Transcript PPT - Wayne State University

Carbon nanomaterials
Gavin Lawes
Wayne State University
[email protected]
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Outline
1.Carbon structures
2. Carbon nanostructures
3. Potential applications for Carbon
nanostructures
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Periodic table
from bpc.edu
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Carbon atom
Electron (-)
Proton (+)
Neutron
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Carbon-based molecules are somewhat
important for life on Earth…
Amino acids
amino group
carboxylic acid
group
from msu.edu/gallego
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Lecithin
from indiana.edu/oso
Phospholipids
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…and are also important for all industrial activity
Pentane
from wikimedia.org
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Electron orbitals
s orbital
p orbital
from britannica.com
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Hybridization
from ASDN.net
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3
sp
hybridized C crystals
from diamonds.net
from cnx.org
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2
sp
hybridized C crystals
from cochise.edu/wellerr
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Graphite consists of
layers of hexagonal
Carbon sheets.
from chem.wisc.edu
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Diamond
Graphite
Electrical insulator
Electrical conductor*
Very hard
Very soft*
Transparent
Opaque
Expensive
Cheap
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Nanoscale carbon structures
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Buckminsterfullerene
Molecule consisting of 60 C atoms
sp2 hybridized bonds
Has 20 hexagons, 12 pentagons
Other related structures have 70 or
84 C atoms
from sciencedaily.com
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C60 is named for
Buckminster Fuller
who designed
geodesic domes.
from unusualife.com
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Original report of C60
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1996 Nobel Prize in Chemistry
Robert Curl, Sir Harold Kroto, Richard
Smalley “for their discovery of fullerenes”.
from Nobelprize.org
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Carbon nanotubes
Rolled up
sheet of sp2
bonded
carbon atoms
from informaworld.com
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Carbon nanotubes can be formed from a
single sheet of C atoms or several sheets
Multiwalled
carbon nanotube
(several sheets
of carbon atoms)
Single walled
carbon nanotube
(single sheet of
carbon atoms)
from rice.edu
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Carbon sheets can also be rolled up in
different directions to give different types of
nanotubes.
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The properties of nanotubes depend on how
they are rolled up
Electrical conductor
Electrical insulator
from phycomp.technion.ac.il
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Nanotube sizes also depend on how they are
rolled up
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Graphene (single sp2 bonded carbon sheet)
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C atoms in
hexagonal array
from cnx.org
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From ncem.lbl.gov
Scale bar 0.2 nm
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Nobel Prize in Physics 2010
Andre Geim and Konstantin Novoselov “for groundbreaking
experiments regarding the two-dimensional material
graphene”.
from Nobelprize.org
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Carbon nanostructures
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Why are carbon
nanostructures interesting?
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They are strong
Multiwall carbon nanotube breaking
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Multiwall carbon nanotube composite
Silica fibres
+MWCNT
Mechanical properties can improve by 50% or more by
adding carbon nanotubes.
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Damascus sabre steel contains nanotubes
Multiwalled carbon
nanotubes found in
17th century sword.
10 nm
These are formed
during the synthesis
and may have
produced the very
good mechanical
properties.
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They have good electrical properties
from bpc.edu
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Carbon nanostructures may be used in new electronic devices
from nanotechweb.org
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Devices made with carbon nanotubes
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Carbon nanotubes can be used for
making electronic devices
Carbon Nanotubes. Advanced Topics in the Synthesis, Structure, Properties
and Applications, 455-93, 2008
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Properties of graphene depend on
the subtrate
from als.lbl.gov
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Geometry of graphene may also
affect the properties
From nanotechweb.org
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Graphene may be used as a transparent electrode
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Carbon nanotube mechanical oscillator
Force sensitivity of 1 fN Hz-1/2
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Graphene mechanical oscillator
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Carbon nanotubes may have biomedical applications
Carbon nanotubes can
be functionalized with
different biologically
relevant molecules.
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Cells incubated with
functionalized carbon
nanotubes
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Electronic bandgap
Energy
Momentum
Metal
Semiconductor
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The electronic bandgap for
graphene looks like a pair of
cones touching at their tips for
certain positions (in
momentum space).
This leads to interesting
electronic properties.
from wikipedia.com
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Schrodinger Equation

h
2
i  
   V
t
2m
2
2
E~p
(for massive particles)
Dirac Equation

i   i aea    iA  m 
t

(for relativistic particles)

E~p
Appropriate for
electrons in graphene
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How do you make carbon nanotubes?
1. Carbon arc discharge. Hold two carbon (graphite)
electrodes at some potential difference in a Helium atmosphere
and bring the electrodes together. At some separation and arc
will be produced, and carbon nanotubes will grow on the
cathode. These will normally be multiwalled nanotubes, but
single walled nanotubes can be grown by adding Ni, Fe, or Co
to the cathode.
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2. Laser ablation. Heat up a lump of graphite to ~1200 C in an
Ar atmosphere, and then blast it with a laser. This can make
single walled nanotubes if the graphite has a catalyst like Co or
Ni included.
3. Catalytic growth. Heat up hydrocarbons (e.g. acetylene) to
high temperatures and then let them settle on a substrate
coated with a catalyst (Fe, Co, Ni). This will form either
multiwalled nanotubes or single walled nanotubes depending
on the growth conditions.
How do you make graphene?
Graphite and scotch tape.
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Open problems
1. To be useful for devices, these carbon nanomaterials need
to be prepared on and/or connected reliably to electrodes.
2. Since the properties of these nanomaterials depend
strongly on structure (e.g. armchair vs zig-zag nanotubes),
we need to have good control over these structural details.
3. Many unanswered physics questions remain, including the
magnetism, superconductivity, and optical properties of these
materials.
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Summary
1. A number of carbon allotropes naturally
form interesting nanostructures
2. These nanostructures have enormous
potential in developing new electronic,
optical, and nano-mechanical devices.
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End
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