Capping agent assisted synthesis and magnetic
characterization of Cobalt doped ZnO nanocrystals
R. Varadhaseshan*, C.Prema, S. Meenakshi Sundar
PG and Research Department of Physics, Sri paramakalyani College,
Tirunelveli, Tamil Nadu, India - 627 412.
*
e-mail:rvseshan@gmail.com, Tel.: +91-95785532207; Fax: +91-4634-283226
Abstract
Polyvinylpyrrolidone
(PVP)
and
Cetyl
trimethylammonium bromide (CTAB) capped Zn0.94Co0.06O
nanocrystals were synthesized by microwave irradiation route
for their magnetic behavior. The presence of metal oxide bond
around 450 cm-1 was confirmed by FTIR spectral analysis. A
weak ferromagnetic behavior is observed in the PVP capped
samples, but the CTAB capped samples show the clear
hysteresis loop.
method for large scale production of nanomaterials. It
is significant to note that the microwave irradiation has
several advantages over conventional methods including
short reaction time, small particle size, narrow size
distribution, and high purity.
Keywords:Semicondutor, Naocrystals, Capping,Ferromagnetic
Introduction
ZnO nanostructures with various morphologies
exhibit unique optical, electrical, magnetic and catalytic
properties, which are distinct from the bulk counterparts
[1,2]. Especially, the study of effect of dopants on
magnetic properties of ZnO based nanomaterials is very
important for spintronics applications. Compared to
undoped semiconductors, doped materials offer the
possibility of using the dopant to tune their electronic,
magnetic and optical properties. Therefore, in addition
to existing advantages which nanomaterials have
offered in terms of controllable parameters such as size,
shape, and surface, dopants offer the additional
flexibility for designing new functionalities and for
altering their properties. However, ZnO nanoparticles
are prone to aggregate due to the large surface area and
high surface energy. In order to improve the dispersion,
it is necessary to modify the surface of ZnO
nanoparticles. The chemical surface modification,
which can be classified as surface grafting and
esterification, is the most promising method because of
the strong covalent bond between the surface modified
particles and polymer chains.
Fig. 1: M-H curve of CTAB capped Zn0.94Co0.06O
Result and discussion
For structural analysis the samples were
examined by XRD technique reveals that single phase
ZnO wurtzite structure. Any other impurity phase,
cluster formation was not deduced in the XRD pattern.
The crystal sizes were calculated by well known DebyeScherrer formula and are in the range 10-20 nm. But
the TEM image shows the small crystal sizes due to
accuracy. The SAED pattern clearly rules out the
secondary phase formation. The functional groups
present in the samples were identified by FTIR
spectrum. The M-H measurement at room temperature
of PVP capped samples shows the weak ferromagnetic
nature and the CTAB capped samples exhibits clear
hysteresis loop shown in Fig. 1. It is concluded from
the M-H measurement the saturation magnetization,
coercivity and retentivity values were increases with the
increase of CTAB content.
Method of synthesis
Transition metal doped ZnO nanocrystals
synthesized by microwave irradiation technique were
already reported by our previous work [3]. In addition
to that the capping agents like PVP and CTAB were
added before the microwave heat treatment of different
mole %. This method is popularly used by the
researchers due to easiest, energy-saving and quick
Reference
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