1. C.6 Liquid Crystals The liquid crystal state Liquid Crystal Examples
Intermediate state of matter with properties between the solid and liquid state. (nematic state)
Share many physical properties with solid crystals, but properties can be easily modified.
Typically made up of long polar organic molecules.
Liquid Crystal Examples
Graphite, cellulose, DNA, spider silk solution

2. Liquid Crystal State Thermotropic liquid crystals:
formed by pure substances over a certain temperature range.
Lyotropic liquid crystals:
Formed by solutions
Properties determined by both temperature and concentration.
Soap example, pg 321

3. LCD devices Often use polar molecules
Ability to transmit light depends on relative orientation of molecules.
Orientation of molecules controlled by application of an electric field (voltage)
Common molecule: pentylcyanophenyl
Chemically stable
Liquid crystal phase over suitable range of temperatures.
Polar, orientation easily affected by electric field.
Responds to changes of voltage quickly.

4. Practice Exercise
Pg. 322, visuals of molecules

5. C.7 Nanotechnology
The research and technology development in the nm range.
“the science of the very small with big potential”
Interdisciplinary, involving chemistry, physics, biology, and materials science.

6. Producing Nanomaterials
Top-down approach:
Start with a bulk material and break it down into smaller materials.
Bottom-up approach:
Build the material from atomic or molecular species.

7. Properties of Nanomaterials
Very different from their bulk/macro-level properties.
Quantum effects play large role.

8. Examples of Nanotech Scanning Tunneling Microscope (STM)
use of ultra fine atomic probe that feels the surface of a material rather than “sees” it.

9. Examples of Nanotech Carbon nanotubes
Buckminsterfullerene (bucky ball): C60
Led to development of “nanotubes”

10. Implications of Nanotech
Current & Potential Uses
Agriculture
Nanoporous zeolites for slow release of water and fertilizers
Healthcare/medicine
Biological nanosensors as diagnostic tools
Energy
Nanoscale catalyst-enhanced fuels for better efficiency; nanomaterials for fuel cells/batteries/solar cells.
Electronics
Carbon nanotube electronic components

11. Implications of Nanotech
Current & Potential Uses
ICT
Flat panel flexible displays using nanotechnology; high-density data storage using nanomagnetic effects; faster processing using quantum computers.
Water treatment
Nanomembranes for water treatment

12. Implications of Nanotech
Possible concerns:
Unknown health effects, immune systems
Toxicity
Reactivity and kinetics
Scientists must be responsible to trial test new substances, assess the risks, and engage in debate with the public to address facts and communicate issues.

13. Practice Exercise:
A carbon nanotube has a diameter of 1 nm and is 10 µm long. How may diameters does this length represent?
These tubes are believed to be stronger than steel. Explain the tensile strength of the tubes on a molecular level.
One problem in the synthesis of nanotubes is that a mixture of tubes with different lengths and orientations is produced. Suggest why this is a problem.
The wavelength of UV light is in the range nm. Many modern sunscreens contain nano-sized particles of titanium dioxide which do not absorb ultraviolet radiation. Suggest how these nono-particles are able to protect skin from UV radiation.