Assessing the colloidal properties of engineered nanoparticles in water: case studies from fullerene C60 nanoparticles and carbon nanotubes

Kai Loon Chen; Billy A. Smith; William P. Ball; D. Howard Fairbrother

doi:10.1071/EN09112

RESEARCH FRONT

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Assessing the colloidal properties of engineered nanoparticles in water: case studies from fullerene C₆₀ nanoparticles and carbon nanotubes

Kai Loon Chen ^A ^D , Billy A. Smith ^B , William P. Ball ^A and D. Howard Fairbrother ^B ^C

+ Author Affiliations

- Author Affiliations

^A Department of Geography and Environmental Engineering, Johns Hopkins University, Baltimore, MD 21218-2686, USA.

^B Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218-2686, USA.

^C Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218-2686, USA.

^D Corresponding author. Email: kailoon.chen@jhu.edu

Kai Loon Chen is an Assistant Professor in the Department of Geography and Environmental Engineering at Johns Hopkins University in Baltimore, Maryland. He completed his B.Eng. and M.Eng. degrees in civil engineering at the National University of Singapore in 2001 and 2003 respectively. He joined the Environmental Engineering Program at Yale University in 2003 and received his Ph.D. in 2008. His current research focusses on understanding the fate and transport of engineered nanoparticles in natural and engineered aquatic systems. He is also interested in utilising nanotechnology for water purification and environmental remediation.

Billy A. Smith is a graduate research assistant pursuing his doctorate in Chemistry in the research group of Professor Howard Fairbrother, Johns Hopkins University (JHU), Baltimore, Maryland. He earned his B.S. in chemistry from Stevenson University (previously known as Villa Julie College) in 2005, and currently holds a masters degree in Chemistry from JHU. In the Fairbrother group, he has used surface analytical techniques in conjunction with time-resolved dynamic light scattering to study the role that oxygen containing functional groups play in determining the colloidal stability and transport properties of oxidised carbon nanotubes.

William P. Ball (P.E., Ph.D., BCEE) is a Professor of environmental engineering in the Department of Geography and Environmental Engineering at Johns Hopkins University. He received his B.S. from the University of Virginia in 1976 and his M.S. and Ph.D. in environmental engineering from Stanford University in 1977 and 1989. Between his M.S. and Ph.D., Professor Ball worked for six years for James M. Montgomery Consulting Engineers. He was previously on the faculty at Duke University and in 1992 joined the faculty at Johns Hopkins University. Professor Ball’s research program is focussed on physical and chemical processes affecting pollutant fate and treatment in natural environments and engineered systems, with focus on complex aquatic systems.

D. Howard Fairbrother is a Professor of Chemistry at Johns Hopkins University in Baltimore, Maryland. He received his B.S. degree from Oxford University, England, in 1989, and his Ph.D. in chemistry from Northwestern University in 1994. After completing a postdoctoral position with Professor Gabor Somorjai at the University of California, Berkeley, he joined the faculty in the Chemistry Department at Johns Hopkins University (JHU) in 1997. His research program at JHU is focussed on surface chemistry, with particular emphasis on characterising the functional groups on environmentally relevant materials and understanding the role of surface chemistry on the behaviour of engineered nanomaterials in aquatic environments.

Environmental Chemistry 7(1) 10-27 https://doi.org/10.1071/EN09112
Submitted: 1 September 2009 Accepted: 11 January 2010 Published: 22 February 2010

Environmental context. The fate and bioavailability of engineered nanoparticles in natural aquatic systems are strongly influenced by their ability to remain dispersed in water. Consequently, understanding the colloidal properties of engineered nanoparticles through rigorous characterisation of physicochemical properties and measurements of particle stability will allow for a more accurate prediction of their environmental, health, and safety effects in aquatic systems. This review highlights some important techniques suitable for the assessment of the colloidal properties of engineered nanoparticles and discusses some recent findings obtained by using these techniques on two popular carbon-based nanoparticles, fullerene C₆₀ and multi-walled carbon nanotubes.

Abstract. The colloidal properties of engineered nanoparticles directly affect their use in a wide variety of applications and also control their environmental fate and mobility. The colloidal stability of engineered nanoparticles depends on their physicochemical properties within the given aqueous medium and is ultimately reflected in the particles’ aggregation and deposition behaviour. This review presents some of the key experimental methods that are currently used to probe colloidal properties and quantify engineered nanoparticle stability in water. Case studies from fullerene C₆₀ nanoparticles and multi-walled carbon nanotubes illustrate how the characterisation and measurement methods are used to understand and predict nanoparticle fate in aquatic systems. Consideration of the comparisons between these two classes of carbon-based nanoparticles provides useful insights into some major current knowledge gaps while also revealing clues about needed future developments. Key issues to be resolved relate to the nature of near-range surface forces and the origins of surface charge, particularly for the reportedly unmodified or ‘pure’ carbon-based nanoparticles.

Additional keywords: aggregation, deposition, DLVO, dynamic light scattering, X-ray photoelectron spectroscopy.

Acknowledgements

K. L. Chen acknowledges financial support from Oak Ridge Associated Universities. D. H. Fairbrother and W. P. Ball acknowledge financial support from the National Science Foundation (grant no. BES0731147), the Environmental Protection Agency (grant no. RD-8338570-0), and the Institute for Nanobiotechnology (INBT) at Johns Hopkins University (JHU). The authors would also like to acknowledge the scientific discussions and insights provided by Professor Charlies O’Melia (Department of Geography and Environmental Engineering, JHU).

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