Geoscience Reference
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hydrothermal synthesis, can be expected to perform as advanced bioimaging
phosphors.
The magnetic nanoparticles are utilized in biotechnology such as in magnetic sepa-
ration
[227]
and MRI
[228]
.FineFe
3
O
4
nanoparticles with high crystallinity and nar-
row size distribution were prepared by supercritical hydrothermal synthesis at 200
C
and 20 MPa with hexaldehyde as the surfactant (
Figure 10.50
). The mean size of the
particles obtained is about 3.4 nm. Superparamagnetic iron oxide particles have been
used in cellular imaging with imaging of in vivo macrophage activity.
Gd(OH)
3
and GdVO
4
:Eu nanoparticles can be also used for bioimaging with
MRI. Also, these nanoparticles are able to be used as X-ray imaging agent, because
Gd presents high X-ray absorption property. For this purpose, it is highly essential
to synthesize these inorganic nanoparticles with controlled particle size. Another
important point is to modify its surface with organic ligands to disperse the parti-
cles perfectly in water (blood) or to attach some biofunctions (like antibodies of
cancers and drugs) on the surface of nanoparticles. Supercritical hydrothermal syn-
thesis is a promising method to synthesize various metal oxides nanoparticles and
their in situ surface modification.
10.7 Hydrothermal Processing of Organic
Inorganic
Hybrid Nanoparticles
The organic
inorganic hybrid nanoparticles are considered to be the most promis-
ing new class of materials that show the trade-off functions between polymers/
organics and inorganics (light and high mechanical strength, high thermal conduc-
tivity, and electrical resistance, transparent and flexible electroconducting films,
Figure 10.50 TEM image of
Fe
3
O
4
nanoparticles synthesized
using a surface modifier.
Source: Photograph courtesy of
T. Adschiri.
