An easy synthesis of nanostructured magnetite-loaded functionalized carbon spheres and cobalt ferrite

Article abstract of DOI:10.1080/00958972.2013.867037

An easy method in a solvothermal system has been developed to synthesize nanostructured magnetite (Fe3O4)-loaded functionalized carbon spheres (CSs) and cobalt ferrite (CoFe2O4). Surface-tunable CSs loaded with iron oxide (Fe3O4) nanoparticles were prepared using an acetylferrocene Schiff base (OPF), whereas spinel cobalt ferrite (CoFe2O4) was synthesized via metal complexes of a ferrocenyl Schiff base with phenol moiety (Co-OPF). The formed composite powder was investigated using X-ray powder diffraction, Raman spectrometry, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. It was found that most of the iron oxide nanoparticles were evenly distributed upon the surface of the CSs. Furthermore, the surface of the iron oxide-loaded CSs has large numbers of functional groups. Good saturation magnetization was achieved for the formed magnetic nanoparticles. 2013

Full text of DOI:10.1080/00958972.2013.867037

This article was downloaded by: [University of Louisville]
On: 18 December 2014, At: 20:37
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered
office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Journal of Coordination Chemistry
Publication details, including instructions for authors and
subscription information:
http://www.tandfonline.com/loi/gcoo20
An easy synthesis of nanostructured
magnetite-loaded functionalized
carbon spheres and cobalt ferrite
Ali M. Hassana, Amr M. Nassara, Nabila M. Ibrahimb, Ahmed M.
Elsamanc & Mohamed M. Rashadc
a Deparment of Chemistry, Faculty of Science, Al-Azhar Univeristy,
Cairo, Egypt
b Department of Organometallic & Organometalloid Chemistry,
National Research Centre, Cairo, Egypt
c Department of Advanced Materials, Central Metallurgical
Research & Development Institute (CMRDI), Cairo, Egypt
Published online: 10 Dec 2013.
To cite this article: Ali M. Hassan, Amr M. Nassar, Nabila M. Ibrahim, Ahmed M. Elsaman &
Mohamed M. Rashad (2013) An easy synthesis of nanostructured magnetite-loaded functionalized
carbon spheres and cobalt ferrite, Journal of Coordination Chemistry, 66:24, 4387-4398, DOI:
10.1080/00958972.2013.867037
To link to this article: http://dx.doi.org/10.1080/00958972.2013.867037
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the
“Content”) contained in the publications on our platform. However, Taylor & Francis,
our agents, and our licensors make no representations or warranties whatsoever as to
the accuracy, completeness, or suitability for any purpose of the Content. Any opinions
and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content
should not be relied upon and should be independently verified with primary sources
of information. Taylor and Francis shall not be liable for any losses, actions, claims,
proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or
howsoever caused arising directly or indirectly in connection with, in relation to or arising
out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any
substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing,
systematic supply, or distribution in any form to anyone is expressly forbidden. Terms &

Conditions of access and use can be found at http://www.tandfonline.com/page/terms-
and-conditions

Journal of Coordination Chemistry, 2013
Vol. 66, No. 24, 4387–4398, http://dx.doi.org/10.1080/00958972.2013.867037
An easy synthesis of nanostructured magnetite-loaded
functionalized carbon spheres and cobalt ferrite
ALI M. HASSAN†, AMR M. NASSAR†, NABILA M. IBRAHIM‡,
AHMED M. ELSAMAN*§ and MOHAMED M. RASHAD§
†Deparment of Chemistry, Faculty of Science, Al-Azhar Univeristy, Cairo, Egypt
‡Department of Organometallic & Organometalloid Chemistry, National Research Centre, Cairo,
Egypt
§Department of Advanced Materials, Central Metallurgical Research & Development Institute
(CMRDI), Cairo, Egypt
(Received 2 August 2013; accepted 13 November 2013)
An easy method in a solvothermal system has been developed to synthesize nanostructured magne-
tite (Fe3O4)-loaded functionalized carbon spheres (CSs) and cobalt ferrite (CoFe2O4). Surface-tun-
able CSs loaded with iron oxide (Fe3O4) nanoparticles were prepared using an acetylferrocene
Schiff base (OPF), whereas spinel cobalt ferrite (CoFe2O4) was synthesized via metal complexes of
a ferrocenyl Schiff base with phenol moiety (Co-OPF). The formed composite powder was investi-
gated using X-ray powder diffraction, Raman spectrometry, Fourier transform infrared spectroscopy,
scanning electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magne-
tometry. It was found that most of the iron oxide nanoparticles were evenly distributed upon the sur-
face of the CSs. Furthermore, the surface of the iron oxide-loaded CSs has large numbers of
functional groups. Good saturation magnetization was achieved for the formed magnetic nanoparti-
cles.
Keywords: Nanostructures; Organometallic compounds; Magnetic material; Magnetite-loaded carbon
sphere
1. Introduction
Iron oxide nanoparticles are employed in numerous environmental applications including
Fischer–Tropsch catalysts, oxygen reduction catalysts in fuel cells, environmental adsor-
bents for CO or arsenic, catalysts for CO oxidation, and destruction of polychlorinated dib-
enzodioxins/dibenzofurans PCDDs/PCDFs [1–4]. Surface modification and/or coating of
carbon spheres (CSs) have been of considerable interest recently. Coating the CSs with
metal, alloy, oxide, or semiconductor nanoparticles could improve the functionality, compat-
ibility, and reactivity of the surface. Therefore, spheres with specific catalytic, magnetic,
electronic, optical, or optoelectronic properties have greatly widened their utility in the
fields of electronics, magnetism, optics, catalysis, and bioscience [5–11]. Carbon provides
several advantages as a metal nanoparticle support including inertness in acidic and basic
conditions, thermal and mechanical stability of the porous structure, and high surface area
*Corresponding author. Email: a.m.elsaman@cmrdi.sci.eg
© 2013 Taylor & Francis

4388
A.M. Hassan et al.
and defined/modifiable porous structure [12]. For example, Wang et al. [13] fabricated ZnO
nanoparticles and nanorods coated on CS surfaces. The results were observed in all prod-
ucts.
Metal-impregnated carbon materials are traditionally prepared in a multi-step process
which includes selection, preparation, and modification of the carbon support; loading of
the metal precursor onto carbon using incipient wetness, excess solution, ion-exchange
impregnation techniques, or chemical vapor deposition; and conversion of the metal precur-
sor to the desired metal oxide or zero-valent form by physical (e.g. heating) or chemical
(e.g. reduction) treatments [14]. Therefore, a continuous, single-step process is developed
for preparing nanostructured porous CSs impregnated with magnetite (Fe3O4) or zero-valent
iron nanoparticles (Fe–C) from ferrocenyl derivatives. In addition, Fe3O4, as a conventional
magnetic material, has shown great potential applications in targeted drug delivery, protein
separation, magnetic recording media, and magnetic resonance imaging (MRI) [15, 16].
The objective of the present work is to describe the synthesis of the magnetite-loaded CS
products. By means of a solvothermal route, the proposed mechanism for their formation is
investigated. On the other hand, it is not easy to coat the CSs with other functional materi-
als, especially in one step. Here an easy method is reported to synthesize iron oxide-loaded
functionalized CSs and cobalt ferrite (CoFe2O4). Then the complex is employed as compos-
ite precursor for synthesis of CoFe2O4. Experiments were carried out using ethylene glycol
(EG), which has been reported as an effective reaction medium due to its special physical
and chemical properties [17–19].
2. Experimental
2.1. Materials
Acetylferrocene was obtained from Sigma Aldrich Chemical Co. and used directly without
further purification. All other reagents were of analytical grade.
2.2. Methods
2.2.1. Synthesis of Fe3O4-loaded CSs. The OPF was synthesized first by dissolving
2-aminophenol (1.09 g, 10 mM) in about 20 mL ethylacetate; then, the formed solution was
added slowly to a magnetically stirred solution of acetylferrocene (2.28 g, 10 mM) in
20 mL ethylacetate. The mixture was refluxed for 2 h. The solution was concentrated to the
appropriate volume. Thereafter, it was cooled at 5 °C, filtered, treated with ethanol solution,
and dried overnight. Then the purity of products was checked by thin layer chromatography
(TLC) on silica gel. The product obtained was recrystallized from 10 to 15 mL hot ethanol
to give OPF. Chemical Formula of OPF: C18H17FeNO which is illustrated in figure 1.
Then, 0.3 g of OPF was dispersed in EG (10 mL) with water (5 mL) with the aid of
ultrasonication at room temperature to form a suspension. The resulting suspension was
sealed in a 25 mL Teflon-lined stainless steel (autoclave) and maintained at 160 °C for
24 h, and then cooled to room temperature naturally. The black products were separated by
centrifugation, washed several times with deionized water, absolute ethanol, and acetone,
and then dried under vacuum at room temperature.

Magnetite Loaded Carbon Sphere
4389
N
CH3
HO
Fe
Figure 1. Suggested structure of OPF.
2.2.2. Synthesis of CoFe2O4. The complexes were prepared by adding 2.0 mM of CoCl2 .
6H2O (dissolved in ca. 20 mL water) in a warmed solution of the ligand (4.0 mM of OPF)
in ethanol (20 mL). The mixture was refluxed for 2.0 h. The complex that separated out on
cooling at 5 °C was filtered, washed twice with cold ethanol, and dried. Chemical formula
of Co (OPF): C36H36CoFe2N2O4. The suggested structure is shown in figure 2.
The cobalt ferrite synthesized from Co (OPF) was dispersed in (10 mL) water with the
aid of ultrasonication at room temperature to form a suspension. The resulting suspension
was autoclaved and maintained at 250 °C for 24 h, and then cooled to room temperature
naturally. The black products were separated by centrifugation, washed several times with
deionized water, absolute ethanol, and acetone, and then dried under vacuum at room
temperature.
CH3
Fe
N
H2O
Co
O
H2O
O
N
CH3
Fe
Figure 2. Suggested structure of Co (OPF).

4390
A.M. Hassan et al.
2.3. Physical characterization
The as-prepared products were characterized using an ultrasonic generator (Dr Hielscher
UP400 S ultrasonic processor) equipped with an H22 sonotrode of 22 mm diameter,
operating at 24 kHz with a maximum power output of 400 W, for the ultrasonic irradiation.
The ultrasonic generator automatically adjusts the power level. X-ray powder diffraction
(XRD) was identified using a Bruker D8-advance (Cu Kα λ = 0.154056 nm). Scanning
electron microscopy (SEM) was performed using a Philips XL-30E. FT-IR and Raman
Spectroscopy were compressed with KBr as disks on the JASCO FT/IR-6300 type A spec-
trometer. Magnetic measurements were measured using a vibrating sample magnetometer
(VSM; Lake Shore, 7600 LDJ, USA) in a maximum applied field of 10 kOe. From the
obtained hysteresis loops, the saturation magnetization (Ms), remanence magnetization (Mr),
and coercive field (Hc) were determined.
3. Results and discussion
In this paper, the Fe3O4 nanoparticle-loaded CSs were obtained by adding EG from the
OPF Schiff base to the reaction medium. The structure and the chemical composition of the
products were determined by XRD. The pattern (figure 3(a)) indicates that the spinel struc-
ture has two cations sites: the tetrahedrally coordinated A sites and the octahedrally coordi-
nated B sites. For Fe3O4, the A and B positions are occupied by Fe3+ and Fe2+ cations,
respectively. For CoFe2O4, the A and B positions are equally occupied by Co and Fe cat-
ions. Fe3O4 and CoFe2O4 have an almost similar lattice parameter: a = 8.3963 Å for Fe3O4,
a = 8.39 Å for CoFe2O4.
To investigate the effect of experimental parameters on the formation of the products, a
series of experiments was carried out: first, using EG with water at 160 °C for 24 h to give
Fe3O4-loaded CSs, and second using 10 mL water at 160 °C for 24 h to produce Fe3O4
Figure 3. (a) Schematic model of the spinel unite cell structure and (b) XRD patterns of: (I) Fe3O4-loaded CSs
and (II) Fe3O4 (III) CoFe2O4-loaded CSs.

Magnetite Loaded Carbon Sphere
4391
only. It is well known that water can serve as a solvent in the liquid phase reaction. There-
fore, the Fe3O4 nanoparticles were obtained without CSs by adding water to the reaction
medium and decomposition of carbon and nitrogen present in chemical constituent of the
Schiff base ligand (OPF) due to the higher temperature of the hydrothermal system than the
boiling point of water, while in the synthesized Fe3O4-loaded CSs the solvothermal system
is 160 °C lower than the boiling point of EG. So, EG has a higher viscosity than water,
increases the viscosity of the reaction medium, and then decreases the diffusion rate of sol-
utes, thus resulting in the formation of CSs from carbon present in OPF. And it is well
known that EG can serve as both a solvent and a reducing agent in the liquid phase reaction
[20–23]. Figure 3(b) (I, II) displays the XRD pattern of the Fe3O4 nanoparticles, which can
be indexed to the Fe3O4 phase with lattice parameter a = 8.398 Å (JCPDS 19-0629). This
presents further evidence of the formation of Fe3O4. Moreover, a weak and broad peak at
around 2θ = 25° was observed in the XRD pattern of Fe3O4-loaded CSs figure 3(b) (I) indi-
cates an amorphous structure of the CSs.
The CoFe2O4 can be synthesized from the Co complex of OPF in 10 mL water at
250 °C for 24 h in the hydrothermal system Also, the decomposition of C and N in the sys-
tem happens by the higher temperature of reaction. In figure 3(b) (III), the resolved diffrac-
tion peaks can be indexed to CoFe2O4 phases which match the standard card of (JCPDS #
33-0664). The CoFe2O4 was synthesized via the cobalt complex Schiff base (Co-OPF),
while the characteristic peaks were observed for other impurities, such as α-Fe2O3, in
CoFe2O4 only. The mass densities for Fe3O4 and CoFe2O4 (in figure 3(b) (I–III)) are almost
identical. Considering the facts of the very small difference in atomic numbers between Co
and Fe and the identical crystal structure, the two phases can be hardly distinguished by X-
ray diffraction, especially with the shape-induced peak broadening [24].
Furthermore, the crystallite sizes of the produced magnetite nanoparticles loaded onto the
CSs (I), magnetite (II), and CoFe2O4 (III) nanoparticles for the most intense peak (311)
planes were calculated from the XRD data based on the Debye–Scherrer formula. It was
found that the crystallite sizes of the formed powders were ~50, 65, and 86 nm,
respectively.
The change in the microstructures of the formed powders was investigated using FESEM
micrographs, as shown in figure 4. The formed particles consist of a large quantity of
Fe3O4-loaded CSs and the CSs have perfect spheres with smooth surfaces with an average
diameter of about 500 nm. It can be seen that the Fe3O4 nanoparticles loaded onto CSs are
evenly distributed as small, round, and uniform white spots on the surface of the CSs.
Moreover, it was found that some Fe3O4 nanoparticles are studded on the surface of the
CSs. This special structure can effectively stabilize the Fe3O4 nanoparticles and prevent
them from aggregation too. Additionally, the energy-dispersive X-ray spectroscopy (EDX)
spectrum of the products indicates that the sample is mainly composed of Fe, O, and C, as
given in figure 4(b).
Figure 5 displays the SEM image of Fe3O4 nanoparticles without CSs. It can be seen that
the CSs become very low where there is the probability of the existence of a small percent-
age of carbon due to non-complete decomposition of carbon in the ligand, which may origi-
nate from the low-viscous solvent. Additionally, the EDX spectrum of the products
indicates that the sample is mainly composed of Fe and O. The addition of water, which
has lower viscosity than EG, decreases the viscosity of the reaction medium and then
increases the diffusion rate of solutes.
Figure 6 demonstrates the SEM micrograph of CoFe2O4 nanoparticles. The particles
appeared as very fine and homogeneous agglomerated grains. Additionally, the EDX

4392
A.M. Hassan et al.
Figure 4. (a) FESEM and (b) EDX spectrum of magnetite-loaded CSs.
Figure 5. (a) SEM and (b) EDX of Fe3O4 without CSs (OPF 0.3 g, 10 mL water, 160 °C, 24 h).
spectrum of the products indicates that the sample is mainly composed of Co, Fe, and O,
identical to the crystal structure of spinel CoFe2O4 phase. Furthermore, we indicate the
quantitative analysis element. Table 1 shows the weight percent and intensity of Fe3O4−
loaded CSs, Fe3O4, and CoFe2O4.
Raman and Fourier transform infrared spectroscopy (FT-IR) spectra were recorded to fur-
ther disclose the structural nature of the products and the results are illustrated in figure 7.
One can clearly see from figure 7(a) that peaks at the main band are centered at 668 cm−1
and peaks at ca. 540 cm−1 and 300 cm−1 have been assigned to A1g, T2g, and Eg vibrations
of magnetite. These peak positions match that of typical Fe3O4 [25], which provides further
support for the formation of the Fe3O4 phase. Prominent peaks in the Raman spectra at
1589 and 1350 cm−1 correspond to the E2g (2) (G band) and disorder-induced (D band)
modes of CSs, respectively. Broad bands at 2700–3200 cm−1 have been observed in the
Raman spectra of both samples. Three bands at 2674, 2914, and 3181 cm−1 for carbon

Magnetite Loaded Carbon Sphere
4393
Figure 6. (a) SEM and (b) EDX spectrum of CoFe2O4.
Table 1. Quantitative analysis and intensity of Fe3O4-loaded CSs, Fe3O4, and CoFe2O4.
Co Fe
Net inte. Net inte.
O
C
wt.%
wt.%
wt.%
Net inte.
wt.%
Net inte.
Fe3O4 loaded CSs
Fe3O4
CoFe2O3
–
–
25.88
42.44
29.35
9994.64
1044.45
2098.81
42.99
57.32
53.45
584.61
8765.34
876.45
31.14
–
–
2381.35
–
–
–
15.22
343.76
spheres (CSs) are obtained after spectral deconvolution (figure 7(a)). The bands at 2674 and
3181 cm−1 can be attributed, respectively, to the second-order D(2 χ D) and G(2 χ G)
modes. The band at 2914 cm−1 is due to the combination mode of D and G bands [26].
Moreover, the FT-IR spectrum of the formed powders shown in figure 7(b) indicate that the
peak at 592 cm−1 was attributed to the stretching vibration of Fe–O in Fe3O4 [27, 28].
Besides, a broad peak at 1060 cm−1 was ascribed to C–OH stretching vibration, whereas
two bands around 1409 and 1595 cm−1 were observed, which can be assigned to the sym-
metric and asymmetric stretching vibration of COO– groups [29, 30]. All of those peaks
revealed that the surface of the Fe3O4-loaded CSs still has large numbers of functional
groups, such as C–OH and COO– groups, which makes surface modification unnecessary.
Moreover, FT-IR spectra of the powders showed that the absorption bands at around 1140,
1620, and 2450 cm−1 are due to the stretching vibrations of the C–O and C=O, respectively.
The broad band centered around 3400 cm−1 was related to anti-symmetric and symmetric
vibration of the OH group of adsorbed water. Furthermore, it is observed that the absorption
peak at 2930 cm−1 represents the stretching vibration of the C–H bond [31]. However, the
FT-IR spectrum of CoFe2O4 has two main broad metal–oxygen bands as shown in figure
7(b). The highest one, generally observed in the range 600–500 cm−1, corresponds to intrin-
sic stretching vibrations of the metal at the tetrahedral site Mtetra–O stretching vibration
bands in CoFe2O4 compounds. A band observed at 731 cm−1 is assigned to the stretching
mode of Co–O.
Based on the results, it was concluded that the Fe3O4-loaded CSs and CoFe2O4 have
been synthesized through adding EG to the reaction medium. In addition, Fe3O4, as a con-
ventional magnetic material, has shown great potential applications in targeted drug

4394
A.M. Hassan et al.
(a)
1589
1350
2752
2944
300
668
540
3190
500
1000
1500
2000
2500
3000
3500
Raman shift (cm-1 )
(b)
Cobaltferrite
Magnetite CSs
3500
3000
2500
2000
1500
1000
500
wavenumber(cm-1)
Figure 7. (a) Raman spectra of Fe3O4. (b) FT-IR spectra of Fe3O4-loaded CSs and CoFe2O4.
delivery, protein separation, magnetic recording media, and MRI, and also facilitates the
absorption of metal ions using the composites as templates for multifunctional hybrid core/
shell structures or hollow/porous composites.
Based on the results, it was concluded that the Fe3O4 without CSs has been synthesized
through addition of water to the reaction medium. Taking into account the literature [13,
32–34] and our experimental results, a possible formation mechanism of the products is
proposed, as schematically shown in figure 8, although the exact formation mechanism is
not yet clear due to the reaction complexity in the sealed system. When the sealed reaction
system was heated to a certain temperature, the precursor molecules in the solution started
to dehydrate; some dehydrated compounds were formed during the initial stage. With the
advancing of reaction, when the system reached a critical condition, the sphere nuclei were
formed by the dehydrated compounds while the carbonization happened. Then, the resulting
nuclei grew by diffusion of solutes to form CSs as driven by minimum interfacial energy.
So, the formation of the CSs may follow dehydration or anhydridisation, nucleation,

Magnetite Loaded Carbon Sphere
4395
Figure 8. A schematic formation of Fe3O4-loaded CSs.
carbonization, and growth processes. At the same time, the Fe atoms reacted with the
molecular water and residual oxygen dissolved in the solution to form FeOOH or Fe(OH)3,
and then the precursor accreted on the CSs was in situ dehydrated finally to form
thermodynamically stable Fe3O4 particles in the sealed system. However, in the mixed solu-
tion, the EG acted as a reducing agent, which limited the oxidation degree of Fe atoms and
promoted the formation of the Fe3O4 particles. As expected, EG plays an important role in
the formation of the Fe3O4 particles.
It is of great interest to investigate the magnetic properties of Fe3O4-loaded CSs, Fe3O4,
and CoFe2O4. The magnetic properties of the samples were investigated using a VSM with
an applied field of 10 kOe. Figure 9 shows M–H hysteresis loops for the prepared samples
measured at room temperature. The saturation magnetization (Ms) was 48.9, 35.3, and 36.1
emu/g whereas the coercivity force was, 12.0, 115.8, and 1189.9 Oe for Fe3O4-loaded CSs,
Fe3O4, and CoFe2O4, respectively, as shown in table 1. The obtained values are lower than
the bulk Fe3O4 value (Ms = 92 emu/g) [35, 36] and they are equal to the previously reported
value by Hu et al. which was 48 emu/g [37]. Magnetic properties of materials are generally
influenced by many factors, such as size, structure, surface disorder, morphologies, shape
anisotropy, etc. [38, 39]. Furthermore, the Ms values were dependent on magnetite particle

4396
A.M. Hassan et al.
60
40
(a)
430
(b)
(c)
20
20
10
0
-10
-20
-20
-430
-40
-60
-10000
-5000
0
5000
10000
H/Oe
Figure 9. M–H hysteresis loops measured at room temperature for: (a) Fe3O4-loaded CSs, (b) Fe3O4, and (c)
CoFe2O4.
size, as can be seen from table 1, where the saturation magnetization increased with the
increase of the particle size. Hence, increasing the particle size in Fe3O4 would result in
fewer crystal defects and more homogenous particle shape [40]. Therefore, the super
exchange interaction of Fe–O–Fe was strengthened, and the magnetic properties of Fe3O4
nanoparticles were better for the aqueous medium sample. However, it is interesting to note
that remanence magnetization (Mr) and coercive force (Hc) of the two samples are incon-
spicuous, as shown in table 2. The very low Hc might be caused by the surface coordination
of hydroxyl, which attached to the particle surfaces, thus altering the exchange interactions
between the neighboring iron ions and eventually leading to a decrease in the remanence
magnetization and coercive force of the magnetite particles. These data mean that the sam-
ples were in superparamagnetic state. However, it is clear that the value of saturation mag-
netization of CoFe2O4 is 36.1 emu/g, which is smaller than the bulk value (~80 emu/g)
[41]. This result can be attributed to the nano-sized CoFe2O4 particles in which the surface
areas are larger, and thus the surface energy and surface tension are high. This result
changes in cationic preferences and led to an increased degree of anti-site defects and thus
Table 2. Crystallite size, average particle size, and magnetic properties of produced ferrites samples.
Magnetic properties
Sample
Crystallite size
(nm)
Saturation magnetization
Remanence magnetization
Coercive field
Hc (Oe)
Ms (emu/g)
Mr (emu/g)
Fe3O4-loaded
CSs
50.0
48.9
1.2
12.0
Fe3O4
65
86
35.3
36.1
5.7
115.8
CoFe2O4
15.9
1189.9

Magnetite Loaded Carbon Sphere
4397
lesser magnetization, i.e. the degree of inversion in CoFe2O4 in which there is exchange of
Co2+ and Fe3+ ions from octahedral and tetrahedral sites and vice versa [42]. Compared
with the Hc value of bulk CoFe2O4 reported in the literature (5400Oe), the produced
CoFe2O4 nanocrystals exhibited smaller coercivity, which is likely attributed to their nano-
structures [43, 44]. More detailed investigations on the magnetic properties of these prod-
ucts are still under way. The magnetic properties enable them to be manipulated easily by
means of an external magnetic field. We believe that the magnetic composites obtained will
have many important applications in advanced magnetic materials and biomedical fields,
such as MRI, targeted drug delivery, and biomolecular detection and separations.
The above experimental results show that this synthesis strategy is simple, easy, and mild
for preparing iron oxide-loaded functionalized CSs. Furthermore, it was also observed that
the strategy has good reproducibility and the as-synthesized composites are highly
air-stable. This strategy presents a novel pathway for the preparation of the composites.
Thus, it can be concluded that Fc and its some derivatives can be used as precursors for the
preparation of the iron oxide-loaded CSs. It is expected that this synthesis strategy may also
be extended to other metallocenes or organometallic compounds for preparing other
functional materials.
4. Conclusions
Size and surface-tunable CSs loaded with ferrites (Fe3O4-loaded CSs or CoFe2O4) nanopar-
ticles. This is the first report on the one-step synthesis of these composites using acetylfer-
rocene and its derivatives as precursor in the solvothermal system. The composites with
many functional groups and magnetic nanoparticles on the surface of the CSs may not only
make possible the loading of other functional molecules for diagnostics and drug delivery
but also contribute to the development of multifunctional magnetic materials for applica-
tions in advanced magnetic materials and biomedical fields. Good saturation magnetization,
48.8 and 36.1emu/g, were achieved for the formed Fe3O4-loaded CSs and CoFe2O4, respec-
tively. Further work on using the composites is in progress.
Acknowledgement
This work was supported by the Central Metallurgical Research and Development Institute
(CRDI), Cairo, Egypt.
References
[1] Ph. Serp, R. Feurer, Ph. Kalck, Y. Kihn. JL. Faria, JL. Figueiredo, Carbon, 39, 621 (2001).
[2] Q. Wang, F. Cao, Q. Chen, C. Chen. Sol. Mater. Lett., 59, 3738 (2005).
[3] H. Hou, A.K. Schaper, F. Weller, A. Greiner. Chem. Mater., 14, 3990 (2002).
[4] Z. Wang, L. Yu, W. Zhang, Z. Zhu, G. He, Y. Chen, G. Hu. Phys. Lett., A307, 249 (2003).
[5] H. Li, Q. Wang, L. Shi, L. Chen, X. Huang. Chem. Mater., 14, 103 (2002).
[6] H. Li, Q. Wang, L. Shi, L. Chen, X. Huang. Carbon, 39, 2211 (2001).
[7] X.L. Li, T.J. Lou, X.M. Sun, Y.D. Li. Chemistry, 43, 5442 (2004).
[8] V.G. Pol, M. Motiei, A. Gedanken, J. Calderon-Moreno, Y. Mastai. Chem. Mater., 15, 1378 (2003).
[9] A.B. Fuertes, P. Tartaj. Small, 3, 275 (2007).
[10] R. Li, H. Li, X. Qiu, L. Chen. Chem. Eur. J., 12, 4083 (2006).
[11] X. Hu, J.C. Yu, J. Gong. J. Phys. Chem. C, 111, 11180 (2007).
[12] X. Sun, Y. Li. Angew. Chem. Int. Ed., 43, 597 (2004).
[13] Q. Wang, H. Li, L. Chen, X. Huang. Carbon, 39, 2211 (2001).

4398
A.M. Hassan et al.
[14] X. Wang, P. Hu, F. Yuan, L. Yu. J. Phys. Chem. C, 111, 6706 (2007).
[15] M.S. Martina, J.P. Fortin, C. Menager, O. Clement, G. Barratt, C. Grabielle-Madelmont, F. Gazeau, V. Cabuil,
S. Lesieur. J Am. Chem. Soc., 127, 10676 (2005).
[16] N.A. Frey, S. Peng, K. Cheng, S. Sun. Chem. Soc. Rev., 38, 2532 (2009).
[17] D. Yu, X. Sun, J. Zou, Z. Wang, F. Wang, K. Tang. J. Phys. Chem. B, 110, 21667 (2006).
[18] Y. Sun, Y. Xia. Science, 298, 2176 (2002).
[19] S.W. Cao, Y.J. Zhu, M.Y. Ma. L. Li, L. Zhang, J. Phys. Chem. C, 112, 1851 (2008).
[20] Y. Zhu, W. Zhao, H. Chen, J. Shi. J. Phys. Chem. C, 111, 5281 (2007).
[21] H. Deng, X. Li, Q. Peng, X. Wang, J. Chen, Y. Li. Angew. Chem. Int. Ed., 44, 2782 (2005).
[22] S.B. Cho, J.S. Noh, S.J. Park, D.Y. Lim, S.H. Choi. J. Mater. Sci., 42, 4877 (2007).
[23] G. Xi, C. Wang, X. Wang. Eur. J. Inorg. Chem., 2008, 425 (2008).
[24] L. Jing, Z. Hao, J. Shouheng Sun, L. Ping, W. Zhong Lin, J. Phys. Chem., 108, 14005 (2004) .
[25] A.E.-H. Abdel-Nasser. Carbon, 41, 713 (2003).
[26] I. Loa, C. M€oschel, A. Reich, W. Assenmacher, K. Syassen, M. Jansen. Phys. Stat. Sol. (b), 223, 293 (2001).
[27] N.T. Mc Devitt, W.L. Baun, Spectrochim. Acta, 20, 799 (1964).
[28] C.J. Serna, M. Ocana, J. Iglesias. J. Phys. C: Solid State Phys., 20, 473 (1987).
[29] Z.H. Jing, S.H. Wu. Mater. Chem. Phys., 92, 600 (2005).
[30] R.M. Mohamed, M.M. Rashad, F.A. Haraz, W. Sigmund. J. Magn. Magn. Mater., 322, 2058 (2010).
[31] C. Yao, Y. Shin, L.Q. Wang Jr, C.F. Windisch, W.D. Samuels, B.W. Arey, et al. J. Phys. Chem. C, 111, 15141
(2007).
[32] Y. Xia, B. Gates, Y. Yin, Y. Lu. Adv. Mater., 12, 693 (2000).
[33] Z. Yi, Y. Liang, X. Lei, C. Wang, J. Sun. Mater. Lett., 61, 4199 (2007).
[34] D. Peng, S. Beysen, Q. Li, J. Jian, Y. Sun, J. Jiwuer. Particuology, 7, 35 (2009).
[35] L. Chen, Z. Lin, C. Zhao, Y. Zheng, Y. Zhou, H. Peng. J. Alloys Compd., 509, L1 (2011).
[36] C.Q. Hu, Z.H. Gao, X.R. Yang. Chem. Phys. Lett., 429, 513 (2006).
[37] T. Hosono, H. Takahashi, A. Fujita, R.J. Joseyphus, K. Tohji, B. Jeyadevan. J. Magn. Magn. Mater., 321,
3019 (2009).
[38] K. He, C.-Y. Xu, L. Zhen, W.-Z. Shao. Mater. Lett., 61, 3159 (2007).
[39] R.Y. Hong, T.T. Pan, H.Z. Li. J. Magn. Magn. Mater., 303, 60 (2006).
[40] S. Ni, X. Wang, G. Zhou, F. Yang, J. Wang, Q. Wang, D. He. Mater. Lett., 63, 2701 (2009).
[41] Z. Zi, Y. Sun, X. Zhu, Z. Yang, J. Dai, W. Song. J. Magn. Magn. Mater., 321, 1251 (2009).
[42] M.M. Rashad, R.M. Mohamed, H. El-Shall. J. Mater. Process. Technol., 198, 139 (2008).
[43] P.D. Thang, G. Rijnders, D.H.A. Blank. J. Magn. Magn. Mater., 295, 251 (2005).
[44] O.N. Shebanova, P.J. Lazor. J. Raman Spectrosc., 34, 845 (2003).