NIST NASA CNT Workshop 2007 Bz Poster
1
Production of Highly-Pure, Semitransparent Single-Walled Carbon Nanotube Membranes for Standard Reference Materials and Conductive Thin Films B. Zhao , H. Hu, D. B. Geohegan, A. A. Puretzky, D. Styers-Barnett, I. Ivanov, P. Britt and C. M. Rouleau the Center for Nanophase Materials Sciences and Materials Science & Technology Division Oak Ridge National Laboratory, Oak Ridge, TN Conclusion A multi-step purification method, including nitric acid oxidation, thermal annealing, H 2 O 2 oxidation, and surfactant washing, have applied to purify SWNTs. The highest purity of purified SWNTs reaches 232% against reference sample. Prototype solid-sample SWNT reference materials have been produced by depositing highly-pure SWNTs on TEM grids for TEM and optical absorption spectroscopy assessment on the same solid sample. The surface resistance of the SWNT films, which is 97ohm/sq at T=65%, can also be used to characterize the reference material. Future Work Continue on optimizing purification method of SWNTs. increase purity, decrease metal residue, improve yield… Optimization of SWNT thin film production to achieve high transmittance and low surface resistance. 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. Characterization of SWNTs 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 Results: • NIR: very high purity 232%! • Raman: D/G ratio decreased from 9:1 to 30:1. • TGA: metal residue decreased to 1wt%. • Dispersible by DMF, SDS/H 2 O, etc. 0.26 0.37 0.39 0.58 0.58 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 Conditi on 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 TGA data Raman Spectroscopy 500 1000 1500 0 20000 40000 Raman Intensity (a.u.) Raman Shift (cm -1 ) 0 10000 20000 tangential mode disorder band Radial mode l exc = 633 nm AP-SWNT G/D=9:1 P-SWNT G/D=30:1 100 200 300 400 500 600 700 800 900 1000 0 20 40 60 80 100 655 residue: 1% Purified SWNT Weight (%) Temperature ( o C) 0 20 40 60 80 100 586 residue: 10% AP-SWNT 0 1 2 0.0 0.5 1.0 ref. sample*: A(S):[A(S)+A(B)] = 0.141 *M. E. Itkis, et. al. Nano Lett. 2003. Solution Phase NIR Spectroscopy For Carbonaceous Purity Study 400 600 800 1000 1200 0.00 0.05 0.10 0.15 0.20 0.25 0.00 0.05 0.10 0.15 0.20 0.25 Absorption Intensity (a.u.) Wavelength (nm) P-SWNT A(S) A(B) AP-SWNT A(S) A(B) A(S):[A(S)+A(B)] = 0.072 A(S):[A(S)+A(B)] = 0.326 Compared to ref. sample*, our SWNT’s purity are: As-prepared SWNT: 50% Purified SWNT: 232% Co-Ni/C target Furnace: 1150 o C Ar 1000 sccm laser carbon nanotube deposition quartz tube Pressure: 500 Torr 1J/500Hz/1ms 10 gram scale production Single walled carbon nanotubes Production of SWNTs by Laser Ablation 1) HNO 3 12M/4h 2) centrifuge/decantation Acid Treated SWNTs 30% H 2 O 2 treatment Raw SWNTs Purified SWNTs Ultra-Purified SWNTs 500 o C, 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% Production of Single Walled Carbon Nanotubes P-SWNT dispersion (1) filtration (2) deposition grid before deposition grid after deposition 500 1000 1500 2000 2500 0 10 20 30 40 50 60 70 80 90 100 grid 1 grid 2 grid 3 Transmittance (%) Wavelength (nm) 10 um 200 nm solution filter membrane transparent thin film Production of SWNT thin films SWNT film on TEM grid 60 65 70 75 80 85 90 95 100 100 1000 SWNT film SWNT film (SOCl 2 doped) Surface Resistance (ohm/sq) Transmittance (%, at 550nm) 4 point probe SWNT Films on Glass: Optical Transmittance and Surface Resistance Study SWNT Films on Substrates and Grids Transmittance measurement Surface resistance measurement Standard sample for purity evaluation SWNT Films on TEM Grids: Standard Sample for Purity Study optical spectra Abstract The first prototype solid-sample SWNT reference materials have been produced by depositing highly-pure SWNTs on TEM grids to permit both transmission electron microscopy and optical absorption spectroscopy on the same solid sample. The electrical conductivity of the SWNT films can also be used to characterize the reference material by depositing the same semitransparent SWNT membranes on glass substrates. SWNTs were synthesized by high-power (600 W) laser ablation of carbon targets with Ni and Co as catalysts in 20 gram/run batches. The purification was carried in 10 gram batches, following nitric acid refluxing, controlled-pH water-extraction, and hydrogen peroxide treatment. The purity of the purified SWNTs was evaluated with 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. Prototype standard SWNT reference materials were produced by depositing purified SWNTs on TEM grids, which can be used for purity comparison with other SWNT samples. Transparent thin films of purified SWNTs were produced by dispersion/filtration/transferring method. The surface resistance of SWNT films is lower than 100 ohm/sq with transmittance of 65%, which is comparable to the best reported SWNT thin films. Purity assessment based on NIR spectra Direct observation of SWNT sample via TEM Both 500 1000 1500 2000 2500 0 20 40 60 80 100 Transmittance (%) Wavelength (nm) 93 89 84 73 64 550nm Transmittance (550nm) SEM and TEM images of SWNTs metal residue amorphous carbon
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Transcript of NIST NASA CNT Workshop 2007 Bz Poster
Production of Highly-Pure, Semitransparent Single-Walled Carbon Nanotube
Membranes for Standard Reference Materials and Conductive Thin Films
B. Zhao, H. Hu, D. B. Geohegan, A. A. Puretzky, D. Styers-Barnett, I. Ivanov, P. Britt and C. M. Rouleau
the Center for Nanophase Materials Sciences and Materials Science & Technology Division
Oak Ridge National Laboratory, Oak Ridge, TN
Conclusion 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.
Prototype solid-sample SWNT reference materials have been produced by
depositing highly-pure SWNTs on TEM grids for TEM and optical absorption
spectroscopy assessment on the same solid sample.
The surface resistance of the SWNT films, which is 97ohm/sq at T=65%, can
also be used to characterize the reference material.
Future Work Continue on optimizing purification method of SWNTs.
increase purity, decrease metal residue, improve yield…
Optimization of SWNT thin film production to achieve high transmittance and low
surface resistance.
AcknowledgementThis 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.
Characterization of SWNTs
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
Results:
• NIR: very high purity 232%!
• Raman: D/G ratio decreased from 9:1
to 30:1.
• TGA: metal residue decreased to 1wt%.
• Dispersible by DMF, SDS/H2O, etc.
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
Conditi
on
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
TGA data
Raman Spectroscopy
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
G/D=9:1
P-SWNT
G/D=30:1
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
ref. sample*: A(S):[A(S)+A(B)] = 0.141
*M. E. Itkis, et. al. Nano Lett. 2003.
Solution Phase NIR Spectroscopy
For Carbonaceous Purity Study
400 600 800 1000 12000.00
0.05
0.10
0.15
0.20
0.25
0.00
0.05
0.10
0.15
0.20
0.25
Absorp
tion Inte
nsity (
a.u
.)
Wavelength (nm)
P-SWNT
A(S)
A(B)
AP-SWNT
A(S)
A(B)
A(S):[A(S)+A(B)] = 0.072
A(S):[A(S)+A(B)] = 0.326
Compared to ref. sample*, our SWNT’s purity are:
As-prepared SWNT: 50%
Purified SWNT: 232%
Co-Ni/C target
Furnace: 1150oC
Ar
1000 sccm
laser
carbon
nanotube
deposition
quartz tube
Pressure: 500 Torr
1J/500Hz/1ms
10 gram scale production
Single walled
carbon nanotubes
Production of SWNTs
by Laser Ablation
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%
Production of Single Walled
Carbon Nanotubes
P-SWNT dispersion
(1) filtration
(2) deposition
grid
before
deposition
grid
after
deposition
500 1000 1500 2000 25000
10
20
30
40
50
60
70
80
90
100
grid 1
grid 2
grid 3
Tra
nsm
itta
nce (
%)
Wavelength (nm)
10 um
200 nm
solution filter
membrane
transparent
thin film
Production of SWNT thin films SWNT film on TEM grid
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
SWNT Films on Glass:
Optical Transmittance and Surface Resistance Study
SWNT Films on Substrates and Grids
Transmittance measurement
Surface resistance measurement
Standard sample for purity evaluation
SWNT Films on TEM Grids:
Standard Sample for Purity Study
optical
spectra
Abstract
The first prototype solid-sample SWNT reference materials have been
produced by depositing highly-pure SWNTs on TEM grids to permit both
transmission electron microscopy and optical absorption spectroscopy on
the same solid sample. The electrical conductivity of the SWNT films can
also be used to characterize the reference material by depositing the
same semitransparent SWNT membranes on glass substrates. SWNTs
were synthesized by high-power (600 W) laser ablation of carbon targets
with Ni and Co as catalysts in 20 gram/run batches. The purification was
carried in 10 gram batches, following nitric acid refluxing, controlled-pH
water-extraction, and hydrogen peroxide treatment. The purity of the
purified SWNTs was evaluated with 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. Prototype
standard SWNT reference materials were produced by depositing
purified SWNTs on TEM grids, which can be used for purity comparison
with other SWNT samples. Transparent thin films of purified SWNTs were
produced by dispersion/filtration/transferring method. The surface
resistance of SWNT films is lower than 100 ohm/sq with transmittance of
65%, which is comparable to the best reported SWNT thin films.
Purity assessment based
on NIR spectra
Direct observation of
SWNT sample via TEM
Both
500 1000 1500 2000 25000
20
40
60
80
100
Tra
nsm
itta
nce (
%)
Wavelength (nm)
93
89
84
73
64550nm Transmittance (550nm)
SEM and TEM images of
SWNTs
metal residue
amorphous carbon
