Characterization of nC60 fullerene particles in natural and synthetic waters.

Fullerenes were named after Buckminster Fuller, the architect

of the geodesic dome. C60 is nicknamed the “Buckyball.”

Materials and Methods

These experiments involved a series of syringe filtra-

tion followed by various methods to characterize C60 parti-

cles. Two experiments were conducted in different media:

(1) “Aqu-nC60,” C60 continuously stirred in

Nanopure water for two years.

(2) “WR-nC60,” C60 stirred in filtered Willamette

River water, in comparison with “SW-nC60,” C60

stirred in synthetic water that has been adjusted

for organic carbon, ionic strength, and pH with

Aldrich humic acid, NaCl, and HCl, respectively.

This experiment is ongoing and full results are

not yet available.

Each solution had 100 mg/L MER 99+% C60 and all me-

dia were made with 17+ MΩ Nanopure water and passed

through a 20 nm-pore size syringe filter.

Analytical methods:

Electrophoretic mobility for zeta potential using the BIC

ZetaPALS Zeta Potential Analyzer

Dynamic light scattering for particle size using the ZetaPALS

particle sizing software

UV-Vis spectrum with a HP 8453 Spectrophotometer

Total organic carbon with a Shimadzu TOC combustion analyzer

Transmission electron microscopy for size and morphology us-

ing a FEI Titan TEM.

Aqu-nC60 Results

Fig. 3: Multimodal size distribution of

unfiltered 2-year aqu-nC60. Diameters

range from 200-1150 nm. MSD intensity

estimation is heavily weighted toward

the few, large particles. Due to instru-

mental limitations, reporting one mean

diameter oversimplifies the polydis-

perse size distribution.

WR-nC60 and SW-nC60 Results

Fig. 4: Mean hydrodynamic diame-

ter of C60 in all three media for three

consecutive filtrations. The aqu-nC60

is smaller, most likely because it had

a longer stirring period. Differences

in media, such as ionic strength and

organic matter content, also affect

size.

Fig. 5: Zeta potential of C60 particles

after two weeks for three filtration

steps. The SW-nC60 has consistently

higher zeta potential than the WR-

nC60, even though ionic strength and

base DOC concentration should be

equal. It is too early to observe

trends over time.

Fig. 6: Absorbance spectra of C60 in

Willamette River and synthetic wa-

ter after being filtered through 1.0

µm and 0.45 µm pore-sized syringe

filters. The C60 shows a small peak at

λ=365 nm. Lower absorbance at the

smaller filtration step indicates that

the concentration is decreasing, and

this is confirmed by TOC data.

Conclusion Already, differences in zeta potential and particle size

have been observed between the WR-nC60 and the SW-

nC60. When assessing C60 behavior in the environment, re-

searchers should considered tests with actual natural wa-

ter, not solely simulated synthetic water, and that time

spent stirring should be carefully chosen. This experiment

is ongoing, and possible work in the future includes C60 as-

sociation with other particles.

Acknowledgements

Much appreciation to: Ben Place and Jennifer Field; Don

Bloomquist, Dylan Stankus, and Ian Maguire; Kathy Motter;

Kurt Langworthy; Mohammad Azizian; and my mentor Jeff

Nason. This project was funded by the Subsurface Biosphere

Initiative.

What is a fullerene?

Unintentionally discovered in 1985,

a fullerene is an allotrope of carbon that

has the structure of hollow spheres or

tubes. With 60 carbon atoms, C60 is the

smallest possible spherical fullerene. Its

atoms are bonded together to form an

icosahedron much like a nano-sized soc-

cer ball. The diameter of a C60 molecule

is only about 7 Å, or 0.7 nm.

Why do we care?

In recent years, fullerenes have been used

in a range of applications, from medical imag-

ing to cosmetics, and the use of fullerenes and

functionalized fullerenes are expanding rap-

idly. Their fate in the natural environment and

potential toxic effects to life forms, however,

are relatively unknown.

C60 is nearly insoluble in water and in aqueous environ-

ments, the molecules cluster into nano– and larger particles.

Recent research focuses much on the characterization of

these unique particles and will allow their transport and

bioavailability in the environment to be better predicted.

Project Introduction

This research project attempts to answer questions

about the nature of the C60 particles that have not yet been

addressed by researchers: What are the differences between

C60 stirred over time in actual natural water as compared to

laboratory synthetic water? What are the characteristics of

C60 that has been continuously stirred in Nanopure water,

without organic solvents, for two years? How can the

polydisperse distribution of particle sizes within the sus-

pensions be accurately measured and reported?

Michelle Adlong • Dr. Jeffrey Nason • School of Chemical, Biological, and Environmental Engineering Oregon State University • Corvallis, OR 97331

Fig. 2: Continuously stirred

C60 at two weeks in (a) Wil-

lamette River water and (b)

synthetic water.

Fig. 1: Structure of C60.

Carbon atoms form 12

pentagons and 20

hexagons connected in

a spherical cage.

Hydrodynamic Diameter (nm)

Rel

ativ

e In

ten

sity

& N

um

be

r

-60

-50

-40

-30

-20

-10

0

Ze

ta P

ote

nti

al

(mV

)

C60 inWillametteRiver Water

C60 inSyntheticWater

Unfiltered 1.0 μm filtered 0.45 μm filtered

Week 1 Week 2 Week 1 Week 1 Week 2 Week 2

0

500

1000

1500

2000

Me

an H

ydro

dyn

amic

Dia

me

ter

(nm

)

WR-nC60, 1 wkstirred

SW-nC60, 1 wkstirred

Aqu-nC60, 2 yrsstirred

Unfiltered 1.0 μm filtered

0.45 μm filtered M

ean

Hyd

rod

ynam

ic D

iam

ete

r

References Bouchard, D., Ma, X., & Isaacson, C. (2009). “Colloidal Properties of Aqueous Fullerenes: Isoelectric Points and Aggregation Kinetics of C60 and C60 Derivatives.” Environmental Science & Technology. July 14, 2009.

Fomkin, A.A. (2009). “Nanoporous Materials and their Adsorption Properties.” Protection of Metals and Physical Chemistry of Surfaces, Vol. 45 (No. 2), 133–149.

Li, Q., Xie, B., Hwang, Y.S., & Xu, Y. (2009). “Kinetics of C60 Fullerene Dispersion in Water Enhanced by Natural Organic Matter and Sunlight.” Environmental Science & Technology. March 2, 2009.

0.00

0.05

0.10

300 350 400

SW 1.0umfiltered

SW 0.45umfiltered

WR 1.0umfiltered

WR 0.45umfiltered

Ab

sorb

ance

(A

U)

Wavelength