Special Focus:Carbon

Nanostructures

Carbon Nanostructures– Buckyballs– Nanotubes

• SWNT & MWNT (single-walled nanotubes & multi-walled

nanotubes)

– Graphene thin layers

http://education.mrsec.wisc.edu/Edetc/pmk/pages/bucky.html

Carbon NanostructuresVariety of properties

Variety of structures

0-D

Metallic conductor (graphite)

Semiconductor (diamond)

Insulating Polymer (hydrocarbon chains)

1-D2-D

3-D

Carbon Fullerenes• 0-dimensional carbon structure• Usually C60, but also refers to C70, C76, Cn (n > 60)• Every carbon site on C60 is equivalent

– Bonded to three other carbons– average bond is 1.44 Å (C-C is 1.46 Å; C=C is 1.40 Å)

• 20 hexagonal faces; 12 pentagonal faces• Diameter: 7.10 Å (7.1 x 10-10 m)

Buckminster Fuller (1895-1983):Architect, engineer, inventor; Developed the geodesic dome

Epcot Center in Disneyworld

Climatron at the Missouri Botanical Garden

Biosphere Museum in Canada

• The shape of the geodesic dome encloses the greatest volume while taking up the least surface area.

• Fuller hoped the design would produce large numbers of inexpensive homes for soldiers returning from WWII.

• The building can withstand high winds such as those found in hurricanes.

Synthesis of Fullerenes• Laser ablation (vaporizing graphite with a laser)• Plasma arcing of graphite or coal

– Fullerenes found in the soot

Anode Cathode

C+

Nanotube deposit

• Combustion synthesis– Burn hydrocarbon at low pressure

e-

Demo: Laser Pointer, watch plate, Charcoal briquette!

• Single-Walled Carbon Nanotubes (SWCNT; SWNT)• Multi-Walled Carbon Nanotubes (MWCNT; MWNT)

• How to make them:– Arc evaporation (plasma arcing)– Laser ablation– PECVD (plasma-enhanced chemical vapor

deposition)– Electrochemical methods

http://www.extremetech.com/extreme/137555-mit-creates-carbon-nanotube-pencil-doodles-some-electronic-circuits?print

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Carbon Nanotubes

(a) Armchair

(b) Zigzag

(c) Chiral

Properties of Carbon Nanotubes• Mechanical

– Stiff and robust structures• C-C bonds in graphite (and nanotubes) is the one

of the strongest bonds in nature– Flexible; do not break when bent

• Conductivity– Extremely high thermal conductivity– Extremely high electrical conductivity

• Potential Applications:- catalysis - hydrogen storage - biological cell electrodes- resistors - flow sensors - electron field emission tips- electronic/mechanical devices - scanning probe tips

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Carbon Nanotube Applications:NEMS: Nanoelectricalmechanical

systems“Nantero is a nanotechnology

company using carbon nanotubes for the development of next-generation semiconductor devices...

In the field of memory, Nantero is developing NRAM™, a high-density nonvolatile Random Access Memory.”

Gold plate ~ (100 nm)2

attached to outer shell of suspended MWCNT (on Si wafer)“electrostatically rotate the outer shell relative to the inner core”

WATCH CLIP FROM “NOVA: Making Things Stronger” about Carbon Nanotubes (Scene Selection)