Page 67 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

Nanomaterials Fabrication 53

4 nm (100)
3 nm

(010)

(220) (220)
(220)
(220)
(a) (b) (c)
Figure 3.13 (a) TEM micrographs with the scale bar as 50 nm of cubic CoFe 2 O 4 nanocrys-
tals. (b) HRTEM micrographs showing a 12-nm cubic CoFe 2 O 4 nanocrystal and (c) an 8-nm
spherical CoFe 2 O 4 nanocrystal [64].

Metal carbonyl complexes are also interesting precursors to synthesize
uniform metal oxide nanoparticles. Thermal decomposition at 100 C of
iron pentacarbonyl, Fe(CO) 5 , in octyl ether in the presence of oleic acid
forms iron nanoparticles which are then transformed to monodisperse
spherical -Fe 2 O 3 nanoparticles by trimethylamine oxide acting as a mild
oxidant (Figure 3.14) [68]. Particle size can be varied from 4 to 16 nm by

50 nm 100 nm

50 nm

Figure 3.14 TEM image of (a) a two-dimensional hexagonal assembly of 11 nm -Fe 2 O 3
nanocrystallites (from Hyeon 2001) and (b) 8 140 nm sized MnO nanorods (from Park
2004a), (c) 75 ± 20 nm tungsten oxide nanorods [71].