Carbon Nanotubes

History of Nanotubes Discovery of buckminsterfullerene in 1985 sparked interest in other stable carbon structures In 1991 Sumio Iijima discovered multi-walled carbon nanotubes and created first protocol for pure nanotubes Carbon “fibers” were seen as byproducts of catalytic experiments since 1976 In 1993 Iijima produced single- walled nanotubes with diameter ~1nm

History of nanotubes M. Endo used a catalytic chemical vapor deposition method (1976) – Not industrially feasible Iijima used an arc- evaporation method – Purer product Efforts to control diameter, number of layers and purity

Producing multi-walled nanotubes The arc-evaporator apparatus produces the highest- quality nanotubes The first nanotubes had two layers with diameter ranging from 3 to 30 nanometers Pass 50 amps of current between two graphite electrodes in a cloud of helium Some of the graphite vaporizes on the cathode, containing carbon nanotubes

Producing single-walled nanotubes Pass a carbon-containing gas, like a hydrocarbon, over a nano-sized metal catalyst (Fe, Ni, or Co) Metal particles catalyze the break down of gaseous molecules into carbon Nanotube begins to grow with the metal at one end Poorer quality but better for volume production Third method comes from vaporizing a metal- graphite target with a laser Results in high yield of single-walled nanotubes

Physical Properties of Carbon Nanotubes Consists of 6-Membered Carbon Rings that Form Long, Thin, Tubular Structures Similar to Graphite Three Different Conformations Arm Chair Zig-Zag Chiral

Physical Properties of Nanotubes II The properties of CNTs are unparalleled by any substance. Strength Conductivity and Ballistic Transport – Electrical – Fourier’s Law H=(ΔQ/Δt)=k*A*(ΔT/x) – Thermal conductivity k=(ΔQ/ΔT)*(1/A)*(x/ΔT) – Optical CTNs will replace common infrastructures in modern technology

Applications of CNTs Commercial Commercial applications for CNTs are not really applicable because of the high cost of CNT production Analysts in 2004 originally thought CNT prices would drop to a reasonable price by the present, but this was far too optimistic There’s little doubt that once the purification and assembly costs go down, CNTs will be wildly used In February, a company was able to make relatively large sheets (6’x3’) and are looking to mass produce by 2012 There are also some issues with the toxicity of CNTs They are normally made with heavy metal catalysts and if they are not purified properly this can lead to poisoning in biological systems It is still useful to examine its possible functions on a smaller scale (following slides)

Electronics The high thermal conductivity and low current resistance makes CNTs very valuable to the future of electronics – Many developers are making smaller and smaller devices and overheating is a large problem – They can also be used in electronics for electromagnetic shielding because it has good electrostatic dissipation properties CNTs may also revolutionize the way speakers are produced. – A team in China created speakers using CNTs that were functional over a wide range of sounds including the range of human hearing – The CNT film a only a few nanometers thick and is used to make the sound using an alternating current.

Medicine CNTs have many potential applications in the medical world – They can be used to generate heat (via radio waves) or as drug vectoring agents – Have major implications for tissue engineering Can be used for “improved tracking of cells, sensing of microenvironments, delivering of transfection agents and scaffolding for incorporating with the hosts body” CNTs are ideal for working in nano environments from nm. Graph below shows how drastically CNT research in the biomedical field has increased CNTs will be most useful as structural supports as tissue scaffolding, making these tissues stronger and their conductivity can be used for directed cell growth

Other Applications Preposterous – Space Elevator Not Crazy – Tennis rackets, bikes, handlebars, hockey and lacrosse sticks – New ultra-light, ultra-strong body armor for soldiers – CNTs have been used to develop Ultra Capacitors Swapping conventional capacitor materials with sheets of CNTs greatly maximizes surface area and creates a much more potent capacitor in a smaller space

Citation Barron, A. Khan, M. “Carbon nanotubes: Opportunities and Challenges”. Advanced Materials and Processes Xiao, L. Chen, Z. et al. “Flexible, Stretchable, Transparent Carbon Nanotube Thin Film Loudspeakers”. NanoLetters Bullis, K. “The Ultra Battery” Technology Review Harrison, B. Atala, A. “”Carbon Nanotube applications for tissue engineering”. Biomaterials. 28(2007): Harris, Peter. "Carbon Nanotubes." A carbon nanotube page. 1 Mar Centre for Advanced Microscopy at University of Reading. 1 Dec Ota, Masahiro. "The Carbon Nanotube, a Product of Nanotechnology." AICHI VOICE (Cutting Edge) Dec