Carbon nanomaterials DCMST June 2 nd, 2011 glawes@wayne.edu Gavin Lawes Wayne State University.

transcript

Carbon nanomaterials

DCMST June 2nd, 2011

glawes@wayne.edu

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.

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

∂tψ = −

2m∇ 2ψ +Vψ

Dirac Equation

(for massive particles)

∂tΨ = iσ aea

μ ∇ μ − iAμ( ) + βm( )Ψ

(for relativistic particles)

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

Carbon nanomaterials DCMST June 2 nd, 2011 glawes@wayne.edu Gavin Lawes Wayne State University.

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