Structures with a nanoscale dimension.Structures with a nanoscale dimension.

Rob SnyderRob SnyderMark TuominenMark Tuominen

University of Massachusetts AmherstUniversity of Massachusetts Amherst

Today’s ActivityToday’s Activity

• Learn about Ben Franklin’s observations of a Learn about Ben Franklin’s observations of a thin film that had a nanoscale dimension.thin film that had a nanoscale dimension.

• Create a very thin film with a very dilute solution Create a very thin film with a very dilute solution of oleic acid.of oleic acid.

• Use data you collect to determine if a thin film Use data you collect to determine if a thin film with a nanoscale dimension formed on the with a nanoscale dimension formed on the surface of water.surface of water.

• Be introduced to the Big Ideas of Nanoscale Be introduced to the Big Ideas of Nanoscale Self-AssemblySelf-Assembly

Was Ben Franklin an Early NanoscientistWas Ben Franklin an Early Nanoscientist??

Excerpt from Letter of Benjamin Franklin to William Brownrig (Excerpt from Letter of Benjamin Franklin to William Brownrig (Nov. 7, 1773) Nov. 7, 1773)

...At length being at Clapham, where there is, on the Common, a large ...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 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 saw it spread itself with surprising Swiftness upon the Surface ... the Oil tho' not more than a Tea Spoonful ... which spread amazingly, and tho' not more than a Tea Spoonful ... which spread amazingly, and extended itself gradually till it reached the Lee Side, making all that 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 Quarter of the Pond, perhaps half an Acre, as smooth as a Looking Glass....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)

V = A T

V = 1 teaspoonful

A = 0.5 acre

~ 2 cm3

~ 2,000 m2

T = V/A

20,000,000 cm2

T = 2 cm3

20,000,000 cm2

T = 0.0000001 cm T = 1 x 10-7 cm T = 1 x 10-9 m T = 1 nanometer

How big are nanoscale structures?

Hair

.

DNA

3 nanometers

6,000 nanometers

100,000 nanometers

Examples of Nanoscale Thin Films

Gold-coated plastic for insulation purposes

"Low-E" windows: a thin metal layer on glass: blocks UV and IR light

Nanofilm on plasticNanofilm on glass

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

Different sizes and shapes of plastic tray can be Different sizes and shapes of plastic tray can be used to experiment with thin films. However, you used to experiment with thin films. However, you need to use much less than a teaspoon of oil.need to use much less than a teaspoon of oil.

Results from groups using large and small trays can be compared.

You will form a thin film of oleic acid You will form a thin film of oleic acid on the surface of water. on the surface of water.

Oleic acid is one of olive oil’s ingredients.Oleic acid is one of olive oil’s ingredients.

You will need to make a double You will need to make a double dilute solution of oleic acid.dilute solution of oleic acid.

• Water is in either a small or large tray. Water is in either a small or large tray. • Make a Make a double dilutedouble dilute solution of oleic acid in alcohol. solution of oleic acid in alcohol.• Determine Determine how many drops of a very dilute solution are in of a very dilute solution are in

one cmone cm33 of the of the secondsecond dilute solution. dilute solution.• Evenly Evenly sprinkle a layer of baby powder or lycopodium sprinkle a layer of baby powder or lycopodium

powder across the surface of the water.powder across the surface of the water.• Let one drop of the very dilute solution of oleic acid Let one drop of the very dilute solution of oleic acid

spread across the surface of the water. spread across the surface of the water. • The alcohol solvent will dissolve in water leaving a thin The alcohol solvent will dissolve in water leaving a thin

film of oleic acid solute on the surfacefilm of oleic acid solute on the surface• Measure the average diameter of the somewhat circular Measure the average diameter of the somewhat circular

layer of oleic acid.layer of oleic acid.

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

AA Sample CalculationSample Calculation

These steps correspond to the sequence of These steps correspond to the sequence of calculationscalculations on the on the calculationcalculation worksheet. worksheet.

Step 1: The volume fraction = 1 / 25Step 1: The volume fraction = 1 / 25

Step 2: 0.04 cmStep 2: 0.04 cm33

Step 3: 0.04 cmStep 3: 0.04 cm33 / 25 = 0.0016 cm / 25 = 0.0016 cm33

A group determined that 40 drops of the second A group determined that 40 drops of the second dilute solution = 1.0 cmdilute solution = 1.0 cm33..

Step 4: If a group determined that 40 drops of the Step 4: If a group determined that 40 drops of the second solution of oleic acid had a volume of 1.0 second solution of oleic acid had a volume of 1.0 cmcm33; Then 0.0016 cm; Then 0.0016 cm33 / 40 = 0.00004 cm / 40 = 0.00004 cm33..

A group recorded the average radius as 7.25 cm

Does the film have a nanoscale dimension?Does the film have a nanoscale dimension?

Step 5: Area = 3.14 x RStep 5: Area = 3.14 x R22 The area of a thin film with a The area of a thin film with a radius of 7.25 cm film is 165.05 cmradius of 7.25 cm film is 165.05 cm22

Step 6: Step 6: If Volume = Area x Depth; If Volume = Area x Depth; Then: Depth = Volume / Area and the thickness of Then: Depth = Volume / Area and the thickness of

the example group’s film would be 2.42 x 10the example group’s film would be 2.42 x 10-7-7 cm. cm.

Step 7: 2.42 x 10Step 7: 2.42 x 10-9-9 meters meters

Step 8: 2.42 x 10Step 8: 2.42 x 10-9-9 m = 2.42 nanometers m = 2.42 nanometers

Why did oleic acid form a thin film?Why did oleic acid form a thin film?

Oleic acid molecules have a polar ends that are attracted to polar water molecules.

When you poured a small amount of oleic acid onto the When you poured a small amount of oleic acid onto the surface of water, electric interactions caused the oleic surface of water, electric interactions caused the oleic

acid molecules to “self-assemble” into a thin layer.acid molecules to “self-assemble” into a thin layer.

- Charge on an oxygen atom

+ charge on a hydrogen atom

Water molecules in a tray.

Weak van der Walls forces describe the attraction between Weak van der Walls forces describe the attraction between adjacent hydrocarbon chains. They are strong enough for the thin adjacent hydrocarbon chains. They are strong enough for the thin

film to maintain its integrity as it spreads across the water.film to maintain its integrity as it spreads across the water.

In a small drop of oleic acid there are In a small drop of oleic acid there are billionsbillions of oleic acid of oleic acid molecules that will stand up like blades of grass on the molecules that will stand up like blades of grass on the

surface of watersurface 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 form on the surface of water.

Non-polar ends of oleic acid

Three molecular substances were used in this activity.

What two roles did alcohol play?

Oleic acid

Isopropyl Alcohol Water

The thin film of oleic acid forms a The thin film of oleic acid forms a Langmuir Langmuir FilmFilm. The thin film can be confined to a specific . The thin film can be confined to a specific area with a barrier. You used baby powder as a area with a barrier. You used baby powder as a confining barrier.confining barrier.

water

hydrophobic end

hydrophilic end

A Few QuestionsA Few Questions

What might be some sources of error What might be some sources of error when calculating the thickness of a thin film when calculating the thickness of a thin film of oleic acid?of oleic acid?

How could the sources of error be How could the sources of error be minimized?minimized?

In what ways in this activity an example In what ways in this activity an example of nanoscale of nanoscale self-assembly?self-assembly?

Some Examples of Self Assembly

The Big Ideas in Nanoscale Self-AssemblyThe Big Ideas in Nanoscale Self-Assembly

• Structural components are Structural components are mobilemobile. . • The goal is a The goal is a low energy equilibriumlow energy equilibrium state. state.• Ordered structuresOrdered structures result from a less ordered result from a less ordered

system.system.• Assembly is a result of Assembly is a result of attractive or attractive or

repulsive forcesrepulsive forces between the components. between the components.• An An environment is selectedenvironment is selected to induce to induce

designed interaction.designed interaction.• Components Components retain physical identityretain physical identity through through

and after.and after.

• The process is The process is reversible or adjustablereversible or adjustable..Whitesides & Boncheva (2002)

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?

UMass Amherst NanotechnologyCurriculum Resources are available at

http://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.

K-12 Curriculum Materials are also available at the Center for Hierarchical Manufacturing’s web site.

http://chm.pse.umass.edu/education_outreach/instructional