Introduction to Chemistry

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Introduction to Chemistry Background for
Nanoscience and Nanotechnology

• Prof. Petr Vanysek

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Introduction to ChemistryHow to go about
making nanomaterials?
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WHAT IS NANO?
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What is so big about nano?

• Sun cream
• Face cream
• Computers
• Sports equipment
• Anti-microbial
• bandages

1965 30 transistors on a computer chip Today
40,000,000 details 90nm
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Whats so big about nano?
Nano-scale materials often have very different
properties from bulk materials e.g. color and
reactivity

• 3nm iron particle has 50 of atoms on the
  surface
• 10nm particle has 20 of atoms on the surface
• 30nm particle has 5 of atoms on the surface

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SMALL
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The scale of things
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Top-down and bottom-up approach
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The top-down approach
Machining or etching larger blocks and composites
to smaller structures

• Compare to traditional sculpture
• Size of detailed features depends on size of
  tools

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The bottom-up approach
Small molecules or particles pre-designed to
self assemble into larger, organised structures
e.g. surfactants
Hydrophilic head group Water loving
oil
oil
oil
water
Hydrophobic tail Water hating
oil
oil
Spherical micelle
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Gold nanoparticles

• Element 79
• Inert
• Need extreme conditions to react (chlorine,
  fluorine, cyanide, aqua regia 13 nitric
  acidHCl)

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Not so inert

• Masatake Haruka (Japan)
• Gold nanoparticles catalyse carbon monoxide
  oxidation
• Highly active even BELOW ROOM TEMPERATURE

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Catalysis the golden age

• Most car pollution in first 5 minutes
• Cold Engine
• Pt/Pd catalysts good gt200?C
• Gold nanoparticles (8nm)
• Active below room temperature

(Science, October 2004, Volume 306, pp. 234-235)
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Emulsions
Add surfactant and mix
OIL
WATER
EMULSION (water in oil)
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The bottom-up approach
Use emulsion to make nanoparticles
Precipitation inside micelles
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Gold nanoparticles
Reducing agent KBH4 (potassium borohydride)
Au3 ions (potassium tetrachloroaurate KAuCl4)
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Gold nanoparticles
oil
oil
oil
oil
oil
oil
oil
oil
oil
oil

• Micelles collide
• Reagents mix inside micelles
• Gold ions reduced to gold metal
• Gold trapped in micelle forms sphere

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Crystalline in nature
www.drexel.edu/coe/enggeo/minerals.html
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Crystalline in nature
Calcium carbonate
Calcium phosphate
Image courtesy of Vicky Swinerd
Nature produces very unusual, irregular crystals
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Changing faces
Calcium carbonate (CaCO3)
Image courtesy of Dr Alex Kulak
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Changing faces
Calcium carbonate (CaCO3) grown on uneven surface
Image courtesy of Nicola Hetherington
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Changing faces
Calcium carbonate (CaCO3) Grown from a solution
containing a polymer
Image courtesy of Dr Alex Kulak
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Changing faces
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Changing faces
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Changing faces
Images courtesy of Dr Simon Hall
Crystals of superconductor Grow into needles when
polymer from crab shell added
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Carbon nanotubes

• Allotrope of carbon
• Graphite sheet rolled into a tube
• 50,000x smaller than human hair
• Members of fullerene family
• (including buckyballs)

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Carbon nanotubes
http//www.seas.upenn.edu/mse/images/nanotube1.jpg
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Single-walled nanotubes

• Capped or uncapped
• All covalent sp2 bonding
• Metallic conductors or semiconductors
• Bundles
• Defects points for reaction

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Multi-walled nanotubes

• 63GPa tensile strength
• (steel 1.2GPa)
• Inner tubes slide without friction

http//www.msm.cam.ac.uk/polymer/research/nanointr
oCNT.html
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Ancient nanotubes?

• Damascus steel swords extremely strong
• Middle Eastern origin 1100-1700AD
• Manufacturing secret lost
• Thought to be pattern welded
• Recent study showed nanowires
• and carbon nanotubes

Nature, 16th November 2006
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Nanotubes today
Carbon nanotubes incorporated in bike frame
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Concerns?
Lots of people suspicious of nanotechnology Worrie
s about nano-robots that could self-replicate

• Not that realistic
• Brownian motion
• Surface forces

BUT body cells are effectively machines, with
working parts on the nano-scale so nature has
done it
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The real safety issue

• Nanoparticles can be much more reactive than
  bulk material
• Physical shape of material can seriously affect
  its toxicity

e.g. Asbestos
Serpentine flat sheets of atoms,
harmless Chrysotile nano-scale tubes
Should treat these new nano-materials with caution
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Self-assembly
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Self-assembly
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Self-assembly
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Mesoscopic self-assembly
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Self-assembly
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Electrons and dimensions
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Examples of nanomaterials
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Nanoparticles and size effects
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Bottom-up to nano
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Ways to the nano world
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Colloids
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Colloids