Chemistry Reference
In-Depth Information
consisting of either crystalline or amorphous phases, is subsequently
heated to yield the required products. As the sol-formation process is
relatively slow and carried out under ambient conditions, this method
allows the elaborate control over the elemental stoichiometry and
the chemical homogeneity of the final products. In particular, when
surfactant reagents are introduced into the initial solution to form
self-assembly entities (micelles and vesicles, for instance) as soft
templates, porous materials can be expected, which find applications
in catalysis, fuel cells, photovoltaics, and so on. In addition, the sol-
gel route can be easily combined with other techniques, for example,
casting and electrospinning, to fabricate films and fibers.
Brezesinski
. demonstrated a concept to fabricate
mesoporous crystalline ceria thin films based on evaporation-
induced self-assembly (EISA) and subsequent heat treatment, using
a suitable block copolymer and an ionic liquid (IL) as templates[38].
Ceria-zirconia solid solution can also be prepared via sol-gel routes.
Thammachart
et
al
. employed urea as the hydrolysis catalyst to
synthesize highly uniform nanoparticles of Ceria-zirconia [39].
Yan
et al
solid solutions
prepared with the assistance of block copolymer as the surfactant
and soft template (Fig. 1.4) [40]. The product shows uniform
mesopores in hexagonal arrangement, with crystalline walls.
et al
. reported ordered mesoporous Ce
Zr
O
1-x
x
2
Figure 1.4
TEM images of the mesoporous Ce
= 0.5) recorded
along the (a) [001] and (b) [110] orientations. The inset in (a)
is the corresponding FFT (fast Fourier transform) diffraction
image, and the one in (b) is the corresponding SAED pattern.
Zr
O
(
x
1-
x
x
2
The sol-gel route also shows robust capability in synthesizing
RE
.
combined the sol-gel technique with hard template approach and
fabricated Eu
O
nanomaterials, including Y
O
:Tb, Y
O
:Eu [41, 42]. Wu
et al
2
3
2
3
2
3
O
nanotubes using anodic aluminum oxide [43].
2
3
