Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Luminescence spectroscopy is a powerful tool to study the chemistry of uranium in trace concentration. Manifold operating mode, e.g. steady state, time-resolved, laser-induced, site-selective, cryogenic, etc. were used to investigate the environmental behavior of uranium in various geological and biological systems.
Hydrolysis is the basis for more complex aquatic systems and thus a deep understanding of those systems is indispensable. In case of U(VI) we demonstrated that a combination of luminescence spectroscopic methods together with state of the art data analysis (parallel factor analysis – PARAFAC) and quantum chemical calculations is a powerful setup to gain information on that system. We were able to extract thermodynamic constants for the mononuclear hydrolysis species using optimized data processing. Furthermore, advanced deconvolution of individual luminescence spectra demonstrates the correlation of luminescence spectroscopy and vibrational spectroscopy.
For kinetic studies of geological or biological sorption phenomena, different microscopic or flow-through cell techniques are useable. For online monitoring and characterization of U(VI) sorption species we develop a new technical in situ luminescence spectroscopy setup in comparability to the well established in situ time resolved ATR FT-IR spectroscopy. For biological systems, we combined microscopy with luminescence spectroscopic measurements for localization, visualization and chemical characterization of uranium complexes. This approach enables us to distinguish between biosorption, intracellular uptake or biomineralization as dominant retention process for uranium in biological samples.
Under reducing conditions expected in the near field of nuclear waste repository, the tetravalent uranium should be the major oxidation state. We studied the U(IV) luminescence characteristics in presence of various inorganic ligands (ClO4–, Cl–, SO42–). By using cryo-TRLFS at 77 K the speciation analysis limit for U(IV) was determined with 5·10–6 M and this corresponds to uranium concentrations occurring in the environment.