@article{BurekEidnerKukeetal.2018,
  author    = {Burek, Katja and Eidner, Sascha and Kuke, Stefanie and Kumke, Michael Uwe},
  title     = {Intramolecular deactivation processes of electronically excited Lanthanide(III) complexes with organic acids of low molecular weight},
  series = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy},
  volume    = {191},
  journal   = {Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {1386-1425},
  doi       = {10.1016/j.saa.2017.09.012},
  pages     = {36 -- 49},
  year      = {2018},
  abstract  = {The luminescence of Lanthanide(Ill) complexes with different model ligands was studied under direct as well as sensitized excitation conditions. The research was performed in the context of studies dealing with deep-underground storages for high-level nuclear waste. Here, Lanthanide(III) ions served as natural analogues for Actinide(III) ions and the low-molecular weight organic ligands are present in clay minerals and furthermore, they were employed as proxies for building blocks of humic substances, which are important complexing molecules in the natural environment, e.g., in the far field of a repository site. Time-resolved luminescence spectroscopy was applied for a detailed characterization of Eu(III), Tb(III), Sm(III) and.Dy(III) complexes in aqueous solutions. Based on the observed luminescence the ligands were tentatively divided into two groups (A, B). The luminescence of Lanthanide(III) complexes of group A was mainly influenced by an energy transfer to OH-vibrations. Lanthanide(Ill) complexes of group B showed ligand-related luminescence quenching, which was further investigated. To gain more information on the underlying quenching processes of group A and B ligands, measurements at different temperatures (77 K <= T <= 353 K) were performed and activation energies were determined based on an Arrhenius analysis. Moreover, the influence of the ionic strength between 0 M <= 1 <= 4 M on the Lanthanide(III) luminescence was monitored for different complexes, in order to evaluate the influence of specific conditions encountered in host rocks foreseen as potential repository sites.},
  language  = {en}
}
@article{BurekKrauseSchwotzeretal.2018,
  author    = {Burek, Katja and Krause, Felix and Schwotzer, Matthias and Nefedov, Alexei and S{\"u}ssmuth, Julia and Haubitz, Toni and Kumke, Michael Uwe and Thissen, Peter},
  title     = {Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements},
  series = {ACS sustainable chemistry \& engineering},
  volume    = {6},
  journal   = {ACS sustainable chemistry \& engineering},
  number    = {11},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {2168-0485},
  doi       = {10.1021/acssuschemeng.8b03244},
  pages     = {14669 -- 14678},
  year      = {2018},
  abstract  = {In this study, the apparent relationship between the transport process and the surface chemistry of the Calcium-Silicate Hydrate (CSH) phases was investigated. For this purpose, a method was developed to synthesize ultrathin CSH phases to be used as a model substrate with the specific modification of their structure by introducing europium (Eu(III)). The structural and chemical changes during this Eu(III)-doping were observed by means of infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and time-resolved laser fluorescence spectroscopy (TRLFS). These alterations of the CSH phases led to significant changes in the surface chemistry and consequently to considerable variations in the interaction with water, as evidenced by measurements of the contact angles on the modified model substrates. Our results provide the basis for a more profound molecular understanding of reactive transport processes in cement-based systems. Furthermore, these results broaden the perspective of improving the stability of cement-based materials, which are subjected to the impact of aggressive aqueous environments through targeted modifications of the CSH phases.},
  language  = {en}
}