Date post: | 27-Dec-2015 |
Category: |
Documents |
Upload: | tracy-todd |
View: | 216 times |
Download: | 0 times |
DCMST June 2nd, 2011
1.Carbon structures
2. Carbon nanostructures
3. Potential applications for Carbon nanostructures
Outline
DCMST June 2nd, 2011
from bpc.edu
Periodic table
DCMST June 2nd, 2011
Electron (-)
Proton (+)
Neutron
Carbon atom
DCMST June 2nd, 2011
from msu.edu/gallego
amino group
carboxylic acid group
Carbon-based molecules are somewhat important for life on Earth…
Amino acids
DCMST June 2nd, 2011
Lecithin
from indiana.edu/oso
Phospholipids
DCMST June 2nd, 2011
Pentane
from wikimedia.org
…and are also important for all industrial activity
DCMST June 2nd, 2011
from britannica.com
s orbital p orbital
Electron orbitals
DCMST June 2nd, 2011
from ASDN.net
Hybridization
DCMST June 2nd, 2011
from cnx.orgfrom diamonds.net
sp3 hybridized C crystals
DCMST June 2nd, 2011
from cochise.edu/wellerr
sp2 hybridized C crystals
DCMST June 2nd, 2011
from chem.wisc.edu
Graphite consists of layers of hexagonal Carbon sheets.
DCMST June 2nd, 2011
Diamond Graphite
Electrical insulator Electrical conductor*
Very hard Very soft*
Transparent Opaque
Expensive Cheap
DCMST June 2nd, 2011
Nanoscale carbon structures
DCMST June 2nd, 2011
from sciencedaily.com
Buckminsterfullerene
Molecule consisting of 60 C atoms
sp2 hybridized bonds
Has 20 hexagons, 12 pentagons
Other related structures have 70 or 84 C atoms
DCMST June 2nd, 2011
from unusualife.com
C60 is named for Buckminster Fuller who designed geodesic domes.
DCMST June 2nd, 2011
Original report of C60
DCMST June 2nd, 2011
1996 Nobel Prize in ChemistryRobert Curl, Sir Harold Kroto, Richard Smalley “for their discovery of fullerenes”.
from Nobelprize.org
DCMST June 2nd, 2011
from informaworld.com
Carbon nanotubes
Rolled up sheet of sp2 bonded carbon atoms
DCMST June 2nd, 2011
from rice.edu
Single walled carbon nanotube (single sheet of carbon atoms)
Multiwalled carbon nanotube (several sheets of carbon atoms)
Carbon nanotubes can be formed from a single sheet of C atoms or several sheets
DCMST June 2nd, 2011
Carbon sheets can also be rolled up in different directions to give different types of nanotubes.
DCMST June 2nd, 2011
from phycomp.technion.ac.il
Electrical conductor
Electrical insulator
The properties of nanotubes depend on how they are rolled up
DCMST June 2nd, 2011
Nanotube sizes also depend on how they are rolled up
DCMST June 2nd, 2011
Graphene (single sp2 bonded carbon sheet)
DCMST June 2nd, 2011
from cnx.org
C atoms in hexagonal array
DCMST June 2nd, 2011
From ncem.lbl.govScale bar 0.2 nm
DCMST June 2nd, 2011
Nobel Prize in Physics 2010Andre Geim and Konstantin Novoselov “for groundbreaking experiments regarding the two-dimensional material graphene”.
from Nobelprize.org
DCMST June 2nd, 2011
Carbon nanostructures
DCMST June 2nd, 2011
Why are carbon nanostructures interesting?
DCMST June 2nd, 2011
Multiwall carbon nanotube breakingThey are strong
DCMST June 2nd, 2011
Silica fibres +MWCNT
Multiwall carbon nanotube composite
Mechanical properties can improve by 50% or more by adding carbon nanotubes.
DCMST June 2nd, 2011
10 nm
Damascus sabre steel contains nanotubes
Multiwalled carbon nanotubes found in 17th century sword.
These are formed during the synthesis and may have produced the very good mechanical properties.
DCMST June 2nd, 2011
from bpc.edu
They have good electrical properties
DCMST June 2nd, 2011
from nanotechweb.org
Carbon nanostructures may be used in new electronic devices
DCMST June 2nd, 2011
Devices made with carbon nanotubes
DCMST June 2nd, 2011
Carbon Nanotubes. Advanced Topics in the Synthesis, Structure, Properties and Applications, 455-93, 2008
Carbon nanotubes can be used for making electronic devices
DCMST June 2nd, 2011
from als.lbl.gov
Properties of graphene depend on the subtrate
DCMST June 2nd, 2011
From nanotechweb.org
Geometry of graphene may also affect the properties
DCMST June 2nd, 2011
Graphene may be used as a transparent electrode
DCMST June 2nd, 2011
Carbon nanotube mechanical oscillator
Force sensitivity of 1 fN Hz-1/2
DCMST June 2nd, 2011
Graphene mechanical oscillator
DCMST June 2nd, 2011
Carbon nanotubes may have biomedical applications
Carbon nanotubes can be functionalized with different biologically relevant molecules.
DCMST June 2nd, 2011
Cells incubated with functionalized carbon nanotubes
DCMST June 2nd, 2011
MetalSemiconductor
Energy
Momentum
Electronic bandgap
DCMST June 2nd, 2011
from wikipedia.com
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.
DCMST June 2nd, 2011
Schrodinger Equation
€
i∂
∂tψ = −
h2
2m∇ 2ψ +Vψ
Dirac Equation
(for massive particles)
€
i∂
∂tΨ = iσ aea
μ ∇ μ − iAμ( ) + βm( )Ψ
(for relativistic particles)
E~p2
E~pAppropriate for electrons in graphene
DCMST June 2nd, 2011
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.
DCMST June 2nd, 2011
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.
DCMST June 2nd, 2011
Open problems1. 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.
DCMST June 2nd, 2011
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.
Summary
DCMST June 2nd, 2011
End