Download “nano-material”?

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Introduction to Nanotechnology
Prof.P. Ravindran,
Department of Physics, Central University of Tamil
Nadu, India
&
Center for Materials Science and Nanotechnology,
University of Oslo, Norway
http://folk.uio.no/ravi/cutn/teaching.html
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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What is nanotechnology?
Nanotechnology is the ability to create and manipulate
atoms and molecules on the smallest of scales. ‘Nano’
comes from the Greek word for dwarf.
A nanometer (nm) is one-billionth of a metre, smaller than
the wavelength of visible light and a hundred-thousandth
the width of a human hair.
Nanotechnology deals with anything measuring between
1 and 100 nm.
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Nanoworld
Nano means ‘dwarf ‘in Greek
Nano = 1 billionth
1nm = 10-9m
smallest thing visible to human eye;
10,000nm diameter
Nano world – world of atoms and molecules
in nanoscale
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
How big is that?
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 Nanotechnology is the manipulation of matter on an atomic and
molecular scale
 Materials, devices, and other structures with at least one dimension
sized from 1 to 100 nanometres
 Nanoparticles: one of the dimensions is less than 100nm
 Eg: DNA (2.5nm), Hb (6.5nm), viruses (10-100nm)
 Nanostructures: at least one dimension roughly between 1nm and
100nm
 Exhibit novel physical, chemical and biological properties
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
Nanotechnology: fabrication of nanostructures

Create new materials, machines, and devices to change the mode of
our living and work

Deliberate design, construction, characterization and utilization of
functional structures , devices and systems through the control of
matter at nanometre dimensions.

Design, assemble and build well defined intricate structures by putting
atoms or molecules at predesigned position using direct mechanical
control & extended to even macroscopic scales

Aim: to learn to exploit the exceptional properties of nanostructures
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
The Scale of Things -- Nanometers and More
Things Natural
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Things Manmade
10-2 m
1 cm
10 mm
Head of a pin
1-2 mm
Ant
~ 5 mm
Dust mite
200 mm
10-4 m
Fly ash
~ 10-20 mm
The
Microworld
Human hair
~ 10-50 mm wide
1,000,000 nanometers =
1 millimeter (mm)
Microwave
10-3 m
10-5 m
0.01 mm
10 mm
O
-6
Red blood cells
Pollen grain
1,000 nanometers =
1 micrometer (mm)
Visible
10 m
ATP synthase
10-8 m
0.1 mm
100 nm
0.01 mm
10 nm
10-9 m
P
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
S
S
S
S
S
S
S
S
Zone plate x-ray “lens”
Outermost ring spacing
~35 nm
Combine nanoscale building
blocks to make novel
functional devices, e.g., a
photosynthetic reaction
center with integral
semiconductor storage
Ultraviolet
The Nanoworld
10-7 m
~10 nm diameter
21st Century
Challenge
0.1 mm
100 mm
Infrared
Red blood cells
with white cell
~ 2-5 mm
MicroElectroMechanical devices
10 -100 mm wide
Nanotube electrode
Nanotube transistor
Soft x-ray
1 nanometer (nm)
DNA
~2-1/2 nm diameter
Atoms of silicon
spacing ~tenths of nm
10-10 m
0.1 nm
Quantum corral of 48 iron atoms on copper surface
positioned one at a time with an STM tip
Corral diameter 14 nm
Carbon nanotube
~2 nm diameter
Office of Basic Energy Sciences
Office of Science, U.S. DOE
Version 03-05-02
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Introduction
Concept of sizes
1 nm = 10 -9 m （one billionth）
length of linear chain consisting of 10 H atoms or 5 Si atoms
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What is Nanotechnology?
Nanotechnology can be defined as being concerned with
materials and systems whose structures and components
exhibit novel and significantly improved physical, chemical
and biological properties, phenomena and processes due to
their nanoscale size.
For example, new properties of nanomaterials include low
melting points or high catalytical activity etc.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Richard P. Feynman
http://www.feynmanonline.com/
The Feynman Lectures on Physics
“There is plenty of room at the bottom.”
December, 1959, exposition of just how much might
be achieved by focusing on the enormous gap between
the nano world and the big world.
•This talk was a social function—an after dinner talk.
•Replication of machines, each smaller than parent.
•Information on head of pin and in head of pin.
Who knows the word “pin”?
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1/16”=1.5875 mm
= 1,587,500 nm
=15,875,000 Å
1/32”=0.79375 mm
=793,750 nm
=7,937,500 Å
Pin head volume: 1.6 × 1018 Å3
Age of universe in seconds: ~3 x 1017
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Visual approach: simply shrink the text.
This requires the text to be reduced by 25,000 times.
Each letter then would then be several tens of atoms
large.
“…there is no question that there is
enough room on the head of a pin
to put all of the Encyclopedia
Britannica.”
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Nonomaterial

Nanotechnology
is the production of functional materials and structures in
the range of 0.1 to 100 nanometers

physical or chemical methods
One hydrogen atom is 0.1 to 0.2 nm and of a small
bacterium about 1,000 nm
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Nanotechnologies are predicted to revolutionize:
(a) the control over materials properties at ultrafine
scales; and
(b) the sensitivity of tools and devices applied in
various scientific and technological fields.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Nanomaterials



It studies materials with morphological features on the
nanoscale, and especially those that have special
properties stemming from their nanoscale dimensions.
A bulk material should have constant physical
properties regardless of its size,
At the nanoscale this is often not the case. Size-
dependent properties are observed such as quantum
confinement in semiconductor particles, and
superparamagnetism in magnetic materials, etc..
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Example

The bending of bulk copper (wire, ribbon, etc.)
occurs with movement of copper atoms/clusters at
about the 50 nm scale.

Copper nanoparticles smaller than 50 nm are
considered super hard materials that do not exhibit
the same malleability and ductility as bulk copper.
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Classifications of Nanotechnology-1
According to the growth media,
 Vapor phase growth includes laser reaction pyrolysis for
nanoparticle synthesis and atomic layer deposition (ALD)
for thin film deposition
 Liquid phase growth includes colloidal processing for the
formation of nanoparticles and self-assembly of monolayers
 Solid phase growth includes phase segregation to make
metallic particles in glass matrix and two-photon-induced
polymerization for the fabrication of three-dimensional
photonic crystals
 Hybrid growth includes vapor-liquid-solid (VLS) growth of
nanowires
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Classifications of Nanotechnology-2
According to the form of products,
 Nanoparticles by means of colloidal processing, flame
combustion and phase segregation
 Nanorods or nanowires by template-based electroplating,
solution-liquid-solid growth (SLS), and spontaneous
anisotropic growth
 Thin films by molecular beam epitaxy (MBE) and atomic
layer deposition (ALD)
 Nanostrucutred bulk materials including photonic bandgap
crystals by self-assembly of nanosized particles
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Femme
Nanotechnology: BIG picture
Nanooptics
Nanomagnetism
Nanotechnology
covers various research areas
fields contributing to
nanotechnology
development
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Properties of Nano
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Greatly increased surface area per unit mass
Changes chemical reactivity
Changes in surface charge
Modified electronic characteristics
(RCEP 2008)
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Nano Gold
Lycurgus Cup (4th century AD),
165mm tall, with decorations in
very intense red color achieved
by gold and silver nanoparticles
contained in the glassy phase.
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The Lycurgus Cup is a 4th-century Roman
glass cage cup made of a dichroic glass.
Red when lit from behind and green
when lit from in front.
The dichroic effect is achieved by making
the glass with tiny proportions of
nanoparticles of gold and silver
"dispersed" (the technical term in
chemistry) in colloidal form throughout
the glass material.
The particles are only about 70 nanometers
across
Dichroic glass: glass containing multiple micro-layers
of metals or oxides which give the glass dichroic
optical properties.
It has a particular transmitted color and a completely
different reflected color
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Emergence of Nanotechnology-1
What’s not new?
The study of biological systems and the engineering of many materials
such as colloidal dispersions, metallic quantum dots, and catalysts have
been in the nanometer regime for centuries.
 Thousand years ago, Chinese used Au nanoparticles as an
inorganic dye to introduce red color into ceramic
porcelains.
 In 1857, Faraday prepared Au colloids that was stable for
almost a century before being destroyed during World War
II.
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Emergence of Nanotechnology-2
What’s new?
Our ability to image, engineer, and manipulate
systems in the nanometer scale and understanding
of atomic scale interactions.
e.g. Discovery of STM, SPM, AFM techniques
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Moore’s Law
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Development of nanotechnology is driven at least partly by the
ever shrinking of devices in the semiconductor industry and
supported
by
the
availability
of
characterization
manipulation techniques in the nanometer level.
50 nm
1-5 nm
1950
1960
Dimensions of
transistors
halves every
18 months
1M
Transistors per chip
1μm
1 st integrated circuit
Moore’s Law Trend Line
1 st transistor
Transistor Size
1 cm
1970
1980
1990
2000
2010
2020
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
and
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Capability of Nanotechnology
High Strength
Material (>10 GPa)
Autonomous Spacecraft
(40% less mass)
Bio-Inspired
Materials
and Processes
Multi-Functional
Materials
Revolutionary Aircraft
Concepts (30% less
mass, 20% less
emission, 25%
increased range)
Reusable Launch
Vehicle (20% less
mass, 20% less
noise)
Adaptive SelfRepairing Space
Missions
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Then there are dreams…
Library of
Congress
•
•
•
•
Library of Congress inside a sugar cube
Bottom-up manufacturing
Materials (100x) stronger but lighter than steel
Speed and efficiency of computer chips &
transistors
• Nano contrast agents for cancer cell detection
• Contaminant removal from water & air
• Double energy efficiency of solar cells
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Library of
Congress?
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Carbon Nanotubes (CNTs)
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CNTs can span 23,000 miles
without failing due to its
own weight.
CNTs are 100 times stronger
than steel.
Many times stiffer than any
known material
Conducts heat better than
diamond
Can be a conductor or
insulator without any
doping.
Lighter than feather.
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Nanomaterials Applications
There are a number of products available that are
already benefiting from nanotechnology.
Using sunscreen as an example, many of them
contain nanoparticles of zinc oxide or titanium
oxide. Older sunscreen formulas use larger
particles, which is what gives most sunscreens their
whitish color.
Smaller particles are less visible, so when the
sunscreen is rubbed into the skin, it doesn't leave a
whitish tinge.
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Other applications include:
•
•
•
•
•
•
mobile phone touch screens;
cosmetics;
tennis rackets;
bicycles;
fabric;
computer technology.
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‘Nano’ foods now
All foods contain nanoparticles.
Examples of foods that contain nanoparticles
include milk and meat.
Milk contains caseins, a form of milk protein
present at the nanoscale.
Meat is made up of protein filaments that are
much less than 100nm thin.
The organisation and change to the structures
of these affects the texture and properties of
the milk or meat.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Uses for nanotechnology in food
 Food packaging applications e.g. plastic polymers
containing or coated with nanomaterials for improved
mechanical or functional properties;
 Nanocoatings on food contact surfaces for barrier or
antimicrobial properties;
 Nano-sized agrochemicals (a chemical used in agriculture,
such as a pesticide or a fertilizer.);
 Nanosensors for food labelling.
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Nanofood examples
 Nanoparticles are being used to deliver vitamins or other
nutrients in food and drinks without affecting the taste or
appearance. These nanoparticles encapsulate the nutrients
and carry them through the stomach into the bloodstream.
 Nanoparticle emulsions are being used in ice cream and
various spreads to improve the texture and uniformity.
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Nanofood examples
New developments in nanoscience and nanotechnology will
allow more control and have the potential of increased
benefits. These include:
•
•
•
•
healthier foods (e.g. lower fat, lower salt) with desirable
sensory properties;
ingredients with improved properties;
potential for removal of certain additives without loss of
stability;
smart-aids for processing foods to remove allergens such
as peanut protein.
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Nano-packaging examples
 Researches have produced smart packages that can tell
consumers about the freshness of milk or meat.
 When oxidation occurs in the package, nanoparticles indicates
the colour change and the consumer can see if the product is
fresh or not.
 Incorporation of nanoparticles in packaging can increase the
barrier to oxygen and slow down degradation of food during
storage.
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Nanopackaging examples
 Bottles made with nanocomposites minimise the leakage of
carbon dioxide out of the bottle.
 This increases the shelf life of fizzy drinks without having to
use heavier glass bottles or more expensive cans.
 Food storage bins have silver nanoparticles embedded in
the plastic. The silver nanoparticles kill bacteria from any
food previously stored in the bins, minimising harmful
bacteria.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
1959: Richard P. Feynman;
Plenty of room at the bottom

As soon as I mention this, people tell me
about miniaturization, and how far it has
progressed today. They tell me about electric
motors that are the size of the nail on your
small finger. And there is a device on the
market, they tell me, by which you can write
the Lord's Prayer on the head of a pin. But
that's nothing; that's the most primitive,
halting step in the direction I intend to
discuss. It is a staggeringly small world that
is below. In the year 2000, when they look
back at this age, they will wonder why it was
not until the year 1960 that anybody began
seriously to move in this direction.
Why cannot we write the entire 24 volumes of
the Encyclopedia Brittanica on the head of a
pin?
He discussed a "great future" in which "we can arrange the atoms
the way we want." Feynman's "great future" arrived in 1989 with the
discovery of ways to manipulate atoms with the Scanning Tunneling
Microscope.
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Nano in nature
Gecko feet are covered with nano-size hairs
that use intermolecular forces, allowing the
lizards to stick firmly to surfaces.
By replicating this scientists have developed
an adhesive that can seal wounds or patch a
hole caused by a stomach ulcer. The
adhesive is elastic, waterproof and made of
material that breaks down as the injury
heals.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Ultra‐sticky Feet
From Nature: Geoko
 Number Of Spatula In A Foot ~1 Billion
 Intermolecular Force Is Resposible For The
Strong Binding With Surfaces
 A Gecko Can Lift 130 Kg Weigth
SPATULA
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Gecko feet: biology
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Millions of hairs called
setae
Fiber radius is
nanometer-scale
Adhesion due to van
der Waals and
capillary forces
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From Nature: Peacock Feathers
NANOPHOTONIC CRYSTALS
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Applications of nanotechnology
Agriculture
Processing
Products
Nutrition
New pesticides
Microencapsulation
of flavours/aromas
UV protection
Neutraceuticals
Genetic
engineering
Gelation agents
Antimicrobials
Nutrient delivery
Identity
preservation
Nano emulsions
Condition and
abuse monitors
Mineral/vitamin
fortification
Sensors to
measure soil
conditions
Anti-caking
High barrier
plastics
Drinking water
purification
Sanitation of
equipment
Security/anti
counterfeiting
Sensory
characteristics of
supplements
Contaminant
sensors
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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The future of nanotechnology in Food
 Research is being carried out to develop nanocapsules
containing nutrients that would be released when
nanosensors detect a deficiency in your body.
 Nanomaterials are being developed to improve the taste,
colour, and texture of foods. For example “interactive” foods
are being developed that would allow you to choose which
flavour and colour a food has!
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Nanoscience and Nanotechnology
 The nanoscale is not just another step towards miniaturization. It is a qualitatively
new scale where materials properties depend on size and shape, as well as
composition, and differ significantly from the same properties in the bulk.
 “Nanoscience” seeks to understand these new properties.
 “Nanotechnology” seeks to develop materials and structures that exhibit novel
and significantly improved physical, chemical, and tribiological properties and
functions due to their nanoscale size.
 The goals of nanoscience and nanotechnology are:
 to understand and predict the properties of materials at the nanoscale
 to “manufacture” nanoscale components from the bottom up
 to integrate nanoscale components into macroscopic scale objects and devices
for real-world uses
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Zhao, S., Ramakrishnan, G., Shen, P., Su, D., Orlov, A. "The first experimental demonstration of
the beneficial effects of sub-nanometer platinum particles for photocatalysis", Chemical
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Engineering Journal,
217, 266–272, 2013.
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New membranes for filtering out water
pollutants
Ramakrishnan, G., Dwivedi, G., Sampath, S., Orlov, A. "Development and
optimization of novel plasma sprayed ceramic microfiltration membranes", Journal
of Membrane Science, 2015, 489, 106.
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Treated
PURETI Clean was sprayed on the concrete flooring of SunLife Stadium in
Miami, FL in a 2 step process. The bio-grime accumulated on the right
over
the course
of just
6 weeks while
row
stayed clean.
P.Ravindran,
Nanomaterials
and Nanotechnology,
Springthe
2016:treated
Introduction
to Nanotechnology
-1
Untreated
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Water Droplets on “Nanoseal” Treated Wood
Nanoparticles adhere directly to the
substrate molecules (molecular
bonding) and assemble into an
invisible ultra-thin nanoscopic mesh
providing a long lasting, selfcleaning, hydrophobic surface. The
wood is protected against decay,
fungi and rot. It is dimensionally
and UV stable. It will not wear off
and cannot be removed by water,
normal cleaning agents or high
pressure equipment.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Wood Surface Repels Water Droplets
Water droplets rest on a wood
surface impregnated with BASF’s
“Lotus Spray”
The surface is superhydrophobic .
Thus contact area between the
surface of the wood and the water
is reduced to a minimum, and the
adhesive
forces
are
greatly
decreased making the water drops
assume a globular form.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Nanocare revolutionizes fabric technology
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This Lee Performance Khaki Pant features
Nanocare fabric
Product Features: * Nanocare fabric repels
liquids*
Wrinkle free Lee Nanocare khaki pant
fabric * Stain resistant
Nano-CareTM fabrics sold since Nov. 2001, incorporate “nanowhiskers” into the fabric to make it stain-resistant to waterbased liquids such as coffee and wine.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Nanomaterials in action…

Wilson Double CoreTM tennis ball has clay nanoparticles
embedded in the polymer lining of its inner wall, which
slows the escape of air from the ball making it last twice as
long.
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Carbon nanotube stabilizers in Tennis
rackets increase torque and flex resistance
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DoD Focused Areas in Nano
*
NANOELECTRONICS/NANOPHOTONICS/NANOMAGNETICS
Network Centric Warfare
Information Dominance
Uninhabited Combat Vehicles
Automation/Robotics for Reduced Manning
Effective training through virtual reality
Digital signal processing and LPI communications
*
NANOMATERIALS “BY DESIGN”
High Performance, Affordable Materials
Multifunction, Adaptive (Smart) Materials
Nanoengineered Functional Materials
Reduced Maintenance costs
*
BIONANOTECHNOLOGY - WARFIGHTER PROTECTION
Chemical/Biological Agent detection/destruction
Human Performance/Health Monitor/Prophylaxis
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Why we are interested in “nano-material”?
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Expecting different behavior of electrons in their
transport (for electronic devices) and correlation
(for optoelectronic devices) from conventional bulk
material.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Physical properties of nanomaterials
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Nanomaterials may have a significantly lower melting point or phase transition
temperature and appreciably reduced lattice constants, due to a huge fraction of
surface atoms in the total amount of atoms
Mechanical properties of nanomaterials may reach the theoretical strength, which are
one or two orders of magnitude higher than that of single crystals in the bulk form.
The enhancement in mechanical strength is due to the reduced probability of defects.
Optical properties of nanomaterials can be significantly different from bulk crystals.
E.g. The optical absorption peak of a semiconductor nanoparticle shifts to short
wavelength, due to an increased band gap. The colour of metallic nanoparticles may
change with their sizes due to surface plasmon resonance.
Electrical conductivity decreases with a reduced dimension due to increased surface
scattering. However, electrical conductivity of nanomaterials could also be enhanced
appreciably, due to the better ordering in microstructure, e.g. polymeric fibrils.
Magnetic properties of nanostructured materials are distinctively different from that
of bulk materials. Ferromagnetism of bulk materials disappears and transfers to
superparamagnetism in the nanometer scale due to the huge surface energy.
Self-purification is an intrinsic thermodynamic property of nanostructures and
nanomaterials. Any heat treatment increases the diffusion of impurities, intrinsic
structural defects and dislocations, and one can easily push them to the nearby surface.
Increased perfection would have appreciable impact on the chemical and physical
properties. For example, chemical stability would be enhanced.
Properties of nanostructured materials are size dependant. Properties can be tuned simply
by adjusting the size, shape or extent of agglomeration.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Properties of a material vary with the
size of the material
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(Bulk) Gold is a shiny yellow metal
Nanoscopic gold, i.e. clusters of gold atoms measuring 1 nm
across, appears red
Bulk gold does not exhibit catalytic properties
Au nanocrystal is an excellent low temperature catalyst.
Therefore, if we can control the processes
that make a nanoscopic material, then we can control the
material’s properties.
Therefore, if we can control the processes that make a nanoscopic
material, then we can control the material’s properties.
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Stages from free-space to nano-material
Free-space
SchrÖdinger equation in free-space:



2
(
 )  r ,t  i  r ,t
2m0
t
Solution:
 k  e

i ( k r  Et /  )
1
 2
2


 |k |
k  2l / L, l  1,2,3,... E 
2m0
Electron behavior: plane wave
63
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
64
Stages from free-space to nano-material
Bulk semiconductor
SchrÖdinger equation in bulk semiconductor:




2

[
  V0 (r )]  r ,t  i  r ,t
2m0
t
e2

 

V0 (r )  V0 (r  lR)
V0 (r )  
r
Solution:
 2
2


 |k |
i ( k r  Et /  )

E
 nk  e
nk
2meff
Electron behavior: Bloch wave
64
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Stages from free-space to nano-material
Nano-material
SchrÖdinger equation in nano-material:

 2




[
  V0 (r )  Vnano (r )]  r ,t  i  r ,t
2m0
t
with artificially generated extra potential contribution:

Vnano (r )
Solution:
 nk  e
iEt / 


Fn ,k (r ) nk
65
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Stages from free-space to nano-material
Electron behavior:
Quantum well – 1D confined and in parallel plane 2D Bloch
wave
Quantum wire – in cross-sectional plane 2D confined and
1D Bloch wave
Quantum dot – all 3D confined – discrete energy levels
66
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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A summary on electron behavior

Free space
– plane wave with inherent electron mass
– continued parabolic dispersion (E~k) relation
– density of states in terms of E: continues square root
dependence

Bulk semiconductor
– plane wave like with effective mass, two different type of
electrons identified with opposite sign of their effective
mass, i.e., electrons and holes
– parabolic band dispersion (E~k) relation
– density of states in terms of E: continues square root
dependence, with different parameters for electrons/holes
in different band
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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A summary on electron behavior

Quantum well
– discrete energy levels in 1D for both electrons and holes
– plane wave like with (different) effective masses in 2D parallel plane
for electrons and holes
– dispersion (E~k) relation: parabolic bands with discrete states inside
the stop-band
– density of states in terms of E: additive staircase functions, with
different parameters for electrons/holes in different band

Quantum wire
– discrete energy levels in 2D cross-sectional plane for both electrons
and holes
– plane wave like with (different) effective masses in 1D for electrons
and holes
– dispersion (E~k) relation: parabolic bands with discrete states inside
the stop-band
– density of states in terms of E: additive staircase decayed functions,
with different parameters for electrons/holes in different band
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
A summary on electron behavior

Quantum dot
– discrete energy levels for both electrons and holes
– dispersion (E~k) relation: atomic-like k-independent discrete energy
states only
– density of states in terms of E: -functions for electrons/holes
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Nanoscale: High Ratio of Surface Area to Volume
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71
Dimensions of Materials
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Size – Dependent Properties
• Nanoscale sizes can lead to different physical and chemical
properties
- Optical properties
- Bandgap
- Melting point
- Surface reactivity
• Even when such nanoparticles are consolidated into
macroscale solids, new properties of bulk materials are
possible.
- Example: enhanced plasticity
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Melting Point
The melting point of gold particles decreases dramatically as
the particle size gets below 5 nm
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Source: Nanoscale Materials in Chemistry, Wiley, 2001
74
Modifications due to :
 Quantum confinement
 Quantum size effect
 Energy bands and electronic transition
 Charge quantization
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Nanostructures Dimension and
Confinement
STRUCTURE
SPATIAL
DIMENSION
CONFINEMENT
DIMENSION
Bulk
3
0
Surface/ Film
(Quantum Well)
2
1
Nanotubes, -wires
(Quantum wire)
1
2
Nano-particles,
clusters (Quantum
dots)
0
3
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Nanomaterials
76
This includes subfields which develop or study materials having
unique properties arising from their nanoscale dimensions.
Interface and Colloid Science
has given rise to many
materials which may be useful
in nanotechnology, such as
carbon nanotubes and other
fullerenes, and various
nanoparticles and nanorods.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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Nanomaterials


Development of applications
incorporating semiconductor
nanoparticles to be used in the
next generation of products, such
as display technology, lighting,
solar cells and biological imaging.
Nanoscale materials can also be
used for bulk applications; most
present commercial applications
of nanotechnology are of this
flavor.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Nanomaterials


Nanoscale materials are sometimes used in solar cells which
combats the cost of traditional Silicon solar cells
Progress has been made in using these materials for medical
applications.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
78

The first “proof of principle” that atoms could be
precisely positioned by man made tool took place in
1989 when scientists at IBM manipulated 35 xenon
atoms to form the letters IBM.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
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CLASSIFICATION OF NANOPARTICLES
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0
81
Nanoparticle
A sub-classification of ultrafine particles with lengths in two
or three dimensions greater than 1 nanometer (nm) and smaller
than about 100 nm, and which may or may not exhibit sizerelated intensive properties.
 Natural nanoparticles: Particles with one or more
dimensions at the nanoscale originating from natural
processes, e.g. soil colloids.

Engineered
nanoparticles:
Less
frequently
also
“manufactured nanoparticles”- Nanoparticles manufactured
to have specific properties or a specific composition.
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
Size-related intensive properties

Physical or chemical properties of a particle that
change as a particle size falls below a certain
threshold (surface charge, conductivity, color, etc.).
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
82
Agglomerate


A group of particles held together by relatively weak
forces.
Ultrafine particles: Term frequently used by those
dealing with industrial products, aerosols and air
pollution, and referring to particulate matter smaller
than 2.5 micrometer.
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83
Nano is different
84
Gold is noble
...but nano-gold is a superb catalyst.
Left: Jewel from Malia, Crete, Greece (ca. 1800 BC);
Right: CO oxidation on Au nanoparticle
(Remediakis, Lopez, Nørskov, Angew. Chem. (2005)).
See also: “Making Gold Less Noble”, Mavrikakis et al., Catal. Lett. (2000).
P.Ravindran, Nanomaterials and Nanotechnology, Spring 2016: Introduction to Nanotechnology - 1
TOOLS IN NANOTECHNOLOGY
•
Two tools for measurement at nano scale
– STM (Scanning Tunneling Microscope)
– AFM (Atomic Force Microscope)
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