TY - CONF A1 - Unger, Wolfgang A1 - Lippitz, A. A1 - Illgen, R. A1 - Ehlert, C. A1 - Girard-Lauriault, P.-L. A1 - Donskyi, Ievgen A1 - Haag, R. A1 - Adeli, M. T1 - Low pressure plasma, UV photo and wet chemical modification of graphite, graphene and carbon nano tubes N2 - Graphene is a two-dimensional carbon network with unique properties, including high mechanical stiffness, strength, and elasticity, outstanding electrical and thermal conductivity, and many others. Despite these advantages, its low solubility, poor reactivity and the limited accessibility of a well-defined basal plane are major challenges for applications. An ideal method to overcome these problems is the covalent attachment of functional molecules to its surface which enables further reactive modifications for specific applications. There is a number of different technologies for surface functionalization of graphene and related CNT materials. However, to get control on the functionalization process and to optimize the performance of the modified surfaces analytical tools for surface chemical characterization are required. X-ray absorption (NEXAFS) and photoelectron spectroscopy (XPS) have been identified to be rather powerful here. Specifically NEXAFS spectroscopy underpinned by quantum chemical spectrum simulations is unique in a way to address changes of aromaticity and defect formation at the graphene surface during functionalization. For relevant surface modification technologies, we present examples on how NEXAFS and XPS can perform well. All presented modifications aim on the production of platforms for defined functional 2D nanomaterials, as for example multifunctional hybrid architectures. In detail, we investigated: • Graphene and carbon nanotube functionalized by a Vacuum-Ultraviolet (VUV) induced photochemical process in NH3 or O2 atmospheres in order to introduce amino or hydroxy functionalities, respectively. • Br bonding on r.f. cw low pressure plasma brominated graphite surfaces by using Br2 and bromoform as plasma gases. • A wet chemical method for covalent functionalization of graphene sheets by a one-pot nitrene [2+1] cycloaddition reaction under mild conditions. Here a reaction between 2,4,6-trichloro-1,3,5-triazine and sodium azide with thermally reduced graphene oxide (TRGO) results in defined dichlorotriazine-functionalized graphene sheets. T2 - The 17th European Conference on Applications of Surface and Interface Analysis CY - Montpellier, France DA - 24.09.2017 KW - Graphene KW - XPS KW - NEXAFS PY - 2017 AN - OPUS4-42787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Streeck, C. A1 - Dietrich, Paul A1 - Fischer, Tobias A1 - Rurack, Knut A1 - Unger, Wolfgang A1 - Beckhoff, B. T1 - Characterization of bio-molecular nano-layers by means of reference-free X-ray Spectrometry N2 - Characterization of bio-molecular nano-layers by means of reference-free X-ray Spectrometry An increasing field of application, e.g. in biotechnology is the dedicated adjustment of surface properties by functionalization with organic molecules. For a detailed understanding and further development of such nano-layers, a quantitative determination of the surface density of molecular species is required. By means of reference-free X-Ray Fluorescence (XRF) spectrometry such surfaces can be analyzed quantitatively by detecting specific marker elements. Using calibrated instrumentation and a quantification approach based on atomic fundamental parameters a SI-traceable quantitative analysis without any calibration sample or reference material is possible. A chemical analysis of molecular bonds can be accomplished by X-Ray Absorption Spectroscopy in the Near-Edge region (NEXAFS). Especially in the soft X-ray range an access to relevant light elements like Carbon C, Nitrogen N and Oxygen is possible. Here, aminated surfaces with varying densities of amino groups prepared from binary mixtures of silanes were investigated. In a complementary analysis by X-Ray Photoelectron Spectroscopy (XPS) and Fluorescence measurements based on laser-excitation in the optical light spectrum the functional-group density of silane monolayers were determined. The nitrogen atom in the head-group of the silane-molecule could be used as specific marker for the reference-free quantitative XRF analysis and were used for traceable calibration of XPS and Fluorescence Spectroscopy. T2 - EMRS Spring Meeting 2017, ALTECH 2017, Symposium S, Analytical techniques for precise characterization of nano materials CY - Strasbourg, France DA - 22.05.2017 KW - XPS KW - XRF KW - Amino silane film KW - Traceability PY - 2017 AN - OPUS4-43374 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Radnik, Jörg A1 - Hodoroaba, Vasile-Dan A1 - Rades, Steffi A1 - Oswald, F. A1 - Narbey, S. T1 - Morphological and surface analytical long-term investigations of a CH3NH3PbI3/TiO2 perovskite solar cell N2 - Long-term investigations over 20 weeks of a organic-inorganic hybrid solar cell with SEM/EDX and XPS will be presented. T2 - Kratos User Meeting 2017 CY - Stuttgart, Germany DA - 17.10.2017 KW - Perovskite solar cell KW - SEM with EDX KW - XPS PY - 2017 AN - OPUS4-42626 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Passiu, Cristiana A1 - Rossi, Antonella A1 - Bernard, Laetitia A1 - Paul, Dennis A1 - Hammond, John A1 - Unger, Wolfgang A1 - Venkataraman, Nagaiyanallur V. A1 - Spencer, Nicholas D. T1 - Fabrication and Microscopic and Spectroscopic Characterization of Planar, Bimetallic, Micro- and Nanopatterned Surfaces JF - Langmuir N2 - Micropatterns and nanopatterns of gold embedded in silver and titanium embedded in gold have been prepared by combining either photolithography or electron-beam lithography with a glue-free template-stripping procedure. The obtained patterned surfaces have been topographically characterized using atomic force microscopy and scanning electron microscopy, showing a very low root-mean-square roughness (<0.5 nm), high coplanarity between the two metals (maximum height difference ≈ 2 nm), and topographical continuity at the bimetallic interface. Spectroscopic characterization using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary-ion mass spectrometry (ToF-SIMS), and Auger electron spectroscopy (AES) has shown a sharp chemical contrast between the two metals at the interface for titanium patterns embedded in gold, whereas diffusion of silver into gold was observed for gold patterns embedded in silver. Surface flatness combined with a high chemical contrast makes the obtained surfaces suitable for applications involving functionalization with molecules by orthogonal adsorption chemistries or for instrumental calibration. The latter possibility has been tested by determining the image sharpness and the analyzed area on circular patterns of different sizes for each of the spectroscopic techniques applied for characterization.This is the first study in which the analyzed area has been determined using XPS and AES on a flat surface, and the first example of a method for determining the analyzed area using ToF-SIMS. KW - XPS KW - AES KW - SIMS KW - Lateral resolution KW - Test pattern PY - 2017 UR - http://pubs.acs.org/doi/abs/10.1021/acs.langmuir.7b00942 DO - https://doi.org/10.1021/acs.langmuir.7b00942 SN - 0743-7463 VL - 33 IS - 23 SP - 5657 EP - 5665 PB - ACS AN - OPUS4-40929 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kok, H. T. A1 - Donskyi, Ievgen A1 - Adeli, M. A1 - Unger, Wolfgang A1 - Haag, R. T1 - 2D nanomaterials with switchable pathogen binding N2 - Graphene and its derivatives have recently attracted much attention for sensing and deactivating pathogens. However, mechanism of multivalent interactions at the graphene-pathogen interface are not fully understood. Since different physicochemical parameters of graphene play a role at this interface, control over graphene’s structure is necessary to study the mechanism of these interactions. In this work, zwitterionic graphene nanomaterials (ZGNMs) were synthesized with defined isoelectric points and exposure, in terms of polymer coverage and functionality. Then, the switchable interactions of ZGNMs with E. coli were investigated to study the validity of the generally proposed “trapping” mechanism for inactivating pathogens by functionalized graphene derivatives. The ZGNMs were able to controllably trap and release E. coli by crossing their isoelectric points. T2 - 4th Erlangen Symposium on Synthetic Carbon Allortopes 2017 CY - Erlangen, Germany DA - 25.09.2017 KW - Graphene KW - XPS KW - NEXAFS KW - Zwitterionic graphene nanomaterials PY - 2017 AN - OPUS4-47084 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Rades, Steffi A1 - Oswald, F. A1 - Narbey, S. A1 - Radnik, Jörg T1 - Time dependent Analysis of Morphology, Elemental and Chemical Composition of CH3NH3PbI3/TiO2 Solar Cell Layered System N2 - The motivation of this work is to produce thin films perovskite solar cells with constant high light conversion efficiency over time. Loss of efficiency may be caused by structural and/or chemical alterations of the complex layered system. As these changes might take place either in the bulk and/or on the surface of the stratified material, analytical tools addressing both key issues are selected and combined. SEM/EDS combined with XPS were chosen as appropriate methodical approach to characterise perovskite laboratory cells in depth and complementary on top, before and after light exposure. The layered perovskite system investigated here is based on glass covered with fluorine doped tin oxide (FTO), followed by three porous thin films of TiO2, ZrO2 and a thick monolithic carbon. The TiO2 film is subdivided into a dense layer covered by a porous one constituted of nanoparticles with a truncated bipyramidal shape. This layered system serves as the matrix for the perovskite. After infiltration of perovskite solution and annealing, EDS spectral maps on cross-sections of the specimen have been measured. The distribution of relevant elements – Si, Sn, Ti, Zr and C – correlates conclusively with layers visible in the acquired SEM images. Lead and iodine are distributed throughout the porous layers C, ZrO2 and TiO2. Specimens were exposed to ambient daylight for 7 weeks. In a SEM micrograph taken of the cross-section of a sample after illumination, the glass substrate and all layers FTO, TiO2, ZrO2 as well as C are clearly identified. EDS data have been acquired under the same measurement conditions as before the illumination. It was found that several weeks of ambient daylight did not change significantly the qualitative elemental composition of lead and iodine throughout the solar cell system. It was confirmed with EDS that nanoparticles identified in high-resolution SEM micrographs contain mainly Pb and I, indicating these to be the perovskite crystals. However, a time-dependent compositional and chemical altering was observed with XPS for the near-surface region of the outermost ~10 nm after 2 months of illumination. T2 - EMAS 2017 - 15th European Workshop on MODERN DEVELOPMENTS AND APPLICATIONS IN MICROBEAM ANALYSIS and IUMAS-7 Meeting CY - Konstanz, Germany DA - 07.05.2017 KW - Perovskite KW - Layer analytics KW - SEM/EDX KW - XPS KW - Solar cells PY - 2017 AN - OPUS4-40253 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Rades, Steffi A1 - Oswald, F. A1 - Narbey, S. A1 - Radnik, Jörg T1 - Morphological and Chemical Composition of a CH3NH3PbI3/TiO2 Solar Cell Layered System N2 - Manufacturing of new perovskite layered solar cells with constant high light conversion efficiency over time may be hampered by the loss of efficiency caused by structural and/or chemical alterations of the complex layered system. SEM/EDX combined with XPS were chosen as an appropriate methodical approach to characterize perovskite laboratory cells in depth and at surface, before and after light exposure. The layered perovskite system investigated here is based on glass covered with fluorine doped tin oxide (FTO), followed by thin films of TiO2, ZrO2 and a thick monolithic carbon. TiO2 film is subdivided into a dense layer covered by porous one constituted of nanoparticles (NPs) of truncated bipyramidal shape. This layered system serves as the matrix for the perovskite. EDX spectral maps on cross-sections of specimen have shown that Pb and I are distributed homogeneously throughout the porous layers C, ZrO2 and TiO2. SEM/EDX data show that 20 weeks of ambient daylight did not change significantly the indepth distribution of the elemental composition of Pb and I throughout the entire solar cell system. It was confirmed with EDX that NPs identified in high-resolution SEM micrographs contain mainly Pb and I, indicating these to be the perovskite crystals. However, a compositional and chemical altering began in the near-surface region of the outermost ~10 nm after 2 months of illumination which was observed with XPS. T2 - 17th European Conference on Applications of Surface and Interface Analysis ECASIA 2017 CY - Montpellier, France DA - 24.09.2017 KW - Perovskite KW - Solar cells KW - SEM/EDX KW - XPS KW - Layer analysis PY - 2017 AN - OPUS4-42657 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hodoroaba, Vasile-Dan A1 - Rades, Steffi A1 - Oswald, F. A1 - Narbey, S. A1 - Radnik, Jörg T1 - Complementary methodical approach for the analysis of a perovskite solar cell layered system N2 - Loss in efficiency of perovskite solar cells may be caused by structural and/or chemical alterations of the complex layered system. As these changes might take place either in the bulk and/or on the surface of the stratified material, analytical tools addressing both key issues are selected and combined. SEM/EDX combined with XPS were chosen as appropriate methodical approach to characterise perovskite laboratory cells in depth and complementary on top, before and after light exposure. The layered perovskite system investigated here is based on glass covered with fluorine doped tin oxide (FTO), followed by three porous thin films of TiO2, ZrO2 and a thick monolithic carbon. The TiO2 film is subdivided into a dense layer covered by a porous one constituted of nanoparticles with a truncated bipyramidal shape. This layered system serves as the matrix for the perovskite. After infiltration of perovskite solution and annealing, EDX spectral maps on cross-sections of the specimen have been measured. The distribution of relevant elements – Si, Sn, Ti, Zr and C – correlates conclusively with layers visible in the acquired SEM images. Lead and iodine are distributed throughout the porous layers C, ZrO2 and TiO2. In a SEM micrograph taken of the cross-section of a sample after illumination, the glass substrate and all layers FTO, TiO2, ZrO2 as well as C are clearly identified. By EDX it was found that several weeks of ambient daylight did not change significantly the qualitative elemental composition of lead and iodine throughout the solar cell system. It was confirmed with EDX that nanoparticles identified in high-resolution SEM micrographs contain mainly Pb and I, indicating these to be the perovskite crystals. However, a time-dependent compositional and chemical altering was observed with XPS for the near-surface region of the outermost ~10 nm after two months of illumination. T2 - Microscopy & Microanalysis 2017 Meeting CY - St. Louis, MO, USA DA - 06.08.2017 KW - Thin films KW - EDX KW - XPS KW - SEM KW - Nanoparticles KW - Perovskite KW - TiO2 PY - 2017 AN - OPUS4-41664 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Heinrich, Thomas A1 - Hupatz, H. A1 - Lippitz, Andreas A1 - Schalley, C. A1 - Unger, Wolfgang T1 - NEXAFS and XPS investigations of a dual switchable rotaxane multilayer N2 - A multilayer consisting of two different rotaxanes was investigated with different analytical methods. The rotaxanes can be switched with two different stimuli - chemical and photochemical. XPS indicates that our layer-by-layer approach worked and a layer growth with every deposition step is present. NEXAFS showed that both stimuli cause an increase of the multilayer's preferential orientation. T2 - BESSY User Meeting CY - Berlin, Germany DA - 13.12.2017 KW - NEXAFS KW - XPS KW - Rotaxanes PY - 2017 AN - OPUS4-43616 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - THES A1 - Ehlert, Christopher T1 - Simulationen von Röntgenabsorptionsprozessen zur Charakterisierung von Systemen in kondensierter Phase N2 - Diese Doktorarbeit ist das Resultat einer intensiven und fruchtbaren Zusammenarbeit zwischen dem Fachbereich 6.1 (Oberflächenanalytik und Grenzflächenchemie) der Bundesanstalt für Materialforschung und -prüfung (BAM) sowie der Arbeitsgruppe Theoretische Chemie von Professor Saalfrank an der Universität Potsdam. Zusammen haben wir die Strukturaufklärung von Systemen in kondensierter Phase unter Verwendung der Röntgenabsorptionsspektroskopie betrieben. Von Seiten der BAM wurden experimentelle Röntgenabsorptionsspektren hoher Auflösung an modernen Synchrotroneinrichtungen (BESSY II, Berlin) aufgenommen. Die Theoretische Chemie liefert, unter Verwendung quantenchemischer Methoden, die Möglichkeit die Spektren zu simulieren. Bei der Röntgenabsorption wird ein Photon hoher Energie von einem molekularen System absorbiert und in einen angeregten Zustand versetzt. Die Intensität der Absorption ist stark abhängig von der eingestrahlten Photonenenergie. Das resultierende Absorptionsspektrum enthält eine Vielzahl von Informationen. Meine Aufgabe bestand darin, die untersuchten Systeme am Computer zu modellieren. KW - XPS KW - NEXAFS KW - Spektrensimulation PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-104844 SP - 1 EP - 142 PB - Universität Potsdam CY - Potsdam AN - OPUS4-39562 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -