OVERVIEW OF A NEW CLASS OF INERT, INNOCUOUS TRACER NANOPARTICLES

As the session rationale points out, the increasing incorporation of nanoparticles into commercial products results in their entering the environment with unknown consequences. Assessing their uptake in the natural environment would be greatly facilitated by a class of inert, innocuous nanoparticles that could provide a mobility reference. Such particles would have other important applications. For example, combined with an inert chemical tracer such particles could measure the degree of flow channelization (one of the fundamental questions of subsurface flow). Because they diffuse less into dead zones, they can measure changes in sweep in laboratory columns much better than chemical tracers. Managing sweep is important in oil recovery and chemical sequestration. An easily synthesized, surprisingly inert, and biologically innocuous carbon-cored particle decorated with highly hydrophilic and fluorescent ethanolamine fibers and fluorescently detectable to ~10 ppb has been discovered at Cornell. Over the last 6 years we have explored the properties and some of the applications of this class of nanoparticle. The history of development, synthesis, health aspects, presently perceived reasons for inertness, and the laboratory and field tests that have been carried out to date will be briefly reviewed. Some of the topics covered will be discussed in more detail in later presentations in this session.