Purification of Single-Walled Carbon

Nanotubes and the Production of SWNT

Thin films and SWNT/Elastin composites

B. Zhao, D. B. Geohegan, A. A. Puretzky, H. Hu,

D. Styers-Barnett, I. Ivanov, P. Britt and C. M. Rouleau

the Center for Nanophase Materials Sciences

and Material Science & Technology Division

Oak Ridge National Laboratory, Oak Ridge, TN

SWNT purification is an important objective:

Develop SWNT standard sample

Evaluate commercial available products

High purity SWNTs for numerous applications

Toxicity study of SWNTs

SWNT thin film processing

SWNT/polymer composite materials

Objective of Single-Wall Carbon Nanotubes

Purification,

Processing,

and Application

Furnace: 1150oC

Ar1000 sccm

laser

carbon target carbon

nanotube

deposition

Synthesis of Single-Wall Carbon Nanotubes

by Laser Ablation Method

quartz tubePressure: 500 Torr

100J/5Hz/20ms

1J/500Hz/1ms

10 gram scale production

carbon nanomaterials with different forms

Catalyst free

carbon

nanotubes

carbon

nanohorns

Ni-Co

plume

0.5% Ni-Co 1.5% Ni-Co1.0% Ni-Co

Morphology of Single-Wall Carbon Nanotubes

Synthesized by Laser Ablation Method

What methods shall we use to evaluate the purity of SWNTs?

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. Solution phase NIR spectra is useful to evaluate

carbonaceous purity of SWNTs

Comprehensive assessment of SWNT purity:

SEM and TEM – morphology of SWNTs

amorphous carbon and defect sites

TGA – metal residue content

inorganic impurities

NIR spectroscopy – interband transition

carbonaceous purity

Raman spectroscopy – D/G ratio

amorphous carbon and defect sites

Purity Evaluation of Carbon Nanotubes

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

Effects of Nitric Acid Treatment

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

The optimized nitric acid treatment condition is 3M/18h and 7M/6h

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: 30~60%

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%

500 nm

SWNTs before purification

SEM and TEM Images of As-Prepared SWNTs

500 nm

SWNTs after purification

SEM and TEM Images of Purified SWNTs

400 600 800 1000 1200 14000.0

0.2

0.4

0.6

0.8

1.0

Frequency (cm-1)

Absorp

tion Inte

nsity (

a.u

.)

raw SWNTs purity: 30%

acid treated SWNTs 40%

washed SWNTs 112%

purified SWNTs 214%

ultra-purified SWNTs 232%

Optical Spectra of SWNTs (solution phase)

500 1000 15000

20000

40000

Ram

an In

tensity (

a.u

.)

Raman Shift (cm-1)

0

10000

20000

tangential

modedisorder

band

Radial

mode

lexc = 633 nm

AP-SWNT

D/G=0.11

P-SWNT

D/G=0.03

Raman Spectra of SWNTs

100 200 300 400 500 600 700 800 900 10000

20

40

60

80

100655

residue: 1%Purified SWNT

We

igh

t (%

)

Temperature (oC)

0

20

40

60

80

100

586

residue: 10%AP-SWNT

0

1

2

0.0

0.5

1.0

Thermal Gravimetric Analysis of SWNTs

Z. Wu, et. al. Sci. 2004

Production of SWNT Transparent

Conductive Thin Films

J. Li. et. al. NanoLett. 2006

OLED have CNT anodes

Production of CNT

Transparent Thin Films

a maximum light output of

3500 cd/m2 and a current

efficiency of 1.6 cd/A

SWNT FET

(150 nm thick SWNT film)

10 um

200 nm

solution filter

membrane

transparent

thin film

Production of SWNT thin films

SWNT film on TEM grid

SWNT Transparent Thin Films

Produced at ORNL

SWNT transparent thin films were produced by a

dispersion/filtration/transferring method.

500 1000 1500 2000 25000

20

40

60

80

100

A

bso

rptio

n I

nte

nsity (

a.u

.)

Wavelength (nm)

NIR Spectra of SWNT Thin Films

93

89

84

73

64550nm

Transmittance (550nm) 60 65 70 75 80 85 90 95 100

100

1000

SWNT film

SWNT film (SOCl2 doped)

Su

rfa

ce

Re

sis

tan

ce

(o

hm

/sq

)

Transmittance (%, at 550nm)

4 point

probe

The surface resistance of SWNT film (63% transmittance) can be 97ohm/sq.

relaxstretch

elastin molecule

cross-link

controlled by pH

and temperature

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.

soluble

insoluble

Properties of Elastin

100 nm

SWNTs

sonication

elastin

solution

SWNT/elastin composite

SWNT/

elastin

solution

Production of Elastin/SWNT Composite

20 nm

TEM image of SWNT/elastin thin film

SWNT network embedded in elastin thin film

Large bundles of SWNTs

small bundles of SWNTs

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 transparent thin films were produced by dispersion/centrifuging/

transferring method. The surface resistance can be 97ohm/sq at 64%

transmittance.

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.