Nanoscience 2000

Synthesis and Characterization of Nanomaterials I

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NanoNano = 10= 10--99 = 1/ 1,000,000,000 = 1/ 1,000,000,000 = 1 / Billionth= 1 / Billionth

A nanometer is about the size of ten atoms in a rowA nanometer is about the size of ten atoms in a row

NanoscienceNanoscience is the study of nanometer size thingsis the study of nanometer size things

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• The study of objects and phenomena at a very small scale, roughly 1 to 100 nanometers (nm)

– 10 hydrogen atoms lined up measure about 1 nm– A grain of sand is 1 million nm, or 1 millimeter, wide

• An emerging, interdisciplinary science involving– Physics– Chemistry– Biology– Engineering– Materials Science – Computer Science

What is Nanoscale Science?2

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how small are these things?

let's do a thought ("gedanken") experiment

Imagine you were "there" at the big bang (creation):

that was about 5 billion years ago…… and…..

you ask your "helper" to do a job for you

the robot is given 12g of carbon-that's a mole and so contains about 6 X 10 23 atoms of C

the job is simple: pick up one atom every second and put it in a new pile (we can pick up single atoms now –and you will see how later in the course)

let's see how the robot it doing:!! ----------- today!

how many atoms are in the new pile and how many are still left?

All we need to do is to work out (roughly) the number of seconds since the big bang

5 x 109 X 500 X 10 X 100 x 100

years days hours mins secs.

I said roughly!!

= 2.5 X 10 18

robot has made quite a pile: but there is a lot left

how much?

600 000 000 000 000 000 000 000-2 500 000 000 000 000 000

599 997 500 000 000 000 000 000

nearly all is still left – that's how small we are looking at!!!

"sees" and picks up atoms

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What kind of nanostructures can we make?

What kind of nanostructures exist in nature?

Carbon Nanotubes

If added to materials like car bumpers, increases strength and flexibility100 time stronger than steel and very flexible

Model of Buckminsterfullerene

Buckyball (C60)• Incredible strength due to

their bond structure and “soccer ball” shape

• Could be useful “shells” for drug delivery • Can penetrate cell walls • Are nonreactive (safe in

blood stream)

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Nanostructures in Nature

A moth’s eye has very small bumps on its surface. They have a hexagonal shape and are a few hundred nanometers tall and apart. Because these patterns are smaller than the wavelength of visible light (350-800nm), the eye surface has a very low reflectance for the visible light so the moth’s eye can absorb more light. The moth can see much better than humans in dim or dark conditions because these nanostructures absorb light very efficiently.

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On the surface of a butterfly’s wings are multilayer nanoscalepatterns. These structures filter light and reflect mostly one wavelength, so we see a single bright color. For instance the wings of the male Morpho Rhetenor appear bright blue. But the wing material is not, in fact, blue; it just appears blue because of particular nanostructures on the surface. More precisely, the nanostructures on the butterfly’s wings are about the same size as the wavelength of visible light and because of the multiple layers in these structures optical interferences are created. There is constructive interference for a given wavelength (around 450nm for the Morpho Rhetenor) and destructive interferences for the other wavelengths, so we see a very bright blue color. In the laboratory, many scientific instruments use this same phenomena to analyze the color of light.

Nanogold

12 nm gold particles look red

Other sizes are other colors

strange things happen at the small scale

If you keep cutting gold until the pieces are in the nanoscalerange, they don’t look gold anymore… They look RED!In fact, depending on size, they can turn red, blue, yellow, and other colors

Why?Different thicknesses of materials reflect and absorb light differently

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iron oxide nanoparticles

these behave strangely too:

-change color in magnetic fields

new types of flat panel displays

100 nm

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reflectivity in different mag fields

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photosynthetic proteins to manipulate platinum at the nanoscale

platinum grown on porhyrins and liposomes

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DNA

"barcode" from DNA scaffolds

AFM image 380 nm square

4 x 4 DNA arrays

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Inorganic nanostructures

e.g, Zeolites

aluminosilicates and related structures

nano hairs : walk up walls??

spacing here is about 2 microns

the forces that hold geckos on walls are called"Van der Waals" forces

- see structure and bonding CHEM*2060

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All very interesting

• but how do we make these structures?• how do we image them?• how do we know the composition

• let's learn!!

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