Introduction to Chemistry Background for Nanoscience and Nanotechnology UEET 101 Part II

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Introduction to Chemistry Background for
Nanoscience and NanotechnologyUEET 101Part II

• Prof. Petr Vanýsek
• NIU Chemistry and Biochemistry

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Wide dynamic range of dimensions

• Electromagnetic spectrum

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Why dimensions matter? Nanomaterials particles
of nanometer size
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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Forms of materialCARBON - GRAPHITE
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Forms of materialDIAMOND - GRAPHITE
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Form of materialCARBON - FULLERENE
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How to go about making materials?Through
chemistryand of course, the same is about
NANOMATERIALS
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Top-down and bottom-up approachChemistry is good
in the bottom-up
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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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Flocullation of water by iron oxide
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Chemical Bonding

• Covalent bonds
• Ionic bonds
• Metal bonding

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Covalent bonds

• Covalent bonding is when electrons are shared
  between to atoms or more.
• The number of covalent bonds an atom is likely to
  form is determined by its place in the periodic
  table and the number of valence electrons it has.
• An atom will share electrons with another atom so
  that it results in them both having a full
  valence shell. Usually this will be 8 electrons.

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Ionic bonds

• When a metal and a non-metal form bonds they are
  typically ionic bonds where electrons are
  transferred from the metal to the non-metal.
• Some metals will lose enough electrons to achieve
  a complete valence shell.
• Non-metals will usually gain enough electrons to
  achieve a complete valence shell.
• Many metals are able to form ions with more than
  one charge.

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Metal bonding

• In metals the atoms are held together by metal
  bonding. Electrons can easily transfer from one
  atom to the next. This suggests a model of
  positive ions in a sea of electrons. Metals can
  conduct electricity because electrons flow easily
  in any direction.

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Polar Molecules

• Polar Molecules
• If the electron density is not distributed evenly
  around a molecule then they are polar.

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Hydrogen Bonding
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Dipole Interaction

• http//www.chemguide.co.uk/atoms/bonding/vdw.html
• The partial positive and negative ends of the
  molecules hold the molecules together.

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London Forces
London forces are induced dipoles caused by
temporary rearrangement of the electron cloud.
Two hexane molecules approach.
The hexane molecules bump into each other.
The electron clouds rearrange to form a temporary
dipole.
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Polymers

• Polymers are large chainlike molecules that are
  built from smaller molecules called monomers.
• For example polyethylene is formed from ethylene
• Proteins are natural polymers.
• http//www.pslc.ws/macrog.htm

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Structure of Materials
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Encapsulation of a drug (cis-platin) into a
nanotube
Hilder and Hill, conference paper
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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?
Nature, 16th November 2006

• 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

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Nanotubes today
Carbon nanotubes incorporated in bike frame
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Class activity Estimate the inside dimension
diameter and volume of the C-60 fullerene.
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Top-down and bottom-up approach
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bumps on bumps
Superhydrophobic effect based on nanostructure of
the leaf surface
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SMALL
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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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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
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Changing faces
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Self-assembly
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Self-assembly
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Self-assembly
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Acceptance of nanotechnology
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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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Babolat VS Nanotube Drive