TY  - JOUR
A1  - Li, Mingjun
A1  - Schlaich, Christoph
A1  - Kulka, Michael Willem
A1  - Donskyi, Ievgen S.
A1  - Schwerdtle, Tanja
A1  - Unger, Wolfgang E. S.
A1  - Haag, Rainer
T1  - Mussel-inspired coatings with tunable wettability, for enhanced antibacterial efficiency and reduced bacterial adhesion
JF  - Journal of materials chemistry : B, Materials for biology and medicine
N2  - Over the last few decades, there has been a tremendous increase in research on antibacterial surface coatings as an alternative strategy against bacterial infections. Although there are several examples of effective strategies to prevent bacterial adhesion, the effect of the wetting properties on the coating was rarely considered as a crucial factor. Here we report an in-depth study on the effect of extreme wettability on the antibacterial efficiency of a silver nanoparticles ( AgNPs)-based coating. By controlling surface polymerization of mussel-inspired dendritic polyglycerol ( MI-dPG) and post-functionalization, surfaces with wetting properties ranging from superhydrophilic to superhydrophobic were fabricated. Subsequently, AgNPs were embedded into the coatings by applying in situ reduction using the free catechols-moieties present in the MI-dPG coating. The resulting polymer coatings exhibited excellent antibacterial ability against planktonic Escherichia coli ( E. coli) DH5a and Staphylococcus aureus ( S. aureus) SH1000. The antibacterial efficiency of the coatings was analyzed by using inductively coupled plasma mass spectrometry ( ICP-MS) and bacterial viability tests. Furthermore, the antifouling properties of the coatings in relation to the antibacterial properties were evaluated.
Y1  - 2019
U6  - https://doi.org/10.1039/c9tb00534j
SN  - 2050-750X
SN  - 2050-7518
VL  - 7
IS  - 21
SP  - 3438
EP  - 3445
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Dietrich, Paul M.
A1  - Glamsch, Stephan
A1  - Ehlert, Christopher
A1  - Lippitz, Andreas
A1  - Kulak, Nora
A1  - Unger, Wolfgang E. S.
T1  - Synchrotron-radiation XPS analysis of ultra-thin silane films: Specifying the organic silicon
JF  - Applied surface science : a journal devoted to applied physics and chemistry of surfaces and interfaces
N2  - The analysis of chemical and elemental in-depth variations in ultra-thin organic layers with thicknesses below 5 nm is very challenging. Energy- and angle-resolved XPS (ER/AR-XPS) opens up the possibility for non-destructive chemical ultra-shallow depth profiling of the outermost surface layer of ultra-thin organic films due to its exceptional surface sensitivity. For common organic materials a reliable chemical in-depth analysis with a lower limit of the XPS information depth z(95) of about 1 nm can be performed. As a proof-of-principle example with relevance for industrial applications the ER/AR-XPS analysis of different organic monolayers made of amino- or benzamidosilane molecules on silicon oxide surfaces is presented. It is demonstrated how to use the Si 2p core-level region to non-destructively depth-profile the organic (silane monolayer) - inorganic (SiO2/Si) interface and how to quantify Si species, ranging from elemental silicon over native silicon oxide to the silane itself. The main advantage of the applied ER/AR-XPS method is the improved specification of organic from inorganic silicon components in Si 2p core-level spectra with exceptional low uncertainties compared to conventional laboratory XPS. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Synchrotron radiation XPS
KW  - Depth profiling
KW  - Silanes
KW  - Monolayer
KW  - Amines
KW  - Amides
Y1  - 2016
U6  - https://doi.org/10.1016/j.apsusc.2015.12.052
SN  - 0169-4332
SN  - 1873-5584
VL  - 363
SP  - 406
EP  - 411
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Ehlert, Christopher
A1  - Holzweber, Markus
A1  - Lippitz, Andreas
A1  - Unger, Wolfgang E. S.
A1  - Saalfrank, Peter
T1  - A detailed assignment of NEXAFS resonances of imidazolium based ionic liquids
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([C(n)C(1)im](+)[NTf2](-) and [C(4)C(1)im](+)[I](-)). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
Y1  - 2016
U6  - https://doi.org/10.1039/c5cp07434g
SN  - 1463-9076
SN  - 1463-9084
VL  - 18
SP  - 8654
EP  - 8661
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - GEN
A1  - Ehlert, Christopher
A1  - Holzweber, Markus
A1  - Lippitz, Andreas
A1  - Unger, Wolfgang E. S.
A1  - Saalfrank, Peter
T1  - A detailed assignment of NEXAFS resonances of imidazolium based ionic liquids
N2  - In Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy X-Ray photons are used to excite tightly bound core electrons to low-lying unoccupied orbitals of the system. This technique offers insight into the electronic structure of the system as well as useful structural information. In this work, we apply NEXAFS to two kinds of imidazolium based ionic liquids ([CnC1im]+[NTf2]- and [C4C1im]+[I]-). A combination of measurements and quantum chemical calculations of C K and N K NEXAFS resonances is presented. The simulations, based on the transition potential density functional theory method (TP-DFT), reproduce all characteristic features observed by the experiment. Furthermore, a detailed assignment of resonance features to excitation centers (carbon or nitrogen atoms) leads to a consistent interpretation of the spectra.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 315 
KW  - ray absorption-spectroscopy
KW  - fine-structure
KW  - spectra
KW  - simulations
KW  - molecules
KW  - dynamics
KW  - graphene
KW  - surface
KW  - salts
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394417
SP  - 8654
EP  - 8661
ER  - 
TY  - JOUR
A1  - Ehlert, Christopher
A1  - Unger, Wolfgang E. S.
A1  - Saalfrank, Peter
T1  - C K-edge NEXAFS spectra of graphene with physical and chemical defects: a study based on density functional theory
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Recently, C K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of graphite (HOPG) surfaces have been measured for the pristine material, and for HOPG treated with either bromine or krypton plasmas (Lippitz et al., Surf. Sci., 2013, 611, L1). Changes of the NEXAFS spectra characteristic for physical (krypton) and/or chemical/physical modifications of the surface (bromine) upon plasma treatment were observed. Their molecular origin, however, remained elusive. In this work we study by density functional theory, the effects of selected point and line defects as well as chemical modifications on NEXAFS carbon K-edge spectra of single graphene layers. For Br-treated surfaces, also Br 3d X-ray Photoelectron Spectra (XPS) are simulated by a cluster approach, to identify possible chemical modifications. We observe that some of the defects related to plasma treatment lead to characteristic changes of NEXAFS spectra, similar to those in experiment. Theory provides possible microscopic origins for these changes.
Y1  - 2014
U6  - https://doi.org/10.1039/c4cp01106f
SN  - 1463-9076
SN  - 1463-9084
VL  - 16
IS  - 27
SP  - 14083
EP  - 14095
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Prescher, Dietrich
A1  - Friedrich, Jörg F.
A1  - Wigant, L.
A1  - Unger, Wolfgang E. S.
A1  - Lippitz, A.
A1  - Wittrich, H.
A1  - Erdmann, J.
A1  - Gorsler, H.-V.
A1  - Nick, L.
T1  - Barrier properties of plasma-modified polypropylene and polyethylenether ephthalate
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Friedrich, Jörg F.
A1  - Wigant, L.
A1  - Unger, Wolfgang E. S.
A1  - Lippitz, A.
A1  - Wittrich, H.
A1  - Prescher, Dietrich
A1  - Erdmann, J.
A1  - Gorsler, H.-V.
A1  - Nick, L.
T1  - Barrier properties of plasma-modified polypropylene and polyethylen eterephthalate
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Prescher, Dietrich
A1  - Friedrich, Jörg F.
A1  - Wigant, L.
A1  - Unger, Wolfgang E. S.
A1  - Lippitz, H.
A1  - Erdmann, J.
A1  - Gorsler, H.-V.
A1  - Wittrich, H.
T1  - Barrier properties of plasma and chemically fluorinated polypropylene and polyethylene-terephthalate
Y1  - 1995
ER  - 
TY  - JOUR
A1  - Giebler, Rainer
A1  - Schulz, Burkhard
A1  - Reiche, Jürgen
A1  - Brehmer, Ludwig
A1  - Wühn, Mario
A1  - Wöll, Christoph
A1  - Smith, Andrew Phillip
A1  - Urquhart, Steven G.
A1  - Ade, Harald W.
A1  - Unger, Wolfgang E. S.
T1  - Near-edge x-ray absorption fine structure spectroscopy on ordered films of an amphiphilic derivate of 2,5- Diphenyl-1,3,4-oxadiazole
N2  - The surfaces of ordered films formed from an amphiphilic derivative of 2,5-diphenyl-1,3,4-oxadiazole by the Langmuir-Blodgett (LB) technique and organic molecular beam deposition (OMBD) were investigated by the use of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. For the assignment of the spectral features of the C, N, and O K- edge absorption spectra, fingerprint spectra of poly(p-phenylene terephthalamide)(Kevlar), poly(ethylene terephthalate), poly(p-phenylene-1,3,4-oxadiazole), and 2,5-di- (pentadecyl)-1,3,4-oxadiazole, which contain related chemical moieties, were recorded. Ab initio molecular orbital calculations, performed with explicit treatment of the core hole, are used to support the spectral interpretations. Angle-resolved NEXAFS spectroscopy at the C, N, and O K-edges suggests a preferentially upright orientation of the oxadiazole derivative in the outermost layer of the films. X-ray specular reflectivity data and molecular modeling results suggest a similar interpretation.
Y1  - 1999
ER  - 
TY  - GEN
A1  - Ehlert, Christopher
A1  - Unger, Wolfgang E. S.
A1  - Saalfrank, Peter
T1  - C K-edge NEXAFS spectra of graphene with physical and chemical defects
BT  - a study based on density functional theory
N2  - Recently, C K-edge Near Edge X-ray Absorption Fine Structure (NEXAFS) spectra of graphite (HOPG) surfaces have been measured for the pristine material, and for HOPG treated with either bromine or krypton plasmas (Lippitz et al., Surf. Sci., 2013, 611, L1). Changes of the NEXAFS spectra characteristic for physical (krypton) and/or chemical/physical modifications of the surface (bromine) upon plasma treatment were observed. Their molecular origin, however, remained elusive. In this work we study by density functional theory, the effects of selected point and line defects as well as chemical modifications on NEXAFS carbon K-edge spectra of single graphene layers. For Br-treated surfaces, also Br 3d X-ray Photoelectron Spectra (XPS) are simulated by a cluster approach, to identify possible chemical modifications. We observe that some of the defects related to plasma treatment lead to characteristic changes of NEXAFS spectra, similar to those in experiment. Theory provides possible microscopic origins for these changes.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - paper 173 
KW  - absorbtion fine-structure
KW  - graphite
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-74429
SP  - 14083
EP  - 14095
ER  -