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  - Lange, Ilja
A1  - Reiter, Sina
A1  - Paetzel, Michael
A1  - Zykov, Anton
A1  - Nefedov, Alexei
A1  - Hildebrandt, Jana
A1  - Hecht, Stefan
A1  - Kowarik, Stefan
A1  - Woell, Christof
A1  - Heimel, Georg
A1  - Neher, Dieter
T1  - Tuning the work function of polar zinc oxide surfaces using modified phosphonic acid self-assembled monolayers
JF  - Advanced functional materials
N2  - Zinc oxide (ZnO) is regarded as a promising alternative material for transparent conductive electrodes in optoelectronic devices. However, ZnO suffers from poor chemical stability. ZnO also has a moderate work function (WF), which results in substantial charge injection barriers into common (organic) semiconductors that constitute the active layer in a device. Controlling and tuning the ZnO WF is therefore necessary but challenging. Here, a variety of phosphonic acid based self-assembled monolayers (SAMs) deposited on ZnO surfaces are investigated. It is demonstrated that they allow the tuning the WF over a wide range of more than 1.5 eV, thus enabling the use of ZnO as both the hole-injecting and electron-injecting contact. The modified ZnO surfaces are characterized using a number of complementary techniques, demonstrating that the preparation protocol yields dense, well-defined molecular monolayers.
KW  - ZnO
KW  - self-assembled monolayers
KW  - phosphonic acid
KW  - surface modification
KW  - electrodes
Y1  - 2014
U6  - https://doi.org/10.1002/adfm.201401493
SN  - 1616-301X
SN  - 1616-3028
VL  - 24
IS  - 44
SP  - 7014
EP  - 7024
PB  - Wiley-VCH
CY  - Weinheim
ER  -