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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. - PowerPoint PPT Presentation
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© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 1
Nature of the Chemical Bond with applications to catalysis, materials
science, nanotechnology, surface science, bioinorganic chemistry, and energy
William A. Goddard, III, [email protected] Beckman Institute, x3093
Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics,
California Institute of Technology
Lecture 12 February 3, 2014Formation bucky balls, bucky tubes
Course number: Ch120aHours: 2-3pm Monday, Wednesday, Friday
Teaching Assistants:Sijia Dong <[email protected]>Samantha Johnson <[email protected]>
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 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!
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 3
Polyyne chain
precursors fullerenes, all even
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 4
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 5
C540
All fullerens have 12 pentagonal rings
© 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 C60Contradicted 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 C60Contradicted 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
© 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
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 8
Energies from QM
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Force Field for sp1 and sp2 carbon clusters
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4n vs 4n+2 for Cn Rings
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Population of various ring and fullerene species with Temperature
Based on free energies from QM and FF
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Bring two C30 rings together
© 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 ringsTS to form tricyclic
E tricyclic
E tricyclic
C40
C34
C60
TS convert
TS to singlet
ring
Bergman cyclization (leads to Jarrold
mechanism)
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 14
Energetics (eV) for initial steps of JarroldIf get here, then get
fullereneJarrold
pathway
Modified Jarrold
Number pi bonds
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 15
Downhill race from tricyclic to bucky ball
Number sp2 bonded centers
ener
getic
s (e
V)
30 eV of energy gain as form Fullerene
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 16
Structures in Downhill race from tricyclic to bucky ball
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 17
Energy contributions to downhill race to fullerene
Number sp2 bonded centers
ener
getic
s (e
V)
© 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
© 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)
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 20
C60 is face centered cubic
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 21
C70 is hexagonal closest packed
© 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
© 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
© 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 NiD. 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
© 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 NiD. 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
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 26
Kiang CNT form 1993
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 27
Kiang CNT form 1993
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 28
Distribution of diameters for carbon SWNT, Kiang 1993
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 29
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 30
Examples Single wall carbon nanotubes
© 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
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 32
Contsruction for (6,10) edge
1 2
3
45
6
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(10,10) armchair carbon SWNT
13.46A diameter
40 atoms/repeat distance
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 34
(14,0) zig-zag Bucky tube
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 35
Crystal packing of (10,10) carbon
SWNT
16,7A
13.5ADensity
SWNT: 1.33 g/ccGraphite 2.27 g/cc
Ec Young’s modulusSWNT 640 GPa
Graphite 1093 GPa
Ea Young’s modulusSWNT 5.2 GPa
Graphite 4.1 GPaHeat formation
Graphite 0C60 11.4
(10,10) CNT 2.72
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 36
Vibrations in (10,10) armchair CNT
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 37
Carbon fibers and tubes
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Vibrations in (10,10) armchair CNT
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 39
Vibrations in (10,10) armchair CNT
© 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)
© 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)
© 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
© copyright 2011 William A. Goddard III, all rights reservedCh120a-Goddard-L07,08 43
Mechanisms Proposed for Nanotube Growth
Stepwise ProcessAdsorption
DehydrogenationSaturationDiffusion
NucleationGrowth
© 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.
© 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.
© 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.
© 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 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
© 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.
© 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.