Geoscience Reference
In-Depth Information
Figure 10.28. TEM images of TiO
2
nanoparticles synthesized at 400
C: (a) without and (b)
with surface modifier.
Source: Photographs courtesy of T. Adschiri.
immediately after the nucleation of the particles, which suppressed the growth
nuclei, and in addition, the formation of the organic layer also suppressed the
aggregation of nanoparticles in the solution. Similarly, titania particles have been
obtained using the reverse micelles with scCO
2
as solvent catcher to eliminate the
organic phase
[126]
.
SEM and high-resolution TEM (HRTEM) images of some representative sam-
ples of selectively doped TiO
2
and ZnO nanomaterials are shown in
Figure 10.29
.
When surplus dopants are used as in the case of silver, they form a separate phase,
and particles are attached to the host TiO
2
and ZnO particles. In most cases,
depending upon the experimental parameters, dopant metals, and surfactants, the
particles are unagglomerated with a definite morphology. Without surfactants big-
ger particles and agglomerated particles were obtained although the other process
parameters were carefully monitored.
10.6.6 Other Metal Oxides
Among this class, the magnetic nanoparticles form an important class of metal oxi-
des exhibiting unusual behaviors as a result of size effects. Several new uses of
these nanoparticles have been proposed in high-density information storage
[127]
and in a number of biomedical applications like MRI, hyperthermia, targeted drug
delivery, and cellular imaging. Also several clinical applications like detection of
liver metastases, metastatic lymph nodes, and inflammatory and/or degenerative
diseases have been carried out. The iron oxide nanoparticles synthesized and deri-
vatized with human transferring are used on human dermal fibroblasts in vitro and
found that they appear to localize to the cell membrane without instigating
receptor-mediated endocytosis, and also induce up-regulation in the cells for many
genes, particularly in the area of cytoskeleton and cell signaling
[128]
. Such special
