample
was weighted and filled into Pt crucibles. The samples
were heated at a rate of 10℃/min from room temperature
to 1400℃ in an oxygen flow of 20 cm3/min. These
measurements were conducted under oxygen flow to
observe iron oxidation.
3. Results and Discussion
3.1. Structural Properties
The phase of the reduced iron nanowires has been
determined from the XRD pattern as shown in Figure 1.
Well defined peaks can be observed in the patterns of
specimen (I) and (V), corresponding to the existence of a
body centered cubic (bcc) phase of iron that coexists with
FeO, Fe3O4 and Fe2O3 phases in the iron nanowires As
indicated in Figure 1(a), specimen (I) is composed of
surface iron oxides. For the hard X-ray irradiation
specimens (II) and PMMA coated specimens (III-IV), the
surface layer of iron oxide gets thicker, as evidenced in
Figures 1(b), (c) and (d). The results indicate that X-ray
irradiation will enhance the oxidation of iron nanowires
and affect the magnetic properties of these specimens.
Interestingly, after X-ray irradiation, the FeO and Fe2O3
phases disappear, and only the Fe3O4 phase can be ob-
served. For specimen (V), a pattern similar to specimen
(I) can be seen, but it lacks a strong iron peak. Although
the synthesis of iron nanowires occurs after X-ray
irradiation, the free radicals generated by X-rays are still
affecting and inducing trans-grains oxidation of iron
nanowires.
3.2. Morphology
The morphologies of iron nanowires and hybrid PMMA/
iron nanowires, fabricated with different processing con-
ditions, were characterized by SEM and HRTEM to
compare the hard X-ray irradiation effects on them. SEM
images of various iron nanowires and PMMA/Fe
nanowires are shown in Figure 2. The nano wires all
show bamboo-like structures. Figures 2(b), (c) and (d)
show that the nanowires have parallel alignment in the
same orientation, which may be due to the irradiation or
hybridization of PMMA. On the other hand, Figures 2(a)
and (e) show random distribution. As evidenced from the
images of electron microscopy, the specimens exhibit
orientation arrangement when the Fe nanowires are irra-
diated by hard X-ray synchrotron radiation. The diame-
ters of both iron nanowires (I) and (II) are all about 40.1
± 4.2 nm, and the lengths of the nanowires are 584.8 ±
47.2 nm. Figures 2(c) and (d) indicate that the diameters
of PMMA/Fe nanowires (III) and (IV) are about 23.3 ±
3.9 nm and 31.5 ± 2.5 nm, respectively, and the lengths
of these nanowires are 2.7 ± 0.5 µm and 1.1 ± 0.2 µm,
respectively. Nanowire (IV) undergoes polymerizations
by X-ray irradiation twice, which increases the thickness
20 30 40 50 60
2(degree)
(e)
(d)
Intensity (a.u.)
(c)
(b)
****
***
***
**
**
**
**
(a) ***
Figure 1. The XRD diffraction patterns of (a) Fe nanowires
(I), (b) Fe nanowires (II) (after hard X-ray irradiation), (c)
PMMA/Fe nanowires (III), (d) PMMA/Fe nanowires (IV)
and (e) PMMA/Fe nanowires (V). (* Fe2O3 peaks, ** Fe3O4
peaks, *** FeO peaks, and **** Fe peaks).

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
Nanowires for Potential Hyperthemia Therapy
53
(a) (b)
(c) (d)
(e)
Figure 2. The SEM images of (a) Fe nanowires (I), (b) Fe nanowires (II) (after hard X-ray irradiation) (c) PMMA/Fe
nanowires (III), (d) PMMA/Fe nanow ires (IV) and (e) PMMA/Fe nanowires (V).
of the PMMA, but shortens the length. From the image
of Figure 2(e), the morphology of PMMA/iron nanowires
looks like a raspberry attached to PMMA/Fe
nanoparticles and nanowires. Flocculation is observed

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
54
Nanowires for Potential Hyperthemia Therapy
between hybrid PMMA/iron nanowires. The average
diameter and the average length of specimen (V) are
about 36.2 ± 2.8 nm and 1.6 ± 0.4 µm, respectively.
HRTEM images were used to characterize the
morphologies and structures of these hybrid materials, as
shown in Figure 3. For specimen (I) and (II), a thin iron
oxide layer formed on the surface of the nanowires, as
shown in Figures 3(a) and (b). The thickness of the iron
oxide layer in specimen (I) and (II) is approximately 4.5
± 0.8 nm and 3.5 ± 0.2 nm, respectively. It is important to
note that for specimen (II), the X-ray irradiation induced
oxidation of a thin oxide layer about 1.0 ± 0.1 nm
(a) (b)
(c) (d)
(e)
Figure 3. TEM images of Fe nanowires and PMMA/iron nanowires hybrid material with different synthesis procedures, (a)
Fe nanowires (I), (b) Fe nanowires (II) (after hard X-ray irradiation), (c) PMMA/Fe nanowires (III), (d) PMMA/Fe
nanowires (IV) and (e) PMMA/F e nanowires (V).

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
55
Nanowires for Potential Hyperthemia Therapy
between the inner nanograins of iron. The diameter of the
iron nanograins was measured from the TEM images in
Figures 3 (a) and (b). From these, the average diameter
of specimen (I) and (II) was determined to be
approximately 61.7 ± 3.8 nm and 40.4 ± 11.4 nm,
respectively. Thus, X-ray irradiation not only induced
oxidation of the iron inner grains, but also refined the
iron grain size. This affects the properties of the iron
nanowires. Figures 3(c), (d) and (e) show the coating of
PMMA on the iron nanowires. The thickness of the
PMMA layer is approximately 4.6 ± 0.5 nm in specimen
(III). In specimen (III), the layer of oxide can also be
observed between iron nanograins as in specimen (II).
This further proves that X-ray irradiation strongly affects
the oxidation of iron between its nanograins. Specimen
(IV) is not uniformly coated with PMMA, with a
thickness of approximately 25.0 ± 0.7 nm.
In this study, iron nanowires were synthesized with or
without an MMA monomer, which then underwent hard
X-ray polymerization to coat the nanowires in PMMA.
Specimen (III) has a more uniform layer coating than
specimen (IV). In addition, the PMMA/Fe nanowires
(specimen (V)) were grown after PMMA synthesis. The
thickness of the PMMA coating layer is approximately
2.6 ± 0.1 nm, which is smaller than specimen (III) and
(IV). The X-ray diffraction patterns shown in Figure 1
indicate that the reduced iron, without a uniform PMMA
protection layer, was seriously oxidized by X-ray
irradiation. The thickness of the iron oxide layer in
hybrid iron nanowires (III), (IV) and (V) are similar and
approximately 2.9 ± 0.3 nm, 3.3 ± 0.5 nm and 2.8 ± 0.2
nm, respectively. Specimen (III), (IV) and (V) have a
thin oxide layer between their inner iron nanograins that
were induced by hard X-ray irradiation and have
thicknesses of 1.2 ± 0.1 nm, 1.2 ± 0.1 nm, and 0.5 ± 0.1
nm, respectively. The iron nanowires in specimens (I), (II)
and (III) were all irradiated with X-rays. X-ray
diffraction patterns indicate that the FeO and Fe2O3
phases disappeared in these specimens. They indicate
that X-ray irradiation induced the reduction of Fe2O3 to
form Fe3O4 and also caused trans-grain oxidation.
3.3. X-ray Absorption Spectroscopy
Iron is widely used in technologically relevant systems.
The oxidation of iron surfaces has been extensively
studied in the past [8]. Understanding the magnetic
properties of these iron nanowires and hybrid
PMMA/Iron nanowires requires a precise knowledge of
the structure and composition of the oxide layer. This
knowledge is important because of the different
crystallographic sites of iron atoms in the oxide phases,
which result in strongly structure dependent magnetic
properties. X-ray absorption spectroscopy is one way to
study the oxidation states and the local symmetry of
atoms in solids. The X-ray absorption near-edge structure
(XANES) depends directly on the oxidation states. The
extended X-ray fine structure (EXAFS) includes
information on the local structures [9].
The near-edge absorption spectra are acquired at the
iron K-edge. The Fe K-edge spectra of the iron nanowires
and hybrid PMMA/Fe nanowires samples are shown in
Figure 4. The pre-edge of the spectra was used to evaluate
the sensitivity of XAS to geometric and electronic
structural changes [10]. Figure 4(b) shows that the iron
pre-edge of iron nanowires without X-ray irradiation in
specimen (I) is similar to that of commercial pure iron in
Figure 4(a). It reveals that a thin oxide layer forms on the
surface of as-received iron nanowires. This thin oxide
layer also appears in the HRTEM image of Figure 3(a).
For specimen (II) to (IV), iron nanowires are all irradiated
by high intensity X-rays. They have a similar iron
pre-edge as shown in Figures 4(c) to (e). The iron
pre-edges of these specimens are different than that of
reference Fe2O3 and commercial iron as shown in Figures
4(g) and (a), respectively. X-ray diffraction patterns
indicate that the Fe3O4 phase is formed in specimen (II) to
(IV). Thus, after X-ray irradiation, the major oxide on the
surface of the iron nanowires is the Fe3O4 phase. This
also reveals that X-ray irradiation will induce oxidation
of pure iron and reduction of the Fe2O3 phase. Specimen
(V) is prepared with iron nanowires after forming
PMMA by X-ray irradiation. Its X-ray diffraction pattern
7080 7090 71007110 7120 71307140 7150 71607170
(a) Com mercial Fe
(b) Fe nanowires (I)
(c) Fe nanowires (II)
(d) PMMA/Fe nanowires ( III)
(e) PMMA/Fe nanowires (IV)
(f) PMMA/Fe nanowires (V)
(g) Com mercial Fe2O3
Energy (eV)
Fe K-edge
E0 = 7112 eV
Norm. Absorption ( a.u.)
(g)
(f)
(b)
(a)
(d)
(c)
(e)
I
II
III
Figure 4. Fe K-edge of EXAFS of (a) commercial Fe, (b) Fe
nanowires (I), (c) Fe nanowires (II) (after hard X-ray
irradiation), (d) PMMA/Fe nanowires (III), (e) PMMA/Fe
nanowires (IV), (f) PMMA/Fe nanowires (V), and (g)
commercial Fe2O3.

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
56
Nanowires for Potential Hyperthemia Therapy
(Figure 1(e)) is similar to the iron nanowires without
X-ray irradiation in Figure 1(a), only with a lower
intensity in the iron peak at around 2θ = 45o. The shape
of the iron pre-edge of specimen (V) is similar to that of
specimen (I) and specimen (II)-(IV). X-ray irradiation
effects on the iron oxidephases are enhanced by the
formation of Fe3O4 and the trans-grain oxidation, as
indicated in Figures 3(b) and (c).
To further examine these results, we differentiated the
data of Figure 4 to obtain the differential pre-edge of the
Fe K-edge, as shown in Figure 5. The absorption edge
differences in these samples are obvious. The first
differential pre-edge peak represents the electron
transition from the 1s to 4d orbital that directly relates to
the oxidation state and geometry of the iron atom [11].
Also, the total intensity of this transition has been shown
to in- crease with decreasing coordination number for
iron due to the loss of inversion symmetry at the iron site
[12]. The differential pre-edge peaks of Fe nanowires are
listed in Table 1. The differential peak of Fe2O3 with
Fe3+ is at 7133.3 eV, which is larger than the 7111.8 eV of
com mercial pure iron with Fe. The differential pre-edges
of Iron nanowires with or without X-ray irradiation and
hybrid PMMA/iron nanowires are all located between
Fe2O3 and pure iron. For pure Fe2O3, there is a second
differential pre-edge peak at 7117.4 eV that is not observed
in other specimens, including pure iron. It has been proven
that synthesized iron nanowires have an iron oxidation state
between Fe2+ and Fe3+ that forms a surface oxide with an
iron core. The position of third differential pre-edge peaks
is only observed as the differences between pure iron and
iron nanowires (I) and the rest of the specimen. The second
7100 7110 7120 7130 7140
(a) Commercial Fe
(b) Fe nanowires (I)
(c) Fe nanowires (II)
(d) PMMA/Fe nanowires (III)
(e) PMMA/Fe nanowires (IV)
(f) PMMA/Fe nanowires(V)
(g) Commercial Fe2O3
(a)
(a)
(g) (g)
(f)
(f)
(d)
(d)
(c)
(e)
(c)
(e)
(b)
Deriv. norm. absorption
Energy (eV)
1s-4d transition
Fe K-edge
1s-4p transition
(b)
Figure 5. The differential pre-edge (NEXAFS) of the Fe-
K-edge of (a) commercial Fe, (b) Fe nanowires (I), (c) Fe
nanowires (II) (after hard X-ray irradiation), (d) PMMA/Fe
nanowires (III), (e) PMMA/Fe nanowires (IV), (f) PMMA/
Fe nanowires (V), and (g) commercial Fe2O3.
and third peaks may have been caused by the 1s-4p
transition [13]. It is not sensitive to different oxidation
states but is between pure iron and iron oxides.
The Fourier-transformed Fe EXAFS data in Figure 6
indicate that the nearest Fe-O bond appears at about 1.4-
1.6 Å for all specimens, corresponding to a tetrahedrally
coordinated cation. For commercial iron and iron
nanowires without X-ray irradiation, the Fe-Fe bond
length of metallic iron is about 2.1Å and can be observed,
but not in other specimens. XAS, in this study, was
measured in fluorescence mode. Specimens (II) to (V)
have a thicker oxide layer compared to specimen (I).
Thus, the Fe-Fe bond is not observed in these specimens.
The radiation distribution of specimen (II) to (V) shows
major differences compared to commercial Fe2O3. A
previous study [14] indicated that the oxide layer in these
nanowires is Fe3O4. XANES of the O K edge spectra in
Figure 7 also shows dramatic differences between Fe2O3
and the rest of specimens. In the O K-edge, split
absorption peaks are observed only in Fe2O3. This shows
that the iron nanowires can be stabilized by the Fe3O4
surface oxide layer.
As seen in the HRTEM images of Figure 3, transgrain
oxidation occurs when X-rays irradiate iron nanowires.
XAS and XRD results indicate that the oxide phase after
X-ray irradiation is mainly Fe3O4. The oxide layer also
got larger after irradiation. The mechanism of X-ray
induced oxidation may be the following;

FeOOFeh
core 22 2

(2)
 surface
h
surface OFeOFeFeO 43 )(
32 


(3)
The iron atoms diffuse out from the core of the
nanoparticles that form the iron nanowires. Under X-ray
irradiation, iron atoms first oxidize into FeO (Equation 2)
and then react with Fe2O3 to form Fe
3O4 (Equation 3).
Thus, the trace Fe2O3 phase in specimen (I) is transferred
into the Fe3O4 phase, a fact that is proven by XRD and
XAS results.
Table 1. The differential pre-edge peaks of Fe nanowires
and PMMA/Fe nanowires.
Specimens First (eV) Second (eV) Third (eV)
Fe nanowires (I) 7112.1 - 7120.3
Fe nanowires (II) 7112.4 - 7122.7
PMMA/Fe nanowires (III) 7112.2 - 7122.7
PMMA/Fe nanowires (IV) 7112.2 - 7122.7
PMMA/Fe nanowires (V) 7112.1 - 7122.7
Commercial Fe2O3 7113.3 7117.4 7122.7
Commercial Fe 7111.8 - 7120.3

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
57
Nanowires for Potential Hyperthemia Therapy
0246810
(g)
(f )
(e)
(d)
(c)
(a) Commercial Fe
(b) Fe nanowires I
(c) Fe nanowires II
(d) PMMA/Fe nano wires III
(e) PMMA/Fe nanowires IV
(f ) PMMA/Fe nanowires V
(g) Commercial Fe2O3
FT, Ix(R)I (a.u.)
(a)
(b)
R (A)
0
Figure 6. Fourier-transformed Fe EXAFS data of (a)
commercial Fe, (b) Fe nanowires (I), (c) Fe nanowires (II)
(after hard X-ray irradiation), (d) PMMA/Fe nanowires
(III), (e) PMMA/Fe nanowires (IV), (f) PMMA/Fe
nanowires (V), and (g) commercial Fe2O3.
510 515 520 525 530 535 540 545 550 555 560
Energy (eV)
Norm. intensity (a.u.)
(a)
(b)
(c)
(d)
(e)
(f)
(g)
O K-edge
Figure 7. XANES normalized intensity of the O K edge spec
tra of (a) commercial Fe, (b) Fe nanowires (I), (c) Fe
nanowires (II) (after hard X-ray irradiation), (d) PMMA/Fe
nanowires (III), (e) PMMA/Fe nanowires (IV), (f)
PMMA/Fe nanowires (V), and (g) commercial Fe2O3.
3.4. TGA Analysis
To measure the mass content of the specimens, the iron
nanowires and the hybrid PMMA/Fe nanowires were
examined by TGA analysis with an SDT2960
Simultaneous DSC-TGA (TA Instruments) system. The
results are shown in Figure 8. The curves show mass
decreases in specimen (I), (II), (III), (IV) and (V) prior to 166,
303, 216, 254 and 324℃, respectively, under oxygen
atmosphere. Specimen (I), (II), (III), (IV) and (V), had around
0200 400 600 800100012001400
65
70
75
80
85
90
95
100
105
110
115
Weight loss (wt%)
Temperature (oC)
(a)Fe nanowires (I)
(b)Fe nanowires (II)
(c)PMMA/Fe nanowires (III)
(d)PMMA/Fe nanowires (IV)
(e)PMMA/Fe nanowires (V)
(a)
(b)
(c)
(d)
(e)
Figure 8. The TGA spectrums of (a) Fe nanowires (I), (b) Fe
nanowires (II) (after hard X-ray irradiation), (c) PMMA/Fe
nanowires (III), (d) PMMA/Fe nanowires (IV) and (e)
PMMA/Fe nanowires (V).
7.18, 11.29, 8.48, 9.56, and 13.31 wt% mass loss,
respectively, including water, methanol and thermal
decomposition of hydroxide materials. Then, the iron
nanowires started to oxidize and PMMA began to
decompose. After PMMA completely decomposed, the
weights of the specimens were greater than 100%, due to
iron oxide formation. Specimens (III), (IV) and (V) have
a peak at around 500℃ that may have been cause by the
carbonization of PMMA. The Curve (a) for specimen (I)
in Figure 8 shows that the oxidation temperature of iron
nanowires is lower than that of other specimens. This
indicates that the iron nanowires without X-ray or
PMMA treatments are oxidized more easily than other
specimens. This shows that the inner nanograins of
specimen (II) to (V) are protected by thin layers of ox-
ides that resist oxidation at lower temperatures. The
weight gain of specimen (I) due to oxidation is great
larger than that of specimen (II). This indicates that the
iron nanowires treated by X-ray irradiation are highly
oxidized. This phenomenon is also proven by the X-ray
dif- fraction pattern in Figure 1. The major diffraction
peak of pure iron in specimen (II) is from dramatic
reduction. Specimens (III) to (V) show the same
phenomenon as specimen (II). Pure PMMA usually
decomposes before 430℃, but the weight gain peak
decreased in specimens (III), (IV) and (V) when the
temperature was higher than 600℃. This may be due to
further decomposition of the residues of carbonized
PMMA. The iron oxides were reduced at temperatures
higher than 1100℃, which causes weight loss in the
TGA thermogram. At temperatures > 1350℃, the

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
58
Nanowires for Potential Hyperthemia Therapy
residual weight of the specimens indicates their iron
content. The residue weight of specimen (II) at 1350℃
is 77.0wt%, less than that of specimen (I), which is about
85.8wt%, as shown in Figure 8. This confirms that X-ray
irradiation induced the oxidation of specimen (II). Thus,
the oxide content in specimen (II) is larger than in
specimen (I). According to residual weight in the TGA
thermogram, the iron contents of specimens (I) to (V) are
about 85.8, 77.0, 81.2, 76.7 and 70.1wt%, respectively.
3.5. Magnetic Properties
It was recently shown that nanometer thick native-oxide
layers can be used as building blocks in new magnetic
structures [15]. For multilayers consisting of alternating
Fe and Fe-oxide layers, the magnetic moments of the Fe
layers are arranged in a non-collinear fashion [16]. The
structure of nanowires after X-ray irradiation can build a
chain of iron nanoparticle/iron nano oxide layer
structures. This may lead to novel magnetic materials for
application in the electronics or medical fields.
The magnetic properties of the various specimens are
examined at room temperature by VSM. Figure 9 and
Table 2 show magnetic hysteresis curves and data of
these specimens, respectively. The hysteresis loops of
specimens (I), (II), (III), (IV) and (V) reveal their
ferromagnetic behavior. Specimen (II), with X-ray
irradiation, has a saturation magnetization (Ms) that is
173 emu/g larger than that of specimen (I) (138 emu/g).
Their remanences (Mr) are 64 and 51 emu/g, respectively.
TEM images of Figure 3 (a) and (b) show that the
diameter of iron nanograins is approximately 40.4 ± 11.4
nm for specimen (II) and 61.7 ± 3.8 nm for specimen (I).
These results demonstrate that hard X-ray irradiation
causes the refinement of grain size and also induces
oxidation reactions in iron nanograins. For specimens (I)
and (II), the coercivity (Hc) is 789 Oe (reduced
remanence ratio 0.37) and 324 Oe (reduced remanence
ratio 0.37), respectively. The saturation magnetization of
PMMA/Fe nanowires (III, IV and V) is 101, 82 and 71
emu/g; the coercivity is 171, 116 and 60 Oe; and
remanence is 39, 31 and 13 emu/g, respectively.
The magnetic properties of these specimens are attributed
to the size and structure of the iron and iron oxides. For
specimens (I) and (II), it is clear that X-ray irradiation
induces size refinement and reduction of iron oxide. The
Fe2O3 phase is reduced to Fe3O4. This is not only the case in
specimen (II). Specimens (III) and (IV) are also only
reduced to Fe3O4 as observed in X-ray diffraction patterns.
These nanowires are synthesized under strong magnetic
fields, which arranged the nanograins in magnetically
preferred orientation.
-20000 -1000001000020000
-200
-150
-100
-50
0
50
100
150
200
(a)F e wire (I )
(b)F e wire (I I)
(c)P MMA/F e wire (III )
(d)PM MA/F e wire (I V )
(e)PM MA/F e (V )
H (Oe)
M (emu/g)
(e)
(d)
(c)
(a)
(b)
Figure 9. The VSM measurements of (a) Fe nanowires (I),
(b) Fe nanowires (II) (after hard X-ray irradiation), (c)
PMMA/Fe nanowires (III), (d) PMMA/Fe nanowires (IV)
and (e) PMMA/Fe nanowires (V).
Table 2. The VSM measured data of Fe nanowires and
PMMA/Fe nanowires.
Specimens Hc
(Oe)
Mr
(emu/g)
Ms
(emu/g) Sr = Mr/Ms
Fe nanowires (I) 789 51 138 0.37
Fe nanowires (II) 324 64 173 0.37
PMMA/Fe nanowires (III) 171 39 101 0.39
PMMA/Fe nanowires (IV) 116 31 82 0.38
PMMA/Fe nanowires (V) 60 13 71 0.18
The magnetic saturation of iron nanowires and
PMMA/iron nanowires is higher than that of the sphere-
cal Fe colloids produced by sonochemical synthesis (101
emu/g) [17] or iron nanoparticles produced by metal
vapor deposition (55 emu/g) [18]. Figure 1 shows the
effect of the remaining Fe2O3 and Fe3O4 phases. Both
remanence and coercivity are affected by the volume
fraction of the Fe3O4 phase. The magnetic properties of
iron nanowires are similar to nanocrystalline soft
materials where the magnetization averages over several
grains [19]. The exchange interactions between iron
nanograins in nanowires due to agglomeration account
for the remanence enhancement and the drop of the
coercive field as shown in specimen (II) with respect to
the Stoner–Wohlfarth value [20].
4. Conclusions
In summary, iron nanowires and hybrid PMMA/Fe
nanowires were successfully synthesized with the

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
59
Nanowires for Potential Hyperthemia Therapy
oo-like structure of the iron nanowires could
be
ements reveal that the
na
ledge the National Science
REFERENCES
[1] L. Menon, M. dyopadhyay and D
ndyopadhyay, L. Menon, N. Kouklin, H. Zeng and
Y. Liu, S. Bandyop-
Z. An, J. Zhang, and G. Song, “Facile Synthesis
. Yadian, B. and Y. Zhang,
. Lin, Y. Hwu and W. Chen,
Ray Absorption
and F. H. P. M.
er,
nd and E. Paris, “Iron
. Eisenberger and W. E.
l, L. Shu, Y. M. Chiou, K. S. Hagen, M. Ito,
pohl, J. G. DeWitt, B. Hedman, K.
G. Harris and M. E.
reducing agent NaBH4 under an externally applied
magnetic field with radiation polymerization. The
externally applied magnetic field played an important
role in the formation of uniform and parallel iron
nanowires.
The bamb
adh
observed by SEM and HRTEM. An oxide layer
formed on the surface of the iron nanowires. XRD results
showed that the Fe2O3 and Fe3O4 phases coexisted in the
iron nanowires without X-ray irradiation. When these
samples are irradiated by hard X-ray from NSRRC,
Fe3O4 is the only phase that can be observed. The Fe and
O K-edges of XAS were used to distinguish the oxide
structures on the surface of the iron nanowires and
PMMA/iron nanowires. The results of XAS show the
phase transformation of Fe2O3 to Fe3O4. Thus, X-ray
irradiation will induce Fe2O3 phase transformation to
Fe3O4 and stabilize these iron nanowires. TGA analysis
is used here to determine the thermal properties and solid
content of these specimens.
Magnetic hysteresis measur iron
Habraken, “Oxidation of Iron: The Relation between Oxi-
dation Kinetics and Oxide Electronic Structure,” Physical
Review Letters, Vol. 84, No. 15, 2000, pp. 3366-3369.
S. Couet, T. H. Diederich, K. Schlage and R. Röhlsberg
nowires displayed ferromagnetic behavior. For the iron
nanowires (specimen (II)) prepared after X-ray
irradiation, the saturation magnetization is 173 (emu/g)
larger than that of the initial iron nanowires (specimen
(I)). The saturation magnetization of the iron nanowires
and PMMA/iron nanowires is higher than that of
spherical Fe colloids produced by sonochemical
synthesis or iron nanoparticles produced by metal vapor
deposition. Iron nanowires-coated PMMA hybrid
materials could be designed to manipulate the magnetic
and biocompatibility properties for application in
magnetic hyperthermia. This study indicates that X-ray
irradiation treatment of these iron nanowires will provide
a way to manipulate the structural and magnetic
properties of novel hybrid nano-materials.
5. Acknowledgements
[9]
The authors gratefully acknow
Blum
Council, Taiwan, for financial support, and the TLS (01A)
team of the National Synchrotron Radiation Research
Center (NSRRC) for technical support.
Zheng, H. Zeng, S. Ban. O. H
J. Sellmyer, “Size Dependence of the Magnetic Properties
of Electrochemically Self-Assembled Fe Quantum Dots,”
Journal of Electronic Materials, Vol. 29, No. 5, pp. 510-
515.
[2] S. Ba McHe
D. J. Sellmyer, “Electrochemically Self-Assembled
Quantum Dot Arrays,” Journal of Electronic Materials,
Vol. 28, No. 5, 2000, pp. 515-519.
[3] M. Zheng, L. Menon, H. Zeng,
yay, R. D. Kirby and D. J. Sellmyer, “Magnetic
Properties of Ni Nanowires in Self-Assembled Arrays,”
Physical Review B, Vol. 62, No. 18, 2000, pp. 12282-
12286.
[4] S. Pan,
of Prickly CoNi Microwires,” Materials Letters, Vol. 64,
No. 3, 2010, pp. 453-456.
[5] P. Liu, Z. Li, B. Zhao, B
“Template–Free Synthesis of Nickel Nanowires by
Magnetic Field,” Materials Letters, Vol. 63, No. 20, 2009,
pp. 1650-1652.
[6] H. Liou, W. Liou, H
“Characterization of Gold/PMMA Hybrid Nanomaterials
Synthesized by Hard X-Ray Synchrotron Radiation,”
Particuology, Vol. 8, No. 3, pp. 234-239.
[7] H. M. Lin, C. K. Lin and Y. K. Hwu, “X-
Techniques in Examination the Structural Properties of
Nanocrystalline Materials,” Fu Jen Studies, Science and
Engineering, Vol. 38, 2004, pp. 1-26.
[8] S. J. Roosendaal, A. M. Vredenberg
“A Compact UHV Deposition System for in situ Study of
Ultrathin Films via Hard X-Ray Scattering and Spec-
troscopy,” Review of Scientific Instruments, Vol. 79, No.
9, 2008, pp. 093908-1-093908-9.
[10] G. Giuli, G. Pratesi, C. Cipriania
Local Structure in Tektites and Impact Glasses by Ex-
tended X-Ray Absorption Fine Structure and High-
Resolution X-Ray Absorption Near-Edge Structure Spec-
troscopy,” Geochimica et Cosmochimica Acta, Vol. 66,
No. 24, 2002, pp. 4347-4353.
[11] R. G. Shulman, Y. Yafet, P
berg, “Observation and Interpretation of X-Ray
Absorption Edges in Iron Compounds and Proteins,” Pro-
ceedings of the National Academy of Sciences of the
United States of America, Vol. 73, No. 5, 1976, pp.
1384-1388.
[12] C. R. Randal
N. Kitajima, R. J. Lachicotte, Y. Zang and L. Jr. Que,
“X-Ray Absorption Pre-Edge Studies of High-Spin Iron
(II) Complexes,” Inorganic Chemistry, Vol. 34, No. 5,
1995, pp. 1036-1039.
[13] T. E. Westre, P. Kenne
odgson and E. I. Solomon, “A Multiplet Analysis of
Fe K-Edge 1s → 3d Pre-Edge Features of Iron Com-
plexes,” Journal of The America Chemical Society, Vol.
119, No. 27, 1997, pp. 6297-6314.
[14] S. Son, M. Taheri, E. Carpenter, V.
nry, “Synthesis of Ferrite and Nickel Ferrite Nano-
particles Using Radio-Frequency Thermal Plasma Torch,”
Journal of Applied Physics, Vol. 91, No. 10, 2002, pp.

Synthesis and Characterization of Novel Hybrid Poly (methyl methacrylate) / Iron
Nanowires for Potential Hyperthemia Therapy
60
ch, F. T. Parker, D. J. Smith, P. A. Crozier
erger, “Non-
and T. Hyeon, “Sonochemica
7589-7591.
[15] G. S. D. Bea
Hadj
and A. E. Berkowitz, “New Magnetic Order in Buried
Native Iron Oxide Layers,” Physical Review Letters, Vol.
91, No. 26, 2003, pp. 267201-1-267201-4.
[16] T. H. Diederich, S. Couet and R. Röhlsb
collinear Coupling of Iron Layers through Native Iron
Oxide Spacers,” Physical Review B, Vol. 76, No. 5, 2007,
pp. 054401-1-054401-5.
[17] K. S. Suslick, M. Fang l
[2
Synthesis of Iron Colloids,” Journal of the America Che-
mical Society, Vol. 118, No. 47, 1996, pp. 11960-11961.
[18] C. F. Kernizan, K. J. Klabunde, C. M. Sorensen and G. C.
ipanayis, “Magnetic Properties of Nanometer-Scale
Iron Particles Generated by Iron Atom Clustering in Cold
Pentane,” Chemistry of Materials, Vol. 2, No. 1, 1990, pp.
70-74.
[19] W. J. M. Mulder, G. J. Strijkers, G. A. F. van Tilborg, A,
W. Griffioen and K. Nicolay, “Lipid-Based Nanoparticles
for Contrast-Enhanced MRI and Molecular Imaging,”
NMR in Biomedicine, Vol. 19, No. 1, 2006, pp. 142-164.
0] E. V. Shtykova, X. Huang, N. Remmes, D. Baxter, B.
Stein, B. Dragnea, D. I. Svergun and L. M. Bronstein,
“Structure and Properties of Iron Oxide Nanoparticles
Encapsulated by Phospholipids with Poly(ethylene glycol)
Tails,” The Journal of Physical Chemistry C, Vol. 111,
No. 49, 2007, pp. 18078-18086.