Radiolabeling - an appropriate tool to study the environmental fate of engineered nanoparticles

To study the environmental fate of nanoparticles it requires versatile tools for detection of nano-particulate materials in complex systems such as soil, sewage sludge or organisms within a wide range of concentration. Challenging are the environmentally relevant low concentrations of nanoparticles and the presence of background concentrations of the respective elements. The radiolabeling of nanoparticles offers an excellent and robust method to enable nanoparticle detection in these complex media down to the ng/L range. Even online in-situ tracing and visualization techniques are accessible to obtain spatio - temporal process information.

Depending on the nature of the nanoparticle and the process of interest different methods for the radiolabeling of nanoparticles can be applied, like the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles.

For our recent studies we produced [44Ti]TiO2, [45Ti]TiO2, [48V]TiO2, [64Cu]CuS, [64Cu]SiO2, [65Zn]CdSe/ZnS, [105Ag]Ag, [110mAg]Ag, [124I]CNTs, [125I]CNTs, [131I]CNTs, [7Be]MWCNT, [139Ce]CeO2 and [194Au]Pt nanoparticles. Due to the choice of the used radionuclide (half-life, decay-mode) and the activity concentrations it was possible to enable different detection methods and time scales for the investigations. All these methods go along with a careful characterization of the radiolabeled nanoparticles in respect of the radiolabeling stability and nanoparticle properties.

The radiolabeled nanoparticles have been successfully used in comprehensive environmental studies, like release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.