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D. R. Baer, J. E. Amonette
Pacific Northwest National Laboratory, Richland, WA 99352
P. G. Tratnyek
Oregon Health and Sciences University, Beaverton OR 97006
Although much research attention has focused on synthesis methods and physical properties of nano-sized objects, the chemical reactivity of nano-materials is often quite different from that of either bulk material or the individual atoms that comprise it. Nano-particles are often polymorphs of the bulk material with different physical (and electronic) structures including those related to surfaces and defects. Some properties of nanoparticles (such as solubility) change simply with size assuming that other properties of the material do not change, but often these other properties also change with size. Understanding the chemistry of nanoparticles requires knowledge of which properties of the particles impact the chemistry as well as the characteristics of specific nanoparticles.
Nature makes a wonderful variety of stable nanoparticles, unfortunately
they are often very complex in structure and composition as well as difficult
to adequately characterize. Although artificial nanoparticles are readily
made in many ways, they can be equally hard to truly characterize. In addition,
they are often unstable as a function of time, easily influenced by contamination
during synthesis or handling and have properties that can be significantly
altered by interactions with their environment. Although it is appropriate
to ask how nanoparticles impact our environment, it is also appropriate
to ask how the environment changes the nanoparticles and their properties.
The presentation will include discussion of different aspects of small particles
that can alter reactivity, observations of nanoparticle stability and measures
of reactivity. Examples will be drawn from our program on the “Reaction
Specificity of Nanoparticles in Solution: Application of the Reaction of
Nanoparticulate Iron with Chlorinated Hydrocarbons and Oxyanions.” In
particular, we are examining the possibility that Fe nanoparticles alter
the branching ratio between a desirable and an undesirable reaction path
in the reductive dechlorination of CCl4.