SWCNT Growth from Chiral and Achiral Carbon Nanorings: Prediction of Chirality and Diameter Influence on Local Growth Rates

SWCNT Growth from Chiral and Achiral Carbon

Nanorings: Prediction of Chirality and Diameter

Influence on Local Growth Rates

Stephan Irle,1 Hai-Bei Li,2 Alister J. Page,2 Keiji Morokuma2,3

2Kyoto University 1Nagoya University

http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp

The Sixth Rice University, Air Force Research Laboratory, NASA, Honda Research Institute

Workshop on Nucleation and Growth Mechanisms of Single Wall Carbon Nanotubes

The Flying L Ranch, Bandera, TX, U.S.A., April 13, 2013

3

Kyoto University Nagoya University

http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp

Dr. Alister J. Pageb

Acknowledgements

Prof. Keiji Morokuma

Dr. Hai-Bei Libnow: Lecturer, University of Newcastle (AUS)

Dr. Joonghan Kim

2

2

Computer resources :

CREST grant 2006-2012

(KM, SI) and AFOSR (to KM)

Funding :

MEXT Tenure Track program, JSPS Kiban (SI)

Acknowledgements

Research Center for Computational Science

(RCCS), Okazaki Research Facilities, National

Institutes for Natural Sciences.

Academic Center for Computing and Media

Studies (ACCMS), Kyoto University

3

Prolog Our QM/MD StudiesADVERTISEMENT

4

“What can be controlled is never completely real;

what is real can never be completely controlled.”

Vladimir V. Nabokov, in: Look at the harlequins! McGraw-

Hill, New York (1974)

Goal SWCNT Chirality Control

The goal: arbitrary (n,m)-specific SWCNT Growth

(5,5) SWCNT

high yield, desired length, defect-free, eventually catalyst-free

ACCVD etc …

Selection of

“appropriate” growth

conditions

diameter

yield

chirality

length

5

Overview

Overview: CCVD SWCNT synthesis

Metal-free SWCNT synthesis from templates

Theoretical Simulations of SWCNT growth from CPPs

(n,n) SWCNT growth from [n]CPPs

(n,m) SWCNT growth from chiral CPPs

Summary: What did we learn?

What is next?

http://kmweb.fukui.kyoto-u.ac.jp/nano http://qc.chem.nagoya-u.ac.jp6

6

Overview

Overview: CCVD SWCNT synthesis


7

• SCC-DFTB; Te = 10,000 K.

• MD; ∆t=1 fs.

• NVT ensemble; Tn= 1,500 K.

• Nosé-Hoover-Chain thermostat.

• 30 C2 deposited onto fcc-Fe38 surface

(1/ps).

• NVT thermal annealing for 400 ps.

Yasuhito Ohta

Overview DFTB/MD of cap nucleation

C2 shooting and annealing on Fe38 particle

8

Y. Ohta, Y. Okamoto, A. J. Page, SI, K. Morokuma, ACS Nano 3, 3413 (2009)

• 10 trajectory replica.


9



Pentagon-first mechanism

Yoshida et al., Nano. Lett. (2008)

SWCNT nucleation:

driven by 5-/6-membered ring formation

from sp carbon

Fe3C nanoparticle



10


Cap structures are relatively random even in “slow” MD simulations


“Random” cap structures in CCVD simulations

11


Cap structures are relatively random even in “slow” DFTB/MD simulations

Carbon Feeding Rate Effect: M38C40+nC

A. Page, S. Minami, Y. Ohta, SI, K. Morokuma, Carbon 48, 3014 (2010)

Timescale

problem in MD

12

Overview Sidewall growth, defects

unpublished

Local Chirality Index (LOCI): Definition

Requires: i) System’s global principal axis in tube direction (GPAZ)

ii) Hexagon’s local principal axis normal to hexagon plane

Local chiral angle 1

13J. Kim, SI, K. Morokuma, Phys. Rev. Lett. 107, 15505 (2011).

Overview Chirality-controlled CCVD

Slow simulations of (5,5) and (8,0) SWCNT growth on Fe38

14J. Kim, A. J. Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 9311 (2012).

+30C

300 ps, 1500K

+30C

300 ps, 1500 K

Error bars: Standard deviation

Trajectory B

Trajectory A



CNT formation Interpretation

15


J. Kim, A. J. Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 9311 (2012).

+30C

300 ps, 1500K

+30C

300 ps, 1500 K

Error bars: Standard deviation

Trajectory D

Trajectory D


16J. Kim, A. J. Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 9311 (2012).

Statistics based on 10 trajectoriesa

Conclusions: (5,5) grows less defects than (8,0), heals faster!


“Confirmation” of Defect/Healing Growth by Experiment

17

Carbon 50, 2407 (2012)

cf: DFTB/MD growth model

Overview Experimental

Consensus among experimentalists and theoreticians:

18

Overview Summary of CCVD

• Chirality-controlled nucleation on Fe or Ni nanoparticles

is difficult! Higher temperature gives “cleaner” tubes

• Growth occurs on “long” timescales (carbon atom

addition on nanosecond scale)

• Atomically faster growth (=higher feedstock pressure)

increases concentration of tube defects

Suggested solutions:

• Avoid catalyst for nucleation,

• grow sidewalls in low pressure, high temperature

• from templates with established (n,m) chiral structure

Overview

Metal-free SWCNT synthesis from templates


19

20

Catalyst-free growth Growth from C60

Nano Lett. 10, 3343 (2010)

Nano Lett. 10, 3343 (2010)

Raman spectra AFM image

=248 cm-1 nm d = 0.86 nm

0.69 nm SWCNTs are not strictly

extensions of C60 cap; C30 too small?

RBM=288 cm-1

Tube length: 40 m mentioned


21

J. Liu, C. Wang et al.:

Vapor-phase “epitaxy”

of SWCNTs Nat. Commun. (2012)

2000 sccm CH4, 300 sccm H2, 900°C, 15 mins

Chirality confirmed; more successful!

Catalyst-free growth Growth from CNTs

22

22

J. Zhang, Z. F. Liu et al.: “Cloning” of SWCNTs Nano Lett. 9, 1673 (2009)

100 sccm CH4, 5 sccm C2H4, 975°C, 15 mins

Extension was short, maintenance of chirality not proven

23

SWCNT growth from [n]cycloparaphenylenes

We have a dream:

Omachi, Matsuura, Segawa, Itami, Angew. Chem. Int. Ed. 49, 10202 (2011)

Prof. ItamiNagoya University

Catalyst-free growth Growth from CPPs

24

SWCNT growth from [n]cycloparaphenylenes: Diels-Alder


E. H. Fort, L. T. Scott, J. Mater. Chem. 21, 1373 (2011), also cited by Wang & Liu

Basic idea: Example: (5,5) SWCNT1. Diels-Alder (DA)

Cycloaddition

2. H2 removal,

Re-aromatization

DA barrier heights for C2H2 +

E. H. Fort, L. T. Scott, J. Mater. Chem. 21, 1373 (2011)

Barriers very high!

(many other processes

may compete)


25


26

“Solution” to high barrier: Vapor phase pyrolysis

A. P. Rudenko, A. A. Balandin, M. M. Zabolotnaya, Russ. Chem. Bull. 10, 916 (1961)

Carbon production on SiO2 from:

CH4

C2H6

C2H4

C2H2


27

“Solution” to high barrier: Vapor phase pyrolysis

C2H radical (ethynyl) …

… as initiator of Diels-Alder C2H2 growth

Overview


(n,n) SWCNT growth from [n]CPPs


28

Growth from CPPs DFTB/MD Methodology

29

QM/MD simulations of [6]CPP growth to (6,6) SWCNTH. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)

• SCC-DFTB: Te = 1,500 K.

• MD; t=0.5 fs.

• NVT ensemble; Tn = 500 K.

• Nose-Hoover-Chain

thermostat.

• Initial annealing of CPP for 5

ps.

• 1 C2H2 added every 10 ps

with near random edge-

carbon.

• (Optional) manual hydrogen

removal at initial stage of

SWCNT growth.

30

Four possible sites for initial H abstraction or

C2H radical addition (sample: 100 trajectories)

42 39

17 1

Number of trajectories

Growth from CPPs Preliminary studies

Growth from CPPs DFTB/PRMD Simulations

31

QM/MD simulations of [6]CPP growth to (6,6) SWCNTH. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)

485 ps, each

frame = 0.2 ps


32

Growth mechanism of C2H and C2H2 addition to CPPsH. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)

Level: B3LYP/6-31G(d)

DA: High barrier Radical initiation:

It only takes 1 C2H!

Radical pathways: low-

energy


33

Growth speed of “CPP ring” versus “SWCNT belt”H. Li, A. J., Page, SI, K. Morokuma, ChemPhysChem 13, 1479 (2012)

Conformational

flexibility of CPPs

hinders growth!


34

Availability of extended (5,5) SWCNT capL. T. Scott et al., J. Am. Chem. Soc. 134, 107 (2012)

X-ray structure

Worth a try.

Overview


(n,m) SWCNT growth from chiral CPPs


35

36

SWCNT growth from chiral organic nanorings

Omachi, Segawa, Itami, Acc. Chem. Res. (2012)

Prof. ItamiNagoya University

Growth from CPPs Chiral SWCNT growth


37

QM/MD simulations of chiral SWCNTs from CPPsH. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)

• SCC-DFTB: Te = 1,500 K.

• MD; t=0.5 fs.

• NVT ensemble; Tn = 500 K.

• Nose-Hoover-Chain

thermostat.

• Initial annealing of CPP for 5

ps.

• 1 C2H2 added every 10 ps

with near random edge-

carbon.

• (Optional) manual hydrogen

removal at initial stage of

SWCNT growth.

(6,6)(8,0)

(4,3) (6,1)

(6,5) (10,1)


38


(6,5)

(10,1)


39


1. Addition of new hexagons

exclusively in armchair bay

2. In case of pure zigzag edge,

a) formation of heptagon

b) followed by 76/3

c) growth proceeds at

armchair edge

3. Growth mechanism in PRMD

follows Ding/Yakobson’s Screw-

dislocation-like (SDL) theory,

PNAS 106, 2506 (2009)


40

Growth termination for (8,0) SWCNTH. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)

“heptagon-first” 76/3New hexagon

@armchair

B3LYP/6-31G(d)


41

C2H-hexagon addition rates consistent with k ~ sin(H. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)

=27° =25°

=5° =8°

Indeed, for C2H addition in

PRMD, armchair edge is a

“cozy corner!”

Ding/Yakobson’s Screw-

dislocation-like (SDL) model,

PNAS 106, 2506 (2009)


42

C2H2-(DA)hexagon addition rates in (n,n) SWCNTs: k ~ dH. Li, A. J., Page, SI, K. Morokuma, J. Am. Chem. Soc. 134, 15887 (2012)

endo

exo

DA barrier H2 removal barrier

B3LYP/6-31G(d)

Overview

Summary: What did we learn?


43

Summary What did we learn?

44

• C2H radicals are feasible via C2H2 pyrolysis on SiO2.

• C2H radicals are able to remove H and add to

SWCNTs with little barrier.

• C2H radicals may initiate radical edge “polymerization”.

• Growth by C2H addition is controlled by SWCNT edge

structure alone

“Radically” New Chemistry:

• New hexagons are formed always near armchair site

(=“cozy corner” in Ding/Yakobson SDL-model)

Growth Mechanism in PRMD simulations:

Summary What did we learn?

45

• DA C2H2 implies hexagon addition rates k ~ d.

• At given C2H/C2H2 ratio, there should be optimal growth

conditions for certain d, combinations.

C2H/C2H2 ratio may allow control of arbitrary (n,m)!!

Overview

What is next?


46


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What is next?

Theoreticians need to address the following urgent issues:

-Timescale problem in MD simulations, e.g. by KMC, will allow to study:

-Role of carbide formation

-Role of defect healing

-More precise atomistic growth mechanisms (no timescale problem of

MD, no arbitrariness as in PRMD)

-Investigate possible mechanism for chirality control at time of nucleation

-Investigate role of hydrogen in greater detail

-Effect of various catalyst substrates in atomic detail

-Effect of etching gases and water

Thank you.


48

Appendix

Appendix

D. A. Gomez-Gualdron, G. D. McKenzie, J. F. J. Alvarado, P. B. Balbuena ACS Nano 6, 720 (2012)

“Random” cap structures in CCVD simulations

49

Overview SIMCAT/MD of cap nucleation

Cap structures are relatively random even in “slower” SIMCAT/MD simulations

Classical reactive MD simulations of cap formation on supported Nix

Experiments for individual SWCNT nucleation and growth

50

Nat. Mater. 11, 231 (2012)

Measuring growth rates v of individual SWCNTs by Raman

Overview Experimental evidence

Nano Lett. 10, 3343 (2010)

Notes:

•baked at 150° in air to remove

solvent (toluene)

•Thermal oxidation in air at 300-

500°C for 30 mins

•Remove “amorphous carbon”:

Temperature up to 900°C in

presence of water, then cool

down

•900°C annealing for 3 mins

(presumably in vacuum)

•20 mins 20 sccm ethanol in 30

sccm Ar/H2 at 900°C (low sccm!)


51

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Scheme to study AC CNT growth by adding C2H radicals

(1) Starts from one initial structure, and then add 6 times C2H radical to

obtain 6 parallel trajectories every 10 ps;

(2) Select two trajectories that could produce uniform AC NT to continue.

Principles for rule (2):

First, whether new 6-m ring formed;

Then whether C2H insert to the edge

of SWCNT;

Then whether H atoms on the rim of

SWCNT abstracted

Then whether H atoms on the sidewall of

SWCNT abstracted

Then whether C2H added to sidewall

53/25

TimescalePRMD

Parallel Replica MD [A. F. Voter, PRB 57, R13985 (1998)]

Disadvantage: computationally very expensiveAlternatives: Metadynamics, umbrella sampling, etc.

Problem there: MD depends on algorithm/bias potential

Technology

SWCNT Growth from Chiral and Achiral Carbon Nanorings: Prediction of Chirality and Diameter Influence on Local Growth Rates