Title: Unit 1, Part 1: Introduction to Nanotechnology (Read Chapter 2 in Di Ventra) Dr. Brian Grady-Lecturer bpgrady@ou.edu
1Unit 1, Part 1 Introduction to Nanotechnology
(Read Chapter 2 in Di Ventra)Dr. Brian
Grady-Lecturerbpgrady_at_ou.edu
2Four Units
- Synthesis Dr. Warren Ford wtford_at_okstate.edu
- Characterization Dr. Brian Grady bpgrady_at_ou.edu
- Applications/Microscopy Dr. Alan Cheville
- Presentation of Review Papers
- Mechanics Issues (On-line quizzes, laboratory
issues etc.) Chris Young nanotechta_at_gmail.com
3Format of Class
- On-line lectures, assigned reading
- On-line quizzes Purpose is to be sure you have
read and comprehended material - Multiple attempts if necessary not graded except
pass-fail
4Format of the Class-Continued
- Three laboratories
- Read material in advance
- On-line video showing you how to do the
experiments - On-line quiz to be completed PRIOR to laboratory
or you will not be allowed in the laboratory - Complete laboratory- on site on Saturday
- Logistical transportation issues will be dealt
with later - Lab report Important part of your grade
- In order to be allowed to do the lab and get
anything but a failing grade for that lab you
must successfully complete ALL of the on-line
quizzes for that unit (unless indicated as not
necessary by an instructor) PRIOR to being
allowed to enter the laboratory
5Format of the Class (cont.)
- Comprehensive review paper
- Topics must be approved by Dr. Grady no later
than November 1st. - Papers due December 7th
- You will also prepare and give a 15-20 minute
presentation at a mini-conference that will be
held on Dec 1st. Location of miniconference will
be at TU
6Format of the Class (continued)
7What is nanotechnology
- Nanomaterials are materials where at least one
dimension is very small (i.e. on the order of
nanometers) - 1 nanometer10 Angstroms.001 microns10-9 meters
- Almost always talking about solids (not liquids
or gases) - Nanotechnology is the study of the
synthesis/manufacture of those materials, the
characterization of those materials and the
application of those materials
8Why Nanotechnology
- Materials having very small sizes have unique
properties - See Figure 1.19 in the text
- The size of the particles controls the colors
that are emitted when the particles are exposed
to UV light - Only certain chemical compositions will have this
property (i.e. this behavior is not generic to
all nanoparticles) - Materials with small sizes can be packed into
small areas and can do lots of stuff - Integrated circuits Millions of electrical
components (resistors, transistors) per square
inch - Materials with small sizes can be packed in a
regular arrangement and do interesting things - See Figure 1.21 on inverse opals (unique colors
due to a regular arrangement of spheres) - By and large, the chemical identity of the
spheres is irrelevant to the effect this is
strictly a size effect.
9Inverse Opals
- If spheres in regular pattern as shown to the
right, and the spheres are the size of the
wavelength of light (400-700 nm) get unique
colors and can change color by changing sphere
size
10Why is nanotechnology unique?
- Certain phenomena occur only when characteristic
dimensions reach the nanometer scale - Quantum tunnelling effects If you put a voltage
across an insulator, then the current is given by
VIR. If the insulator becomes small less than
100 nm the current is much higher (orders of
magnitude!) than that predicted by the formula
due to tunnelling - Surface effects are very important (surface to
volume ratio is extremely large) - One sense how atoms are arranged at the surface
have a very large influence on all properties,
not just surface properties - 2nd sense Certain phenomena that are surface
phenomena become dominant phenomena at nanoscale.
For example, in flow through a pipe (think of
water flowing through your garden hose!) the
fluid right near the wall acts very differently
than the rest of the fluid. This fact has a
negligible effect though on the behavior of the
water coming out of the hose end. If the garden
hose becomes of nanoscale dimensions, all of the
fluid is near the wall and all of the laws that
tell you (for example) how much fluid comes out
of your garden hose as a function of the pressure
of the water do not apply.
11Why study nanotechnology?
- Today there is a large amount of research, but,
outside of integrated circuits, not a large
number of commercial applications of
nanotechnology - Still primarily in the realm of start-up
companies, and in the research departments of
large companies
12Is nanotechnology the wave of the future?
- Certain politicians think so (i.e. money!)
- I think most people would agree that the term
microelectronics will (or at least should!)
eventually be replaced by the term
nanoelectronics - Already niche applications in other areas
- Take advantage of small size leading to some
unique characteristic or the fact that the
material changes behavior entirely because the
surface to volume ratio is so high - The other logical area that one would think where
nanotechnology will be huge is medicine - Blood vessels etc. are pretty small, and to be
able to navigate those vessels without disrupting
function, which nanosize things should be able to
do, should prove very useful.
13Two Important Introductory Concepts
- Bulk vs. Surface Properties
- Arrangement of Atoms
14Bulk vs. Surface
- Think of Scotch Tape
- Surface Property Adhesion. Scotch tape sticks
to things - Bulk Property Strength. How much force does it
take to pull scotch tape apart - Surface properties are determined by atoms within
a few angstroms of the surface - In nanotechnology surface properties are much
more important relatively than bulk properties
than with other materials because surface/volume
ratio is so high
15Examples
- Examples of Surface Properties
- Surface energy (adhesion ability), charge on a
particle (i.e. can it be made to have static
electricity), catalytic ability (ability to cause
reactions), ability to nucleate (think of putting
boiling chips in heated water). - Examples of Bulk Properties
- Mechanical strength, stiffness and flexibility,
electrical conductivity, density etc.
16Arrangement of Atoms
- Consider a solid
- Three possibilities atoms are arranged in a
regular pattern, atoms are not arranged in a
regular pattern, some atoms are arranged in a
regular pattern and some are not - If atoms are all arranged in a regular pattern
crystalline - If atoms are not arranged in a regular pattern
amorphous - If some atoms are arranged in a regular pattern
and some are not semi-crystalline
17What do I mean by regular pattern
- Think of a single type of atom material, e.g.
gold - Gold atoms are arranged in cubes (atoms at
corners and at 6 faces).
Ball and Stick Model
Space Filling Model
This particular structure is called
face-centered cubic
18- Stack Cubes in all three directions to make up
repeating structure. This is how atoms lie in
regular patterns
(Dont show in and out of page because drawing
becomes too confusing)
19Crystalline
- All crystalline materials are made up of regular
cubic-like structures (cubes, rhombohedrans,
cubes with lengths of sides not equal there are
seven total) with atoms at the same positions
within every cube. There are only 230 different
atom/cube combinations. - Most of the time, each side of these cubic-like
structures have dimensions between 0.5 nm and 2
nm - Amorphous materials have no such cubes, i.e. if
you draw cubes atoms arent in the same position
within every cube.
20Something to Consider
- Suppose we make spherical gold nanoparticles that
contains enough volume for 10000 unit cells
(which is equivalent to a 5.5 nm diameter
particle). Note that in this particle
approximately 1/3 of the unit cells have one side
touching the surface! - Since gold forms into cubes, one could easily see
how a nanoparticle could be cubic but how
spherical and still have cubic unit cell??? - The answer is that it is not possible either the
outside of the sphere has to look like this
or the atoms
have to change positions at the surface. If atoms
change positions, how deep into the nanoparticle
does this go? - It turns out that in some systems, you can make a
material that is normally crystalline into an
amorphous material, or even change the crystal
structure entirely. Of course, the properties of
the material change dramatically if this happens
21Surface Composition
- For a single atom material, the arrangement of
atoms at the surface can be very different than
the arrangement of atoms in the bulk - 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 - For example, say we have the compound AB.
Overall, we have equal amounts of A and B, but it
is possible at the surface we have much more A
than B. In non-nanomaterials, 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 effects the bulk
properties since there is much more B in the bulk
than A, since the amount of material at the
surface is NOT miniscule.
22On to Synthesis