TY - JOUR A1 - Bassil, A. A1 - Wang, Xin A1 - Chapeleau, X. A1 - Niederleithinger, Ernst A1 - Abraham, O. A1 - Leduc, D. T1 - Distributed fiber optics sensing and coda wave interferometry techniques for damage monitoring in concrete structures N2 - The assessment of Coda Wave Interferometry (CWI) and Distributed Fiber Optics Sensing (DFOS) techniques for the detection of damages in a laboratory size reinforced concrete beam is presented in this paper. The sensitivity of these two novel techniques to micro cracks is discussed and compared to standard traditional sensors. Moreover, the capacity of a DFOS technique to localize cracks and quantify crack openings is also assessed. The results show that the implementation of CWI and DFOS techniques allow the detection of early subtle changes in reinforced concrete structures until crack formation. With their ability to quantify the crack opening, following early detection and localization, DFOS techniques can achieve more effective monitoring of reinforced concrete structures. Contrary to discrete sensors, CWI and DFOS techniques cover larger areas and thus provide more efficient infrastructures asset management and maintenance operations throughout the lifetime of the structure. KW - Distributed fiber optic sensors KW - Coda wave interferometry KW - Reinforced concrete KW - Cracks KW - Damage detection KW - Structural health monitoring PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-472549 DO - https://doi.org/10.3390/s19020356 SN - 1424-8220 VL - 19 IS - 2 SP - 356, 1 EP - 15 PB - MDPI AN - OPUS4-47254 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - El-Khatib, A. H. A1 - Radbruch, H. A1 - Trog, S. A1 - Neumann, B. A1 - Paul, F. A1 - Koch, A. A1 - Linscheid, M. W. A1 - Jakubowski, Norbert A1 - Schellenberger, E. T1 - Gadolinium in human brain sections and colocalization with other elements N2 - Recent recommendations by the Food and Drug Administration1 and the European Medicines Agency2 are to limit the clinical use of linear gadolinium-based contrast agents (GBCAs) due to convincing evidence of deposition in tissues. Macrocyclic GBCA continued to be considered safe, provided that patients have normal renal function. To date, given the low sensitivity of conventional MRI, there has been a debate about the signal increase following the injections of a macrocyclic GBCA. KW - Gadolinium PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-471309 DO - https://doi.org/10.1212/NXI.0000000000000515 SN - 2332-7812 VL - 6 IS - 1 SP - e515, 1 EP - 3 PB - American Academy of Neurology AN - OPUS4-47130 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Heck, Christian A1 - Kanehira, Y. A1 - Kneipp, Janina A1 - Bald, Ilko T1 - Amorphous Carbon Generation as a Photocatalytic Reaction on DNA-Assembled Gold and Silver Nanostructures N2 - Background signals from in situ-formed amorphous carbon, despite not being fully understood, are known to be a common issue in few-molecule surface-enhanced Raman scattering (SERS). Here, discrete gold and silver nanoparticle aggregates assembled by DNA origami were used to study the conditions for the formation of amorphous carbon during SERS measurements. Gold and silver dimers were exposed to laser light of varied power densities and wavelengths. Amorphous carbon prevalently formed on silver aggregates and at high power densities. Time-resolved measurements enabled us to follow the formation of amorphous carbon. Silver nanolenses consisting of three differently-sized silver nanoparticles were used to follow the generation of amorphous carbon at the single-nanostructure level. This allowed observation of the many sharp peaks that constitute the broad amorphous carbon signal found in ensemble measurements. In conclusion, we highlight strategies to prevent amorphous carbon formation, especially for DNA-assembled SERS substrates. KW - Amorphous carbon KW - DNA origami KW - SERS KW - Nanoparticle dimers KW - Nanolenses PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-486484 DO - https://doi.org/10.3390/molecules24122324 SN - 1420-3049 VL - 24 IS - 12 SP - Article Number: 2324-1 EP - 10 PB - MDPI AN - OPUS4-48648 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schürmann, Robin A1 - Ebel, Kenny A1 - Nicolas, C. A1 - Milosavljevic, A. R. A1 - Bald, Ilko T1 - Role of valence band states and plasmonic enhancement in electron-transfer-induced transformation of nitrothiophenol N2 - Hot-electron-induced reactions are more and more recognized as a critical and ubiquitous reaction in heterogeneous catalysis. However, the kinetics of these reactions is still poorly understood, which is also due to the complexity of plasmonic nanostructures. We determined the reaction rates of the hot-electron-mediated reaction of 4-nitrothiophenol (NTP) on gold nanoparticles (AuNPs) using fractal kinetics as a function of the laser wavelength and compared them with the plasmonic enhancement of the system. The reaction rates can be only partially explained by the plasmonic response of the NPs. Hence, synchrotron X-ray photoelectron spectroscopy (XPS) measurements of isolated NTP-capped AuNP clusters have been performed for the first time. In this way, it was possible to determine the work function and the accessible valence band states of the NP systems. The results show that besides the plasmonic enhancement, the reaction rates are strongly influenced by the local density of the available electronic states of the system. KW - Photocatalytic reduction KW - Raman-spectroscopy KW - Hot-electrons KW - Work function KW - Surface KW - Nanaoparticles KW - Scattering KW - Molecule KW - Carriers KW - Layers PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-486464 DO - https://doi.org/10.1021/acs.jpclett.9b00848 SN - 1948-7185 VL - 10 IS - 11 SP - 3153 EP - 3158 PB - American Chemical Society CY - Washington, DC AN - OPUS4-48646 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaghdoudi, Maha A1 - Kömmling, Anja A1 - Jaunich, Matthias A1 - Wolff, Dietmar T1 - Scission, cross-linking, and physical relaxation during thermal degradation of elastomers N2 - Elastomers are susceptible to chemical ageing, i.e., scission and cross-linking, at high temperatures. This thermally driven ageing process affects their mechanical properties and leads to limited operating time. Continuous and intermittent stress Relaxation measurements were conducted on ethylene propylene diene rubber (EPDM) and hydrogenated nitrile butadiene rubber (HNBR) samples for different ageing times and an ageing temperature of 125 °C. The contributions of chain scission and cross-linking were analysed for both materials at different ageing states, elucidating the respective ageing mechanisms. Furthermore, compression set experiments were performed under various test conditions. Adopting the two-network model, compression set values were calculated and compared to the measured data. The additional effect of physical processes to scission and cross-linking during a long-term thermal exposure is quantified through the compression set analysis. The characteristic times relative to the degradation processes are also determined. KW - Ageing KW - Scission KW - Cross-linking KW - Compression set KW - Physical relaxation PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-486091 DO - https://doi.org/10.3390/polym11081280 SN - 2073-4360 VL - 11 IS - 8 SP - 1280, 1 EP - 12 PB - MDPI AN - OPUS4-48609 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Emmerling, Franziska A1 - Stock, Norbert A1 - Tadei, Marco A1 - Demel, Jan A1 - Cabeza, Aurelio A1 - Viviani, Riccardo A1 - Demadis, Konstantinos A1 - Vassaki, Maria T1 - New directions in metal phosphonate and phosphinate chemistry N2 - In September 2018, the First European Workshop on Metal Phosphonates Chemistry brought together some prominent researchers in the field of metal phosphonates and phosphinates with the aim of discussing past and current research efforts and identifying future directions. The scope of this perspective article is to provide a critical overview of the topics discussed during the workshop, which are divided into two main areas: synthesis and characterisation, and applications. In terms of synthetic methods, there has been a push towards cleaner and more efficient approaches. This has led to the introduction of high-throughput synthesis and mechanochemical synthesis. The recent success of metal–organic frameworks has also promoted renewed interest in the synthesis of porous metal phosphonates and phosphinates. Regarding characterisation, the main advances are the development of electron diffraction as a tool for crystal structure determination and the deployment of in situ characterisation techniques, which have allowed for a better understanding of reaction pathways. In terms of applications, metal phosphonates have been found to be suitable materials for several purposes: they have been employed as heterogeneous catalysts for the synthesis of fine chemicals, as solid sorbents for gas separation, notably CO2 capture, as materials for electrochemical devices, such as fuel cells and rechargeable batteries, and as matrices for drug delivery. KW - Metal phosphonates KW - Metal–organic frameworks KW - X-ray and electron diffraction PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-484346 DO - https://doi.org/10.3390/cryst9050270 SN - 2073-4352 VL - 9 IS - 5 SP - 270, 1 EP - 36 PB - MDPI AN - OPUS4-48434 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ghasem Zadeh Khorasani, Media A1 - Elert, Anna Maria A1 - Hodoroaba, Vasile-Dan A1 - Agudo Jácome, Leonardo A1 - Altmann, Korinna A1 - Silbernagl, Dorothee A1 - Sturm, Heinz T1 - Short- and long-range mechanical and chemical interphases caused by interaction of Boehmite (γ-AlOOH) with anhydride-cured epoxy resins N2 - Understanding the interaction between boehmite and epoxy and the formation of their interphases with different mechanical and chemical structures is crucial to predict and optimize the properties of epoxy-boehmite nanocomposites. Probing the interfacial properties with atomic force microscopy (AFM)-based methods, especially particle-matrix long-range interactions, is challenging. This is due to size limitations of various analytical methods in resolving nanoparticles and their interphases, the overlap of interphases, and the effect of buried particles that prevent the accurate interphase property measurement. Here, we develop a layered model system in which the epoxy is cured in contact with a thin layer of hydrothermally synthesized boehmite. Different microscopy methods are employed to evaluate the interfacial properties. With intermodulation atomic force microscopy (ImAFM) and amplitude dependence force spectroscopy (ADFS), which contain information about stiffness, electrostatic, and van der Waals forces, a soft interphase was detected between the epoxy and boehmite. Surface potential maps obtained by scanning Kelvin probe microscopy (SKPM) revealed another interphase about one order of magnitude larger than the mechanical interphase. The AFM-infrared spectroscopy (AFM-IR) technique reveals that the soft interphase consists of unreacted curing agent. The long-range electrical interphase is attributed to the chemical alteration of the bulk epoxy and the formation of new absorption bands. KW - Nanocomposites KW - Interphase KW - Intermodulation AFM KW - Electron microscopy KW - Infrared nano AFM PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483672 UR - https://www.mdpi.com/2079-4991/9/6/853/htm DO - https://doi.org/10.3390/nano9060853 SN - 2079-4991 VL - 9 IS - 6 SP - 853, 1 EP - 20 PB - MDPI AN - OPUS4-48367 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Martins, Inês C.B. A1 - Al-Sabbagh, Dominik A1 - Meyer, Klas A1 - Maiwald, Michael A1 - Scholz, G. A1 - Emmerling, Franziska T1 - Insight into the Structure and Properties of Novel Imidazole-Based Salts of Salicylic Acid N2 - The preparation of new active pharmaceutical ingredient (API) multicomponent Crystal forms, especially co-crystals and salts, is being considered as a reliable strategy to improve API solubility and bioavailability. In this study, three novel imidazole-based salts of the poorly water-soluble salicylic acid (SA) are reported exhibiting a remarkable improvement in solubility and dissolution rate properties. All structures were solved by powder X-ray diffraction. Multiple complementary techniques were used to solve co-crystal/salt ambiguities: density functional Theory calculations, Raman and 1H/13C solid-state NMR spectroscopies. In all molecular salts, the Crystal packing interactions are based on a common charged assisted +N-H SA)...O-(co-former) hydrogen bond interaction. The presence of an extra methyl group in different positions of the co-former, induced different supramolecular arrangements, yielding salts with different physicochemical properties. All salts present much higher solubility and dissolution rate than pure SA. The most promising results were obtained for the salts with imidazole and 1-methylimidazole co-formers. KW - Salicylic acid KW - Imidazole KW - Salts KW - Powder X-ray diffraction KW - SsNMR KW - DFT PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502825 DO - https://doi.org/10.3390/molecules24224144 VL - 24 IS - 22 SP - 4144 PB - MDPI AN - OPUS4-50282 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Burek, K. A1 - Dengler, J. A1 - Emmerling, Franziska A1 - Feldmann, Ines A1 - Kumke, M. U. A1 - Stroh, Julia T1 - Lanthanide Luminescence Revealing the Phase Composition in Hydrating Cementitious Systems N2 - The hydration process of Portland cement in a cementitious system is crucial for development of the high-quality cementbased construction material. Complementary experiments of Xray diffraction analysis (XRD), scanning electron microscopy (SEM) and time-resolved laser fluorescence spectroscopy (TRLFS) using europium (Eu(III)) as an optical probe are used to analyse the hydration process of two cement systems in the absence and presence of different organic admixtures. We Show that different analysed admixtures and the used sulphate carriers in each cement system have a significant influence on the hydration process, namely on the time-dependence in the formation of different hydrate phases of cement. Moreover, the effect of a particular admixture is related to the type of sulphate carrier used. The quantitative information on the amounts of the crystalline cement paste components is accessible via XRD analysis. Distinctly different morphologies of ettringite and calcium-silicate-hydrates (C-S-H) determined by SEM allow visual conclusions about formation of these phases at particular ageing times. The TRLFS data provides information about the admixture influence on the course of the silicate reaction. The dip in the dependence of the luminescence decay times on the hydration time indicates the change in the structure of C-S-H in the early hydration period. Complementary information from XRD, SEM and TRLFS provides detailed information on distinct periods of the cement hydration process. KW - Cement admixtures KW - Cement hydration KW - Europium KW - Luminescence KW - SEM KW - X-ray diffraction PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-504842 DO - https://doi.org/10.1002/open.201900249 VL - 8 IS - 12 SP - 1441 EP - 1452 PB - Wiley-VCH AN - OPUS4-50484 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Belenguer, A. A1 - Michalchuk, Adam A1 - Lampronti, G A1 - Sanders, J T1 - Understanding the unexpected effect of frequency on the kinetics of a covalent reaction under ball-milling conditions N2 - We here explore how ball-mill-grinding frequency affects the kinetics of a disulfide exchange reaction. Our kinetic data show that the reaction progress is similar at all the frequencies studied (15–30 Hz), including a significant induction time before the nucleation and growth process starts. This indicates that to start the reaction an initial energy accumulation is necessary. Other than mixing, the energy supplied by the mechanical treatment has two effects: (i) reducing the crystal size and (ii) creating defects in the structure. The crystal-breaking process is likely to be dominant at first becoming less important later in the process when the energy supplied is stored at the molecular level as local crystal defects. This accumulation is taken here to be the rate-determining step. We suggest that the local defects accumulate preferentially at or near the crystal surface. Since the total area increases exponentially when the crystal size is reduced by the crystal-breaking process, this can further explain the exponential dependence of the onset time on the milling frequency. KW - Mechanochemistry KW - Kinetics KW - Diffraction PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-483361 DO - https://doi.org/10.3762/bjoc.15.120 SN - 2195-951X VL - 15 SP - 1226 EP - 1235 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, M. AN - OPUS4-48336 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -