2. Nanotechnology
Nanotechnology can be defined
as the design, synthesis, and
application of materials and
devices whose size and shape
have been engineered at the
nanoscale. It exploits unique
chemical, physical, electrical,
and mechanical properties that
emerge when matter is structured
at the nanoscale.
3. Nanomaterials
Nanomaterials are materials
that have structural components
smaller than 1 micrometer in at
least one dimension. While the
atomic and molecular building
blocks (~0.2 nm) of matter are
considered nanomaterials,
examples such as bulk crystals
with lattice spacing of
nanometers but macroscopic
dimensions overall, are
commonly excluded.
4. Nanoparticles
Nanoparticles are particles
with at least one dimension
smaller than 1 micron and
potentially as small as atomic
and molecular length scales
(~0.2 nm). Nanoparticles can
have amorphous or
crystalline form and their
surfaces can act as carriers
for liquid droplets or gases.
7. Dimensionality
1D nanomaterials. Materials
with one dimension in the
nanometer scale are typically
thin films or surface coatings,
and include the circuitry of
computer chips and the
antireflection and hard coatings
on eyeglasses. Thin films have
been developed and used for
decades in various fields, such as
electronics, chemistry, and
engineering.
8. Dimensionality
2D nanomaterials. Two-dimensional
nanomaterials have two dimensions
in the nanometer scale. These
include 2D nanostructured films, with
nanostructures firmly attached to a
substrate, or nanopore filters used
for small particle separation and
filtration. Free particles with a large
aspect ratio, with dimensions in the
nanoscale range, are also considered
2D nanomaterials. Asbestos fibers are
an example of 2D nanoparticles.
9. Dimensionality
3D nanomaterials. Materials
that are nano-scaled in all
three dimensions are
considered 3D nanomaterials.
These include thin films
deposited under conditions that
generate atomic-scale porosity,
colloids, and free nanoparticles
with various morphologies.
10. Nanoparticle
Morphology
Morphological characteristics to be
taken into account are: flatness,
sphericity, and aspect ratio.
A general classification exists
between high- and low-aspect ratio
particles. High aspect ratio
nanoparticles include nanotubes
and nanowires, with various shapes,
such as helices, zigzags, belts, or
perhaps nanowires with diameter
that varies with length.
Small-aspect ratio morphologies
include spherical, oval, cubic,
prism, helical, or pillar. Collections
of many particles exist as powders,
suspension, or colloids.
11. Nanoparticle
Composition
Nanoparticles can be composed
of a single constituent material
or be a composite of several
materials. The nanoparticles
found in nature are often
agglomerations of materials
with various compositions,
while pure single-composition
materials can be easily
synthesized today by a variety
of methods.
12. Nanoparticle
Uniformity and
Agglomeration
Based on their chemistry and
electro-magnetic properties,
nanoparticles can exist as
dispersed aerosols, as
suspensions/colloids, or in an
agglomerate state.
In an agglomerate state,
nanoparticles may behave as
larger particles, depending on
the size of the agglomerate.
15. Engineered
Nanomaterials
Engineered nanomaterials have
been deliberately engineered
and manufactured by humans to
have certain required
properties.
Legacy nanomaterials are those
that were in commercial
production prior to the
development of nanotechnology
as incremental advancements
over other colloidal or
particulate materials. They
include carbon
black and titanium dioxide
nanoparticles.
16. Incidental
source
Nanomaterials may be
incidentally produced as a
byproduct of mechanical or
industrial processes. Sources of
incidental nanoparticles include
vehicle engine exhausts, welding
fumes, combustion processes
from domestic solid fuel heating
and cooking. Incidental
atmospheric nanoparticles are
often referred to as ultrafine
particles, and are a contributor
to air pollution.
17. Natural source
Natural sources of
nanoparticles include
combustion products forest
fires, volcanic ash, ocean
spray, and the radioactive
decay of radon gas. Natural
nanomaterials can also be
formed through weathering
processes of metal- or anion-
containing rocks, as well as
at acid mine drainage sites.
18. Applications of
Nanomaterials
Electronics
Microelectronics. By achieving a
significant reduction in the size
of circuit elements, the
microprocessors (or better said,
nanoprocessors) that contain
these components could run
faster and incorporate more
logic gates, thereby enabling
computations at far higher
speeds.
19. Applications of
Nanomaterials
Electronics
Displays. The resolution of a
television or a monitor
improves with reduction of
pixel size. The use of
nanocrystalline materials can
greatly enhance resolution and
may significantly reduce cost.
20. Applications of
Nanomaterials
Electronics
Data storage. Devices, such as
computer hard-disks function
based on their ability to magnetize
a small area of a spinning disk to
record information, are
established nano-applications.
Discs and tapes containing
engineered nanomaterials can
store large amounts of
information.
21. Applications of
Nanomaterials
Electronics
High energy density batteries.
New nanomaterials show promising
properties as anode and cathode
materials in lithium-ion batteries,
having higher capacity and better
cycle life than their larger-particle
equivalents. Among them are:
aerogel intercalation electrode
materials, nanocrystalline alloys,
nanosized composite materials,
carbon nanotubes, and nanosized
transition metal oxides.
22. Applications of
Nanomaterials
Electronics
High-sensitivity sensors. Due to
their high surface area an
increased reactivity, nanomaterials
could be employed as sensors for
detecting various parameters, such
as electrical resistivity, chemical
activity, magnetic permeability,
thermal conductivity, and
capacitance.
25. Application of
Nanomaterials
Pollution Remediation
Elimination of pollutants. Due
to their enhanced chemical
activity, nanomaterials can be
used as catalysts to react with
toxic gases (such as carbon
monoxide and nitrogen oxide) in
automobile catalytic converters
and power generation
equipment.
26. Application of
Nanomaterials
Pollution Remediation
Water Remediation. Iron
nanoparticles with a small
content of palladium are tested
to transform harmful products in
groundwater into less harmful
end products. The nanoparticles
are able to remove organic
chlorine (a carcinogen) from
water and soil contaminated
with the chlorine-based organic
solvents (used in dry cleaners)
and convert the solvents to
benign hydrocarbons.
27. Application of
Nanomaterials
Cosmetics
Titanium dioxide and zinc oxide
become transparent to visible
light when formed at the
nanoscale, however are able to
absorb and reflect UV light,
being currently used in
sunscreens and in the cosmetic
industry
28. Application of
Nanomaterials
Coatings
Self-cleaning windows. Self-
cleaning windows have been
demonstrated that are coated in
highly hydrophobic titanium
dioxide. The titanium dioxide
nanoparticles speed up, in the
presence of water and sunlight,
the breakdown of dirt and
bacteria that can then be
washed off the glass more easily.
29. Application of
Nanomaterials
Coatings
Scratch resistant materials.
Nanoscale intermediate layers
between the hard outer layer
and the substrate material
significantly improve wear and
scratch resistant coatings. The
intermediate layers are designed
to give a good bonding and
graded matching of mechanical
and thermal properties, leading
to improved adhesion.
30. Application of
Nanomaterials
Coatings
Textiles. Nanoparticles have
already been used in coating
textiles such as nylon, to provide
antimicrobial characteristics.
Also the control of porosity at
the nanoscale and surface
roughness in a variety of
polymers and inorganic materials
led to ultrahydrophobic -
waterproof and stain resistant
fabrics.
31. Application of
Nanomaterials
Materials
Insulation materials.
Nanocrystalline materials
synthesized by the sol-gel
technique exhibit a foam-like
structure called an "aerogel".
Aerogels are composed of three-
dimensional, continuous
networks of particles and voids.
Aerogels are porous, extremely
lightweight, and have low
thermal conductivity.
32. Application of
Nanomaterials
Materials
Nanocomposites. Composites
are materials that combine two
or more components and are
designed to exhibit overall the
best properties of each
component (mechanical,
biological, optical, electric, or
magnetic)
33. Application of
Nanomaterials
Materials
Paints. Nanoparticles confer
enhanced desired mechanical
properties to composites, such as
scratch resistant paints based on
encapsulated nanoparticles. The
wear resistance of the coatings is
claimed to be ten times greater
than that for conventional acrylic
paints.
34. Application of
Nanomaterials
Mechanical Engineering
Cutting tools made of
nanocrystalline materials (such
as tungsten carbide, WC) are
much harder than their
conventional due to the fact that
the microhardness of nanosized
composites is increased
compared to that of microsized
composites.
36. Synthesis of
Nanomaterials
Bottom-up approach
These approaches include the
miniaturization of materials
components (up to atomic level) with
further selfassembly process leading
to the formation of nanostructures.
During self-assembly the physical
forces operating at nanoscale are used
to combine basic units into larger
stable structures. Typical examples
are quantum dot formation during
epitaxial growth and formation of
nanoparticles from colloidal
dispersion.
37. Synthesis of
Nanomaterials
Top-down approach
These approaches use larger
(macroscopic) initial structures, which
can be externally-controlled in the
processing of nanostructures. Typical
examples are etching through the
mask, ball milling, and application of
severe plastic deformation.
