carbon nanomaterials dcmst june 2 nd, 2011 [email protected] gavin lawes wayne state university

Carbon nanomaterials

DCMST June 2nd, 2011

[email protected]

Gavin LawesWayne State University


1.Carbon structures

2. Carbon nanostructures

3. Potential applications for Carbon nanostructures

Outline


from bpc.edu

Periodic table


Electron (-)

Proton (+)

Neutron

Carbon atom


from msu.edu/gallego

amino group

carboxylic acid group

Carbon-based molecules are somewhat important for life on Earth…

Amino acids


Lecithin

from indiana.edu/oso

Phospholipids


Pentane

from wikimedia.org

…and are also important for all industrial activity


from britannica.com

s orbital p orbital

Electron orbitals


from ASDN.net

Hybridization


from cnx.orgfrom diamonds.net

sp3 hybridized C crystals


from cochise.edu/wellerr

sp2 hybridized C crystals


from chem.wisc.edu

Graphite consists of layers of hexagonal Carbon sheets.


Diamond Graphite

Electrical insulator Electrical conductor*

Very hard Very soft*

Transparent Opaque

Expensive Cheap


Nanoscale carbon structures


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


from unusualife.com

C60 is named for Buckminster Fuller who designed geodesic domes.


Original report of C60


1996 Nobel Prize in ChemistryRobert Curl, Sir Harold Kroto, Richard Smalley “for their discovery of fullerenes”.

from Nobelprize.org


from informaworld.com

Carbon nanotubes

Rolled up sheet of sp2 bonded carbon atoms


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


Carbon sheets can also be rolled up in different directions to give different types of nanotubes.


from phycomp.technion.ac.il

Electrical conductor

Electrical insulator

The properties of nanotubes depend on how they are rolled up


Nanotube sizes also depend on how they are rolled up


Graphene (single sp2 bonded carbon sheet)


from cnx.org

C atoms in hexagonal array


From ncem.lbl.govScale bar 0.2 nm


Nobel Prize in Physics 2010Andre Geim and Konstantin Novoselov “for groundbreaking experiments regarding the two-dimensional material graphene”.

from Nobelprize.org


Carbon nanostructures


Why are carbon nanostructures interesting?


Multiwall carbon nanotube breakingThey are strong


Silica fibres +MWCNT

Multiwall carbon nanotube composite

Mechanical properties can improve by 50% or more by adding carbon nanotubes.


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.


from bpc.edu

They have good electrical properties


from nanotechweb.org

Carbon nanostructures may be used in new electronic devices


Devices made with carbon nanotubes


Carbon Nanotubes. Advanced Topics in the Synthesis, Structure, Properties and Applications, 455-93, 2008

Carbon nanotubes can be used for making electronic devices


from als.lbl.gov

Properties of graphene depend on the subtrate


From nanotechweb.org

Geometry of graphene may also affect the properties


Graphene may be used as a transparent electrode


Carbon nanotube mechanical oscillator

Force sensitivity of 1 fN Hz-1/2


Graphene mechanical oscillator


Carbon nanotubes may have biomedical applications

Carbon nanotubes can be functionalized with different biologically relevant molecules.


Cells incubated with functionalized carbon nanotubes


MetalSemiconductor

Energy

Momentum

Electronic bandgap


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.


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


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.


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.


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.


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


End

carbon nanomaterials dcmst june 2 nd, 2011 [email protected] gavin lawes wayne state university

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