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TOPICS IN (NANO) BIOTECHNOLOGY Carbon nanotubes. 10th June 2003. Carbon nanotubes. Overview. Introduction Synthesis & Purification Overview of applications Single nanotube measurements Energy storage Molecular electronics Conclusion and future outlook. Introduction: common facts.

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slide1

TOPICS IN (NANO) BIOTECHNOLOGY

Carbon nanotubes

10th June 2003

overview
Overview
  • Introduction
  • Synthesis & Purification
  • Overview of applications
  • Single nanotube measurements
  • Energy storage
  • Molecular electronics
  • Conclusion and future outlook
introduction common facts
Introduction: common facts
  • Discovered in 1991 by Iijima
  • Unique material properties
  • Nearly one-dimensional structures
  • Single- and multi-walled
slide5

Definition

Single-wall carbon nanotubes are a new form of carbon made by rolling up a single graphite sheet to a narrow but long tube closed at both sides by fullerene-like end caps..

However, their attraction lies not only in the beauty of their molecular structures: through intentional alteration of their physical and chemical properties fullerenes exhibit an extremely wide range of interesting and potentially useful properties.

slide6

History

  • 1991 Discovery of multi-wall carbon nanotubes
  • 1992 Conductivity of carbon nanotubes
  • 1993 Structural rigidity of carbon nanotubes
  • 1993 Synthesis of single-wall nanotubes
  • 1995 Nanotubes as field emitters
  • 1997 Hydrogen storage in nanotubes
  • 1998 Synthesis of nanotube peapods
  • 2000 Thermal conductivity of nanotubes
  • 2001 Integration of carbon nanotubes for logic circuits
  • 2001 Intrinsic superconductivity of carbon nanotubes
nanotube structure
Nanotube structure
    • Armchair structure
    • Zigzag structure
    • Chiral structure
  • Defects result in bends and transitions
  • Roll a graphene sheet in a certain direction:
special properties
Special properties
  • Difference in chemical reactivity for end caps and side wall
  • High mechanical strength
  • Special electrical properties:
    • Metallic
    • Semi conducting
slide9

Special properties

  • Metallic conductivity(e.g. the salts A3C60 (A=alkali metals))
  • Superconductivitywith Tc\'s of up to 33K (e.g. the salts A3C60 (A=alkali metals))
  • Ferromagnetism(in (TDAE)C60 - without the presence of d-electrons)
  • Non-linear optical activity
  • Polymerizationto form a variety of 1-, 2-, and 3D polymer structures
slide10

Special properties

  • Nanotubes can be either electrically conductive or semiconductive, depending on their helicity.
  • These one-dimensional fibers exhibit electrical conductivity as high as copper, thermal conductivity as high as diamond,
  • Strength 100 times greater than steel at one sixth the weight, and high strain to failure.
slide11

Current Applications

  • Carbon Nano-tubes are extending the ability to fabricate devices such as:
  • Molecular probes
  • Pipes
  • Wires
  • Bearings
  • Springs
  • Gears
  • Pumps
slide12

Synthesis: overview

  • Commonly applied techniques:
    • Chemical Vapor Deposition (CVD)
    • Arc-Discharge
    • Laser ablation
  • Techniques differ in:
    • Type of nanotubes (SWNT / MWNT / Aligned)
    • Catalyst used
    • Yield
    • Purity
synthesis growth mechanism
Synthesis: growth mechanism
  • Metal catalyst
  • Tip growth / extrusion growth
synthesis cvd
Synthesis: CVD
  • Gas phase deposition
  • Large scale possible
  • Relatively cheap
  • SWNTs / MWNTs
  • Aligned nanotubes
  • Patterned substrates
synthesis arc discharge
Synthesis: Arc Discharge
  • It was first made popular by Ebbessen and Ajayan in 1992
  • It is still considered as one of the best methods for producing carbon nanotubes other than CVD
  • In order to produce a good yield of high quality nanotubes, the pressure, consistent current, and efficient cooling of the electrodes are very important operating parameters
synthesis arc discharge1
Synthesis: arc discharge
  • Relatively cheap
  • Many side-products
  • MWNTs and SWNTs
  • Batch process
synthesis laser ablation
Synthesis: laser ablation
  • Catalyst / no catalyst
  • MWNTs / SWNTs
  • Yield <70%
  • Use of very strong laser
  • Expensive (energy costs)
  • Commonly applied
purification
Purification
  • Contaminants:
    • Catalyst particles
    • Carbon clusters
    • Smaller fullerenes: C60 / C70
  • Impossibilities:
    • Completely retain nanotube structure
    • Single-step purification
  • Only possible on very small scale:
    • Isolation of either semi-conducting SWNTs
purification1
Purification
  • Removal of catalyst:
    • Acidic treatment (+ sonication)
    • Thermal oxidation
    • Magnetic separation (Fe)
  • Removal of small fullerenes
    • Micro filtration
    • Extraction with CS2
  • Removal of other carbonaceous impurities
    • Thermal oxidation
    • Selective functionalisation of nanotubes
    • Annealing
potential applications
Potential applications
  • < AFM Tip
  • > Molecular electronics
      • Transistor
  • > FED devices:
    • Displays
  • < Others
  • Composites
  • Biomedical
  • Catalyst support
  • Conductive materials
  • ???
  • < Energy storage:
    • Li-intercalation
    • Hydrogen storage
    • Supercaps
conclusions
Conclusions
  • Mass production is nowadays too expensive
  • Many different techniques can be applied for investigation
  • Large scale purification is possible
  • FEDs and CNTFETs have proven to work and are understood
  • Positioning of molecular electronics is difficult
  • Energy storage is still doubtful, fundamental investigations are needed
slide23

Homework

  • Find an article from 2003-2004 describing a biological application of carbon nanotubes and make a short summary to explain to the rest of the class next week.
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