Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
Preparat ion of mag netic nanoparticles with surfactant-controlled size and shape
Aysel Bayrak 1 ,Sema Vural 1 ,Yavuz Çelik 1 , Turgay Seçkin 1 *
1 Department of Chemistry, University of Inonu, Malatya, TR Türkiye 44280
Abstract-This manuscript describes a simple one-pot reaction that affords cobalt iron oxide nanoparticles with unprecedented dimensions as
large as 30 nm in monodisperse form. Unique synthetic method, which requires no multiple growth steps typical of other methods, utilizes the
thermal decomposition of metal precursor complexes in the presence of speci
and shape of these unusually large magnetic nanoparticles (MNPs) can be manipulated at will simply by adjusting the surfactant composition,
leading to enhanced control over the dimensions of the nanoparticles because of the surface-differentiating in
the produced ferrites were investigated by X-ray diffraction analysis (XRD), scanning electron microscope (SEM) and vibrating sample
magnetome-ter (VSM).
Monodisperse magnetic nanoparticles (MNPs) with
controlled sizes and shapes are of great interest for
fundamental science and for both existing and developing
technological applications. The morphology of MNPs strongly
in
especially their magnetic and electrical properties. More
speci
strongly depend on the size, shape, functionality, and
magnetization of the MNPs.
Cobalt ferrite (CoFe 2 O 4 ), with a partially inverse spinel
structure, is one of the most important and most abundant
magnetic materials. As a conventional magnetic material, with
a Curie temperature (TC) around 793 K, CoFe 2 O 4 is well
known to have large magnetic anisotropy, moderate saturation
magnetization, remarkable chemical stability and a mechanical
hardness, which make it a good candidate for the recording
med ia[1,2]. CoFe 2 O 4 ultrafine powders [3–4] and films have
attracted considerable attention for their wide range of
technological applications such as transformer cores,
recording heads, antenna rods, memory, ferro fluids,
biomedical application and sensors, etc.. Over recent years,
the chemical solution routes were successively emerging as
effective, convenient, less energy demanding and less
materials consuming synthetic techniques for material
preparation. However, the hydrothermal route is one of the
most used ones, owing to its economics and the high degree of
compositional control. In addition, the hydrothermal synthesis
requires neither extremely high processing temperature nor
sophisticated processing. For example, ferrites can be prepared
via the hydrothermal method at a temperature of about 150 C,
whereas the solid-state method requires a temperature of 800
C. Hydrothermal synthesis of several ferrites has been
reported. However, there is little report on the synthesis of
single-crystalline CoFe 2 O 4 nanorods. We present here a
simple hydrothermal route without a preformed template for
the preparation of CoFe 2 O 4 nanorods.
The growth rate has been shown to be an important factor in
controlling the shape of magnetic nanoparticles. Moreover, the
wet chemical synthesis of monodisperse large nanoparticles
typically involves precise control over the growth rate by
using a high concentration of metal cation and controlling the
strength of binding between various ligands and the emerging
metal surface.
In a typical procedure for the preparation of CoFe2O 4 , 1 g of
cationic surfactant cetyltrimethylammonium bromide (CTAB)
was dissolved in 35 ml deionized water to form a transparent
solution. Then ferric chloride hexahydrate (FeCl3.6H2O) of 1
g was added to the solution. After 10 min stirring,
stoichiometric amount of CoCl 2 was introduced into the
mixed solution under vigorous stirring. Deionized water was
added to make the solution for a total volume of 40 ml, and
pH of the solution was adjusted to 11.0. Before being
transferred to a Teflon-lined auto-clave of 50.0 ml capacity,
the solution mixture was pretreated under an ultrasonic water
bath for 30– 40 min. Hydrothermal synthesis was carried out
at 130 ºC for 15 h in an electric oven without shaking or
stirring. Afterwards, the autoclave was allowed to cool to
room temperature gradually. The black precipitate collected
was washed with distilled water three times in an ultrasonic
bath to remove any possible impurities. The solid was then
heated at 80 ºC and dried under vacuum for 2 h.
Figure 1. X-ray diffraction patterns of the prepared CoFe 2 O 4
particles and nanorods via hydrothermal for 15 h without CTAB (a)
andwith CTAB (b).
The product morphology changes from tetrapods, nanorods,
and nanoparticles as the reaction temperature increases from
40 to 70 C with various surfactants.
We note that monodisperse particles of this size represent an
ideal compromise for many applications, offering the potential
for both a strong magnetic moment and electrical properties.
We also evaluated the key magnetic characteristics of our
iron-manganese oxide nanoparticles. In particular, magnetic
hysteresis loops and magnetic relaxation were measured for
these particles at room temperature. The superparamagnetic
nature of these particles is characterized by M-H hysteresis
loop behavior at 290 K and rapid relaxation.
*Corresponding author: 1Ttseckin@inonu.edu.tr
[1] Mornet, S.; Vasseur, S.; Grasset, F.; Duguet, E.J. Mater.
Chem.2004, 14, 2161.
[2] Gleich, B.; Weizenecker, J.Nature2005,435, 1214.
[3] Mannix, R. J.; Kumar, S.; Cassiola, F.; Montoya-Zavala, M .;
Feinstein, E.; Prentiss, M.; Ingber, D. E.Nat. Nanotechnol.2008,3,
36.
[4] Weitschies, W.; Ko¨titz, R.; Bunte, T.; Trahms, L.Pharm.
Pharmacol. Lett.1997,7,1.
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