Engineering Physics study materials discusses nanoscience and nanotechnology. It defines nanotechnology as manipulating matter at the atomic or molecular scale to produce novel structures and devices. When matter is reduced to the nanoscale, quantum confinement occurs and energy levels become quantized. This can increase the band gap and surface area to volume ratio. Nanomaterials are classified based on dimensionality (0D, 1D, 2D) and properties (metallic, semiconducting, insulating). Synthesis methods include top-down (milling) and bottom-up (self-assembly) approaches. Carbon nanotubes are discussed in detail, including their unique electrical, mechanical, and thermal properties, and applications in fields like electronics, composites,

1. Engineering Physics study materials – by Praveen N. Vaidya, Dept. Physics, SDMCET Dharwad.
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B a s ic s o f N a no s c ie nc e a nd
te c hno lo g y:
Nanotechnology is a branch of science and a recent
concept to study of materials at sub micron level.
Nanoscience deals with the synthesis and study of
characteristic properties like electrical, magnetic,
optical, elastic and thermal etc., of materials in
nanoscale. Usually the matter sizes ranging
between 1nm to 100nm are called as nano
materials.
Nanotechnology:
Nanotechnology is the art and science of
manipulating matter at the atomic or molecular
scale to produce structures, devices and systems of
novel properties and non harmful.
Quantum Confinement:
This is process of the confining the any matter to
nano scale. When matter reduced to nano scale it,
the energy levels becomes more and more discrete
to create quantization.
More specifically, quantization increases with the
decrease in volume.
Therefore Quantum confinement of Quantization
of energy achieved when size of matter is
compared with the de-Broglie wavelength of
electron.
Effect of Quatntum confinement:
1. Increase of surface to volume ratio
(specific surface area).
2. Widening of band gap.
3. Variation of density of states.
4. Increase in Surface energy
1. Increase of surface to volume ratio: When
a bulk matter cut into smaller pieces the
surface area increases exponentially keeping
volume constant, if the pieces are in nano size
surface to volume ratio is very large.
As large number of atoms exposed in nano
range, the surface energy high, hence the
material become more reactive, hence they can
serve as very potent catalysts, for ex. Nano
gold
2. Widening of Bandgap: Smaller the number
atoms, matter shows higher the Quantization.
Hence the difference between valence band
maxima and conduction band minima
increases.
For ex. Silicon particle of 4.5nm has band gap
1.7 eV and for 2.4 nm has 2.2eV.
Bulk Nano Sub-nano

2. Engineering Physics study materials – by Praveen N. Vaidya, Dept. Physics, SDMCET Dharwad.
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Classification Nanomaterials:
They are classified in two ways
1) Based on the Shape (Direction of confinement)
2) Based on the intrinsic Properties
1. based on shape:
(1) zero-dimensional (0-D), (2) One-
dimensional (1-D), (3) Two-dimensional (2-D),
Zero-dimensional (0-D),
Materials in which all the dimensions are confined
to nano scale (no dimensions are larger than 100
nm).
The zero-dimensional nanomaterials are also called
as nanoparticles or Quantum dots.
The colour of the nano particles changes with their
size. Smaller nano particles show Blue shift
where as larger the particle size shows Red
shift.
The bandgap appears in nano particles and it
increases with the decrease in particle size.
Hence nanoparticles show quantization of
energy levels.
One-dimensional nanomaterials
The nanomaterials formed by enhancing along
one dimension confining other two in nano
size are called one dimensional Nano
materials. These are also called Quantum wire.
Examples, nanotubes (carbon nanotubes),
nanorods, and nanowires (Zn nano wire).
Two-dimensionalnanomaterials
The nanomaterials formed by enhancing along
two dimension confining other two in nano
size are called two dimensional Nano
materials.
They are also called nano planes or Quantum
planes. For ex. Thin films
Density of states: In any material the
electrons are moving around the respective
atoms in various energy levels. In case of
solids each energy level divided into n number
of energylevels, if n atoms are present in a
1D
L
d < 100nm
Two dimensions are in Nanoscale

3. Engineering Physics study materials – by Praveen N. Vaidya, Dept. Physics, SDMCET Dharwad.
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piece of material. Hence a group of energy level is
called as energy band.
In above fig. number atoms along X-axis and
Energy along Y-axis. The split of energylevel
shown dependent on the number of atoms in solid,
if 1023 atoms are there and each atom splits into
2023 energy levels.
Similarly, The density of energy states (DOS) i.e.
number of energy levels per unit volume also
dependent on the energy. DOS increases with
energy initially at higher energy, the DOS slowly
goes to constant. DOS also dependent on the
dimensions confinement.
Variation of Density of States in Nano Systems:
Let us recall the three dimensional systems like
bulk systems, in which the density of states varies
as function of square root of energy.
As shown in above tables D(E) is the density of
states of Nano materials confined in different
dimensions. Variation gives smooth curve (Fig.
2.5a).
In case bulk materials i.e. no confinement
variation of density of states with Energy is given
by,
D(E)  E1/2,
In case Two dimensional nano materials i.e.
in quantum planes (quantum well), Density of
states is independent of Energy.
D(E) = Constant,
Variation gives step function (fig. 2.5b).
In case of One dimensional nano materials
i.e. quantum wires, variation of density of
states with Energy is given by,
D(E)  E -1/2,
variation gives zig-zag curve(fig. 2.5c).
In case of Zero dimensional nano materials
or Quantum dots, i.e. electrons are confined
in all the dimensions hence no free electrons
are available, hence it gives delta function
D(E) = 2 (E – Ec)
variation is discrete function(fig. 2.5d)
Hence it gives aconstant values of density of
states at each energy values.
Classification based on intrinsic properties:
There are three types again
1. Metallic Nanomaterials
2. Semiconducting Nanomaterials
3. Insulator Nanomaterials

4. Engineering Physics study materials – by Praveen N. Vaidya, Dept. Physics, SDMCET Dharwad.
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1. Metallic Nanomaterials: These are
nanoderivatives of metals. For Ex. Gold nano
particles. Used in catalysis, memory units,
sensors, bio sensors etc.
2. Semiconducting Nanomaterials: These are
nanosize particles or films of semiconductors.
Most semiconducting nanomaterials are made
of compound semiconductors. These are used
in LED, Laser or any electronic devices.
3. Insulating nanomaterials: These are nanosize
materials made of insulators for ex. SiO2
nanomaterials, Diamond nanomaterials.
Size dependent Properties:
Importance of the nanomaterials is lies behind its
changing properties when they are reduced size
from bulk to nano and reduction in nano size itself.
Physical Properties:
When size reduced from bulk nano the surface to
volume ratio increases. The appearance of also
changes. For ex. Gold powder of nano size appears
deep red.
Chemical Properties:
The reactivity of the materials increases in particle
size reduced to nano, due to in complete bonding
of surface atoms, these atoms are become highly
reactive and acts as catalyst for ex. Bulk gold is
inert but nanogold is highly reactive.
Thermal Properties
Gold slab macro size has melting point 1064 °C,
whereas gold nanoparticles melt at much lower
temperatures (~300 °C for 2.5 nm size)
Optoelectronic Properties
Due to increase in bandgap when a material
turn into nano, the absorption spectra show
blue shift with the reduction of size of nano
particles.
Magnetic Propeties
Ferroelectric materials smaller than 10 nm can
switch their magnetization direction using
room temperature thermal energy, thus
making them unsuitable for memory storage.
Mechanical properties:
Nanoparticle surface strongly interact with
liquid molecules to overcome gravity effect,
hence they can be suspended in liquid.
The high surface to volume ratio of
nanoparticles provides a tremendous driving
force for diffusion, especially at elevated
temperatures.
Clay nanoparticles when incorporated into
polymer matrices increase reinforcement,
leading to stronger plastics.
Synthesis of Nano material:
There are two approaches
1) Top down 2) Bottom up
Top down Approach: In this method the bulk
material is broken into grains of extremely
smaller size between 1nm to 100nm.
Care should be taken that its crystal structure
should not be altered.
In this case the powder of cryastal which
contains grain micro size is furder grind into
controlled conditions to form nano materials.

5. Engineering Physics study materials – by Praveen N. Vaidya, Dept. Physics, SDMCET Dharwad.
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The temperature and grinding is such a way so that
crystal structure should not altered Examples Ball
millig,
In other method, the solid matter is evaporated and
sublimate to form a film on a surface called
substrate. Here thickness of film is in nano range.
Electron lithography, vapor deposition techniques
etc.
Bottom-up approach refers to the build-up of a
material from the bottom: atom-by-atom,
molecule-by-molecule, or cluster-by-cluster. In
organic chemistry and/or polymer science, we
know polymers are synthesized by connecting
individual monomers together. In crystal growth,
growth species, such as atoms, ions and molecules,
after impinging onto the growth surface, assemble
into crystal structure one after another.
Ex: Solgel, Chemical bath, Spray pyrolysis,
Laser ablation etc.
Laser ablation
Laser ablation means the removal of material from
a surface by means of laser irradiation. The term
“laser ablation” is used to emphasize the
nonequilibrium vapor/plasma conditions
created at the surface by intense laser pulse.
As shown above diagram, there are two
essential parts in the laser ablation device, a
pulsed laser (CO2 laser, Nd-YAG laser) and
an ablation chamber. The high power of the
laser beam induces large light absorption on
the surface of target, which makes temperature
of the absorbing material increase rapidly. As
a result, the material on the surface of target
vaporizes into laser plume. In some cases, the
vaporized materials condensate into cluster
and particle without any chemical reaction. In
some other cases, the vaporized material reacts
with introduced reactants to form new
materials. The condensed particle will be
either deposited on a substrate or collected
through a filter system consisting of a glass
fiber mesh. Then, the collected nanoparticle
can be coated on a substrate through drop-
coating or screen-printing process.
Carbon Nanotubes
Carbon Nanotubes first identified in 1991 by
Sumio Iijima of Nec, Japan, and formed from
hexagonal arrays of carbon atoms.
The honeycomb-shaped net in the form of
tube, each vertex contain carbon atom which
are covalently bond.
There two types based on concentric tubes
present,
1. Single Walled Carbon Nanotubes
(SWCNT): This type of CNTs consists of

6. Engineering Physics study materials – by Praveen N. Vaidya, Dept. Physics, SDMCET Dharwad.
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single cylinder of the one atomic layercarbon
sheet. The diameter of cylinder is about 0.7 nm and
length may be million times of the diameter.
Multi walled nanotubes (MWCNT):
The multi walled Carbon Nanotubes consists of
more than one concentric rings of carbon
nanotubes, whose properties are varies as the
function of diameter of the each concentric
cylinder. The structure of the nanotube influences
its properties - including electrical and thermal
conductivity, density, and lattice structure.
The Carbon nanotubes are relates to the property of
graphite.
When graphene sheets are rolled into a cylinder
and their edges joined, they form CNTs.
Based on shape there are three types of CNTs as
shown in figure,
a) Arm chair b) Zig Zag c) Chiral
Properties of Carbon Nanotubes:
a) Electrical Conductivity
CNTs can be semiconducting or conducting
based on degree of twist as well as their
diameter. Conductivity in MWNTs is quite
complex. Some types of “armchair”-structured
CNTs appear to conduct better than other
metallic CNTs.
b) Strength and Elasticity
Because of strong bonds, the basal plane
elastic modulus of graphite is one of the
largest of any known material. For this reason,
CNTs are expected to be the ultimate high-
strength fibers.
Thermal Properties:
CNTs show very high thermal conductivity.
CNTs have been shown to exhibit
superconductivity below 20°K (aaprox. -
253°C). The almost zero in-plane thermal
expansion but large inter-plane expansion of
single walled nanotubes implies strong in-
plane coupling and high flexibility against
non-axial strains.
d) Field Emission:Under the application of a
strong electric field, CNTs are showing field
emission. Even for moderate voltages, a strong
electric field develops at the free end of
supported CNTs because of their sharpness.
e) Highly Absorbent: The large surface area
and high absorbency of CNTs make them
ideal candidates for use in air, gas, and water
filtration. A lot of research is being done in

7. Engineering Physics study materials – by Praveen N. Vaidya, Dept. Physics, SDMCET Dharwad.
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replacing activated charcoal with CNTs in certain
ultra high purity applications.
Applications of Carbon Nanotubes:
a) Field Emission: Due to best field emitters,
CNTs can carry an astonishingly high current
density and extremely stable current. This property
used in field-emission flat-panel displays, low-
voltage cold-cathode lighting sources, lightning
arrestors, and electron microscope sources.
b) Conductive or Reinforced Plastics:
Since CNTs have the highest aspect ratio and have
natural tendency to form ropes, Applications that
exploit this behavior of CNTs include EMI/RFI
shielding composites; transparent conductive
coatings; and radar-absorbing materials for stealth
applications.
c) Conductive Adhesives and Connectors
The same properties that make CNTs attractive as
conductive fillers for use in electromagnetic
shielding, ESD materials, etc., such as adhesives,
potting compounds, coaxial cables, and other types
of connectors.
d) Molecular Electronics
The geometry, electrical conductivity, and ability
to be precisely derived, make CNTs the ideal
candidates for the connections in molecular
electronics. In addition, they have been
demonstrated as switches themselves.
e) Thermal Materials
The exceptional Thermal conductivity of CNT
found application in electronics, particularly heat
sinks for chips used in advanced computing, The
technology for creating aligned structures and
ribbons of CNTs is a step toward realizing
incredibly efficient heat conduits.
f) Structural Composites
The CNTs show superior mechanical
properties, such as stiffness, toughness, and
strength. These properties lead to a wealth of
applications exploiting them, including
advanced composites requiring high values of
one or more of these properties.
h) Catalyst Support
CNTs intrinsically have an enormously high
surface area; hence it will get ability to attach
essentially any chemical species to their
sidewalls through unsatisfied bonds, provides
an opportunity for unique catalyst supports.