Nano Technology

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Unit-IV
Nano Technology
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SIZE A meter is about the distance from the tip
of your nose to the end of your hand (1 meter
3.28 feet). Millimeter- One thousandth of
meter.(10-3m) Micron a micron is a millionth
of a meter (or) one thousandth of millimeter
(10-6m) Nanometer A nanometer is one
thousandth of a micron (109m) (or) a billionth
of a meter. ie.,one billion nanometers in a
meter.
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• Composites made from particles of nano-size
  ceramics or metals smaller than 100 nanometers
  can suddenly become much stronger than predicted
  by existing materials-science models.
• For example, metals with a so-called grain size
  of around 10 nanometers are as much as seven
  times harder and tougher than their ordinary
  counterparts with grain sizes in the micro meter
  range.
• The Nano particles affects many properties such
  as
• Melting point
• Boiling point
• Band gap
• Optical properties
• Electrical properties
• Magnetic properties
• .Even the structure of materials changes with
  respect to Size

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The properties of materials can be different at
the Nanoscale for two main reasons
First, Nanomaterials have a relatively larger
surface area when compared to the same mass of
material produced in a larger form. Nano
particles can make materials more chemically
reactive and affect their strength or electrical
properties.
Second, quantum effects can begin to dominate the
behaviour of matter at the Nanoscale

• Nanoscale materials are divided into three
  category,
• Zero dimension length , breadth and heights are
  confined at single point. (for example, Nano
  dots)
• One dimension It has only one parameter either
  length (or) breadth (or) height ( examplevery
  thin surface coatings)
• Two dimensions- it has only length and breadth
  (for example, nanowires and nanotubes)
• Three dimensions -it has all parameter of
  length, breadth and height. (for example, Nano
  Particles).

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What do you mean by Nano Particles ?
Nano Particles are the particles of size between
1 nm to 100 nm

• 1 nm is only three to five atoms wide.
• 40,000 times smaller than the width of an
  average human hair

• Nanometer - One billionth (10-9) of a meter
• The size of Hydrogen atom 0.04 nm
• The size of Proteins 1-20 nm
• Feature size of computer chips 180 nm
• Diameter of human hair 10 µm

At the nanoscale, the physical, chemical, and
biological properties of materials differ in
fundamental and valuable ways from the properties
of individual atoms and molecules or bulk matter
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Why Nano Particles ?
Noparticles are of interest because of the new
properties (such as chemical reactivity and
optical behaviour) that they exhibit compared
with larger particles of the same materials.
For example, titanium dioxide and zinc oxide
become transparent at the nanoscale and have
found application in sunscreens. Nanoparticles
have a range of potential applications In the
short-term application such as in cosmetics,
textiles and paints. In the longer term
applications such as drug delivery where they
could be to used deliver drugs to a specific site
in the body. Nanoparticles can also be arranged
into layers on surfaces, providing a large
surface area and hence enhanced activity,
relevant to a range of potential applications
such as catalysts.
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Examples - Carbon Nanotubes - Proteins,
DNA - Single electron transistors
AFM Image of DNA
Carbon Nanotubes
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Nanotechnology deals with the creation of USEFUL
materials, devices and systems using the
particles of nanometer length scale and
exploitation of NOVEL properties (physical,
chemical, biological) at that length scale
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Various Nanomaterials and Nanotechnologies
Based on the size and shape, the Nano materials
are classified as follows
Nanotubes Nanosprings Nanobelts Quantum
dots Nanofluidies
Nanoparticles Nanocapsules Nanofibers Nano
wires Fullerenes (carbon 60)
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• Quantum well
• It is a two dimensional system
• The electron can move in two directions and
  restricted in one direction.
•  Quantum Wire
• It is a one-dimensional system
• The electron can move in one direction and
  restricted in two directions.
•  Quantum dot
• It is a zero dimensional system
• The electron movement was restricted in entire
  three dimensions

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Why called Quantum ?

• Because, the electronic property is quantized
• The spatial distance is very very small

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Quantum wire
Quantum wires are ultra fine wires or linear
arrays of Nano dots, formed by self-assembly

• They can be made from a wide range of materials
  such as Semiconductor Nanowires made of silicon,
  gallium nitride and indium phosphide.
• Nanowires have potential applications in
• In high-density data storage, either as
  magnetic read heads or as patterned storage
  media
• In electronic and opto-electronic
  Nanodevices, for metallic interconnects of
  quantum devices and Nanodevices.
• Nanowires can be prepared by growth techniques
  such as
• Chemical Vapour deposition (CVD)
• Electroplating

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Quantum wire cont
In quantum wire, Two dimensions are reduced and
one dimension remains large
Therefore, the electrical resistivity of quantum
wire can be calculated using conventional formula
as follows,
We need two dimension to calculate area of
conducting material, but not present in quantum
wire
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• General properties of Nanowire
• Diameter 10s of nanometers
• Single crystal formation -- common
  crystallographic orientation along the nanowire
  axis
• Minimal defects within wire
• Minimal irregularities within nanowire arrays

Some example of Nanowire
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Magnetic nanowires

• Example Cobalt, gold, copper and cobalt-copper
  nanowire arrays
• Important for storage device applications
• Electrochemical deposition is the fabrication
  technique
• lt20 nm diameter nanowire arrays can be fabricated
  by electrochemical deposition

Cobalt nanowires on Si substrate
(UMass Amherst, 2000)
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In quantum dot all the three dimensions are
reduced to zero
Quantum dot
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Dimension Variation ?
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Properties of Nano Materials
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Melting Point
The melting point decreases dramatically as the
particle size gets below 5 nm
Source Nanoscale Materials in Chemistry, Wiley,
2001
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Band gap
The band gap is increases with reducing the size
of the particles
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Surface Area
The total surface area (or) the number of surface
atom increases with reducing size of the
particles
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Size-Dependent Properties of semiconductor and
magnetic materials
For semiconductors such as ZnO, CdS, and Si,
the bandgap changes with size - Bandgap is
the energy needed to promote an electron from
the valence band to the conduction band - When
the bandgaps lie in the visible spectrum,
changing bandgap with size means a change in
color For magnetic materials such as Fe, Co,
Ni, Fe3O4, etc., magnetic properties are size
dependent - The coercive force (or magnetic
memory) needed to reverse an internal
magnetic field within the particle is size
dependent - The strength of a particles
internal magnetic field can be size dependent
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Applications of Nano Materials
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1. Nanotechnology Applications in Medicine

• Because of their small size, nanoscale devices
  can readily interact with biomolecules on both
  the surface of cells and inside of cells.
• By gaining access to so many areas of the body,
  they have the potential to detect disease and the
  deliver treatment.

• Nanoparticles can can deliver drugs directly
  to diseased cells in your body. 
• Nanomedicine is the medical use of
  molecular- sized particles to deliver drugs,
  heat, light or other substances to specific
  cells in the human body.

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• Quantum dot- that identify the location of cancer
  cells in the body.
• Nano Particles - that deliver chemotherapy drugs
  directly to cancer cells to minimize damage to
  healthy cells.
• Nanoshells - that concentrate the heat from
  infrared light to destroy cancer cells with
  minimal damage to surrounding healthy cells. 
• Nanotubes- used in broken bones to provide a
  structure for new bone material to grow.

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Nano shells as Cancer Therapy Nano shells are
injected into cancer area and they recognize
cancer cells. Then by applying near-infrared
light, the heat generated by the light-absorbing
Nano shells has successfully killed tumor cells
while leaving neighboring cells intact.
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Nanowires used as medical sensor

• In this diagram (next page), Nano sized sensing
  wires are laid down across a micro fluidic
  channel. As particles flow through the micro
  fluidic channel, the Nanowire sensors pick up the
  molecular identifications of these particles and
  can immediately relay this information through a
  connection of electrodes to the outside world.
• These Nanodevices are man-made constructs made
  with carbon, silicon Nanowire.
• They can detect the presence of altered genes
  associated with cancer and may help researchers
  pinpoint the exact location of those changes

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2. Nano Computing Technology
Past Shared computing thousands of people
sharing a mainframe computer
Present Personal computing
Future Ubiquitous computing
thousands of computers sharing each and everyone
of us computers embedded in walls, chairs,
clothing, light switches, cars. characterized
by the connection of things in the world with
computation.
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3. Sunscreens and Cosmetics

• Nanosized titanium dioxide and zinc oxide are
  currently used in some sunscreens, as they absorb
  and reflect ultraviolet (UV) rays.
• Nanosized iron oxide is present in some lipsticks
  as a pigment.

4. Fuel Cells
The potential use of nano-engineered membranes to
intensify catalytic processes could enable
higher-efficiency, small-scale fuel cells.
5. Displays

• Nanocrystalline zinc selenide, zinc sulphide,
  cadmium sulphide and lead telluride are
  candidates for the next generation of
  light-emitting phosphors.
• CNTs are being investigated for low voltage
  field-emission displays their strength,
  sharpness, conductivity and inertness make them
  potentially very efficient and long-lasting
  emitters.

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6. Batteries

• With the growth in portable electronic equipment
  (mobile phones, navigation devices, laptop
  computers, remote sensors), there is great demand
  for lightweight, high-energy density batteries.
• Nanocrystalline materials are candidates for
  separator plates in batteries because of their
  foam-like (aerogel) structure, which can hold
  considerably more energy than conventional ones.
• Nickelmetal hydride batteries made of
  nanocrystalline nickel and metal hydrides are
  envisioned to require less frequent recharging
  and to last longer because of their large grain
  boundary (surface) area.

7. Catalysts
In general, nanoparticles have a high surface
area, and hence provide higher catalytic
activity.
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8. Magnetic Nano Materials applications

• It has been shown that magnets made of
  nanocrystalline yttriumsamariumcobalt grains
  possess unusual magnetic properties due to their
  extremely large grain interface area (high
  coercivity can be obtained because magnetization
  flips cannot easily propagate past the grain
  boundaries).
• This could lead to applications in motors,
  analytical instruments like magnetic resonance
  imaging (MRI), used widely in hospitals, and
  microsensors.
• Nanoscale-fabricated magnetic materials also have
  applications in data storage.
• Devices such as computer hard disks storage
  capacity is increased with Magnetic Nano
  materials

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9. Medical Implantation

• Unfortunately, in some cases, the biomedical
  metal alloys may wear out within the lifetime of
  the patient. But Nano materials increases the
  life time of the implant materials.
• Nanocrystalline zirconium oxide (zirconia) is
  hard, wear resistant, bio-corrosion resistant and
  bio-compatible.
• It therefore presents an attractive alternative
  material for implants.
• Nanocrystalline silicon carbide is a candidate
  material for artificial heart valves primarily
  because of its low weight, high strength and
  inertness.

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10. Water purification

• Nano-engineered membranes could potentially lead
  to more energy-efficient water purification
  processes, notably in desalination process.

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11. Military Battle Suits

• Enhanced nanomaterials form the basis of a
  state-of- the-art battle suit that is being
  developed.
• A short-term development is likely to be
  energy-absorbing materials that will withstand
  blast waves
• longer-term are those that incorporate sensors to
  detect or respond to chemical and biological
  weapons (for example, responsive nanopores that
  close upon detection of a biological agent).

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Physisorption vs Chemisorption
http//www.soton.ac.uk