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Introduction to Nanoscience

What’s happening lately at a very, very small scale

Copyright © 2005 SRI International

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What is Nanoscale Science?

  • 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

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Source: http://www.cs.utexas.edu/users/s2s/latest/bialt1/src/WhatIsNano/images/molecule.gif

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How Big is a Nanometer?

  • Consider a human hand

white blood cell

skin

DNA

atoms

nanoscale

Source: http://www.materialsworld.net/nclt/docs/Introduction%20to%20Nano%201-18-05.pdf

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Are You a Nanobit Curious?

  • What’s interesting about the nanoscale?
    • Nanosized particles exhibit different properties than larger particles of the same substance
  • As we study phenomena at this scale we…
    • Learn more about the nature of matter
    • Develop new theories
    • Discover new questions and answers in many areas, including health care, energy, and technology
    • Figure out how to make new products and technologies that can improve people’s lives

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So How Did We Get Here?

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New Tools!

As tools change, what we can see and do changes

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Using Light to See

  • The naked eye can see to about 20 microns
    • A human hair is about 50-100 microns thick
  • Light microscopes let us see to about 1 micron
    • Bounce light off of surfaces to create images

Light microscope

(magnification up to 1000x)

to see red blood cells (400x)

Sources: http://www.cambridge.edu.au/education/PracticeITBook2/Microscope.jpg

http://news.bbc.co.uk/olmedia/760000/images/_764022_red_blood_cells300.jpg

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Using Electrons to See

  • Scanning electron microscopes (SEMs), invented in the 1930s, let us see objects as small as 10 nanometers
    • Bounce electrons off of surfaces to create images
    • Higher resolution due to small size of electrons

Greater resolution to see things like blood cells in greater detail

(4000x)

Sources: http://www.biotech.iastate.edu/facilities/BMF/images/SEMFaye1.jpg

http://cgee.hamline.edu/see/questions/dp_cycles/cycles_bloodcells_bw.jpg

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Touching the Surface

  • Scanning probe microscopes, developed in the 1980s, give us a new way to “see” at the nanoscale
  • We can now see really small�things, like atoms, and move them too!

This is about how big atoms are compared with the tip of the microscope

Source: Scientific American, Sept. 2001

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Scanning Probe Microscopes

  • Atomic Force Microscope (AFM)
    • A tiny tip moves up and down in response to the electromagnetic forces between the atoms of the surface and the tip
    • The motion is recorded and used to create an image of the atomic surface
  • Scanning Tunneling Microscope (STM)
    • A flow of electrical current occurs between the tip and the surface
    • The strength of this current is used to create an image of the atomic surface

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So What?

  • Yes, but it’s also a whole lot more. Properties of materials change at the nanoscale!

Is nanoscience just seeing and moving really small things?

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Is Gold Always “Gold”?

  • Cutting down a cube of gold
    • If you have a cube of pure gold and cut it, what color would the pieces be?
    • Now you cut those pieces. What color will each of the pieces be?
    • If you keep doing this - cutting each block in half - will the pieces of gold always look “gold”?

Source: http://www.uwgb.edu/dutchs/GRAPHIC0/GEOMORPH/SurfaceVol0.gif

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Nanogold

  • Well… strange things happen at the small scale
    • If you keep cutting until the gold pieces are in the nanoscale range, they don’t look gold anymore… They look RED!
    • In fact, depending on size, they can turn red, blue, yellow, and other colors

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Source: http://www.nano.uts.edu.au/pics/au_atoms.jpg

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  • Why?
    • Different thicknesses of materials reflect and absorb light differently

12 nm gold particles look red

Other sizes are other colors

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Nanostructures

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What kind of nanostructures can we make?

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What kind of nanostructures exist in nature?

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Carbon Nanotubes

  • Using new techniques, we’ve created amazing structures like carbon nanotubes
    • 100 time stronger than steel and very flexible
    • If added to materials like car bumpers, increases strength and flexibility

Source: http://www.library.utoronto.ca/engineering-computer-science/news_bulletin/images/nanotube.jpeg

Model of a carbon nanotube

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Carbon Buckyballs (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 (move safely through blood stream)

Model of Buckminsterfullerene

Source: http://digilander.libero.it/geodesic/buckyball-2Layer1.jpg

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Biological Nanomachines in Nature

  • Life begins at the nanoscale
    • Ion pumps move potassium ions into and sodium ions out of a cell
    • Ribosomes translate RNA sequences into proteins
    • Viruses infect cells in biological organisms and reproduce in the host cell

Source: http://faculty.abe.ufl.edu/~chyn/age2062/lect/lect_06/lect_06.htm

http://www.zephyr.dti.ne.jp/~john8tam/main/Library/influenza_site/influenza_virus.jpg

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Influenza virus

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Building Nanostructures

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How do you build things that are so small?

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Fabrication Methods

  • Atom-by-atom assembly
    • Like bricklaying, move atoms into place one at a time using tools like the AFM and STM
  • Chisel away atoms
    • Like a sculptor, chisel out material from a surface until the desired structure emerges
  • Self assembly
    • Set up an environment so atoms assemble automatically. Nature uses self assembly (e.g., cell membranes)

IBM logo assembled from individual xenon atoms

Polystyrene spheres self-assembling

Source: http://www.phys.uri.edu/~sps/STM/stm10.jpg; http://www.nanoptek.com/digitalptm.html

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Example: Self Assembly By Crystal Growth

  • Grow nanotubes like trees
    • Put iron nanopowder crystals on a silicon surface
    • Put in a chamber
    • Add natural gas with carbon (vapor deposition)
    • Carbon reacts with iron and forms a precipitate of carbon that grows up and out

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Growing a forest of nanotubes!

  • Because of the large number of structures you can create quickly, self-assembly is the most important fabrication technique

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Source: http://www.chemistry.nmsu.edu/~etrnsfer/nanowires/

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