Environmental Engineering Reference
In-Depth Information
12.4.5 Fe
3
O
4
Nanoparticles
Fe
3
O
4
nanoparticles find wide applications in the biomedical field as anticancer
agent [
28
,
29
] and corrosion protective pigments in paints and coatings [
30
]. Fe
3
O
4
nanoparticles are amongst the common ferrite materials which exhibit unique
electrical and magnetic properties due to the transfer of electrons between Fe
2+
and Fe
3+
on octahedral sites [
31
]. Rahman et al. [
32
] have studied EMR spectra of
nano ferrites. Authors have confirmed the superparamagnetic nature of nano ferrite
from EMR studies. Their EMR study reveals a relatively weak transition other than
the main strong feature of X-Band solid state EMR line. They have suggested that
the weaker transition confirms the super paramagnetic nature of these nano ferrites.
Zhao et al. [
33
] designed and synthesized novel functional nanoparticles with
nitroxide free radicals spin labeling in order to investigate their new applications
EMR bioprobes. Their results of the EMR measurement of carboxylic acids mod-
ified Fe
3
O
4
nanoparticles indicated that the spin-labeled nanoparticles with both the
superparamagnetism of ferrimagnetic nanoparticles and the paramagnetism of
nitroxide free radicals could act as a potential vehicle to deliver drugs.
Gamarra et al. [
34
] have studied the kinetics of the biodistribution and the
elimination of the biocompatible Fe
3
O
4
ferrofluid (Endorem) covered with dextran
after intravenous administration to Winstar rats. They have used EMR to determine
the iron content found in the liver and the blood samples of rats.
Rakhmatullin et al. [
35
] have recently reported EMR characterization of CeO
2
:
Er
3+
nanoparticles. The obtained results are compared with appropriated character-
istics of the Er-doped CeO
2
single crystal and the macroscopic powder of commer-
cial pure cerium dioxide. They found that Er
3+
ions in CeO
2
nanoparticles with
average grain sizes of 22 and 300 nm occupy mainly cubic sites, similar to the
single crystal with the same low concentration of these ions. However, the line
widths observed in nanoparticles of CeO
2
reveal increased distortions with the
decrease of the grain size. They have concluded that the vacancies are located in the
next nearest neighbor positions. Authors have pointed out that these studies may
lead to design and enhance catalytic properties of cerium dioxide.
12.5 EMR of Irradiated and Activated Nanoparticle
Systems
12.5.1 Photo-Generated Charge Carriers in Nanocrystalline
Powders
Paramagnetic intermediates produced in the irradiated titanium dioxide systems can
be investigated using EMR spectroscopy [
36
]. Brezova et al. [
37
] have reported
EMR study of species generated upon UV exposure of anatase and rutile nanocrys-
talline powders, along with their analogs containing up to 90 % of
17
O atoms. They
