Chemistry Reference
In-Depth Information
Figure
1.22
TEM images of transition metal and rare earth oxide hollow
spheres: (a) CoO, (b) Mn
O
, (c) NiO, (d) Cr
O
, (e) CeO
, (f)
3
4
2
3
2
Lu
O
.
2
3
Karakoti
reported the self-assembly of small ceria
nanoparticles into nanorods during the structural formation of ice
(Fig. 1.23) [205]. They proposed that during the freezing and the
aging (2-3 weeks) of the ceria suspension, the trapped nanoparticles
tend to combine via an oriented attachment process, which results
in the formation of nanorods.
et al.
Figure 1.23
TEM images of the ceria solution: (a) immediately after the
formation of ceria nanoparticles (10-15 nm agglomerates
contains 3-5 nm ceria nanocrystals), and after freezing and
subsequent aging for (b) one day—the zigzag alignment of
nanoparticles into a 1D self-assembled structure is apparent;
(c) one week—initial ceria nanocrystals agglomerated in ice
arrange anisotropically to form long nanorods; (d) samples
aged for one week showing complete nanorods; (e) two
weeks—a long nanorod (aspect ratio 1:20) formed after aging
in ice; (f) two weeks—high magnification image of the nanorod
in (e) showing the polycrystalline nature of nanorods with 3-5
nm nanocrystallites.
