Cent. Eur. J. Chem. • 11(3) • 2013 • 358-363
DOI: 10.2478/s11532-012-0165-4
Central European Journal of Chemistry
Development of FeOOH nanoarrays
using magnetic cations
Research Article
Perla E. Garcia-Casillas*, Carlos A. Martinez-Pérez,
Claudia Rodríguez González, Héctor Camacho-Montes,
Santos A. Martel Estrada, Imelda Olivas Armendáriz
Institute of Engineering and Technology, Autonomous University of Juarez,
UACJ, 32320 Cd. Juárez, Chihuahua, Mexico
Received 13 August 2012; Accepted 16 October 2012
Abstract: In this work, FeOOH arrays were obtained using two different magnetic cations. The nanoparticles were grouped into a package having
different orientations through the van der Waals interaction with the magnetic cations. With Fe2+, the FeOOH nanoparticles have a rod
shape with a 30-nm diameter and approximately 1-micron length, and are aligned in a star structure. With Co2+, a somatoidal shape
was observed, with 20-nm diameter and 150-nm length and a pathway structure to the array. The chemical synthesis method was
used to obtain the nanoarrays. The morphology and the average size of the nanorods and nanowires were determined using Field
Emission Scanning Electron Microscopy (FESEM). Fourier Transform Infrared Spectroscopy (FTIR) was used to study the interaction
between the nanorods and the cobalt ions. The phases of the material were identified using X-ray Diffraction.
Keywords: Arrays • Synthesis • Nanoparticles • Magnetism • Ion
© Versita Sp. z o.o.
1. Introduction
Magnetic nanowires have drawn a lot of research interest
due to their unique physical properties and potential
applications in magnetic recording, spin electronics,
optics, sensors and thermoelectronics devices [1-4].
Many researchers have been focused on the control
and modeling of materials with dimensions of roughly
1-100 nm due to the particular and significant sizedependent properties [5-7]. This research area has
been searching for unique phenomena to enable novel
application of nanomaterials. Through nanotechnology,
many properties of matter have been modified to enhance,
for example, the strength and hardness of ceramics or
the coercivity and magnetization of mixed ferrites; as well
as to control optical properties by the variation of the size
and microstructure of nanoclusters [8-11]. Therefore,
the present leading concept in nanomagnetism is to
organize surfactant-mediated nanoparticles into regular
arrays.
Recently, one of the most exciting areas in materials
science has been the study of nanoarrays due to their
358
potential application in fields such as magnetic storage,
optoelectronics, as well as electronic and memory
devices [12]. The impact of array technologies on the
life sciences has been important, in conjunction with
bioinformatics tools, to process and analyze the large
amount of data generated by modern devices. Arrays
have spawned new approaches to new technological
capabilities in electronics applications, optoelectronic,
memory devices, etc. Magnetic-metal nanotube arrays
with giant magnetoresistance may find applications
as magnetic sensors with improved signal due to the
larger resistance of a tube configuration with thin walls
compared with nanowires of a similar diameter [13].
Many methods have been used in order to obtain
arrays. Guohong and Ying synthesized an array of
nanowires using an anodic aluminium oxide template
[14,15]. Assembly of a Co/Fe3O4 nanoparticle array has
been performed using a microelectromagnetic matrix
[16], while Ni nanotube arrays have been obtained by
electrochemical synthesis [17]. This paper describes
the synthesis of FeOOH nanoparticles using magnetic
cations, Co2+ and Fe2+. As a result, a FeOOH nanoarray
* E-mail: perlaelviagarcia@yahoo.com
pegarcia@uacj.mx
J. G. Camacho-Meza et al.
with some special magnetic properties was obtained.
A mechanism for the formation of FeOOH-Fe2+ and
FeOOH-Co2+ is discussed.
2. Experimental procedure
2.1. FeOOH with Fe2+
In order to synthesize FeOOH, 1.3523g of FeCl3•6H2O,
0.6852 g of FeSO4•7H2O and 1.20g of (NH2)2CO were
dissolved in 50 mL of deoxygenated water, then were
heated at 70ºC for 1 hour with a reflux condenser.
A yellow precipitate was obtained. Afterward, the
temperature was increased to 90-95ºC. This condition
was maintained for 18 h, followed by cooling and aging
for 12 h at room temperature.
2.2. FeOOH with Co2+
Nanoparticles of FeOOH were prepared by the
hydrolysis of 0.64M ferric chloride (FeCl3•6H2O) (ecc.1)
and the decomposition of urea ((NH2)2CO) (ecc.2) at
90°C for 2 h, after which the solution was left for 16 h at
room temperature. In order to remove residual ions, the
obtained powder was centrifuged and washed several
times until a pH of 7 was reached, and then was dried
at 100°C.
Field emission scanning electron microscopy
(FESEM; JEOL 7000F) was used to analyze the
morphology, and particle-size distribution was
determined using Scandium software with FESEM
images of the precursor and the cobalt ferrite. In order
to understand the interaction mechanism between
nanorods and Fe2+ and Co2+ cations, Fourier transform
infrared spectroscopy (FTIR; ThermoScientific Nicolet
6700) was used. X-Ray Diffraction (XRD; PANalytical
XRD84) was used to confirm the crystalline structure.
The magnetic properties were measured by a vibrating
sample magnetometer (VSM). Magnetic measurements
were performed at room temperature in magnetic field
up to 20 kOe.
3. Results and discussion
3.1. FeOOH with Fe2+
In the growth of FeOOH particles, there are many
steps. In the first step, Fe3+ and Fe2+ are precipitated
as amorphous materials (Fig. 1A) where some swelling
is observed (Fig. 1B), indicating the nucleation
of nanoparticles of FeOOH. Afterwards, small
protuberances started to grow from the amorphous
materials (Fig. 1C), these small rods grew inside the raw
materials with a few nanometers diameter (Fig. 1D). The
particles were grouped with 6 to 8 rods; these groups
emerge in different directions with a star structure
(Figs. 1E, 1F) takes it to an extreme of the rods. The
nanorods have a 30-nm diameter and an approximate
length of 1 micron.
The infrared spectrum of FeOOH was obtained
with the KBr pressed disk technique and is shown in
Fig. 2. An intense band due to the bulk hydroxyl stretch
is observed at 3140 cm-1. The OH bending bands at
892 cm-1 (δ-OH) and 795 cm-1 (γ-OH), which vibrate in
and out, respectively, of the (001) plane, are important
diagnostic bands and also provide information about
crystallinity. The frequencies of these vibrations depend
on both the OH sites and resonance phenomena [18].
In this case, the difference between the two bands is
97 cm-1, indicating well-crystallized goethite [19].
The band at 630cm-1 is due to Fe-O interaction, this
vibration is affected by the morphology and crystallinity,
and corresponds to a transverse moment in the (010)
plane.
Fig. 3 shows the XRD pattern of the particles
of FeOOH with and without Fe2+. In the first case, a
tetragonal phase was found of the FeOOH, corresponding
to akaganeite, and some peaks corresponding to
maghemite were found. When the Fe2+ was added,
maghemite was the principal phase.
The suggested formation mechanism is:
FeCl3 + 3 H2O ⇒ Fe(OH)3 + 3HCl
(1)
0 oC
Fe(OH)3 ⇒ FeOOH + H2O
(2)
FeSO4 + 2H2O ⇒ Fe(OH)2 + H2SO4
(3)
0 oC
(NH2)2CO + H2O ⇒ 2NH3 + CO2
(4)
FeOOH + Fe(OH)2 ⇒ Fe3O4
(5)
3.2. FeOOH with Co2+
In this case, the particles’ shape was somatoidal. In
Fig. 4, an image of the FeOOH array is shown. The
particles were grouped in a package forming different
routes (Figs. 4A,4B). The particle diameter was 20 nm
and length averaged 150 nm (Fig. 4C).
The infrared spectrum of FeOOH was obtained with
the KBr pressed disk technique and is shown in Fig. 5.
The spectrum shows the absorption band at ∼430 cm-1,
which is the energy translation of Fe-O Stretch. This
spectrum shows a wide band at ∼689 cm-1 attributed
to the double band of the O-H⋅⋅⋅O bonds. The 820 cm-1
band is due to the O-H bond. These bands are related
to the characteristic vibration of akaganeite (β-FeOOH).
359
Development of FeOOH nanoarrays using magnetic cations
Figure 1.
360
(a)
(b)
(c)
(d)
(e)
(f)
FeOOH array with Fe2+ interaction. (a) Amorphous material, (b) little swelling in amorphous material, (c) protuberance started grow,
(d) small rods grew inside the raw materials, (e) and (f) star structure of FeOOH.
J. G. Camacho-Meza et al.
100
90
80
% Transmitance
70
60
50
40
30
20
10
0
3900
3400
2900
2400
1900
Wave number (cm-1)
1400
900
400
Figure 2. FTIR spectra of FeOOH nanoparticles with Fe2+.
Figure 3. X-ray diffraction pattern of FeOOH with and without Fe2+.
(a)
Figure 4.
(b)
(c)
SEM image of FeOOH arrays with Co2+ interaction.
361
Development of FeOOH nanoarrays using magnetic cations
120
% Transmitance
100
80
60
40
20
0
3900
Figure 5.
3400
2900
2400
1900
Wave number (cm-1)
1400
900
400
FTIR spectra of FeOOH with Co2+.
Figure 6. X-ray diffraction pattern of FeOOH with and without Co2+.
The ∼3400 and ∼1640 cm-1 bands are due to OH- and
H-O-H stretch of H2O. Additional bands were found
(2940, 1380, 1520, 1640 cm-1), which are attributed to
the KBr. When the cobalt was added, the 820 cm-1 band
due to the O-H bond disappeared, indicating a possible
interaction with the cobalt; however, no more bands
were detected, so we can assume the cobalt can be
bound to the oxygen by van der Waals forces. For this
reason, the formation of the nanoparticle arrays could
be attributed to the presence of cobalt ions.
The crystallinity of the FeOOH nanoparticles
has been altered with the added Co2+; in Fig. 6,
the DRX pattern of FeOOH shows the crystalline
planes of tetragonal akaganeite, βFeOOH, but
when Co2+ was added, the FeOOH particles were
amorphous.
362
Suggested formation mechanism:
Fe+3 + 3OH- ⇒ Fe(OH)3
(6)
Fe(OH)3 ⇒ FeOOH + H2O
(7)
Co2+ + 2OH- ⇒ Co(OH)2
(8)
2FeOOH + Co(OH)2 ⇒ CoFe2O4+ 2H2O
(9)
4. Conclusion
The influence of magnetic cations in the synthesis of
FeOOH nanoparticles was studied. The formation of
star and pathway arrays was obtained by the van der
J. G. Camacho-Meza et al.
Waals interaction of FeOOH particles with Fe2+ and
Co2+ using chemical synthesis. The particle shape
was modified by the presence of these cations, and the
kinetics of formation of the rods and somatoidal particles
of FeOOH were studied.
Acknowledgments
The authors are very grateful to the Science and
Technology Council of México for financial support
through the project CONACYT SEP-2004-C01-47290.
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