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Macro Micro Nano

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Can see with your eyes

MicroRed blood cells

Nano

DNA (width)

MacroGrains of sand

Often requires a microscope to see

Requires a highly specialized microscope, such as a Scanning Electron Microscope (SEM), to see

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Contact Angle

High contact angle Low contact angle

Hydrophobic surface Hydrophilic surface

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Making Predictions

1. Examine the slide under the microscope

2. Predict how a drop of water will behave

Rounded Flat

OR

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SEM of Soot

Int. J. Electrochem. Sci., 6 (2011) 1269 – 1276

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What is nanotechnology?

1. The nanometer is extremely small.

2. At the nanometer scale, many things behave differently.

3. We can use this new behavior to make new technologies.

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What is nanotechnology?

Nanotechnology is the understanding and control of matter 1 to 100 nanometers in size.

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Nanotechnology

Scientists coat surfaces with nanoparticles to prevent biofouling, seen here on a submarine.

Anti-biofouling applications

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Nanotechnology

Biomedical applicationsResearch is currently underway that incorporates nano-sized features on implants to prevent bacterial growth, and to encourage the body grow the correct type of cells on the implant.

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The Lotus Effect

Lotus leaves and nasturtium leaves are self-cleaning due to nano and microscale structures and a waxy coating.

Together these features create a superhydrophobic surface.

Close-up of a nasturtium leaf, which exhibits the Lotus Effect, with a droplet of water

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The Lotus Effect

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Hydrophobic Surfaces

• Water “fearing”

• Repel water

• Non-polar

• Rounded water drop

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Superhydrophobic Surfaces

• VERY water “fearing”

• Non-polar

• Nano-scale surface features

• Water rolls off when surface is held at an angle

• Water drop is very rounded (contact angle greater than 150°)

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Hydrophilic Surfaces

•Water “loving”

•Polar

•Flat water drop

•Water drop may absorb into material

•Leaves a streak of water when rolling off

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Chemical Formula: H2O

2 Hydrogens covalently bonded to 1 Oxygen

WaterCovers 70% of the Earth’s surface!

Essential for life

Universal solvent

The only molecule that exists naturally as a gas, liquid, and solid

Unique properties

Water Molecule

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Properties of Water

1. Polarity

2. Hydrogen Bonding

3. High Surface Tension

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δ+ δ+

Polarity of Water

Water is polar!

Oxygen attracts electrons much more strongly than hydrogen

Partially negative

Partially positive

δ-

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Hydrogen Bonding

Attraction between water molecules

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Surface Tension of Water

Polarity and Hydrogen Bonding cause water to form a “skin” of molecules at the surface