deb newberry dakota county technical college and nano-link deb… and interactions activity...
TRANSCRIPT
Deb Newberry
Dakota County Technical College and Nano-Link
www.nano-link.org
© Deb Newberry 2008
The “Big Ideas” of Nanoscale Science* Size and scale
Structure of matter
Forces and interactions
Quantum effects
Size dependent properties
Self-assembly
Tools and instrumentation
Models and simulations
Science, technology and society
Understanding of these concepts requires an integration of the disciplines of math, biology, chemistry, physics and engineering
Get info into traditional courses - tie into existing standards
*These ideas are a result of efforts by several NSF funded groups to determine the priority knowledge concepts required to understand nanoscience concepts. This work has been carried out over the last 5 years. In general, the listed below are a consensus from the working groups.
Burnt-out tungsten filament
Some Questions How does surface area affect the interactions?
What do different interactions tell us about the molecular structure of the materials involved?
What are typical strengths of different interaction forces?
What are the units of these forces?
What environmental considerations may impact the interactions? By how much?
What are some of the applications of this technology?
Forces and Interactions
It is all a matter of priority!
Forces and Interactions Electrostatic
Magnetic
Gravitational
Thermal
Vibration
Adhesion
Surface tension
Friction
Chemical
Quantum
Which forces or interactions are most important at different size scales? Why?
Sub Nano Nano Micro Macro/Micro Macro
Quantum
weak force
strong force
Electrostatic
van der Waals
Brownian
Vibration
Chemical
quantum
Electrostatic
Thermal
van der Waals
Brownian
Vibration
surface tension
chemical
Gravity
Friction
Thermal
electrostatic
Gravity
Friction
Thermal
What is the strength and distance impacted?
Interaction Strength Effective Distance
Electrostatic 0.1 – 10 kJ/mol 0.4 – 20 nm
Van der Waals 10 – 100 kJ/mol 0.4 – 30 nm
Chemical bonding 100 – 1000 kJ/mol 0.1 – 0.2 nm
Van der Waals forces are a combination of Keesom, Debye and London forces
These different forces arise because of the pairing variations between induced andpermanent charge {non-uniform} distributions
Force Between Two Charged Bodies
Where k = Coulombs constant = 8.987 x 109 N m2/C2
q1 = charge on the first bodyq2 = charge on the second bodyr = distance between the 2 bodies
Gravitational Force Between Two Masses
Where G = Gravitational Constant = 6.6 x 10-11 N m2/kg2
m1 = mass of the first objectm2 = mass of the second objectr = distance between the 2 objects
It all comes down to atoms and molecules
And what we learned in second grade…
Surface Properties Chemistry or Nanotechnologyor BOTH?
Surface Tension
Ref: wikipedia
Water – A most amazing molecule
Polymers
Chemistry
Ionic and Covalent Bonds, Hydrogen Bonds
Bond Strngth
Physics
Surface tension
Forces and Interactions
Exponentials,
Unit conversions
Crystals Polymers
Proteins Cells
Molecular Structures
Each bondbetween atoms has a specific strength
A different atom or molecule introduced into this polymer “system” can form or break bonds dependent upon the relative strengths.
Changes in bonds will result in a change in the atomic arrangement(molecular structure) and potentially change the properties of the “system”.
Cross-Linked Polymer
Activity: Cross-linked Polymer
Magic Snow (Steve Spangler Science)
Cross Linked Polymer – similar to collagen or cellulose – the “zigzag” of the polymer gives it the elastic property and the cross-linking between zigzags helps keep the structure (stiffness)
Place a small amount of the material in a Petri dish -- Feel it and observe it’s physical properties
Using a plastic transfer pipette add some water to the material
Observe what happens
Now feel the resulting material – How have the physical properties changed?
What do you think happened?
Answer: The water, a dipole molecule interacted with and affected the cross-linking bonds “releasing” the polymers – We changed the atomic arrangement and as a result changed the physical properties of the material.
PolymersTwo Variations on a Theme Cross-linked
Ringed
Super Absorbing Polymers (Found in diapers) are ringed type polymers
Surface tension(balanced cohesive and adhesive forces)“traps” moisture in the ring structure.Similar to the ring blower shape for soap bubbles
Cut a small area of diaperAdd water until saturatedMeasure the amount of water (volume or weight)Determine number of water molecules in the amount absorbedDetermine surface area that could be covered by a 1 atom thick layeri.e. assuming a water molecule has a vol. of .4 nm x .4 nm x.3nm
5 cc of water would cover 130m x 130m
Hydrophobic Surfaces
Chemistry
Ionic and Covalent Bonds
Physics
Cohesive vsadhesive forces
Forces and Interactions
Exponentials,
unit conversions
“weird” units
Hydrophobic/Hydrophilic/Super-hydrophobic
Super-hydrophobic Surfaces: Hydrophobic surface
having nano-scale roughness.
water
superhydrophobic
Hydrophobic Surfaces: “Water-fearing surface” Water
tries to minimize contact with surface.
Examples: Teflon, oily surfaces
water
hydrophobic surface
Hydrophilic Surfaces: “Water-loving surface” Water
tries to maximize contact with surface.
Examples: Glass, rusted metal surfaces
waterhydrophilic surface
SEM images of lotus leaf surface
Cheng, Y. T., et. al. Applied Physics Letters 2005, 87, 194112.
A water droplet beads
up on a lotus leaf due to
the hydrophobic
nanostructures
http://www.pbase.com/yvesr
Air drying: Water (dyed blue) and hexadecane (dyed red), an oil, bead up on an omniphobic surface, which repels all liquids. The droplets in this photo, which are separated from the surface by air pockets, are about three millimeters in diameter. Credit: Anish Tuteja/Wonjae ChoMIT TR November 2008
Staying dry: A chemically treated plastic surface is rough on the nanoscale, forcing water droplets to form beads that can roll off. GE researchers have now done the same with metal. Credit: GE Global Research Center MIT TR October 2008
© Deb Newberry 2008
Water in NanotubeSource: Yury Gogotsi
References:Environmental Scanning Electron Microscopy Study of Water in
Carbon NanopipesM. Pía Rossi, Haihui Ye, Yury Gogotsi, Sundar Babu, Patrick Ndungu, and Jean-Claude Bradley Nano Lett.; 2004; ASAP Web Release Date:
15-Apr-2004; (Letter) DOI: 10.1021/nl049688u
Description:The ability of the Environmental Scanning Electron Microscope
(ESEM) to condense and evaporate liquids has enabled the in situ dynamic study of condensation, evaporation and transport of water inside carbon nanotubes. It has been possible to see liquid menisci
inside straight, CVD-fabricated carbon nanotubes (CNTs) having disordered walls. From the measured contact angles, it is clear that
these CNTs are hydrophilic. Complex meniscus shapes and slow liquid dynamics due to water confinement and strong interaction with tube
walls have been observed.
The above ESEM images show the dynamic behavior of a water plug close to the open end of a nanotube. The meniscus shape changes
when, at a constant stage temperature, the vapor pressure of water in the chamber is changed (a) 5.5 Torr, (b) 5.8 Torr, (c) 6.0 Torr, (d) 5.8 Torr and (e) 5.7 Torr, where the meniscus returns to the shape seen in (a). The asymmetrical shape of the meniscus, especially the complex
shape of the meniscus on the right side in (a, e), is a result of the difference in the vapor pressure caused by the open left end and
closed right end of the tube. (f) TEM image showing a similar plug shape in a closed CNT under pressure.
ActivitySuper hydrophobic Sand
Preparations Materials: Magic Sand from Steve Spangler Science Place rubber cement on one half of an index card or piece of stiff paper Coat the rubber cement with a layer of Magic Sand
Additional Materials Water (in a beaker or cup) Plastic eyedroppers or transfer pipettes Pepper
Drop some water on the sand and the bare index card Describe the difference What are the forces or interactions involved here? (Gravity, cohesive and adhesive forces) Sprinkle some pepper over the sand surface Drop water on the surface and move over the pepper Describe the forces and interactions between the 3 materials Using materials other than pepper (flakes) – like different spices observe the difference in adhesion
between the water and the material
Forces and Interactions
Some Questions How does surface area affect the interactions?
What do different interactions tell us about the molecular structure of the materials involved?
What are typical strengths of different interaction forces?
What are the units of these forces?
What environmental considerations may impact the interactions? By how much?
What are some of the applications of this technology?
Courtesy of:
Dr. Prashant Jain
UCBerkeley