Purification of Single-Walled Carbon Nanotubes and the Production

of Nanotube/Elastin composite

B. Zhao, A. A. Puretzky, D. Styers-Barnett, H. Hu, I. Ivanov, C. M. Rouleau, and D. B. Geohegan

the Center for Nanophase Materials Sciences and Material Science & Technology Division

Oak Ridge National Laboratory, Oak Ridge, TN

Abstract

Single-walled carbon nanotubes (SWNTs) have great potentials in many applications

because of their unique structure and properties. We report a scalable purification of

SWNTs synthesized by high-power laser vaporization, and the production of SWNT/elastin

composites. Such material would be promise for new generalization of biocomposites.

SWNTs were synthesized by high-power (600 W) laser ablation facility of carbon targets

with Ni and Co as catalysts at 20 gram scale. The purification carries out at 10 gram per run

by using nitric acid refluxing, controlled-pH water-extraction, and hydrogen peroxide

treatment. The purification efficiency of each step was monitored by SEM, TEM, TGA, and

solution phase NIR spectroscopy. The purified SWNTs contain metal residue less than 1%

and carbonaceous purity among the highest ever reported.

Purified SWNTs are used to make nanotube/elastin composites. SWNT/elastin composite

is produced at controlled temperature and pH conditions. The electrical and mechanical

properties of SWNT/elastin composite thin film are studied.

Conclusion

SWNTs can be synthesized by high power laser ablation at 20 gram scale.

A multi-step purification method, including nitric acid oxidation, thermal annealing, H2O2

oxidation, and surfactant washing, have applied to purify SWNTs. The highest purity of

purified SWNTs reaches 232% against reference sample.

SWNT/elastin composite material is produced at controlled pH and temp. conditions, which

is a potential material in biological application.

Future Work

Continue on optimizing purification method of SWNTs.

Study the biocompatibility and conductivity of SWNT/elastin composite material.

Application of SWNT/elastin composite material in artificial skin.

Acknowledgement

This research was conducted in the Functional Nanomaterials Theme at the Center for

Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the

Division of Scientific User Facilities, U.S. Department of Energy.

Collaboration: please visit http://www.cnms.ornl.gov for user project information.

Synthesis of Single-Wall Carbon Nanotubes

by Laser Ablation Method

Co-Ni/Dylon target

Furnace: 1150oC

Ar

1000 sccm

laser

carbon

nanotube

deposition

quartz tube

Pressure: 500 Torr

Characterization of as-prepared SWNTs and Purified SWNTs

TGA data

Purity Evaluation of SWNTs

Tools to assess SWNT purity:

SEM and TEM – amorphous carbon and defect sites

TGA – metal content

NIR spectroscopy – interband transition

Raman spectroscopy – D/G ratio

Production of SWNT/Elastin Composite Material

Raman Spectroscopy

100J/5Hz/20ms

1J/500Hz/1ms

10 gram scale production

carbon materials with different forms

catalyst

free

carbon

nanotubes

carbon

nanohorns

Carbon Nanotube Purification Method

1) HNO3 12M/4h

2) centrifuge/decantation

Acid treated SWNTs

30% H2O2 treatment

Raw SWNTs

Purified SWNTs

ultra-Purified SWNTs

500oC, air, 30min

wash with 6M HCl

dry under vacuum

• remove metal catalyst

• remove amorphous carbon

• exfoliate SWNT bundle

• introduce functionalities

Purity: 30~50%

Metal: 10~15wt%

Purity: 160~200%

Metal: 3~5wt%

Yield: 8~10%

Purity: 210~230%

Metal: ~1wt%

Yield: 4~5%

• remove amorphous carbon

• remove amorphous carbon

• remove metal catalyst

Purity: 80~120%

Metal: 2~3wt%

Yield: 40~60%

Purity evaluation by solution phase NIR method

8000 10000 120000.0

0.2

0.4

REFERENCE (R)

AA(T,R)

Absorb

ance

Wavenumber (cm-1)

0.0

0.1

AA(S,R)

R

8000 10000 12000

AA(T,X)

SWNTs: 67%

CARBONACEOUS

IMPURITIES: 33%

XAA(S,X)

AA(S, R)

AA(T, R)= 0.141

AA(S, X)

AA(T, X)= 0.095

Purity of X against R = (0.095/0.141)*100% =67%

M. E. Itkis, et. al. Nano Lett. 2003, 3, 309.

Amphiphilic fibrous proteins (contains proline, glycine, lycine, etc.).

Cross-linked polypeptide chains to form rubberlike, elastic fibers.

Reversible uncoiling/recoiling forms based on pH and temperature.

relaxstretch

elastin molecule

cross-link

controlled by pH

and temperature

400 600 800 1000 1200 14000.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Ab

so

rptio

n I

nte

nsity (

a.u

.)

raw SWNTs purity: 30%

acid treated SWNTs 40%

washed SWNTs 112%

purified SWNTs 214%

ultra-purified SWNTs 232%

Results:

• NIR: very high purity 232%!

• Raman: D/G ratio decreased from 0.11 to 0.03

• TGA: metal residue decreased to 1%

• Dispersible by DMF, SDS/H2O, etc.

100 200 300 400 500 600 700 800 900 10000

20

40

60

80

100655

residue: 1%Purified SWNT

Weig

ht (%

)

Temperature (oC)

0

20

40

60

80

100

586

residue: 10%AP-SWNT

0

1

2

0.0

0.5

1.0

500 1000 1500 2000

0

20000

40000

Ultra-purified SWNTs

D/G = 0.03

Ram

an Inte

nsity (

a.u

.)

Frequency (cm-1)

0

10000

20000As-prepared SWNTs

D/G = 0.11

SEM and TEM images of Raw SWNTs

Synthesized with Different Amount of Catalysts

0.5% Ni-Co

1.0% Ni-Co

1.5% Ni-Co

Images of Purified SWNTs

Solution Phase NIR Spectroscopy

soluble

insoluble

Elastin

- elastic fiber

100 nmMethod

SWNTs

sonicationelastin

solution

SWNT/elastin

solution

SWNT/elastin composite

TEM image of SWNT/elastin thin film

20 nm

SWNT network

embedded in elastin

500 1000 1500 20000.0

0.2

0.4

0.6

0.8

1.0

1.2

Ab

sorp

tion

In

ten

sity

(a

.u.)

Wavelength (nm)

SWNT/elastin

elastin

0 . 2 6

0 . 3 70 . 3 9

0 . 5 8 0 . 5 8

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

12M /4h 7M /18h 3M /48h 3M /18h 7M /6h

Nitric Acid Effects to SWNTs

Condition

Purity

(%)

Yield

(%)

Met. Residue

(wt%)

Purification

Effect*

12M/4h 51 52 1.7 0.26

7M/18h 88 42 2 0.37

3M/48h 74 53 2 0.39

3M/18h 83 70 2.2 0.58

7M/6h 80 73 2.4 0.58

* Purification Effect = Purity X Yield