TY - JOUR A1 - Wetzel, Annica A1 - von der Au, Marcus A1 - Dietrich, P. M. A1 - Radnik, Jörg A1 - Özcan Sandikcioglu, Özlem A1 - Witt, Julia T1 - The comparison of the corrosion behavior of the CrCoNi medium entropy alloy and CrMnFeCoNi high entropy alloy JF - Applied Surface Science N2 - This work presents the determination of the corrosion characteristics of CrCoNi (medium entropy alloy) and CrMnFeCoNi (high entropy alloy) in 0.1 M NaCl and 0.1 M H2SO4. The morphology and chemical composition of the oxide layers formed on CrCoNi and CrMnFeCoNi were comparatively analyzed by scanning Kelvin probe microscopy (SKPFM) and scanning electron microscopy (SEM) and supported with chemical analysis by means of inductively coupled plasma mass spectrometry (ICP-MS) and X-Ray photoelectron spectroscopy (XPS). The analysis of the 3p core level peaks showed that the oxide layer (native and after anodic passivation) on CrCoNi consisted mainly of Cr oxides, while the oxide layer on CrMnFeCoNi was primarily composed of a mixture of Cr and Fe oxides. In addition, XPS was utilized to assess the oxide layer thicknesses. These results were compared to the thicknesses obtained by means of electrochemical impedance spectroscopy (EIS), with both approaches yielding values up to about 4 nm depending on the electrolyte and the alloy. Cyclic polarization measurements indicated superior corrosion resistance of CrCoNi in both aqueous environments compared to CrMnFeCoNi, as well as to AISI 304 stainless steel. KW - Medium entropy alloy KW - High entropy alloy KW - SKPFM KW - XPS KW - Passivation KW - Corrosion PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-559902 DO - https://doi.org/10.1016/j.apsusc.2022.154171 SN - 0169-4332 VL - 601 SP - 1 EP - 10 PB - Elsevier B.V. AN - OPUS4-55990 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wittmar, J. A1 - Meyer, Susann A1 - Sieling, T. A1 - Kunte, Hans-Jörg A1 - Smiatek, Jens A1 - Brand, Izabella T1 - What Does Ectoine Do to DNA? A Molecular-Scale Picture of Compatible Solute−Biopolymer Interactions JF - The Journal of Physical Chemistry N2 - Compatible solutes are accumulated in the cytoplasm of halophilic microorganisms. These molecules enable their survival in a high salinity environment. Ectoine is such a compatible solute. It is a zwitterionic molecule which strongly interacts with surrounding water molecules and changes the dynamics of the local hydration shell. Ectoine interacts with biomolecules such as lipids, proteins and DNA. The molecular interaction between ectoine and biomolecules in particular the interaction between ectoine and DNA is far from being understood. In this paper we describe molecular aspects of the interaction between ectoine and double stranded DNA(dsDNA). Two 20 base pairs long dsDNA fragments were immobilized on a Gold surface via a thiol-tether. The interaction between the dsDNA monolayers with diluted and concentrated ectoine solutions was examined by means of X-ray photoelectron and polarization modulation infrared reflection absorption spectroscopies (PM IRRAS). Experimental results indicate that the ability of ectoine to bind water reduces the strength of hydrogen bonds formed to the ribose-phosphate backbone in the dsDNA. In diluted (0.1 M) ectoine solution, DNA interacts predominantly with water molecules. The sugar-phosphate backbone is involved in the formation of strong hydrogen bonds to water, which with elapsing time leads to a reorientation of the planes of nucleic acid bases. This reorientation destabilizes the hydrogen bonds strength between the bases and leads to a partial dehybridizaiton of the dsDNA. In concentrated ectoine solution (2.5 M), almost all water molecules interact with ectoine. Under this condition ectoine is able to interact directly with DNA. Density functional theory (DFT) calculations demonstrate that the direct interaction involves the nitrogen atoms in ectoine and phosphate groups in the DNA molecule. The results of the quantum chemical calculations Show that rearrangements in the ribose-phosphate backbone, caused by a direct interaction with ectoine, facilitates contacts between O atom in the phosphate group and H atoms in a nucleic acid base. In the PM IRRA spectra, an increase in the number of the IR absorption modes in the base pair frequency region proves that the hydrogen bonds between bases become weaker. Thus, a sequence of reorientations caused by interaction with ectoine leads to a breakdown of hydrogen bonds between bases in the double helix. KW - Compatible solute KW - Ectoine KW - DNA KW - Self-assembled monolayer KW - IR spectroscopy KW - XPS PY - 2020 DO - https://doi.org/10.1021/acs.jpcb.0c05273 VL - 124 IS - 37 SP - 7999 EP - 8011 PB - ACS Publicatios AN - OPUS4-51182 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yegen, E. A1 - Lippitz, Andreas A1 - Treu, Dieter A1 - Unger, Wolfgang T1 - Derivatization of amino groups by pentafluorobenzaldehyde (PFB) as observed by XPS and NEXAFS spectroscopy on spin coated 4,4'-methylenebis(2,6-diethylaniline) films JF - Surface and interface analysis N2 - A toluene solution of 4,4´-methylenebis(2,6-diethylaniline) was spin coated on Si wafers. The samples were derivatized with pentafluorobenzaldehyde (PFB) in order to determine the primary amino groups on the surface. XPS C 1s and N 1s and C and N K-edge NEXAFS of underivatized and derivatized films were carefully analyzed. The result was that after 10 min of exposure the gas-surface reaction was already completed. A reasonable derivatization reaction yield in the order of 90% is derived from the experiments. This number correlates well to a reaction yield obtained by a wet chemical approach. KW - Amino groups KW - Derivatization KW - PFB KW - XPS KW - NEXAFS PY - 2008 DO - https://doi.org/10.1002/sia.2685 SN - 0142-2421 SN - 1096-9918 VL - 40 IS - 3-4 SP - 176 EP - 179 PB - Wiley CY - Chichester AN - OPUS4-17193 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Yegen, E. A1 - Zimmermann, Uwe A1 - Unger, Wolfgang A1 - Braun, T. T1 - C-F bond cleavage during derivatization reactions of amino groups with TFBA and PFB at plasma-processed organic surfaces? JF - Plasma processes and polymers N2 - Chemical derivatization XPS is used for the quantitative determination of amines at conventional organic surfaces, and it is also applied to plasma-processed aminated surfaces. When using TFBA and PFB as derivatization reagents for tagging primary amino groups, unexpected fluorine species were observed in the second case. The existence of reaction pathways other than those expected for amine derivatization with PFB or TFBA has to be assumed. This phenomenon is tentatively interpreted as the result of C—F bond cleavage during derivatization reactions of TFBA and PFB at plasma-polymerized allylamine and other plasma-processed aminated surfaces. As a consequence, quantification procedures based on derivatization by PFB or TFBA will underestimate amine surface concentrations. KW - Aminated surfaces KW - Chemical derivatization KW - ESCA KW - Plasma polymers KW - XPS PY - 2009 DO - https://doi.org/10.1002/ppap.200800100 SN - 1612-8850 SN - 1612-8869 VL - 6 IS - 1 SP - 11 EP - 16 PB - Wiley-VCH Verl. CY - Weinheim AN - OPUS4-18686 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Österle, Werner A1 - Dörfel, Ilona A1 - Urban, Ingrid A1 - Reier, T. A1 - Schultze, J. T1 - XPS and XTEM study of AlN formation by N+2 implantation of aluminium JF - Surface and coatings technology N2 - X-ray photoelectron spectroscopy (XPS) and cross-sectional transmission electron microscopy (XTEM) were used to study the formation of AlN films by N+2 ion implantation of aluminium at energies of 3 keV and 100 keV. In both cases, a two-stage mechanism was found, comprising first the oriented precipitation of small particles of the hexagonal AlN-phase, followed by growth and coalescence finally forming a continuous AlN-layer while increasing the implantation dose from 1×1017 cm-2 to 2×1017 cm-2. The results of both methods are in excellent agreement and furthermore provide complementary information concerning chemical composition and binding energies as well as microstructural details. KW - AIN KW - Aluminium KW - N2+ KW - Implantation KW - XPS KW - XTEM PY - 1998 DO - https://doi.org/10.1016/S0257-8972(98)00355-7 SN - 0257-8972 VL - 102 IS - 1-2 SP - 168 EP - 174 PB - Elsevier Science CY - Lausanne AN - OPUS4-2363 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -