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Rice UniversityCBEN
Center for Biological and Environmental Nanotechnology
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The Environmental Chemistry of Nanoscale Carbons

This project is concerned with characterizing the possible environmental implications upon the use and release of engineered nanomaterials into environmental systems. We see such work as central to achieving our Theme 3 applications objective, which is the scale-up of nanoparticle-enabled water treatment systems, in an ecologically-responsible manner. This ambitious goal requires not only that improved technologies be demonstrated, but also that the nanoparticle impacts are well understood and controlled. Characterizing environmental impact of potential systems at this early stage is extremely challenging, but important enough to justify an entirely distinct center outcome which is to enable a full risk assessment of engineered nanoparticles through the development of a heuristic model and dataset for one model system. Within CBEN we break down this big challenge into three delineated research areas: Chemistry (Project 9.3.2.1), Fate and Transport (Project 9.3.2.2), and Biology (Project 9.3.2.3) of nanoparticles in natural waters. The boundaries between these projects are extremely porous, and this organizational structure seems to primarily serve CBEN in enhancing external communication about this complex and interwoven research activity.

This team began in 2001 evaluating nanoparticles in water, and quickly found that the environmental chemistry of even simple nanoparticles could be extraordinarily complicated. Fullerenes, in particular C60, became a model system for CBEN work. Even in pure water we found these systems aggregated into well defined clusters, and we reported on the physical and chemical properties of these stable fullerene water suspensions (nC60) in 2004 and 2005.(Sayes, Fortner et al. 2004; Fortner, Lyon et al. 2005) Since then, this group has continued to refine the analytical tools and improve our chemical understanding of this model system.

The specific objective of this project (Project 9) is to understand the physical and chemical processes affecting the properties of carbon based nanomaterials in natural aqueous environment. The results from this project provide information for predicting nanoparticle properties in the aqueous phase, and are the basis for studies in fate and transport (Project 9.3.2.2) and biological interactions (Project 9.3.2.3). To date, this group has successfully characterized aqueous C60 nanoparticles, nC60, formed through different pathways under a wide range of solution conditions representing various water qualities found in the environment. It was also found in our study that aquatic natural organic matter (NOM) and sunlight plays a critical role in the rate at which C60 can enter the aqueous phase as well as the physical and chemical properties of nC60 particles formed.(Li, Xie et al. 2009) The presence of NOM greatly enhances C60 dispersion, and the dispersion process is further accelerated by sunlight. In addition, this group has found that nC60 formed in water undergo photochemical transformation, resulting in surface oxygenation/hydroxylation.  A paper based on this study was recently accepted by Environmental Science and Technology.

This year the team expands its efforts in investigating the potential chemical transformation of aggregated fullerene in typical aqueous and soil environment and the physicochemical interactions of fullerenes with organic contaminants. Li investigates the photochemistry of aqueous fullerenes suspensions, focusing on the properties of photochemical products and relevant transport properties.  Alvarez evaluates the reaction of nC60 with hydroxyl radical in water.  Of particular focus is the quantification of its fundamental reactivity with •OH. Masiello applies new analytical tools drawn from geochemistry to the analytical challenges of fullerenes in the environment; she optimizes existing organic geochemical techniques for improved performance in the detection of nanocarbon in environmentally complex matrices. Li and Masiello apply the developed analytical tools to identify reaction products or derivative of fullerene in simulated natural waters. Such efforts will make studies of the fate and transport of nanocarbons in soil and water more feasible.  Tomson evaluates the adsorption and desorption of hydrophobic organic contaminants (HOCs) on colloidal nC60 nanoparticles, which is the key process to determine the mobility of HOCs as well as the toxicity of nC60in the subsurface.

Participating Researchers: