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TOPICS IN (NANO) BIOTECHNOLOGY Carbon nanotubes

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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TOPICS IN (NANO) BIOTECHNOLOGY Carbon nanotubes

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  1. TOPICS IN (NANO) BIOTECHNOLOGY Carbon nanotubes 10th June 2003

  2. Carbon nanotubes

  3. Overview • Introduction • Synthesis & Purification • Overview of applications • Single nanotube measurements • Energy storage • Molecular electronics • Conclusion and future outlook

  4. Introduction: common facts • Discovered in 1991 by Iijima • Unique material properties • Nearly one-dimensional structures • Single- and multi-walled

  5. 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.

  6. 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

  7. Nanotube structure • Armchair structure • Zigzag structure • Chiral structure • Defects result in bends and transitions • Roll a graphene sheet in a certain direction:

  8. Special properties • Difference in chemical reactivity for end caps and side wall • High mechanical strength • Special electrical properties: • Metallic • Semi conducting

  9. 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

  10. 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.

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

  12. 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

  13. Synthesis: growth mechanism • Metal catalyst • Tip growth / extrusion growth

  14. Synthesis: CVD • Gas phase deposition • Large scale possible • Relatively cheap • SWNTs / MWNTs • Aligned nanotubes • Patterned substrates

  15. 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

  16. Synthesis: arc discharge • Relatively cheap • Many side-products • MWNTs and SWNTs • Batch process

  17. Synthesis: arc discharge

  18. Synthesis: laser ablation • Catalyst / no catalyst • MWNTs / SWNTs • Yield <70% • Use of very strong laser • Expensive (energy costs) • Commonly applied

  19. 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

  20. 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

  21. Potential applications • < AFM Tip • > Molecular electronics • Transistor • > FED devices: • Displays • < Others • Composites • Biomedical • Catalyst support • Conductive materials • ??? • < Energy storage: • Li-intercalation • Hydrogen storage • Supercaps

  22. 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

  23. 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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