A Nanoscale Thin Film Activity for the Middle and High School STEM Curriculum Rob Snyder University of Massachusetts Amherst

Thin films with nanoscale dimensions improve many products. Gold-coated plastic can be used as insulation. Nanoscale thin films on glass make windows more energy efficient. Nanofilm on plastic Nanofilm on glass

Nanoscale thin films are being developed to make flexible sheets of solar panels.

Nanoscale thin films on eyeglasses and camera lenses can make them water-repellent, antireflective, self-cleaning, resistant to ultraviolet or infrared light and scratch-resistant.

A nanoscale structure has a length, width, diameter and/or thickness of between 1 and 100 nanometers. 1 nanometer = 1 billionth of a meter or 1 nanometer = meters or 1 nanometer = 1 x meters nano.gov

Today’s Activity Learn that Ben Franklin experimented with making a thin film of oil that had a nanoscale dimension.Learn that Ben Franklin experimented with making a thin film of oil that had a nanoscale dimension. Use graduated cylinders to make a very dilute solution of oleic acid. Household oils can also be used.Use graduated cylinders to make a very dilute solution of oleic acid. Household oils can also be used. Put a very small volume of oleic acid onto the surface of water.Put a very small volume of oleic acid onto the surface of water. Make measurements of a circular area of a thin film of oleic acid.Make measurements of a circular area of a thin film of oleic acid. Use the formula for the volume of a disc to calculate the thickness of a thin film of oleic acid. Learn why oleic acid molecules form a very thin film. Discover that your may have measured the length of a molecule. Be introduced to the Big Ideas of a nanoscale process called Self-AssemblyBe introduced to the Big Ideas of a nanoscale process called Self-Assembly

Was Ben Franklin an Early Nanoscientist ?

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....

... 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) If: V = A T V = 1 teaspoonful A = 0.5 acre ~ 2 cm 3 ~ 2,000 m 2 Then: T = _V_ A 20,000,000 cm 2 T = 2 cm 3 20,000,000 cm 2 T = cm T = 1 x cm T = 1 x m T = 1 nanometer

. It would be difficult to produce a thin film on the UMass Amherst campus pond.

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. 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.

Thin Film Documents A student document with directions for both a small tray and a large tray of water. A calculations worksheet. One side has hints for making calculations. Sample calculations that can be provided for students who are having difficulty. A teacher’s guide with a sample calculation

You will form a thin film of oleic acid on the surface of water. Oleic acid is one of the liquids in olive oil. Water is in a small or large tray.Water is in a small or large tray. Make a double dilute solution of oleic acid in alcohol.Make a double dilute solution of oleic acid in alcohol. Determine of a very dilute solution are in of the dilute solution.Determine how many drops of a very dilute solution are in one cm 3 of the second dilute solution. sprinkle a layer of baby powder or lycopodium powder across the surface of the water.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.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 surfaceThe 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.Measure the average diameter of the somewhat circular layer of oleic acid.

A thin film usually does not form a perfect disc shape. But you can calculate the area of a somewhat circular thin film by determining its average radius.

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

This sample calculation reveals that the thin layer of oleic acid had a nanoscale dimension. Step 5: Area = 3.14 x R 2 The area of a thin film with a radius of 7.25 cm film is cm 2 Step 6: If Volume = Area x Depth; If Volume = Area x Depth; Then: Depth = Volume / Area and the thickness of the example group’s film would be 2.42 x cm. Then: Depth = Volume / Area and the thickness of the example group’s film would be 2.42 x cm. Step 7: 2.42 x meters Step 8: 2.42 x m = 2.42 nanometers

You experimented with three different molecules. What two roles did alcohol play so that you could form a thin film of oleic acid? Oleic acid Isopropyl Alcohol Water

A polar end of an oleic acid molecule is hydrophilic. The hydrogen atom at one end of the oleic acid molecule is more positive than the rest of the molecule. The region around the oxygen end of a water molecule is more negative than the rest of the molecule

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 an oxygen atom in each water molecule + charge on a hydrogen atom in each oleic acid molecule Water molecules in a tray.

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.

In your one small drop of oleic acid there many billions of oleic acid molecules that stood up like blades of grass on the surface of water In your one small drop of oleic acid there many billions of oleic acid molecules that stood 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.

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

A Few Questions What measurement skills were required to do this activity?What measurement skills were required to do this activity? What math skills were required to do this activity?What math skills were required to do this activity? What might be some sources of error when calculating the thickness of a thin film of oleic acid?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?How could the sources of error be minimized?

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