Post on 15-May-2020
Carbon Nanotube and Graphene Quantification
Kyle DoudrickSRC TeleSeminarJuly 11th 2013
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Current Methods Available
• Thermogravimetric analysis• Only accounts for weight change
• Radiolabeling• Must be pre-labled• Very sensitive
• Fluorescence• Only valid for semiconducting SWCNTs
• Electrophoresis• Sensitive• Anything dark in color may interfere• Not all CNTs will stay at gel interface
• Metal analysis (ICP)• Only valid for CNTs containing metals• Sensitive
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Method Development
Doudrick, K., P. Herckes, P. Westerhoff. Detection of carbon nanotubes in environmental matrices using programmed thermal analysis. Environ. Sci. Technol., 46(22), 12246–12253, 2012.
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Instrument used to developed analytical method
• Sunset Laboratory (Forest Grove, OR) Thermal Optical Transmittance
• Traditionally used to measure soot in air using NIOSH standards (Method 5040B) and also organic (OC) and elemental carbon (EC) in air pollution studies
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Sample Filters
Sample Holder
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Thermogram and carbon definitions
Sucrose
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CNT Characterization
CNT ID CNT Type State Puritya Metal Contentb
Outer Diameter (nm)
Inner Diameter (nm)
Length (µm)
MW-O MWCNT Raw >95% <6% 20-30 5-10 10-30 MW-P MWCNT Purified >98% <2% 20-30 5-10 10-30 MW-F MWCNT Functionalized >99.9% <0.01% 20-30 5-10 10-30 MW-15 MWCNT Raw >95% <5% 7-15 3-6 0.5-200 MW-20 MWCNT Raw >95% <5% 10-20 5-10 0.5-200 MW-30 MWCNT Raw >95% <5% 10-30 5-10 0.5-500 MW-100 MWCNT Raw >95% <5% 60-100 5-10 0.5-500 MW-OH MWCNT Functionalized >95% <1.5% 8-15 3-5 10-50 MW-COOH MWCNT Functionalized >95% <1.5% 8-15 3-5 10-50 MW-15Gc MWCNT Annealed >97% <1% 7-15 3-6 0.5-200 MW-Mitsui MWCNT Raw >98% <1% 20-70 NA NA MW-Arc MWCNTd Raw <50% 0% 5-10e NA NA SW SWCNT Raw <50% <10% 1.1 NA 0.5-100 SW-65 SWCNT Purified <75% <10% 0.8 NA 0.45-2
aCNT content reported by manufacturer. MW-P and MW-F calculated assuming no amorphous carbon remaining.bMetal content reported by manufacturer except for MW-F and MW-P determined using energy dispersive X-ray spectroscopy and MW-15G using thermogravimetric analysis.cMW-15 annealed at ~2000°C in UHP He.dSynthesized using arc method; all others are CVD.eObtained from TEM images; all others reported by manufacturer. 7
CNT Thermograms
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FID
Sig
nal (
for
CN
Ts)
Tem
pera
ture
(°C
)
Time (seconds)
TemperatureMW-OMW-PMW-FMW-15MW-20MW-30MW-100MW-OHMW-COOHMW-15GMW-MitsuiMW-ArcSW
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0100200300400500600700800900
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Tem
pera
ture
(°C
)
Perc
ent C
NT
Mas
s Rem
aini
ng
Time (seconds)
MW-ArcMW-15MW-FMW-OSW-65MW-PTemperature
01002003004005006007008009001000
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100%
Tem
pera
ture
(°C
)
Time (seconds)
Perc
ent C
NT
Mas
s Rem
aini
ng
SW-65SWMW-FMW-OMW-15MW-15GMW-MitsuiMW-Arc
Inert Conditions
Oxidizing Conditions
Using NIOSH 5040B method, some CNTs desorb/oxidize at higher temperatures
These are classified as “weak,” while all that withstand higher temps are “strong”
Some CNTs oxidize very early on at low temps
These are classified as “weak,” while all that withstand higher temps are “strong”
Method Development
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120%
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Perc
ent C
NT
Mas
s Rem
aini
ng
Time (seconds)
MW-O-675MW-O-700MW-O-750MW-O-870
Method Development – Inert Conditions
• Examined different maximum temperature conditions for a representative weak CNT• 675 °C was the max temp where no CNT loss occurred
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Can we measure CNTs Directly (w/o extraction)?
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Tem
pera
ture
(°C
)
Perc
ent M
ass R
emai
ning
Time (seconds)
MilkHuman serumUrban airSedimentMW-FMW-15MW-ArcTemperature
At ~95% weak CNT mass remaining, there is still 70% urban air, 60% sediment, 50% serum, and 30% milk. Sediments are the most challenging with <10% interference with even the strongest CNT
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Matrix Interference
0%
10%
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50%
Perc
ent N
EC
in S
ampl
e Simple Complex• NEC: Non-CNT
Elemental Carbon (i.e., soot, PEC)
• Simple: NEC < 10%
• Complex: NEC ≥ 10%
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Using Raman to Determine CNT Thermal Classification
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Inte
snity
Raman Shift (cm-1)
MW-PMW-Arc
G-bandD-band
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Inte
nsity
Raman Shift (cm-1)
SW
MW-P
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CNT Thermal Classification
IG
ID0.0
0.4
0.8
1.2
1.6
2.0
600 700 800 900 1000
I D/I
GR
atio
Oxidation Temperature at 50% Mass Loss (°C)
R2 = 0.96Weak
Strong
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Extraction
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Extraction is key – CNT Recovery
• Eight different reagents (acids, alkalis, enzymes)• 60 °C for 24 hrs with mixing• Centrifugal separation with water washing in between• Quantified using PTA
0%
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100%
CN
T Pe
rcen
t Rec
over
y S-CNT
W-CNT
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How to Compare Reagents and Analyze Damage to CNTs?
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Tem
pera
ture
(°C
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FID
Sig
nal
Time (s)
Untreated
Water
Solvable
Hydroxide
Nitric
Sulfuric
Hydrochloric
Hydrofluoric
Peroxide
Proteinase K
F-CNT
Temperature12
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5
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Thermograms are overly complicated!
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Tim
e to
50%
Mas
s Los
s (s)
Frac
tion
of T
otal
Pea
k A
rea
500 °C 550 °C 600 °C 650 °C 700 °C 750 °C Time to 50%
Thermogram Analysis – Weak CNTs
• Solvable, HCl, HF, and pro K showed no change (<5%)• HNO3 had a 5-10% change• “Water,” NaOH, H2O2, and H2SO4 had a 10-20% change• Functionalized CNTs had a 40% decrease
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600
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750
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1.0
Tim
e to
50%
Mas
s Los
s (s)
Frac
tion
of T
otal
Pea
k A
rea
700 °C 750 °C 800 °C 910 °C Time to 50%
Thermogram Analysis – Strong CNTs
• Solvable, HF, HNO3, H2O2, NaOH, and H2SO4, and pro K showed no change (<5%)• “Water” and HCl had a 5-10% change
• So – HNO3, HCl, and HF should be okay to use if separation method can be improved19
Separation
• Filtration was only optimal for CNTs that were aggregated – Functionalized or fully dispersed CNTs passed partly through the filter
• Filtration does not allow for washing of sample to remove interferences
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Reagent selection – Instrument Damage
• Possibly residual acids cause corrosion• Additional washing steps could be incorporated into method, but this
may reduce recovery
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Application – Cyanobacteria
• Cyanobacteria was a complex matrix and pretreatment was necessary
• Solvable or HNO3 was adequate to dissolve CB
• Raman revealed the CNT to correctly to a strong CNT
CNT Concentration, µg CNT/g CB (CNT
mass, µg)Recovery
10 (0.51) 160 ± 29%
54 (2.7) 99 ± 1.9%
220 (11) 96 ± 3.0%0
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FID
Sign
al
Tem
pera
ture
(C)
Time (s)
Inert Oxidizing
CNTs
ID/IG = 0.26 ± 0.08
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Application – Rat lungs• Solvable, proteinase K, nitric acid, and ammonium hydroxide were
optimal at dissolving tissue• Solvable emerged as the best solution because of its ability to
remove background carbon, form compact CNT pellets, and minimize damage to the instrument
(b)
(e)
(d)(c)(a)
(g)(f) (h)
Centirfuged rat lung tissue after treatment with the chemical digestion reagents: (a) Solvable, (b) hydroxide, (c) nitric, (d) sulfuric, (e) hydrochloric, (f) hydrofluoric, (g) peroxide, and (h) proteinase K.
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Car
bon
Mas
s (µg
)
Tem
pera
ture
(°C
)
Time (s)
TemperatureFID
(a)
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Car
bon
Mas
s (µg
)
Tem
pera
ture
(°C
)
Time (s)
TemperatureFID
(b)
Rat lung tissue treatment with Solvable only
Some interference remains at higher temperatures where CNTs evolve
Rat lung tissue treatment with Solvable and proteinase K
Proteinase K successfully removed the remaining interfering carbon
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Extraction and quantification of CNTs in whole rat lungs
AlkaliTreatment
EnzymaticTreatment
CNT Transfer1 2
Collect CNTs
Result: CNT Dose
Analyze CNTs
A recovery of 93±15% of a 3.6 µg body burden deposited in individual whole rat lungs was achieved.
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Graphene and in-situ reduction of graphene oxide
01002003004005006007008009001000
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Tem
pera
ture
(°C)
Carb
on M
ass (
µg)
Time (s)
Graphene Oxide Reduced Graphene Oxide Temperature
Graphene oxide has a 1:1 O:C ratio – How do we increase thermal strength?
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Application – Composites
Original CNT Graphene
Composite compositionEPON 862 (Phenol-Formaldehyde Polymer Glycidyl Ether)EPIKURE W (diethylmethylbenzenediamine)
CNT or Graphene pellet
Treatment
CNT or Graphene shavings 27
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Carb
on M
ass (
µg)
Tem
pera
ture
(°C)
Time (s)
TemperatureCompositeCNT CompositeGraphene Composite
Analysis of treated composite pellet
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Going Forward
• Continue to develop extraction methods for other complex matrices (e.g., sediment)
• Develop alternative separation methods• Finalize method for removing oxygen in-situ and examine effect on
matrix carbon• Is graphene and CNT separation possible?
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Summary
• PTA is ideal for directly analyzing CNTs and graphene in simple matrices
• Extraction is necessary for complex matrices with embedded CNTs or a large amount of interfering carbon
• Extraction can also be used to concentrate samples with small CNT amount
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Thanks!
• People• Paul Westerhoff• Rolf Halden• Pierre Herckes• Matt Fraser• Andrea Clements
• Funding Support• Science Foundation Arizona• National Institutes of Health• Semiconductor Research Corporation• National Science Foundation• Arizona State University (Ira A. Fulton, Paul
and Elyse Johnson, GPSA)• AZ Water
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