1. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 Ch120a- Goddard- L01 1 Nature of the Chemical Bond with applications to catalysis, materials science, nanotechnology, surface science, bioinorganic chemistry, and energy William A. Goddard, III, wag@wag.caltech.eduwag@wag.caltech.edu 316 Beckman Institute, x3093 Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics, California Institute of Technology Lecture 12 February 3, 2014 Formation bucky balls, bucky tubes Course number: Ch120a Hours: 2-3pm Monday, Wednesday, Friday Teaching Assistants:Sijia Dong Samantha Johnson sjohnson@wag.caltech.edu

2. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 2 C 60 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. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 3 Polyyne chain precursors fullerenes, all even

4. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 4

5. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 5 C 540 All fullerens have 12 pentagonal rings

6. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 6 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 Ring growth road. Jarrold 1993. based on He chromatography Arc environment: mechanism goes through atomic species (isotope scrambling) He chromatography  Go through carbon rings and form fullerenes Has high temperature gradients

7. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 7 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

8. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 8 Energies from QM

9. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 9 Force Field for sp1 and sp2 carbon clusters

10. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 10 4n vs 4n+2 for Cn Rings

11. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 11 Population of various ring and fullerene species with Temperature Based on free energies from QM and FF

12. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 12 Bring two C30 rings together

13. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 13 Energetics (eV) for isomerizations converting bicyclic ring to monocyclic or Jarrold intermediates for n = 30, 40, 50 2 rings TS to form tricyclic E tricyclic C 40 C 34 C 60 TS convert TS to singlet ring Bergman cyclization (leads to Jarrold mechanism)

14. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 14 Energetics (eV) for initial steps of Jarrold If get here, then get fullerene Jarrold pathway Modified Jarrold Number pi bonds

15. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 15 Downhill race from tricyclic to bucky ball Number sp2 bonded centers energetics (eV) 30 eV of energy gain as form Fullerene

16. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 16 Structures in Downhill race from tricyclic to bucky ball

17. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 17 Energy contributions to downhill race to fullerene Number sp2 bonded centers energetics (eV)

18. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 18 C60 dimer Prefers packing of 6 fold face De = 7.2 kcal/mol Face-face=3.38A

19. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 19 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)

20. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 20 C60 is face centered cubic

21. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 21 C70 is hexagonal closest packed

22. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 22 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

23. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 23 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". Nature 358: 220–222. Outer diameter of MW NT inner diameter of MW NT

24. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 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

25. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 25 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 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). Ching-Hwa Kiang grad student with wag on leave at IBM san Jose

26. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 26 Kiang CNT form 1993

27. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 27 Kiang CNT form 1993

28. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 28 Distribution of diameters for carbon SWNT, Kiang 1993

29. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 29

30. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 30 Examples Single wall carbon nanotubes

31. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 31 Some bucky tubes (8,8) armchair (14,0) zig-zag (6,10) chiral

32. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 32 Contsruction for (6,10) edge 1 2 3 4 5 6

33. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 33 (10,10) armchair carbon SWNT 13.46A diameter 40 atoms/repeat distance

34. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 34 (14,0) zig-zag Bucky tube

35. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 35 Crystal packing of (10,10) carbon SWNT 16,7A 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 Heat formation Graphite 0 C60 11.4 (10,10) CNT 2.72

36. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 36 Vibrations in (10,10) armchair CNT

37. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 37 Carbon fibers and tubes

38. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 38 Vibrations in (10,10) armchair CNT

39. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 39 Vibrations in (10,10) armchair CNT

40. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 40 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)

41. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 41 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)

42. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 42 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

43. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 43 Mechanisms Proposed for Nanotube Growth Stepwise Process Adsorption Dehydrogenation Saturation Diffusion Nucleation Growth

44. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 44 Vapor-Liquid-Solid (Carbon Filament) Mechanism 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.

45. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 45 Yarmulke Mechanism Dai, et al. Chem. Phys. Lett. 1996, 260, 471. Raty, et al. Phys. Rev. Lett. 2005 95, 096103. 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.

46. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 46 Experimental Confirmation of a Yarmulke Mechanism Hofmann, S. et al. Nano Lett. 2007, 7, 602. Atomic-scale, video-rate environmental transmission microscopy has been used to monitor the nucleation and growth of single walled nanotubes.

47. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 47 Role of the Catalyst Particle in Nanotube Formation 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 C 2 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

48. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 48 Tip vs. Base Growth Mechanisms Huang, S.; et al. Nano Lett. 2004 4, 1025. Kong, J.; et al. Chem. Phys. Lett. 1998, 292, 567. 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.

49. © copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 49 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.