Agriculture Reference
In-Depth Information
tal properties differ from those of the corresponding bulk material. The
commonly used definition of “dissolved” is in most cases operationally
defined by all compounds passing through a filter, in many cases with a
cutoff at 0.45 mm (450 nm). The colloidal fraction is defined as having a
size between 1 nm and 1 mm, (Buffle, 2006) therefore overlapping with the
nano-particles (NP). A wide variety of materials can
be used to make such
nanoparticles, such as metal oxide ceramics
and silicates, magnetic mate-
rials, lyposomes, dendrimers, emulsions,
etc.
The size dimension of some
naturally occurring materials are given in Table 9.1.
TABLE 9.1
Size Dimensions of Different Natural Materials
Name
Size
Molecules
< 1 nm
Colloids
1-1000 nm
Nanoparticles
1-100 nm
Virus
10-100 nm
Red Blood Cell
2000-5000 nm
Bacteria
250 nm-1000 nm
Tissue Cell
10,000 nm
Width of Human Hair
80,000 nm
Intracellular Spaces in Seed Coat Parenchyma
< 10,000 nm
Nano particles (NPs) are generally defined as materials that are <100
nm size (0.1 µm) in at least one dimension. This means that nano materi-
als can be three-dimensional particles (Spherical, Cuboids etc), or two-
dimensional particles (Ultra thin film) or one-dimensional (fine rods).
Their chemical (reactivity, solubility, etc.), mechanical (elasticity, hard-
ness, etc.), electronic (conductivity, redox behavior) and nuclear (mag-
netic) properties often change as a function of size. These changes can be,
and often are dramatic. This is precisely what leads to their exceptional
scientific and commercial value and their anticipated enigmatic behavior
in already extraordinarily complex earth environment.
