Synthesis of monodisperse MFe
2
O
4
(M = Fe and Zn) nanoparticles for
polydiethylsiloxane-based ferrofluid with a solvothermal method
Wei Wang
a,b
, Lin Zhuang
a,
*
, Yong Zhang
b
, Hui Shen
a
a
State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, School of Physics
and Engineering, Sun Yat-Sen University, Guangzhou 510275, PR China
b
Laboratory of Nanophotonic Functional Materials and Devices, Institute of Optoelectronic Materials and Technology, South China Normal University,
Guangzhou 510631, PR China
ARTICLE INFO
Article history:
Available online 26 December 2014
Keywords:
Magnetic materials
Magnetic properties
Ferrofluid
Viscosity
ABSTRACT
Monodisperse MFe
2
O
4
(M = Fe, Zn) nanoparticles were successfully synthesized for the application of
polydiethylsiloxane-based (PDES) ferrofluids (FFs) via a novel solvothermal method, with which 1-
octanol and 1-octanamine act as binary solvent, oleic acid (OA) as the surfactant and metal
acetylacetonate [M(acac)
3
](M = Fe and Zn) as the metal source. X-ray diffractometer confirms that the
resultant nanoparticles are pure MFe
2
O
4
with a spinel structure. Infrared spectroscopy indicates that
oleic acid is bound to the surface of MFe
2
O
4
through a covalent bond between carboxylate (COO
) and
metal cations. The ratio of 1-octanol and 1-octanamine plays a key role in the formation of the sphere-
shaped morphology. Transmission electron microscopy (TEM) images confirm that the Fe
3
O
4
particles
are of 4–11nmwith good monodispersity and a narrow size distribution. The saturation magnetization of
Fe
3
O
4
nanoparticles with sizes of 7 nm can reach up to 73.06 emu/g. Polydiethylsiloxane-based (PDES)
FFs show relatively smaller changes of the viscosity with low temperatures (from 7to20
C) than the
polydimethylsiloxane-based (PDMS) FFs. For FFs applications, the relationship between viscosity and
temperature is also discussed.
ã 2014 Elsevier Ltd. All rights reserved.
1. Introduction
Magnetite nanoparticles (MNPs) are one of the most widely
studied materials [1] for the applications of pressure seals [2],
magnetic separation [3] and drug delivery [4]. MFe
2
O
4
nano-
particles represent a well-known and important class of iron oxide
materials for their tunable high magnetic permeability and
electrical resistivity properties [5]. By adjusting the chemical
identity of M
2+
, the magnetic configurations of MFe
2
O
4
can be
molecularly engineered to provide a wide range of magnetic
properties. High temperature decomposition of metal complexes
has become the popular method to prepare MNPs. Sun et al.
reported that high-temperature reaction of Fe(acac)
3
in the
presence of alcohol, oleic acid, and oleylamine can be used to
produce size-controlled monodisperse Fe
3
O
4
nanoparticles [6].
Maity et al. studied water-soluble magnetite nanoparticles by
thermal decomposition of Fe(acac)
3
in triethylene glycol (TREG)
[7], and Pereira et al. reported that MFe
2
O
4
(M = Fe, Co, Mn) with
4.2–11.7 nm were synthesized through a one-step aqueous
coprecipitation method under strong alkaline conditions [8].
These methods for preparing the MNPs in solution phase require
refluxing conditions and inert atmosphere including N
2
or a flow of
argon gas.
Ferrofluids (FFs) [9] are stable colloidal suspensions which
consist of MNPs dispersed in carrier liquid such as oil or water. It
retains the properties of fluid even in the presence of high
magnetic fields and particles cannot be separated from the carrier
liquid. Union of both fluid and magnetic properties makes FFs
useful for numerous industrial applications. Polydimethylsiloxane
(PDMS) is chosen as carrier liquid of FFs owing to its excellent
thermostability and low volatility by several groups [10]. However,
since the chain structure of PDMS is difficult to meet the demand of
low temperature materials in extreme cold applications, poly-
diethylsiloxane (PDES) as carrier liquid under low temperature
conditions should be better. For PDES, the siloxane side chain or
terminal methyl groups (CH
3
) part is replaced by the ethyl (C
2
H
5
)
functional group, the crystallization temperature of the polymer
will be reduced because of the destruction of the regularity of
dimethyl siloxane structure, and hence the cold resistant perfor-
mance of the silicone polymer materials can be enhanced. For our
* Corresponding author. Tel.: +86 20 3933 2863 613; fax: +86 20 3933 2866.
E-mail address: stszhl@mail.sysu.edu.cn (L. Zhuang).
http://dx.doi.org/10.1016/j.materresbull.2014.12.058
0025-5408/ã 2014 Elsevier Ltd. All rights reserved.
Materials Research Bulletin 69 (2015) 61–64
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