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Introduction to Chemistry of Nanomaterials UEET103/UEET235 Lecture I

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Introduction to Chemistry of Nanomaterials UEET103/UEET235 Lecture I Prof. Petr Van sek Department of Chemistry and Biochemistry 4 September 2012 – PowerPoint PPT presentation

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Title: Introduction to Chemistry of Nanomaterials UEET103/UEET235 Lecture I


1
Introduction to Chemistry of Nanomaterials UEET103
/UEET235 Lecture I
  • Prof. Petr Vanýsek
  • Department of Chemistry and Biochemistry
  • 4 September 2012

2
Why Study Chemistry?
  • Chemistry is the study of the properties of
    materials and the changes that materials undergo.
  • Chemistry is central to our understanding of
    other sciences.
  • It is substantial part of nanoscience and
    nanotechnology

3
The Study of Chemistry
  • The Molecular Perspective of Chemistry
  • Matter is the physical material of the universe.
  • Matter is made up of relatively few elements.
  • On the microscopic level, matter consists of
    atoms and molecules.
  • Atoms combine to form molecules.
  • As we see, molecules may consist of the same type
    of atoms or different types of atoms.

4
Molecular Perspective of Chemistry (Space filling
models)
5
How to understand structures Space filling Wire
frame Ball and stick
6
Classification of Matter
  • Three States of Matter
  • Matter can be a gas, a liquid, or a solid.
  • These are the three states of matter.
  • Gases take the shape and volume of their
    container.
  • Gases can be compressed to form liquids.
  • Liquids take the shape of their container, but
    they do have their own volume.
  • Solids are rigid and have a definite shape and
    volume.

7
Classification of Matter
8
Properties of Matter
  • Physical vs. Chemical Properties
  • Physical properties can be measure without
    changing the basic identity of the substance
    (e.g., color, density, odor, melting point)
  • Chemical properties describe how substances react
    or change to form different substances (e.g.,
    hydrogen burns in oxygen, iron (steel) corrodes
    (oxidizes) in air)
  • Intensive physical properties do not depend on
    how much of the substance is present.
  • Examples density, temperature, and melting
    point.
  • Extensive physical properties depend on the
    amount of substance present.
  • Examples mass, volume, pressure.

9
States of Matter
Solid Keeps shape Keeps volume Salt, gold, copper
Liquid Takes shape of container Keeps volume Water, alcohol, oil
Gas Takes shape of container Takes volume of container Air, argon, helium, methane
Plasma like a gas of charged particles. Takes shape of container Takes volume of container Stars, nebula, lightning, plasma reactors
10
Matter
  • Solution A uniform mixture of two substances
    such that molecules are separate from each other
    and move around randomly. Usually these are
    liquids. Solutions are usually transparent.
  • Colloids A mixture of much larger particles
    ranging from 20 nm to 100 µm. Milk and paint are
    examples of colloids.
  • Grains Some materials are made up of many small
    crystals called grains. A grain is an individual
    crystal of such a solid. Different grains may
    have the crystal lattice oriented in different
    directions.

11
Elements, Atoms and Molecules
  • Atoms All matter is made up of tiny particles
    called atoms.
  • Molecules Sometimes two or more atoms are found
    bound together to form molecules.
  • The atoms can be categorized into about 115
    different types based on the charge of the
    nucleus.
  • Elements are made up of only one type of atom.
  • The element carbon takes the form of graphite,
    diamond and buckminsterfullerene as well as
    others.
  • It is only possible to change one type of atom
    into another through nuclear processes such as
    take place in a nuclear power plant, the sun,
    atomic bombs or particle accelerators.
  • The elements do not change in ordinary chemical
    reactions.

12
Units of measurement
  • Basic unit one meter
  • prefixes used to describe smaller units
  • millimeter (10-3 m)
  • micrometer (10-6 m)
  • nanometer (10-9 m) (from Greek nanos, a
    dwarf)
  • picometer (10-12 m)
  • size of an atom (10-10 m)

13
Squared and cubed distance
  • Area distance squared
  • Volume distance cubed

the liter is a basic volume unit in chemistry, is
is one decimeter cubed, of 10x10x101000 cm
cubed. It is somewhat larger than one quart
14
Why dimensions matter? Nanomaterials particles
of nanometer size
Nano-scale materials often have very different
properties from bulk materials e.g. color and
reactivity
  • 30nm particle has 5 of atoms on the surface
  • 10nm particle has 20 of atoms on the surface
  • 3nm iron particle has 50 of atoms on the surface

15
  • What is nanotechnology?
  • Ability to understand, create, and use
    structures, devices and systems that have
    fundamentally new properties and functions
    because of their nanoscale structure
  • Ability to image, measure, model, and manipulate
    matter on the nanoscale to exploit those
    properties and functions
  • Ability to integrate those properties and
    functions into systems spanning from nano- to
    macro-scopic scales
  • Research and technology development aimed to
    understand and control matter at dimensions of
    approximately 1 - 100 nanometer the nanoscale

16
Moores Law - one motivation for nanotechnology
17
  • Size-Dependent Properties
  • Even on macro scale properties of material can
    depend on the size of the object treated.
  • For example,
  • Dissolving powder vs. dissolving large chunks
  • (2) Starting fire with a timber log vs. using
    kindling

18
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19
Size-Dependent Properties Powder has larger
surface area than a chunk of the same material
exposed to the liquid, which does the
dissolution Splints made from a log have much
larger surface area than the log from which
they came hence large surface exposure to air
(oxygen) needed for combustion.
20
Size-Dependent Properties At the nanometer scale,
properties become dramatically size-dependent. Fo
r example, (1) Thermal properties melting
temperature (2) Mechanical properties adhesion,
capillary forces (3) Optical properties
absorption and scattering of light (4) Electrical
properties tunneling current (5) Magnetic
properties superparamagnetic effect New
properties enable new applications
21
An electronic device with a nanotube
22
1. What could be the purpose of this device? 2.
What methodology has to be mastered? 3. What (if
anything) is wrong with this picture?
23
"Lately the prefix trend has been shrinking.
During the 1980s, 'mini-' gave way to 'micro-,'
which has yielded to 'nano-.' In the new
millennium, companies such as Nanometrics,
Nanogen and NanoPierce Technologies have all
embraced the prefix, despite complaints their
products were hardly nano-scale (a billionth of a
meter or smaller). Even Eddie Bauer sells
stain-resistant nano-pants. (They're available in
'extra-large' for the retailer's not-so-nano
customers.) (Alex Boese, "Electrocybertronics."
Smithsonian, March 2008)
24
Melting Temperature
Nanocrystal size decreases surface
energy increases melting
point decreases
e.g., 3 nm CdSe nanocrystal melts at 700 K
compared to bulk CdSe at 1678 K
25
The melting point of gold particles decreases
dramatically as the particle size gets below 5 nm
Source Nanoscale Materials in Chemistry, Wiley,
2001
26
Electrical Properties Tunneling current
At the nanometer scale, electrical insulators
begin to block current flow. The current
increases exponentially as the thickness of the
insulator is decreased.
Certain phenomena occur only when characteristic
dimensions reach the nanometer scale e.g.,
quantum tunneling effectsWhen you put a voltage
across an insulator, then the current is given by
UIR. When the insulator becomes small (less than
100 nm) the current is much higher by orders of
magnitude than predicted due to tunneling
27
Historical Use of Nanoparticles Stained Glass
The Lycugus Cup. This cup is made of dichroic
glass that has colloidal gold and silver
nano-scale particles in the glass. When held up
to the light, the ordinarily green cup (from the
silver particles) shows up as red due to the gold
nanoparticles in the glass. More information, and
the original images are available from The
British Museum. 
28
  • What is nanotechnology?
  • Ability to understand, create, and use
    structures, devices and systems that have
    fundamentally new properties and functions
    because of their nanoscale structure
  • Ability to image, measure, model, and manipulate
    matter on the nanoscale to exploit those
    properties and functions
  • Ability to integrate those properties and
    functions into systems spanning from nano- to
    macro-scopic scales
  • Research and technology development aimed to
    understand and control matter at dimensions of
    approximately 1 - 100 nanometer the nanoscale

29
Why is nanotechnology unique? Surface effects are
very important surface to volume ratio is
extremely large Think of water flowing through
your garden hose - the fluid right near the wall
acts very differently than the rest of the fluid.
This has a negligible effect on the water coming
out of the hose end. When the garden hose shrinks
to nanoscale dimensions - all of the fluid is
near the wall, and the laws that predict how
much fluid comes out as a function of pressure no
longer apply.
30
Why is nanotechnology unique? For materials with
more than one atom, not only can the arrangement
of atoms at the surface be different, but the
composition can be different. Say we have the
compound AB- Overall, we have equal amounts of A
and B, but it is possible that at the surface we
have more A than B. In conventional materials,
this surface enhancement of A does not affect the
bulk properties, since the amount of material at
the surface is miniscule. In nanomaterials, this
surface enhancement not only affects the
surface properties, but it also affects the
bulk properties since there is much more B in
the bulk, since the amount of material at the
surface is significant.
31
  • Unique properties of the material when the size
    goes down
  • Quantum size effects result in unique mechanical,
    electronic, photonic, and magnetic properties of
    nanoscale materials
  • Chemical reactivity of nanoscale materials
    greatly different from more macroscopic form,
    e.g., gold
  • Vastly increased surface area per unit mass,
    e.g., upwards of 1000 m2 per gram
  • New chemical forms of common chemical elements,
    e.g., fullerenes, nanotubes of carbon, titanium
    oxide, zinc oxide, other layered compounds

32
Atoms and molecules are generally less than a nm
and we study them in chemistry. Condensed matter
physics deals with solids with infinite array of
bound atoms. Nanoscience deals with
the in-between meso-world Quantum chemistry
does not apply (although fundamental laws hold)
and the systems are not large enough for
classical laws of physics Size-dependent
properties Surface to volume ratio - A 3 nm
iron particle has 50 atoms on the surface - A
10 nm particle 20 on the
surface - A 30 nm particle only 5
on the surface
33
SURFACE vs. VOLUME
Source Nanoscale Materials in Chemistry, Ed.
K.J. Klabunde, Wiley, 2001
34
Many existing technologies already depend on
nanoscale materials and processes -
photography, catalysts are old examples -
developed empirically decades ago In existing
technologies using nanomaterials/processes, role
of nanoscale phenomena not understood until
recently serendipitous discoveries - with
understanding comes opportunities for
improvement Ability to design more complex
systems in the future is ahead - designer
material that is hard and strong but low
weight - self-healing materials
35
Various Nanomaterials and Nanotechnologies
Nanocrystalline materials Nanoparticles Nano
capsules Nanoporous materials Nanofibers Nan
owires Fullerenes Nanotubes Nanosprings Na
nobelts Dendrimers
Molecular electronics Quantum dots NEMS,
Nanofluidics Nanophotonics, Nano-optics Nanoma
gnetics Nanofabrication Nanolithography Nano
manufacturing Nanomedicine Nano-bio
36
NANOSCALE PROPERTIES
Size-dependent properties color, specific
heat, melting point, conductivity.. I-U of a
single nanoparticle (Electrochemistry) Adsorpti
on - principles - some examples Nanomateria
l reinforcement in composites - multifunctionali
ty - self-healing
37
SOME CONCEPTS AND DEFINITONS
Cluster - A collection of units (atoms or
reactive molecules) of up to about 50
units Colloids - A stable liquid phase
containing particles in the 1-1000 nm range.
A colloid particle is one such 1-1000 nm
particle. Nanoparticle - A solid particle in
the 1-100 nm range that could be
noncrystalline, an aggregate of crystallites
or a single crystallite Nanocrystal - A
solid particle that is a single crystal in the
nanometer range
38
For semiconductors such as ZnO, CdS, and Si,
the bandgap changes with size of the
particle - 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, a change in 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
39
COLOR
In a classical sense, color is caused by the
partial absorption of light by electrons in
matter, resulting in the visibility of the
complementary part of the light On most
smooth metal surfaces, light is totally reflected
by the high density of electrons, hence no
color, just a mirror-like appearance. Small
particles absorb, leading to some color. This is
a size dependent property. Example Gold,
which readily forms nanoparticles but is not
easily oxidized, exhibits different colors
depending on particle size. - Gold
colloids have been used to color glasses since
early days of glass making. Ruby-glass
contains finely dispersed gold-colloids.
- Silver and copper also give attractive colors
40
Surface Adsorption
41
Adsorption is like absorption except the
adsorbed material is held near the surface
rather than inside In bulk solids, all
molecules are surrounded by and bound to
neighboring atoms and the forces are in balance.
Surface atoms are bound only on one side,
leaving unbalanced atomic and molecular forces
on the surface. These forces attract gases and
molecules ? Van der Waals force, ? physical
adsorption or physisorption At high
temperatures, unbalanced surface forces may be
satisfied by electron sharing or valence
bonding with gas atoms ? chemical adsorption or
chemisorption - Basis for heterogeneous
catalysis (key to production of fertilizers,
pharmaceuticals, synthetic fibers, solvents,
surfactants, gasoline, other fuels, automobile
catalytic converters) - High specific surface
area (area per unit mass)
42
Physisorption of gases by solids increases with
decreasing T and with increasing P Weak
interaction forces low heats of adsorption lt
80 kJ/mol physisorption does not affect the
structure or texture of the absorbent Desorpti
on takes place as conditions are
reversed Mostly, testing is done at LN2
temperature (77.5 K at 1 atm.). Plot of gas
adsorbed as volume Va at 0 C and 1 atm (STP)
vs. P/Po (Po is vapor pressure) is called
adsorption isotherm.
43
Nanomaterial reinforcement in composites
Processing them into various matrices follow
earlier composite developments such
as - Polymer compounding - Producing filled
polymers - Assembly of laminate
composites - Polymerizing rigid rod
polymers Purpose - Replace existing
materials where properties can be
superior - Applications where traditionally
composites were not a candidate
44
Nanotechnology provides new opportunities for
radical changes in composite functionality Maj
or benefit is to reach percolation threshold at
low volumes (lt 1) when mixing nanoparticles in
a host matrix Functionalities can be added
when we control the orientation of the
nanoscale reinforcement.
45
Some fundamental science issues
  • What novel quantum properties will be enabled by
    nanostructures (at room temperature)?
  • How different from bulk behavior?
  • What are the surface reconstructions and
    rearrangements of atoms in nanocrystals?
  • Can carbon nanotubes of specified length and
    helicity be synthesized as pure species?
    Heterojunctions in 1-D?
  • What new insights can we gain about polymer,
    biologicalsystems from the capability to
    examine single-molecule properties?
  • How can one use parallel self-assembly techniques
    to control relative arrangements of nanoscale
    components according to predesigned sequence?
  • 7. Are there processes leading to economic
    preparation of nanostructures with control of
    size, shape, etc., for applications?

46
Forms of material DIAMOND - GRAPHITE
47
Forms of material CARBON - GRAPHITE
48
Fullerenes
49
Fullerenes
50
The Nobel Prize in Physics 2010
Awarded jointly to Andre Geim and Konstantin
Novoselov "for groundbreaking experiments
regarding the two-dimensional material graphene"
University of Manchester, UK
51
The Nobel Prize in Physics 2010 Graphene
Graphene is an atomic-scale honeycomb lattice
made of carbon atoms. Photo Alexander Alus
www.nobelprize.org
52
Carbon nanotube extremely strong Theoretical
tensile strength 300 Gpa Highest reported 63
Gpa Kevlar 2.7 GPa steel piano wire 2.4
GPa spider silk 1 GPa diamond - up to 60 GPa
Single walled nanotube
53
How is the strength measured? Theoretical
calculation Experiment
Atomic force microscopy
Min-Feng Yu, Oleg Lourie, Mark J. Dyer, Katerina
Moloni, Thomas F. Kelly, Rodney S. Ruoff Science
Vol 287, 28 Jan. 2000)
54
Inserting nanotubes into a circuit
Single electron transistor
55
Nanofabrication Top-down Chisel away material to
make nanoscale objects Bottom-up Assemble
nanoscale objects out of even smaller units
(e.g., atoms and molecules) Ultimate Goal Dial
in the properties that you want by designing and
building at the scale of nature (i.e., the
nanoscale)
56
Top-Down Photolitography
Chisel away material to make nanoscale objects
57
Bottom-Up Molecular Self-Assembly
Assemble nanoscale objects out of even smaller
units (e.g., atoms and molecules)
Carbon Nanotube Synthesis
58
Acceptance of nanotechnology
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