1. 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

2. Objective of Single-Wall Carbon Nanotubes
Purification,
Processing,
and Application
 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

3. Synthesis of Single-Wall Carbon Nanotubes
by Laser Ablation Method
carbon target carbon
nanotube
deposition
laser
Ar
1000 sccm quartz tube
Furnace: 1150oC Pressure: 500 Torr
plume
Ni-Co carbon
1J/500Hz/1ms
nanotubes
Catalyst free
100J/5Hz/20ms
carbon
nanohorns
 10 gram scale production
 carbon nanomaterials with different forms

4. Morphology of Single-Wall Carbon Nanotubes
Synthesized by Laser Ablation Method
0.5% Ni-Co 1.0% Ni-Co 1.5% Ni-Co
What methods shall we use to evaluate the purity of SWNTs?

5. Purity Evaluation by Solution Phase NIR Method
0.1
R X
AA(S,R) AA(S,X)
Absorbance
0.0
0.4
AA(T,X)
AA(T,R)
0.2
SWNTs: 67%
REFERENCE (R) CARBONACEOUS
IMPURITIES: 33%
0.0
8000 10000 12000 8000 10000 12000
-1
Wavenumber (cm )
AA(S, R) AA(S, X)
= 0.141 = 0.095
AA(T, R) AA(T, X)
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

6. Purity Evaluation of Carbon Nanotubes
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

7. 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
0.7
0.58 0.58
0.6
0.5
0.39
0.37
0.4
0.3 0.26
0.2
0.1
0
12M /4h 7M /18h 3M /48h 3M /18h 7M /6h
The optimized nitric acid treatment condition is 3M/18h and 7M/6h

8. Carbon Nanotube Purification Method
Raw SWNTs Purity: 30~60%
Metal: 10~15wt%
• remove metal catalyst
• remove amorphous carbon
1) HNO3 12M/4h
• exfoliate SWNT bundle
2) centrifuge/decantation
• introduce functionalities
Purity: 80~120%
Acid treated SWNTs Metal: 2~3wt%
Yield: 40~60%
• remove amorphous carbon 30% H2O2 treatment
Purity: 160~200%
Purified SWNTs
Metal: 3~5wt%
Yield: 8~10%
• remove amorphous carbon 500oC, air, 30min
• remove metal catalyst wash with 6M HCl
dry under vacuum
ultra-Purified SWNTs Purity: 210~230%
Metal: ~1wt%
Yield: 4~5%

9. SEM and TEM Images of As-Prepared SWNTs
500 nm
SWNTs before purification

10. SEM and TEM Images of Purified SWNTs
500 nm
SWNTs after purification

11. Optical Spectra of SWNTs (solution phase)
1.0
raw SWNTs purity: 30%
acid treated SWNTs 40%
Absorption Intensity (a.u.)
0.8 washed SWNTs 112%
purified SWNTs 214%
ultra-purified SWNTs 232%
0.6
0.4
0.2
0.0
400 600 800 1000 1200 1400
-1
Frequency (cm )

12. Raman Spectra of SWNTs
Radial disorder tangential
mode band mode
Raman Intensity (a.u.) 20000
AP-SWNT
10000 D/G=0.11
0
40000
P-SWNT
20000
D/G=0.03
0
500 1000 1500
-1
Raman Shift (cm )
lexc = 633 nm

13. Thermal Gravimetric Analysis of SWNTs
100 1.0
586
80
60 0.5
40
Weight (%)
20 AP-SWNT residue: 10%
0.0
0 2
100
655
80
60 1
40
20 Purified SWNT
residue: 1%
0
0
100 200 300 400 500 600 700 800 900 1000
o
Temperature ( C)

14. Production of SWNT Transparent
Conductive Thin Films
Production of CNT
Transparent Thin Films
OLED have CNT anodes
Z. Wu, et. al. Sci. 2004
J. Li. et. al. NanoLett. 2006
a maximum light output of
3500 cd/m2 and a current
efficiency of 1.6 cd/A
SWNT FET
(150 nm thick SWNT film)

15. SWNT Transparent Thin Films
Produced at ORNL
SWNT film on TEM grid
10 um
solution filter transparent
membrane thin film
200 nm
Production of SWNT thin films
SWNT transparent thin films were produced by a
dispersion/filtration/transferring method.

16. NIR Spectra of SWNT Thin Films
100
Absorption Intensity (a.u.)
80
Surface Resistance (ohm/sq)
60 1000
93
40 89
84 4 point
probe
73 100
20 550nm SWNT film
64 SWNT film (SOCl2 doped)
Transmittance (550nm) 60 65 70 75 80 85 90 95 100
Transmittance (%, at 550nm)
0
500 1000 1500 2000 2500
Wavelength (nm)
The surface resistance of SWNT film (63% transmittance) can be 97ohm/sq.

17. Properties of Elastin
insoluble
stretch relax controlled by pH
and temperature
elastin molecule
soluble
cross-link
 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.

18. Production of Elastin/SWNT Composite
SWNTs
SWNT/
elastin elastin
solution solution
sonication 100 nm
SWNT/elastin composite

19. TEM image of SWNT/elastin thin film
20 nm
Large bundles of SWNTs
small bundles of SWNTs
SWNT network embedded in elastin thin film

20. 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.

21. 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.