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Analytical Sciences has developed from Ostwald’s “unentbehrlichen Dienstmagd” to a chemical discipline at the core of many of today’s fundamental and applied scientific problems and innovations. An atomic or molecular understanding of basic processes in chemistry, soft matter physics, materials and life science is enabled only through new analytical methods and instrumentation. Similar observations can be found for pressing sociopolitical conflicts of the future: A rational discussion of global climate change or new energy sources is only possible with reliable analytical results. Progress in Analytical Sciences is only possible if the underlying interdisciplinary character is acknowledged and valued. The talk will illustrate the scope of modern Analytical Science through examples from process analysis relevant to modern process intensification and industry 4.0 to bioanalysis and the use of synchrotron radiation to elucidate fundamental reactions materials.
The influence of starting materials and synthesis route on the properties and the structure of cementitious sodium aluminosilicate gels is not fully understood, partly due their amorphous nature and the fact that they often contain residual reactants, which can make the results of single-pulse NMR spectroscopy applied to these materials difficult to interpret or ambiguous. To overcome some of these limitations, 29Si{27Al} TRAPDOR NMR as well as 27Al{29Si} and 27Al{1H} REDOR NMR spectroscopy were applied to materials synthesized by the one-part alkali-activation route from three different amorphous silica starting materials, including rice husk ash. The latter led to formation of a fully amorphous sodium aluminosilicate gel (geopolymer), while the materials produced from the other silicas contained amorphous phase and crystalline zeolites. Application of the double-resonance NMR methods allowed to identify hydrous alumina gel domains in the rice husk ash-based material as well as significantly differing amounts of residual silica in the three cured materials. Four-coordinated Al existed not only in the aluminosilicate gel framework but also in a water-rich chemical environment with only a small amount of Si in proximity, likely in the alumina gel or possibly present as extra-framework Al in the aluminosilicate gel. The results demonstrate how the employment of different silica starting materials determines the phase assemblage of one-part alkali-activated materials, which in turn influences their engineering properties such as the resistance against chemically/biologically aggressive media.
Absorption edge tomography, also known as differential tomography at absorption edges, is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. Synchrotron radiation is the best source for absorption edge tomography, because of its small bandwidth, high intensity and easily adjustable photon energy. The synchrotron beamline BAMline at the synchrotron radiation facility BESSY II in Berlin, which is operated by the Bundesanstalt für Materialforschung und -prüfung (BAM), provides a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%, when the double multilayer monochromator is used. Together with the microtomography setup, this enables differential tomography with submicron resolution at the K edge of the elements from chromium up to the lanthanides, and up to uranium, when the L edges are used as well.
In this work, metal organic frameworks (MOFs) embedded in polymer are characterized using differential tomography. MOFs are microporous structures of metal ions, coordinated by organic linker molecules, that can be used in a broad field of applications, especially in gas storage and catalysis. In this work, polymer embedded MOFs were extruded into filaments, which could be used for 3d-printing to profit from the specific properties of the MOFs in polymeric materials combined with the arbitrary shapes provided by 3d-printing. For the extrusion, different polymer classes like ABS, polyester- and polyetherurethanes, as well as different MOFs (ZIF-8, ZIF-67, HKUST-1) were used to create MOF containing filaments with a nominal diameter of 3.0 mm. Differential tomography at the edges of the Zn, Co, and Cu was then used to find the distribution of the corresponding MOF in the filament and to analyze the shape of the inclusions.
The common characterization and identification of pollen is a time-consuming task that mainly relies on microscopic determination of the genus-specific pollen morphology. A variety of spectroscopic and spectrometric approaches have been proposed to develop a fast and reliable pollen identification using specific molecular information. Amongst them, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) shows a high potential for the successful investigation of such complex biological samples. Based on optimized MALDI sample preparation using conductive carbon tape, the application of multivariate statistics (e.g. principal components analysis, PCA) yields an enormous improvement concerning taxonomic classification of pollen species compared to common microscopic techniques.
Since multivariate evaluation of the recorded mass spectra is of vital importance for classification, it’s helpful to implement the applied sequence of standard Matlab functions into a graphical user interface (GUI). In this presentation, a stand-alone application (GUI) is shown, which provides multiple functions to perform fast multivariate analysis on multiple datasets. The use of a GUI enables a first overview on the measured dataset, conducts spectral pretreatment and can give classification information based on HCA and PCA evaluation. Moreover, it can be used to improve fast spectral classification and supports the development of a simple routine method to identify pollen based on mass spectrometry.
Organic/inorganic mixtures were prepared from ordinary Portland cement (OPC), water (w/c 0.22), a fluorescent dye in aqueous solution (stable at alkaline pH; BAM-I), and two different comb shape polycarboxylates (PCEs), i.e., high charge (PCE-HC) and low charge (PCE-LC), respectively. Rheological and calorimetric measurements were performed prior to optical studies in order to select PCE concentrations. Absorption and fluorescence spectroscopy of the system OPC + BAM-I (CBAM-I) revealed maxima of dye BAM-I located at 645 nm and 663 nm, respectively. In presence of PCE-HC and PCE-LC, these mixtures displayed a small red shift in reflectance and a faster decrease in intensity compared to studies with CBAM-I; however, only slight differences were observed between the different PCEs. With time, all systems exhibited a decrease in intensity of BAM-I in absorption/reflectance and emission. This could be caused by dye adsorption and possibly decomposition when in contact with cement particles or hydration products.
The damage caused by ionizing radiation to DNA and proteins is the reason to treat cancer by radiation therapy. A better understanding of the molecular processes and quantification of the different damaging mechanisms is the prerequisite to develop more efficient therapies. Hereby the understanding of the processes involved in the damage to DNA are of key interest due to its central role in reproduction and mutation.
For radiation with low linear energy transfer (LET), most of the damage is caused by the secondary particles produced by scattering of the ionizing radiation with water. Thereby a multitude of species are produced, whereby especially kinetic low energy electrons, prehydrated electrons, OH-radicals and ions are of importance. With higher LET the relative amount of the direct damaging effects increases. This is especially important considering the increased usage of high LET nucleons in radiation therapy. Therefore, the quantification of the contribution to DNA damage of direct and indirect effects and the different secondary species is of high interest due to the increase of radio biological efficiency when applying high LET radiation.
Here we present an approach to investigate the relative contributions to DNA strand break yield for radiation of different LET within a single electron microscope in combination with electron scattering simulations.
Polynuclear aluminium species (Al13 keggin cluster) find application in different areas like water purification [1], contaminant transport [2], and as pilling clays with high specific surface areas[3], due to their strong binding ability to aggregates and high positive charge.
In the present contribution, we report on the in situ investigation of the Al13 sulfate synthesis by synchrotron wide-angle X-ray scattering (WAXS). Al13 cluster were crystallized by precipitating hydrolyzed aluminum solutions by the addition of sodium sulfate. The measurements were performed using a custom-made acoustic levitator as sample holder. The study provides information about the intermediates during the crystallization process. From the data, a mechanism was derived indicating the influence of the crystallization process.
At first, formation of cycles in commercial poly(Llactide)s is discussed and compared with benzyl alcoholinitiated polymerizations performed in this work. This comparison was extended to polymerizations initiated with 4-cyanophenol and pentafluorothiophenol which yielded cyclic polylactides via end-biting. The initiator/catalyst ratio and the acidity of the initiator were found to be decisive for the extent of cyclization. Further polymerizations of L-lactide were performed with various diphenols as initiators/co-catalysts. With most diphenols, cyclic polylactides were the main reaction products. Yet, only catechols yielded even-numbered cycles as main reaction products, a result which proves that their combination with SnOct2 catalyzed a ring-expansion polymerization (REP). The influence of temperature, time, co-catalyst, and catalyst concentrations was studied. Four different transesterification reactions yielding cycles were identified. For the cyclic poly(L-lactide)s weight average molecular weights (Mw’s) up to 120,000 were obtained, but 1H NMR end group analyses indicated that the extent of cyclization was slightly below 100%.
The influence of various parameters like structure of Initiator and catalyst and temperature on the formation of cyclic poly(Llactide)s has been investigated. Depending on the chosen conditions, the course of the polymerization can be varied from a process yielding exclusively linear polylactides to mainly cyclic polylactides. Three different reaction pathways for cyclization reactions have been identified.
Der Mangel an Anwendungsrichtlinien und Validierungsverfahren für struktur-eingebettete faseroptische Dehnungssensoren, insbesondere auf Faser-Bragg-Gitter (FBG)-Basis, führte bislang dazu, dass diese Sensoren trotz ihrer hervorragenden Eigenschaften im Bereich der kommerziellen Material- und Strukturüberwachung nur in geringem Umfange eingesetzt wurden. Fragen zur Degradation der Sensoren unter Beanspruchung, Alterung durch klimatische Einflüsse und Enthaftung infolge Belastung der Struktur konnten bisher nur theoretisch simuliert oder anhand exemplarischer Proben für einzelne einflussnehmende Parameter im Labor untersucht werden. Die Erfassung des Sensorverhaltens im Bauteil unter komplexen Umwelteinflüssen während des Bauteilbetriebes, um damit eine Aussage zur Zuverlässigkeit der Sensormessdaten zu gewinnen, war bisher nicht möglich.
Im Forschungsprojekt FAMOS² wurde deshalb von 2014 bis 2018 die Realisierung eines Autodiagnoseverfahrens für faseroptische Dehnungssensoren erarbeitet, um die Funktionszuverlässigkeit und Langzeitstabilität der Sensoren während des Bauteilbetriebes innerhalb einer Bauteilstruktur bewerten zu können. Im Rahmen des Forschungsprojektes wurde gezeigt, dass ein FBG-Sensor mit einer speziell angepassten magnetostriktiven Schicht magnetisch so angeregt werden kann, dass mit einer zugeschnittenen Messmethodik zu jedem Zeitpunkt eine Bewertung der Sensorzuverlässigkeit unter Betriebsbedingungen möglich ist. Die auf den Sensor aufgebrachte magnetostriktive Schicht erzeugt bei Anregung mit einem passenden Magnetfeld eine gepulste, synthetische Dehnung. Diese Dehnung steht in einem definierten Verhältnis zum anregenden Magnetfeld und wird optisch über die Verschiebung der Bragg-Wellenlänge ausgelesen. Die Konstanz dieses Verhältnisses stellt dann ein Maß für die korrekte Funktionsfähigkeit des Sensors dar. Das Beschichtungs-verfahren, das magnetische Anregungs- und optische Ausleseverfahren, wie auch die Validierung des Sensors unter Berücksichtigung faseroptischer Effekte wurden während des Projekts konzeptionell entwickelt, aufgebaut und charakterisiert. Qualitativ kann mit diesem Verfahren zunächst eine Gut-/Schlecht-Beurteilung des Sensors vorgenommen werden. Perspektivisch bietet das Verfahren jedoch auch die Möglichkeit, verschiedene Versagensmechanismen bestimmen und klassifizieren zu können. Es zeichnete sich schon während des Projektverlaufs ab, dass sich aus den erzielten Ergebnissen über das Autodiagnoseverfahren hinaus weitere Anwendungsmöglichkeiten für den Einsatz des kombinierten magnetostriktiv-faseroptischen Sensorprinzips, beispielsweise als reiner Magnetfeldsensor, ergeben.
Nach Abschluss dieses Forschungsprojekts besteht nun die Möglichkeit, den Funktionszustand faseroptischer Dehnungssensoren jederzeit unabhängig von Alter, Belastung oder Kenntnis eines Referenzzustands zu einem bestimmten Zeitpunkt bestimmen zu können. Aufbauend auf diesen Ergebnissen können weiterführende Forschungen die Messmethodik vertiefend charakterisieren und weitere Anwendungsfälle erschließen.
In this talk sample prep/handling, instrument calibration and data acquisition methods with examples from XPS, Auger and SIMS will be addressed in terms of their contributions to the reproducibility of data delivered by the methods.
Active parties in the field are VAMAS TWA 2 “Surface chemical analysis” (http://www.vamas.org/twa2/index.html), ISO/TC 201 “Surface chemical analysis” (https://www.iso.org/committee/54618.html) and the Surface Analysis Working Group (SAWG) at the International Meter Convention (https://www.bipm.org/en/ committees/cc/wg/sawg.html). The tools to improve the reproducibility of spectra, depth profiles and images at these international platforms are inter-laboratory comparisons, validated SOPs, standards and certified reference materials (CRM) as well as uncertainty budgets and establishment of traceability chains. The last point is of specific importance because all the methods, XPS, Auger and SIMS, are not primary methods.
To address quantitative XPS, AES and SIMS results of relevant inter-laboratory comparisons organized by SAWG considering measurands as alloy surface composition and thickness of thin films will be introduced. These comparisons delivered results which are viewed to be benchmarking, some of them resulted in ISO/TC 201 standards. For quantitative XPS and AES the principal outline of an uncertainty budget will be discussed together with the audience. Another issue of quantitative XPS which definitely needs consideration are valid methods for a determination of the transmission function of the instruments and even for the emission angle in the respective experiments.
Concerning the field of depth profiling it has to be investigated together with the audience whether the ISO (or ASTM) standards we have are sufficient to guarantee comparable results. Having in mind the number of different sputter ion species available today and range of samples of interest (metals, semiconductors, organic films) this might be questionable. And, how do depth profiling by AR-XPS and variable excitation energy XPS compete here?
For imaging surface chemical analysis, the characterization of the imaging system is an issue to be investigated. Here the determination of lateral resolution is a relevant topic.
Finally, the future needs to develop metrology for new applications e.g., ambient-pressure XPS, bio samples, and core-shell nanoparticles, will be issues raised for a discussion with the audience.