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.
• 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
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)
V =AT
T = V/A
V = 1 teaspoonful
A = 0.5 acre
~ 2 cm3
~ 2,000 m2
20,000,000 cm2
2 cm3
T=
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
6,000 nanometers
DNA
.
100,000
nanometers
3 nanometers
Examples of Nanoscale Thin Films
Nanofilm on plastic
Gold-coated plastic for
insulation purposes
Nanofilm on glass
"Low-E" windows: a thin
metal layer on glass:
blocks UV and IR light
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
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.
You will form a thin film of oleic acid
on the surface of water.
Oleic acid is one of olive oil’s ingredients.
You will need to make a double
dilute solution of oleic acid.
• 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.
Thin films of oleic acid will have many shapes and
require more than one measurement of diameters.
A Sample Calculation
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
Does the film have a nanoscale dimension?
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
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
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.
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 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.
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?
Isopropyl Alcohol
Water
Oleic acid
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
A Few Questions
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?
Some Examples
of Self Assembly
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)
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 Nanotechnology
Curriculum 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