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What is a Carbon Nanotube ?

What is a Carbon Nanotube ?. Start with Carbon Graphite C 60 Single Wall Carbon Nanotubes Multi Wall Carbon Nanotubes. Start with Carbon. Carbon contains six electrons (1s) 2 , 2s, 2px,2py, 2pz 1s quantum number N=1 (2 electrons) N=2 , four electrons

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What is a Carbon Nanotube ?

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  1. What is a Carbon Nanotube? • Start with Carbon • Graphite • C60 • Single Wall Carbon Nanotubes • Multi Wall Carbon Nanotubes

  2. Start with Carbon • Carbon contains six electrons • (1s)2, 2s, 2px,2py, 2pz • 1s quantum number N=1 (2 electrons) • N=2 , four electrons • s orbital spherically symmetric about nucleous • p directed charge distribution • s and p form chemical bond • Y = s + lp • Solid carbon two main structures • Diamond sp3 109 degree bonds • Graphitic sheet sp2 120 degree bonds. Each bond in same plane • Graphite s, px, py • Sheets held together by weaker van der Waals Forces

  3. Sp3 and sp2 Bonds

  4. Discovery of C60 • Soccer ball-like molecule containing 60 carbon atoms • Motivated by understanding light transmission through interstellar dust • Optical extinction: absorption and scattering of light from interstellar dust • C60 envisioned by theoretical chemist • High powered pulsed laser simulate conditions of hot carbon • Prof. Richard Smalley (Rice) observed mass number 720 mass spectrometer (carbon mass #12) • Smalley won Nobel prize

  5. C60 Ref: Intro to Nanotechnology

  6. Closed Network From Other Atoms Ref: Intro to Nanotechnology

  7. Extension of C60, C70, C80 End closed

  8. Formation of an Armchair Nanotube Chiral vector is bent 2D Graphene Sheet armchair (n,n)

  9. Unit Cell of 2D Graphene (a) The unit cell and (b) Brillouin zone of two-dimensional graphite are shown as the dotted rhombus and shaded hexagon, respectively. ai, and bi, (i = 1, 2) are unit vectors and reciprocal lattice vectors, respectively. Energy dispersion relations are obtained along the perimeter of the dotted triangle connecting the high symmetry points, , K and M.

  10. “Roll” Carbon Nanotube from Graphite The unrolled honeycomb lattice of a nanotube, showing the unit vectors a1 and a2 for the graphene sheet. When we connect sites O and A, and B and B’, a nanotube can be constructed. OA and OB define the chiral vector Ch and the translational vector T of the nanotube, respectively. The rectangle OAB’B defines the unit cell for the nanotube. The figure corresponds to Ch = (4, 2)

  11. Constructing Nanotubes from a Graphene Sheet Roll-up vector a1 a2

  12. 3D Examples of 3 Types of Nanotubes

  13. Some More Properties of Nanotubes • 1-50nm in diameter • 10 - 100 micrometer long • End capped with half fullerene molecule • Single and multi-wall nanotubes • Chirality refers to how the tubes are rolled • One-third metallic, two-thirds semiconducting • Energy gap: 1/(diameter of tube) • Diameter of tube increases, bandgap decreases

  14. Metallic and Semiconducting CNT

  15. Examples of Band Structures One-dimensional energy dispersion relations for (a) armchair (5, 5), (b) zigzag (9, 0), and (c) zigzag (10, 0) carbon nanotubes.

  16. Bandgap of Semiconductor Tube

  17. Observed Nanotube Species

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