Environmental Engineering Reference
In-Depth Information
(a)
(d)
50 nm
(b)
(e)
50 nm
(c)
(f )
50 nm
FIGURE 14.4
(a through c) Transmission electron microscopy (TEM) images of Fe
3
O
4
nanocubes with various sizes: (a) 6.5 nm,
(b) 15.0 nm, and (c) 30.0 nm. (d through f) TEM images of monodispersed cubic iron oxide nanoparticles.
(Modiied from Yang C, Wu J, Hou Y,
Chemical Communications
, 47, 5130, 2011; Yang H, Ogawa T, Hasegawa D
et al.,
Journal of Applied Physics
, 103, 07D526, 2008; Hwang SO, Kim CH, Myung Y et al.,
The Journal of Physical
Chemistry C
, 112, 13911, 2008.)
via thermal decomposition of Fe(acac)
3
in a mixed solution of OA and benzyl ether [41].
The anisotropic growth of nanocrystals depends on the reaction time and the monomer
concentration.
14.2.2 Structurally Functionalized MNMs
14.2.2.1 One-Dimensional and Two-Dimensional Fe
3
O
4
Nanomaterials
One-dimensional (1-D) nanostructures are promising building blocks owing to their spe-
ciic properties such as unique electron transport behaviors. Nucleation and anisotropic
growth processes are crucial for preparing 1-D Fe
3
O
4
nanostructures [46]. In the nucleation
process, octahedral Fe
3
O
4
nanoparticles always form as a nucleus and expose the (111) facet
owing to the energetic stability of the (111) facet. However, factors such as catalysts [47],
substrates [48], reaction matrix [49], templates [50], and external applied magnetic ield [41]
will determine the growth of longitude during the elongation process.
Nanorods or nanowires are typical 1-D nanostructures. The fabrication of large-scale,
single-crystalline Fe
3
O
4
nanopyramid arrays by utilizing CH
4
and N
2
plasma sputtering of
hematite (0001) wafers without any template or catalyst (Figure 14.5) has been reported [48].
It is believed that the energetic stability of the (111) faces determines the 1-D growth along
