Analysis of carbonaceous nanomaterials

in environmental and biological samples

P. Lee Ferguson

Nicholas School of the Environment and Department of Civil & Environmental Engineering, Duke University, Durham, NC

2012 NSF Nanoscale Science and Engineering Grantees Conference

December 3, 2012, Arlington, VA

Carbon-based nanomaterials are seeing

increased production and use

Chemical & Engineering News, (2007) v 85, no. 46 pp. 29-35

Woodrow Wilson International Center for Scholars, Project on Emerging Nanotechnologies (2010)

Nanomaterial use in consumer products

Challenges for analyzing carbon

nanomaterials in environmental media

• Both fullerenes and CNTs are expected to occur at very low

concentrations in the ambient environment (ppb to ppt)

• “Particle characterization” methods (e.g. microscopy and light

scattering) fail to perform in highly complex media with low

nanoparticle concentrations.

• Carbon nanomaterials offer a “contrast problem” for detection

against a carbon-rich environmental background.

• Fullerenes and CNTs have very limited solubility in most organic

solvents, complicating sample preparation.

• Most environmental analytical laboratories are poorly-equipped

for particle separation and detection.

Analytical methods for detecting

fullerenes in environmental samples

• Because fullerenes are molecular

species, they can be efficiently

solubilized and separated by HPLC.

• UV-vis absorbance detection is

useful for detecting fullerenes in

pure solutions and at high (ppm or

above) concentrations.

• In complex mixtures and at trace

(ppb or ppt) concentrations, HPLC-

MS is the method of choice.

X. Xia et al. 2006. HPLC-UV-vis analysis of nano-C60 in protein solution, porcine plasma, and skin extract. Journal of

Chromatography A, 1129 (2), p. 216-

222)

Quantitation of nano-C60 in drinking water

by HPLC-APCI-MS

Z. Chen, et al. 2008. Quantification of

C60 Fullerene Concentrations in Water.

Environmental Toxicology and

Chemistry, 27 (9), p. 1852-1859.

MDL = 0.30 ± 0.09 μg/L

MDL = 3.33 ± 1.06 μg/L

MDL = 2.78 ± 0.88 μg/L

Recovery from tap

water: < 35 %

• Solid phase extraction was used to isolate nano-C60 colloids from

water prior to HPLC-MS analysis.

• Recoveries were non-quantitative but ppt detection limits attained.

Analysis of fullerenes in wastewater

suspended solids by HPLC-ESI-MS

M. Farre, et al. 2010. First

determination of C60 and C70 fullerenes

and N-methylfulleropyrrolidine C60 on

the suspended material of wastewater

effluents by liquid chromatography

hybrid quadrupole linear ion trap

tandem mass spectrometry. Journal of

Hydrology, 383, p. 44-51.

• Filtration and solvent extraction was used to isolate fullerenes

from suspended solids in WWTP effluent prior to HPLC-MS.

• Excellent detection limits were achieved but with limited recovery.

C60 MDL = 0.005 μg/L

Recovery = 63 ± 7 %

C70 MDL = 0.008 μg/L

Recovery = 59 ± 7 %

N-methylfullero-pyrrolidine

MDL = 0.02 μg/L

Recovery = 58 ± 6 %

Methods for carbon nanotube

characterization

• Carbon nanotubes are challenging to analyze at trace levels in the

environment – they are not molecules and MS is of little use.

• Electron microscopy

− Provides information on size, physical state, sample purity

− Qualitative, limited sensitivity, poor performance in complex

mixtures

• Raman spectroscopy

− Distinctive bands provide purity assessment, some structural

information

− Relatively poor sensitivity, susceptible to interferences

• Near infrared fluorescence spectroscopy

− Spectra provide diameter, structural information

− Very high sensitivity, tolerant of complex background, only useful for

semiconductive SWNT species

SWNT have unique structural

characteristics

The integers (n,m) uniquely define the diameter and

chirality of the quantized SWNT species.

Semiconductive SWNT are represented with black

numbers, while conductive SWNT are shown in red.

 

d = 0.0794 n2 + nm+m2

Adapted from Fluorometric Characterization of SWCNT, Weisman, RB, 2009.

30°

0°

Qualitative characterization of CoMoCat

SWNT type SG65 by NIRF spectroscopy

P.A. Schierz, et al. 2012. Characterization and

Quantitative Analysis of Single-Walled Carbon

Nanotubes in the Aquatic Environment Using Near-

Infrared Fluorescence Spectroscopy, Environmental

Science & Technology, 2012. 46 (22), pp 12262–

12271

7000 8000 9000 10000 11000 12000

638 nm excitation

691 nm excitation

782nm excitation

em

iss

ion

po

we

r [

nW

cm

-1]

wave number [cm-1

]

Detection of CoMoCat SWNT type SG65

in sediment by NIRF

• CoMoCat SWNT were spiked into

estuarine sediment at 10 mg/g

concentration.

• Sequential extractions were performed

with 2% sodium deoxycholate

(ultrasonication at 40 W for 10 minutes).

6000 7000 8000 9000 10000 11000 12000

0.00000

0.00001

0.00002

0.00003

0.00004

0.00005

1. extraction

2. extraction

3. extraction

4. extraction

5. extraction

em

issio

n p

ow

er

[nW

cm

-1]

wave number [cm-1]

638 nm excitation wave length

SWNT extracted

from sediment:

81 ± 5 %

Quantitative performance of NIRF

spectroscopy for SWNT in 2% SDC

25 ng/mL

SWNT in mesocosm water attenuated

rapidly Water column C SWNT,0 = 2.5 mg L-1, 0.5% GA

7000 8000 9000 10000 11000 12000

0.00000

0.00005

0.00010

0.00015

638 nm excitation

691 nm excitation

782nm excitation

wave number [cm-1]

em

issio

n p

ow

er

[nW

cm

-1]

11 mg L-1

7000 8000 9000 10000 11000 12000

0.0000000

0.0000005

0.0000010

0.0000015

em

issio

n p

ow

er

[nW

cm

-1]

wave numer [cm-1]

c < DL

5 mg L-1

7000 8000 9000 10000 11000 12000

0.000000

0.000002

0.000004

0.000006

em

issio

n p

ow

er

[nW

cm

-1]

wave number [cm-1

]

670 mg L-1

0.0 0.5 1.0 1.5 2.0 2.5-5

-4

-3

-2

-1

0

time (d)

ln (

C/C

0)

SWNT t1/2 = 7.4 hours

SWNT in mesocosm water attenuated

rapidly Water column C SWNT,0 = 2.5 mg L-1, 0.5% GA

0 10 20 30-3

-2

-1

0

1

cSWNT (µg g-1)

depth

(cm

)A

D

C

B

1 cm

0.00000

0.00005

0.00010

em

iss

ion

po

we

r [n

W c

m-1]

0.00000

0.00005

0.00010

638 nm exciation wave length

691 nm exciation wave length

782 nm exciation wave length

em

iss

ion

po

we

r [n

W c

m-1

]

0.00000

0.00005

0.00010

em

iss

ion

po

we

r [n

W c

m-1]

7000 8000 9000 10000 11000 12000

0.00000

0.00005

0.00010

wave number [cm-1]

em

iss

ion

po

we

r [n

W c

m-1

]

A

B

C

D

SWNT were deposited in mesocosm

surface sediments after 6 months

NIRF imaging reveals SWNT ingestion by

mosquitofish in mesocosms

Room lighting NIR Laser illumination

Control mesocosm fish

SWNT mesocosm fish

SWNT in intestines

CNTs are resistant to chemothermal

oxidation treatment

• SWNT and MWNT survived air oxidation at

375° C for 24 hrs.

• CNTs in sediments would likely be detected

along with soot carbon using the CTO-375

method.

A. Sobek and T.D. Bucheli. 2009.

Testing the resistance of single- and

multi-walled carbon nanotubes to

chemothermal oxidation used to isolate

soots from environmental samples.

Environmental Pollution, 157, p. 1065-

1071.

SWNT 1 MWNT 4

MWNT 10

MWNT 13

Programmed thermal analysis can detect

strong CNTs in environmental matrices

• Some MWNT were sufficiently thermally

resistant that they could be separated from

background carbon in samples

• Residual black carbon in samples can cause

interferences.

MDL ~ 0.33μg

K Doudrick, et al. 2012. Detection of

Carbon Nanotubes in Environmental

Matrices Using Programmed Thermal

Analysis. Environmental Science &

Technology, 2012. 46 (22), pp 12246–

12253

TGA-MS could distinguish CNTs from

environmental matrices

• Hydrogen-assisted

thermal degradation

separated CNTs from

other carbonaceous

material

• Diagnostic ion ratios

could be used to

quantify CNTs in e.g.

sediments

D.L. Plata, et al. 2012.

Thermogravimetry–Mass Spectrometry

for Carbon Nanotube Detection in

Complex Mixtures. Environmental

Science & Technology, 2012. 46 (22),

pp 12254–12261

MDL ~ 4.0 μg

Carbon nanotubes have unique metal

catalyst compositions

• Residual metal catalyst impurities in SWNT

may prove useful as tracers for these

materials

• Ratiometric analysis may distinguish

manufacturers/synthesis processes

D.L. Plata et al. 2008. Industrailly

synthesized single-walled carbon

nanotubes: Compositional data for

users, environmental risk assessments,

and source apportionment.

Nanotechnology, 19, p. 1-13.

Research needs for carbon nanomaterial

analysis in the ambient environment

• Analytical methods for fullerenes seem to be maturing:

– Technologies (chromatography and mass spectrometry) are in-place.

– Method development efforts should focus on sample-preparation and

purification.

– Methods for qualitative analysis (e.g. modification state) are lacking.

• There are currently few methods for CNT analysis in

environmental samples:

– Thermal analysis methods lack sensitivity and specificity for CNTs.

– Only a single trace-analytical method exists for SWNT (author’s laboratory).

• Fundamental research is necessary to develop or adapt new detection methods for CNTs.

• Combination of particle-separation (e.g. field flow fractionation) methods with spectroscopic detection techniques holds particular promise.

Acknowledgement

RD83385

9

Dr. Ariette Schierz and Ashley Parks (Duke)

Dr. Tara Sabo-Attwood and Dr. Joseph Bisesi

(U. Florida)

Dr.Navid Saleh (U. South Carolina)

Dr. Phil Wallis and Dr. Samina Azad (South

West Nanotechnology)

Dr. Sergei M. Bachilo (Applied

Nanofluorescence)