TY  - JOUR
A1  - Burek, Katja
A1  - Krause, Felix
A1  - Schwotzer, Matthias
A1  - Nefedov, Alexei
A1  - Süssmuth, Julia
A1  - Haubitz, Toni
A1  - Kumke, Michael Uwe
A1  - Thissen, Peter
T1  - Hydrophobic Properties of Calcium-Silicate Hydrates Doped with Rare-Earth Elements
JF  - ACS sustainable chemistry & engineering
N2  - 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.
KW  - Rare-earth elements
KW  - Europium
KW  - Luminescence
KW  - Metal-proton exchange reaction
KW  - Contact angle
KW  - Infrared spectroscopy
KW  - X-ray photoelectron spectroscopy
Y1  - 2018
U6  - https://doi.org/10.1021/acssuschemeng.8b03244
SN  - 2168-0485
VL  - 6
IS  - 11
SP  - 14669
EP  - 14678
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Kröner, Dominik
A1  - Ehlert, Christopher
A1  - Saalfrank, Peter
A1  - Holländer, Andreas
T1  - Ab initio calculations for XPS chemical shifts of poly(vinyl-trifluoroacetate) using trimer models
JF  - Surface science
N2  - X-ray photoelectron spectra (XPS) of the polymer poly(vinyl-trifluoroacetate) show C(1s) binding energy shifts which are unusual because they are influenced by atoms which are several bonds away from the probed atom. In this work, the influence of the trifluoroacetate substituent on the 1s ionization potential of the carbon atoms of the polyethylene chain is investigated theoretically using mono-substituted, diad and triad models of trimers representing the polymer. Carbon 1s ionization energies are calculated by the Hartree-Fock theory employing Koopmans' theorem. The influence of the configuration and conformation of the functional groups as well as the degree of substitution are found to be important determinants of XPS spectra. It is further found that the 1s binding energy correlates in a linear fashion, with the total electrostatic potential at the position of the probe atom, and depends not only on nearest neighbor effects. This may have implications for the interpretation of high-resolution XP spectra.
KW  - Ab initio quantum chemical methods and calculations
KW  - X-ray photoelectron spectroscopy
KW  - Insulating films
Y1  - 2011
U6  - https://doi.org/10.1016/j.susc.2011.05.021
SN  - 0039-6028
VL  - 605
IS  - 15-16
SP  - 1516
EP  - 1524
PB  - Elsevier
CY  - Amsterdam
ER  -