Agriculture Reference
In-Depth Information
Fig. 11.8
XRD pattern of
ZnO nanorods. (Adopted
with kind permission from
Ahmed et al.
2011a
)
Figure
11.8
shows the typical XRD pattern of as-prepared ZnO nanopowder, which
was indexed using POWDER-X software as the pure hexagonal phase ZnO with the
lattice parameters a = 3.254 Å and c = 5.197 Å. No diffraction peaks from any other
impurities are detected and the sharpness of the peaks implies the good crystallinity
of the as-prepared ZnO nanorods. Figure
11.9a
shows the typical FESEM images of
the ZnO nanostructures. It can clearly be seen from the image that the as-synthesized
ZnO nanorods are flowerlike clusters. Complementary morphological description is
achieved through the TEM equipped with the SAED, as shown in Figs.
11.9b
,
c
. The
diameter of the nanorods is within 150-190 nm (tip diameter ~15 nm) with a length
of about 2 μm. Figure
11.9c
shows a typical TEM image of a single ZnO nanorod
to confirm the crystal quality and growth direction. Well-resolved lattice spacing
of 0.265 nm corresponding to the d spacing of the wurtzite ZnO (002) plane also
indicates that the ZnO nanorod is of a single crystal in nature and referentially grows
along the [001] direction (c-axis), which is further confirmed by the SAED pattern.
Figure
11.9d
shows the chemical composition of the nanorods determined by EDS.
Only oxygen and zinc signals have been detected, which confirms that the nanorods
are primarily ZnO.
4 Mechanism of Nanomaterials-Plants Interaction
Nowadays, a lot of attention is being given to the effect of different nanoparticles
on plant growth and their metabolic functions. Plants cell walls, having a primary
site for interaction, serve as a barrier for the entry of any external agent, including
nanoparticles into plant cells. Major cell wall components include carbohydrates and
proteins (Heredia et al.
1993
; Knox et al.
1995
), and these walls are semi-permeable
in nature which permits the entry of small molecules and blocks the larger ones.
