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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NT

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s Rem

aini

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Time (seconds)

MW-ArcMW-15MW-FMW-OSW-65MW-PTemperature

01002003004005006007008009001000

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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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Perc

ent C

NT

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s Rem

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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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ass R

emai

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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

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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

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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

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CN

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y S-CNT

W-CNT

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How to Compare Reagents and Analyze Damage to CNTs?

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Untreated

Water

Solvable

Hydroxide

Nitric

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Peroxide

Proteinase K

F-CNT

Temperature12

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5

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Thermograms are overly complicated!

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otal

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k A

rea

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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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otal

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rea

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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

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al

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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

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s (µg

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pera

ture

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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

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ture

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ass (

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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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ass (

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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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