Photon Sciences Directorate Seminar

The appearance and behavior of engineered nanoparticles in the environment determine their distribution, their fate and the exposure of organisms.
This behavior is governed by several well-known parameters as surface potential of the particles, particle size and shape and of course the water chemistry. However a detailed understanding how the inter-connected processes of aggregation, transport, settling and transformation are influenced by these parameters is still missing. From the perspective of risk assessment it would be essential to be able to predict behavior, fate and transformation, but meaningful predictions derived from first principles remain difficult, even in fairly simple systems. For certain engineered nanoparticles like citrate stabilized Gold-NPs for example, which come with a fairly simple surface chemistry, the prediction of reactions may be more straight forward than for others, especially metal-oxide particles. Hence as long as process understanding remains underdeveloped empiric approaches will be necessary. We have addressed this issue by developing a testing approach to generate empiric data for the dispersion stability of nanoparticles in a wide variety of conditions. The testing procedure itself and the comparison of conditions and materials will be presented and discussed with respect to the application to real world conditions including analytical challenges in real surface waters and soils, limitations due to reduced complexity of the set-up, and the problem of heterogeneity and property distributions of the nanoparticles.