Nanotechnology: ferrofluids to liquid crystals  (Page 4/4)

Part iii. synthesis of cholesteryl ester liquid crystals

Chemicals

• Cholesteryl oleyl carbonate
• Cholesteryl pelargonate

• Cholesteryl benzoate
• Vials
• Heat gun

Liquid crystal synthesis

• Place 0.65 g cholesteryl oleyl carbonate, 0.25 g cholesteryl pelargonate, and 0.10 g cholesteryl benzoate in a vial.
• In a hood, with the cap off, melt the solid in with a heat gun.
• While the mixture is still a liquid, divide it into separate vials using a disposable pipette. Put the caps back on the vials. Allow the vials to cool and observe their properties.
• Clean up your bench area.
• Listed below is a chart of the different ratios that produce liquid crystals with different transition temperatures. Placing liquid crystals with different transition temperatures next to each other on a clear piece of contact paper makes it possible to make a thermometer.

Pre-lab: nanotechnology

(total 10 points)

Hopefully here for the Pre-Lab

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’work (including your laboratory partner) or misrepresent your own data (see honor code).

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

Part i. demo of gold nanoparticles

• In a 3 nm gold particle, what percentage of the atoms are on the surface? Hint: You need to find the radius of a single gold atom and the equation for the volume of a sphere is also helpful. Remember that the volume of a shell is Vshell=4/3πr3 (r3-(r-2r)3).
  I am giving them this because all the students had trouble with this. The other things are easier to find but this isn’t.

Part ii. synthesis of an aqueous ferrofluid

• How would you make a 100 mL solution of 1.0 M ${\text{FeCl}}_3$ in 2.0 M HCl from ${\text{FeCl}}_3\cdot {\mathrm{6H}}_{2}O$ and concentrated HCl solution? Show all calculations. Hint: First find volume of water needed to make concentrated HCl ~12.1 M

Part iii. liquid crystal synthesis

• In your own words, explain what a liquid crystal is.

Report: nanotechnology

On my honor, in preparing this report, I know that I am free to use references and consult with others.

Hopefully here for the Report Form

Note: In preparing this report you are free to use references and consult with others. However, you may not copy from other students’work (including your laboratory partner) or misrepresent your own data (see honor code).

Name(Print then sign): ___________________________________________________

Lab Day: ___________________Section: ________TA__________________________

Part i. demo of gold nanoparticles

• What was the starting color of the ${\text{HAuCl}}_4$ solution?

• What was the beginning oxidation state of Au?

• What was the ending oxidation state of Au?

• What is the purpose of the sodium citrate solution?

• What is the total surface area of 3 g of 5 nm gold particles assuming gold has a density of $9\text{.}\mathrm{3g}/{\text{cm}}^3$ ?

• What is the total surface area of 3 g of 5 micrometer gold particles assuming gold has a density of $9\text{.}\mathrm{3g}/{\text{cm}}^3$ ?

Part ii. synthesis of an aqueous ferrofluid

• Write out the over-all balanced equation for the ferrofluid synthesis.

• Why did we rinse the nanoparticles three times with water (what are you specifically removing)?

• What is the purpose of the surfactant? Chemically explain the process.

• Other than those listed, what are three uses for ferrofluids.

Part iii. liquid crystal synthesis

• As the color of the liquid crystal changes, what is happening to the pitch length?

• If the color is green and changes to red, chemically/physically explain what has happened to the liquid crystal and be specific. .Hint: Look at the wavenmber values assigned to each color. Does this correspond to a temperature increase or decrease? Why?

• A student measures 0.66 g cholesteryl oleyl carbonate, 0.69 g cholesteryl pelargonate, 0.15 g cholesteryl benzoate and combines them to make a liquid crystal. What is the most likely transition temperature?