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Today’s Activity

Structures with a nanoscale dimension. Rob Snyder Mark Tuominen University of Massachusetts Amherst. Today’s Activity. Learn about Ben Franklin’s observations of a thin film that had a nanoscale dimension. Create a very thin film with a very dilute solution of oleic acid.

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Today’s Activity

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  1. Structures with a nanoscale dimension.Rob SnyderMark TuominenUniversity of Massachusetts Amherst

  2. Today’s Activity • Learn about Ben Franklin’s observations of a thin film that had a nanoscale dimension. • Create a very thin film with a very dilute solution of oleic acid. • Use data you collect to determine if a thin film with a nanoscale dimension formed on the surface of water. • Be introduced to the Big Ideas of Nanoscale Self-Assembly

  3. Was Ben Franklin an Early Nanoscientist?

  4. Excerpt from Letter of Benjamin Franklin to William Brownrig (Nov. 7, 1773) ...At length being at Clapham, where there is, on the Common, a large Pond ... I fetched out a Cruet of Oil, and dropt a little of it on the Water. I saw it spread itself with surprising Swiftness upon the Surface ... the Oil tho' not more than a Tea Spoonful ... which spread amazingly, and extended itself gradually till it reached the Lee Side, making all that Quarter of the Pond, perhaps half an Acre, as smooth as a Looking Glass....

  5. 2 cm3 T = 20,000,000 cm2 ~ 2 cm3 V = 1 teaspoonful A = 0.5 acre ~ 2,000 m2 ... the Oil tho' not more than a Tea Spoonful ... ... perhaps half an Acre CHALLENGE: How thick was the film of Ben Franklin’s oil? Volume = (Area)(Thickness) V = A T T = V/A T = 0.0000001 cm T = 1 x 10-7 cm T = 1 x 10-9 m T = 1 nanometer 20,000,000 cm2

  6. DNA 6,000 nanometers 3 nanometers How big are nanoscale structures? Hair . 100,000 nanometers

  7. Examples of Nanoscale Thin Films Nanofilm on glass Nanofilm on plastic Gold-coated plastic for insulation purposes "Low-E" windows: a thin metal layer on glass: blocks UV and IR light

  8. It would be difficult to conduct a thin film experiment on the UMass Amherst campus pond.

  9. Different sizes and shapes of plastic tray can be used to experiment with thin films. However, you need to use much less than a teaspoon of oil. Results from groups using large and small trays can be compared.

  10. You will form a thin film of oleic acid on the surface of water. Oleic acid is one of olive oil’s ingredients.

  11. Water is in either a small or large tray. Make a double dilute solution of oleic acid in alcohol. Determine how many drops of a very dilute solution are in one cm3 of the second dilute solution. Evenly sprinkle a layer of baby powder or lycopodium powder across the surface of the water. Let one drop of the very dilute solution of oleic acid spread across the surface of the water. The alcohol solvent will dissolve in water leaving a thin film of oleic acid solute on the surface Measure the average diameter of the somewhat circular layer of oleic acid. You will need to make a double dilute solution of oleic acid.

  12. Thin films of oleic acid will have many shapes and require more than one measurement of diameters.

  13. These steps correspond to the sequence of calculations on the calculation worksheet. Step 1: The volume fraction = 1 / 25 Step 2: 0.04 cm3 Step 3: 0.04 cm3 / 25 = 0.0016 cm3 A group determined that 40 drops of the second dilute solution = 1.0 cm3. Step 4: If a group determined that 40 drops of the second solution of oleic acid had a volume of 1.0 cm3; Then 0.0016 cm3 / 40 = 0.00004 cm3. A group recorded the average radius as 7.25 cm ASample Calculation

  14. Step 5: Area = 3.14 x R2 The area of a thin film with a radius of 7.25 cm film is 165.05 cm2 Step 6: If Volume = Area x Depth; Then: Depth = Volume / Area and the thickness of the example group’s film would be 2.42 x 10-7 cm. Step 7: 2.42 x 10-9 meters Step 8: 2.42 x 10-9 m = 2.42 nanometers Does the film have a nanoscale dimension?

  15. Why did oleic acid form a thin film? Oleic acid molecules have a polar ends that are attracted to polar water molecules.

  16. When you poured a small amount of oleic acid onto the surface of water, electric interactions caused the oleic acid molecules to “self-assemble” into a thin layer. + charge on a hydrogen atom - Charge on an oxygen atom Water molecules in a tray.

  17. Weak van der Walls forces describe the attraction between adjacent hydrocarbon chains. They are strong enough for the thin film to maintain its integrity as it spreads across the water.

  18. In a small drop of oleic acid there are billions of oleic acid molecules that will stand up like blades of grass on the surface of water.If you formed a monolayer, then you also calculated the length of an oleic acid molecule. The generally accepted value for the length of an oleic acid molecules 1.97 nanometers.

  19. Perhaps you did not form a monolayer. Multiple layers of oleic acid can form on the surface of water. Non-polar ends of oleic acid

  20. Three molecular substances were used in this activity. What two roles did alcohol play? Isopropyl Alcohol Water Oleic acid

  21. The thin film of oleic acid forms a Langmuir Film. The thin film can be confined to a specific area with a barrier. You used baby powder as a confining barrier. hydrophobic end water hydrophilic end

  22. What might be some sources of error when calculating the thickness of a thin film of oleic acid? How could the sources of error be minimized? In what ways in this activity an example of nanoscale self-assembly? A Few Questions

  23. Some Examples of Self Assembly

  24. The Big Ideas in Nanoscale Self-Assembly • Structural components are mobile. • The goal is a low energy equilibrium state. • Ordered structures result from a less ordered system. • Assembly is a result of attractive or repulsive forces between the components. • An environment is selected to induce designed interaction. • Components retain physical identity through and after. • The process is reversible or adjustable. Whitesides & Boncheva (2002)

  25. A Few More Questions • How many ways can the oleic acid thin film activity be seamlessly integrated into the K-12 STEM Curriculum? • What essential knowledge is associated with this activity? • What essential skills are associated with this activity?

  26. UMass Amherst NanotechnologyCurriculum Resources are available athttp://umassk12.net/nano/ Materials include student activity documents, teacher guides that include sample calculations, worksheets (with and without hints for making calculations), multimedia modules that enrich what students learn doing an activity and PowerPoints presentations.

  27. K-12 Curriculum Materials are also available at the Center for Hierarchical Manufacturing’s web site. http://chm.pse.umass.edu/education_outreach/instructional

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