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Nature of the Chemical Bond with applications to catalysis, materials science, nanotechnology, surface science, bioinor

Lecture 12 February 3, 2014 Formation bucky balls, bucky tubes. Nature of the Chemical Bond with applications to catalysis, materials science, nanotechnology, surface science, bioinorganic chemistry, and energy. Course number: Ch120a Hours: 2-3pm Monday, Wednesday, Friday.

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Nature of the Chemical Bond with applications to catalysis, materials science, nanotechnology, surface science, bioinor

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  1. Ch120a-Goddard-L01 Lecture 12 February 3, 2014 Formation bucky balls, bucky tubes Nature of the Chemical Bond with applications to catalysis, materials science, nanotechnology, surface science, bioinorganic chemistry, and energy Course number: Ch120a Hours: 2-3pm Monday, Wednesday, Friday William A. Goddard, III, wag@wag.caltech.edu 316 Beckman Institute, x3093 Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics, California Institute of Technology Teaching Assistants:Sijia Dong <sdong@caltech.edu> Samantha Johnson <sjohnson@wag.caltech.edu>

  2. C60 fullerene No broken bonds Just ~11.3 kcal/mol strain at each atom 678 kcal/mol Compare with 832 kcal/mol for flat sheet Lower in energy than flat sheet by 154 kcal/mol!

  3. Polyyne chain precursors fullerenes, all even

  4. C540 All fullerens have 12 pentagonal rings

  5. Mechanism for formation of fullerenes Heath 1991: Fullerene road. Smaller fullerenes and C3 etc add on to pentagonal sites to grow C60 Contradicted by He chromatography and high yield of endohedrals Smalley 1992: Pentagonal road. Graphtic sheets grow and curl into fullerenes by incorporating pentagonal C3 etc add on to pentagonal sites to grow C60 Contradicted by He chromatography Arc environment: mechanism goes through atomic species (isotope scrambling) He chromatography Go through carbon rings and form fullerenes Has high temperature gradients Ring growth road. Jarrold 1993. based on He chromatography

  6. He chromatography (Jarrold) Relative abundance of the isomers and fragments as a function of injection energy in ion drifting experiments Conversion of bicyclic ring to fullerene when heated

  7. Energies from QM

  8. Force Field for sp1 and sp2 carbon clusters

  9. 4n vs 4n+2 for Cn Rings

  10. Population of various ring and fullerene species with Temperature Based on free energies from QM and FF

  11. Bring two C30 rings together

  12. Energetics (eV) for isomerizations converting bicyclic ring to monocyclic or Jarrold intermediates for n = 30, 40, 50 TS to singlet ring Bergman cyclization (leads to Jarrold mechanism) 2 rings TS to form tricyclic C40 E tricyclic C34 TSconvert E tricyclic C60

  13. Energetics (eV) for initial steps of Jarrold Jarrold pathway If get here, then get fullerene Modified Jarrold Number pi bonds

  14. Downhill race from tricyclic to bucky ball 30 eV of energy gain as form Fullerene energetics (eV) Number sp2 bonded centers

  15. Structures in Downhill race from tricyclic to bucky ball

  16. Energy contributions to downhill race to fullerene energetics (eV) Number sp2 bonded centers

  17. C60 dimer Prefers packing of 6 fold face De = 7.2 kcal/mol Face-face=3.38A

  18. Crystal structure C60 Expect closest packing: 6 neighbors in plane 3 neighbors above the plane and 3 below But two ways ABCABC face centered cubic ABABAB hexagonal closet packed Predicted crystal structure 3 months before experiment Prediction of Fullerene Packing in C60 and C70 Crystals Y. Guo, N. Karasawa, and W. A. Goddard III Nature 351, 464 (1991)

  19. C60 is face centered cubic

  20. C70 is hexagonal closest packed

  21. Vapor phase grown Carbon fiber, R. T. K. Baker and P. S. Harris, in Chemistry and Physics of Carbon, edited by P. L. Walker, Jr. and A. Thrower (Marcel Dekker, New York, 1978), Vol. 14, pp. 83–165; G. G. Tibbetts, Carbon 27, 745–747 (1989); R. T. K.Baker, Carbon 27, 315–323 (1989). M. Endo, Chemtech 18, 568–576 (1988). Formed carbon fiber from 0.1 micron up Xray showed that graphene planes are oriented along axis but perpendicular to the cylindrical normal

  22. Multiwall nanotubes "Helical microtubules of graphitic carbon". S. Iijima, Nature (London) 354, 56–58 (1991). Ebbesen, T. W.; Ajayan, P. M. (1992). "Large-scale synthesis of carbon nanotubes". Nature358: 220–222. Outer diameter of MW NT inner diameter of MW NT

  23. Single wall carbon nanotubes, grown catalytically S. Iijima and T. Ichihashi, "Single-shell carbon nanotubes of 1-nm diameter".Nature (London) 363, 603–605 (1993) used Ni D. S. Bethune, C.-H. Kiang, M. S. de Vries, G. Gorman, R. Savoy, J. Vazquez, and R. Beyers, "Cobalt-catalyzed growth of carbon nanotubes with single-atomic-layer walls".Nature (London) 363, 605–607 (1993). used Co Ching-Hwa Kiang grad student with wag on leave at IBM san Jose

  24. Single wall carbon nanotubes, grown catalytically S. Iijima and T. Ichihashi, "Single-shell carbon nanotubes of 1-nm diameter".Nature (London) 363, 603–605 (1993) used Ni D. S. Bethune, C.-H. Kiang, M. S. de Vries, G. Gorman, R. Savoy, J. Vazquez, and R. Beyers, "Cobalt-catalyzed growth of carbon nanotubes with single-atomic-layer walls".Nature (London) 363, 605–607 (1993). used Co Ching-Hwa Kiang grad student with wag on leave at IBM san Jose Catalytic Synthesis of Single-Layer Carbon Nanotubes with a Wide Range of Diameters C.- H. Kiang, W. A. Goddard III, R. Beyers, J. R. Salem, D. S. Bethune, J. Phys. Chem. 98, 6612–6618 (1994). Catalytic Effects on Heavy Metals on the Growth of Carbon Nanotubes and Nanoparticles C.-H. Kiang, W. A. Goddard III, R. Beyers, J. R. Salem, and D. S. Bethune, J. Phys. Chem. Solids 57, 35 (1995). Effects of Catalyst Promoters on the Growth of Single-Layer Carbon Nanotubes; C.-H. Kiang, W. A. Goddard III, R. Beyers, J. R. Salem, and D. S. Bethune, Mat. Res. Soc. Symp. Proc. 359, 69 (1995) Carbon Nanotubes With Single-Layer Walls," Ching-Hwa Kiang, William A. Goddard III, Robert Beyers and Donald S. Bethune, " Carbon 33, 903-914 (1995). "Novel structures from arc-vaporized carbon and metals: Single-layer carbon nanotubes and metallofullerenes," Kiang, C-H, van Loosdrecht, P.H.M., Beyers, R., Salem, J.R., and Bethune, D.S., Goddard, W.A. III, Dorn, H.C., Burbank, P., and Stevenson, S., Surf. Rev. Lett. 3, 765-769 (1996).

  25. Kiang CNT form 1993

  26. Kiang CNT form 1993

  27. Distribution of diameters for carbon SWNT, Kiang 1993

  28. Examples Single wall carbon nanotubes

  29. Some bucky tubes (8,8) armchair (14,0) zig-zag (6,10) chiral

  30. 2 Contsruction for (6,10) edge 1 3 6 4 5

  31. (10,10) armchair carbon SWNT 13.46A diameter 40 atoms/repeat distance

  32. (14,0) zig-zag Bucky tube

  33. Crystal packing of (10,10) carbon SWNT 13.5A Density SWNT: 1.33 g/cc Graphite 2.27 g/cc Ec Young’s modulus SWNT 640 GPa Graphite 1093 GPa Ea Young’s modulus SWNT 5.2 GPa Graphite 4.1 GPa 16,7A Heat formation Graphite 0 C60 11.4 (10,10) CNT 2.72

  34. Vibrations in (10,10) armchair CNT

  35. Carbon fibers and tubes

  36. Vibrations in (10,10) armchair CNT

  37. Vibrations in (10,10) armchair CNT

  38. Mechanism for gas phase CNT formation Polyyne Ring Nucleus Growth Model for Single-Layer Carbon Nanotubes C-H. Kiang and W. A. Goddard III Phys. Rev. Lett. 76, 2515 (1996)

  39. Mechanism for gas phase CNT formation A two-stage mechanism of bimetallic catalyzed growth of single-walled carbon nanotubes Deng WQ, Xu X, Goddard WA Nano Letters 4 (12): 2331-2335 (2004)

  40. But mechanism of gas phase C SWNT, no longer important The formation of Carbon SWNT by CVD growth on a metal nanodot on a support is now the preferred mechanism for forming SWNT

  41. Stepwise Process Adsorption Dehydrogenation Saturation Diffusion Nucleation Growth Mechanisms Proposed for Nanotube Growth

  42. Vapor carbon feed stock adsorbs unto liquid catalyst particle and dissolves. Dissolved carbon diffuses to a region of lower solubility resulting in super-saturation and precipitation of the solid product. Originally developed to explain the growth of carbon whiskers/filaments. Temperature, concentration or free energy gradient is implicated as the driving force responsible for diffusion. Wagner, R. S.; Ellis, W. C. Appl. Phys. Lett. 1964, 4, 89. Bolton, et al. J. Nanosci. Nanotechnol. 2006, 6, 1211. Vapor-Liquid-Solid (Carbon Filament) Mechanism

  43. Dai, et al. Chem. Phys. Lett.1996, 260, 471. Raty, et al. Phys. Rev. Lett. 2005 95, 096103. Yarmulke Mechanism • Carbon-carbon bonds form on the surface (either before or as a result of super-saturation). • Diffusion of carbon to graphene coating can be an important rate limiting step. • Coating of more than a complete hemisphere results in poisoning of catalyst. • New layers can start beneath the original layer after/as it lifts off the surface resulting in MWNT.

  44. Hofmann, S. et al. Nano Lett.2007, 7, 602. Experimental Confirmation of a Yarmulke Mechanism Atomic-scale, video-rate environmental transmission microscopy has been used to monitor the nucleation and growth of single walled nanotubes.

  45. Size of catalyst particles is related to the diameter of the nanotubes formed. Catalyst nanoparticles are known to deform (elongate) during nanotube growth. Structural properties of select catalyst surfaces (Ni111, Co111, Fe1-10) exhibit appropriate symmetry and distances to overlap with graphene and allow thermally forbidden C2 addition reaction. Graphene is believed to stabilize the high energy nanoparticle surface. MWNT have been observed growing out of steps, which they stabilize. Hong, S.; et al. Jpn J. Appl. Phys. 2002, 41, 6142. Vinciguerra, V.; et al. Nanotechnol. 2003, 14, 655. Hofmann, S. et al. Nano Lett.2007, 7, 602 Role of the Catalyst Particle in Nanotube Formation

  46. Huang, S.; et al. Nano Lett.20044, 1025. Kong, J.; et al. Chem. Phys. Lett.1998, 292, 567. Tip vs. Base Growth Mechanisms Same initial reaction step: absorbtion, diffusion and precipitation of carbon species. Strength of interaction between catalyst particle and catalyst support determines whether particles remains on surface or is lifted with growing nanotube. Images of nanotubes show catalyst particles trapped at the ends of nanotubes in the case of tip growth, or nanotubes bound to catalysts on support in the case of base growth. Alternatively capped nanotube tops show base growth. A kite (tip) growth mechanism has been used to explain the growth of long (order of mm), well ordered SWNTs.

  47. Limiting Steps for Growth Rates Diffusion of reactive species either through the catalyst particle bulk or across its surface can play an important role in determining the rate of nanotube growth. In the case of carbon species which dissociate less readily the rate of carbon supply to the particle can act as the rate limiting step. The rate of growth must also take into account a force balance between the friction of the nanotube moving through the surrounding feedstock gas and the driving force for/from the reaction. Vinciguerra, V.; et al. Nanotechnol. 2003, 14, 655. Hofmann, S. et al. Nano Lett.2007, 7, 602. Hafner, J. H.; et al. Chem. Phys. Lett.1998, 296, 195.

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