Browsing by Organization "Department Chemie - Biologie"

Copolymer thin films showing induced supramolecular chirality are of considerable interest for optoelectronic applications such as organic light-emitting diodes. Here, we introduce a new helicene-like chiral additive with two octyloxy substituents which displays excellent chiral induction properties in an achiral polyfluorene copolymer, leading to a circular dichroism (CD) response of up to 10,000 mdeg. This chiral inducer also displays very good thermal stability, which enables us to perform an extended study on the induced chiroptical properties of the cholesteric copolymer thin films annealed at different temperatures in the range 140-260 °C. Starting from about 180 °C, a distinct change in the morphology of the CD-active film is observed by CD microscopy, from micrometre-size granular to extended CD-active regions, where the latter ones display skewed distributions of the dissymmetry parameter gabs. Broadband Müller matrix spectroscopy finds a pronounced CD and circular birefringence (CB) response and only weak linear dichroism (LD, LD') and linear birefringence (LB, LB'). Ultrafast transient CD spectroscopy with randomly polarised excitation reveals a clean mirror-image-type transient response, which shows a second-order decay of the S1 population due to singlet-singlet annihilation processes.

This proceedings volume gathers papers presented at the symposium “Cultural Appropriation of Spaces and Things” held in Siegen, Germany in October 2019. All over the world, children are confronted with an increasingly complicated and fast-moving world. Children need elementary cultural techniques and skills to shape their own lives and enable them to find individual interpretations of meaning. In addition to the acquisition of classical cultural techniques such as arithmetic, writing and reading, the competent handling of spaces and things – through manifold processes of appropriation and reflection – is crucial. It forms the basis and prerequisite for the development of competences or abilities that are suitable for understanding the dimensions, the complexity and changeability of their world and enable them to critically deal with associated problems and find appropriate solutions. The aim of the conference was to find suitable ways for children all over the world for a methodically and didactically guided examination of their natural, social and technical environment. At the same time, the aim was to achieve a mutual enrichment of monodisciplinary research accesses. It also included a self-critical reflection of one’s own culturally shaped approaches of research.

In this work a solid state NMR methodology based on the “NMR visibility” and the concept of NMR blind sphere was established. This method can be used for the study of doping homogeneity of paramagnetic ions, and the resulting “NMR homogeneity” was shown to correlate to the functional material performance. The method has been successfully applied in the model sample series and NMR blind sphere radii for paramagnetic dopants could be obtained. First, in section 3.1, the correlation between NMR signal and the dopant distribution was established, via the development of the “NMR visibility” and the NMR visibility function f(x) curve, which is the visibility f as a function of the doping level x. Such “NMR visibility” was defined as the molar peak area of paramagnetic doped sample normalized by that of the diamagnetic host. The NMR visibility model was tested on Sr1‑xEuxH2 sample series and the formula of the NMR visibility function for homogeneous sample series was developed to be f(x)=exp(-ar0^3x), where the r0 is the NMR blind sphere radius and a is a number density parameter related to the host. The visibility curve calculated from 1H MAS NMR experimental data was consistent with the visibility function f(x) as well as the results calculated by a home-written Fortran90 program based on a random distribution model. Subsequently, in section 3.2, the method was tested in different model compounds series including hopeite (Zn1‑xMnx)3(PO4)2·4H2O with the paramagnetic dopant Mn2+ and NMR nuclei 1H and 31P, Sr1‑xEuxGa2S4 with the paramagnetic dopant Eu2+ and NMR nucleus 71Ga, and monazite La1‑xLnxPO4 with paramagnetic dopants Ln3+ (Ln = Nd, Gd, Dy, Ho, Er, Tm, Yb) and NMR nucleus 31P. For all homogeneously doped sample series the NMR visibility method could be applied and the NMR blind sphere radii were obtained, which lay typically in the Å to nm range. Additionally, the theoretical study of the NMR blind sphere radii was shown. In section 3.3, the NMR visibility function was shown to be able to differentiate a heterogeneous doping scenario from a homogeneous one, as for heterogeneously doped samples a deviation from the visibility function was observed. The term “NMR homogeneity” was thus introduced for homogeneous samples tested by the NMR visibility method. Samples with higher NMR homogeneity were also shown to be positively correlated to better luminescence performance, including intensity and decay time. Furthermore, in section 3.4, the NMR visibility function was extended to co-doped systems including La1‑x‑yGdxDyyPO4, La1‑x‑yNdxTmyPO4 and La1‑x‑yNdxHoyPO4. For La1‑x‑yNdxHoyPO4, a 3D NMR visibility map instead of the 2D NMR visibility curve was developed. As the radii of NMR blind spheres were in Å to nm range, the NMR homogeneity determined by the NMR visibility model was also on a similar length scale. Together with SEM-EDX mapping and SEM-CL techniques, co-doping homogeneity or heterogeneity can be systematically studied from Å to nm range. Overall, the NMR visibility method has been shown to be useful both for theoretical NMR blind sphere studies and for applications in paramagnetic systems as long as NMR nuclei are present.

Nanopartikel (NP), darunter vor allem Silber (Ag) NPs und Titandioxid (TiO2) NPs sind heutzutage in einer Vielzahl von Konsumgütern enthalten, und werden durch den täglichen Gebrauch in das urbane Abwasser und damit in die aquatische Umwelt eingeleitet. Die Toxizität von unbehandelten („pristine“) AgNPs und TiO2NPs auf das aquatische Ökosystem ist hinreichend bekannt. Diese Betrachtung spiegelt aber kein realistisches Bild der Belastung von aquatischen Ökosystemen wider. Während des Klärprozesses in kommunalen Kläranlagen und damit vor dem Eintrag von NPs in die Umwelt, finden Transformationsprozesse statt, die einen großen Einfluss auf deren Toxizität haben können. Eine ökotoxikologische Analyse von sogenannten „wastewater-borne“ NPs wurde bisher nicht ausreichend durchgeführt. Das Projekt „FENOMENO - Fate and effect of wastewater-borne manufactured nanomaterials in aquatic ecosystems” hatte sich daher zum Ziel gesetzt das Verhalten, mit möglichen Transformationsprozessen von NPs zu analysieren und zu charakterisieren und das ökotoxikologische Potential von „wastewaterborne“ AgNPs und TiO2NPs entlang der aquatischen Nahrungskette, Alge-Daphnia-Fisch, zu untersuchen. Im Rahmen dieses Projektes, habe ich in meiner Doktorarbeit die Auswirkungen von „wastewater-borne“ AgNPs und TiO2NPs auf zwei Schlüsselorganismen des aquatischen Ökosystems, Daphnia magna und Danio rerio, untersucht. Im Speziellen habe ich dabei Studien zum Verhalten von D. magna und D. rerio, zum Reproduktionserfolg von sechs aufeinander folgenden Generationen von D. magna unter dem Einfluss von „wastewaterborne“ AgNPs und TiO2NPs durchgeführt. Alle Studien wurden in Konzentrationsbereichen im umweltrelevanten Bereich (basierend auf PEC Werten) und im Vergleich mit „pristine“ AgNPs und TiO2NPs durchgeführt, um eine Aussage über die Toxizität der NPs im Ausfluss der Kläranlage zu treffen. Darüber hinaus habe ich die Ausbildung von Abwehrmechanismen gegenüber Fressfeinden bei D. magna unter dem Einfluss von „pristine“ AgNPs und das Nahinfrarot Sehen von D. rerio Larven untersucht. Ich konnte mit den durchgeführten Experimenten zeigen, dass die Toxizität von „wastewater-borne“ AgNPs im Vergleich zu „pristine“ AgNPs signifikant reduziert ist. So zeigten sich in der Mehrgenerationsstudie mit D. magna keine negativen Effekte auf wichtige Parameter des Lebenszyklus, wie Reproduktionserfolg, Körperlänge oder Tag der ersten Nachkommenschaft. Die Behandlung mit „pristine“ AgNPs führte dagegen zu einer signifikanten Reduktion des Reproduktionserfolgs in allen sechs untersuchten Generationen. Dieses Ergebnis konnte durch die Auswertung von verhaltensrelevanten Endpunkten in den durchgeführten Verhaltensstudien, wie Schwimmhöhe, Ortswechsel und Aufenthaltszeit für D. magna und Schwimmgeschwindigkeit und zurückgelegte Distanz für D. rerio Larven, untermauert werden. Die reduzierte Toxizität von „wastewaterborne“ AgNPs kann hauptsächlich durch die Transformation von AgNPs zu Silbersulfid (Ag2S) erklärt werden. Durch die geringe Wasserlöslichkeit und die verringerte Bildung von Ag+ Ionen ist die Bioverfügbarkeit von Ag deutlich reduziert worden, wodurch das toxische Potential von Ag für aquatische Organismen deutlich sinkt. Weitere Experimente mit umweltrelevanten Konzentrationen an „wastewater-borne“ und „pristine“ TiO2NPs zeigten keinen Einfluss auf Verhaltensrelevante- und Lebenszyklusparameter in beiden untersuchten Schlüsselorganismen. Darüber hinaus konnte ich zeigen, dass keine Ausbildung von Abwehrmechanismen gegenüber Fressfeinden in der nachfolgenden Generation stattfindet, wenn adulte D. magna mit „pristine“ AgNPs behandelt wurden, obwohl sie diese selber zeigen. Die Nachkommen von adulten Daphnien, die mit „pristine“ AgNPs behandelt wurden, zeigten signifikant verringerte Endpunkte, wie z.B. verkürzte Stachelspitze im Verhältnis zur Körperlänge. Dieser Effekt konnte bei „pristine“ TiO2NPs nicht nachgewiesen werden, da hier die Ausbildung der Abwehrmechanismen auch in der nächsten Generation nicht negativ beeinflusst wurde. Entgegen aller bisherigen Annahmen konnte ich zeigen, dass D. rerio Larven nahinfrarotes Licht (NIR) bis zu einer Wellenlänge von 860 nm wahrnehmen können und ein negativ phototaktisches Verhalten zeigen. Dieses Muster ist auch bei visuellem Licht zu erkennen. Wellenlängenbereiche ab 960 nm werden von den Larven nicht mehr wahrgenommen und können für Verhaltensversuche als „dunkele“ Lichtquelle verwendet werden. Durch die Einbeziehung von natürlichen Transformationsprozessen im Lebenszyklus von NPs und von umweltrelevanten Konzentrationen kann meine Arbeit eine realistischere Risikoabschätzung von AgNPs und TiO2NPs für aquatische Organismen liefern. Zusammenfassend habe ich herausgefunden, dass das ökotoxikologische Potential von „wastewater-borne“ NPs als sehr gering einzuschätzen ist und das Risiko für das aquatische Ökosystem bislang deutlich überschätzt wurde. Diese Aspekte sollten in der Risikobewertung und Zulassung von Nanopartikeln, aufgrund ihrer besonderen chemischen Eigenschaften untersucht und berücksichtig werden. Das Wahrnehmen von NIR-Licht von D. rerio Larven stellt zudem eine wichtige Erkenntnis für ökotoxikologische Untersuchungen dar.

Women with cystic fibrosis (CF) have a significantly lower life expectancy compared to men, which is indicated by an earlier impairment of lung function due to chronic colonization with biofilm formed by Pseudomonas aeruginosa. There is growing evidence that blood serum concentrations of the steroid sex hormone estradiol (E2) correlate with the occurrence of pulmonary exacerbations in CF but also play a role in the mucoid switch of P. aeruginosa. This study aims to shed light on possible microbiological reasons for sexual dimorphism in CF by investigating the influence of E2 on biofilm formation of P. aeruginosa CF isolates. For this purpose, 10 CF isolates of the respiratory tract derived from different CF patients have been treated with E2 in a microtiter plate biofilm model. Biofilms have been examined by crystal violet assays, field emission scanning electron microscopy (FE-SEM), 3D laser scanning microscopy (LSM), and quorum sensing (QS) reporter assays of the supernatants taken from biofilms. This allowed us to simultaneously investigate the effects of E2 on attached biofilm mass, biofilm ultrastructure, and QS activity. Upon E2 treatment, six out of 10 investigated CF isolates showed an increase of attached biofilm mass, whereas biofilms from two tested non-CF laboratory strains (PAO1 and ATCC19660) did not. Moreover, FE-SEM and 3D LSM analyses of the E2 responsive CF biofilms revealed ultrastructural remodeling of biofilm structure at different scales with increased formation of prominent biofilm spots, enhanced coverage with extracellular polymeric substance (EPS), and extended average surface roughness. QS activity measurements performed in biofilm supernatants via luminescence acyl homoserine lactone (AHL) reporter assays further showed that E2 treatment may also modulate QS signaling, as shown in an E2 sensitive CF isolate. Together, our results suggest the biofilm modulating effects of E2 on various clinical CF isolates that are documented by both biomass and ultrastructural changes of biofilms. The gained new insight into the influence of steroid hormones on P. aeruginosa biofilm phenotypes might pave the way for novel future approaches in personalized medicine based on the patients’ sex and hormonal status.

Children like to experiment, but many teachers apparently do not. This pointedly formulated statement is supported, for example, by studies by HARLEN (1997) (1997) and MÖLLER (2004), which show that science topics – especially physical and chemical topics – as well as experimentation as a subject method are strongly underrepresented in the actual implementation of lessons in general science in primary school. Among other reasons for this underrepresentation are the teachers' lack of professional knowledge, personal reservations due to their own negative learning biography, and the lack of interest and motivation, often coupled with a low self-concept and low expectations of self-efficacy. To address the underrepresentation, the intervention study focuses on the preparatory service in the second phase of practically based teacher training. The research question is: Can an explicit intervention on experimentation in general science in primary school using the example of bubbling gas strengthen the interest, self-concept, self-efficacy, and professional knowledge of trainee teachers in the long term? The intervention is designed as a learning task relevant to everyday life. By thematically raising the question: "What's bubbling in the lemonade?" it explicitly includes an example from the chemical and physical domain with the subject matter carbon dioxide. From a methodological point of view, the intervention allows a constant change between practical experimentation phases and exchange and reflection phases and thus meets the demand for a hands-on as well as minds-on approach in experimental teaching. For the longitudinal study, a mixed-methods approach is chosen for the research methodology. The intervention is investigated by means of a closed, quantitatively evaluated questionnaire for self-assessment along the characteristics of interest, self-concept, self-efficacy, and professional knowledge in a pre-post-follow-up design. After two years, the results were qualitatively validated and deepened with the help of facultative, guided interviews. The results of the pre-post survey suggest that the intervention contributed in the short term to strengthen interest, self-concept and self-efficacy in relation to practical experimentation. The results of the follow-up survey after two years show that the typification of the individual cases into profiteers, non-profiteers and against-expectation types, which was carried out after the pre-post survey, is no longer recognisable. For the evaluation of the interviews, it can be summarized that indirectly moderating variables such as the examined personality traits interest, self-concept, self-efficacy and professional knowledge are directly related to the strongly moderating variables such as the found school reality and that they are mutually dependent. The intervention during the second training phase with a high level of practical relevance to primary schools is considered by the interviewed teachers to be profitable and can thus be evaluated as an important component to counteract the underrepresentation of experiments in lessons in general science in primary school.

The investigation of the response of the immune system, which is influenced by the communication between cells of the same as well as different species (interkingdom signalling), is a crucial part in biomedical research. Especially the sensing of signalling molecules that are produced by bacteria can induce a response of eukaryotic cells present in the immune system. For the studies of cellular response in vitro, the extracellular matrix (ECM), which surrounds the cells in their natural environment, needs to be simulated. The creation of an artificial three-dimensional (3D) environment is essential and affects the cell adhesion, proliferation as well as migration. Thereby, the cell detachment and separation can be induced. In this Thesis, different approaches to generate suitable cell culture platforms were explored and their suitability for future work in cell communication investigated. In particular, polymer brushes as well as lipid bilayers were examined as approaches to spatially and temporally control selective cell attachment and detachment. Furthermore, hydrogel-based scaffolds were prepared and investigated regarding their suitability to create viable environments for cell encapsulation. Thermoresponsive poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA) brushes were successfully used for selective separation of human umbilical vein endothelial cells (HUVEC) from a coculture with macrophages without the use of additional compounds, such as releasing agents or antibodies. The decrease of the temperature below the transition temperature of 35 °C for (5 ± 1) nm thin PDEGMA brushes, resulted in a change of the chain conformation and thus cause a desorption of cell adhesion proteins. HUVECs and macrophages attached and spread in a coculture on (5 ± 1) nm thin PDEGMA brushes at 37 °C. In contrast to macrophages HUVECs, which possess a lower adhesion strength, detached from the brushˈ surface after decreasing the temperature to 22 °C. HUVECs could be reseeded on a new surface with a yield of 71 % and a purity of almost 100 %. Square-shaped, patterned polymeric lipid bilayers that were modified with PDEGMA and poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) brushes with brush thicknesses of 26 nm and 20 nm, respectively, were investigated in terms of selective cell attachment. Mouse fibroblasts (NIH 3T3) cells were able to attach and spread on polymeric lipid bilayer. In contrast, polymer brushes possess cell repulsive properties, so that the cells are only able to attach on bare glass squares. The use of patterned polymeric lipid bilayers, which are modified with polymer brushes, allows a selective cell attachment. The adhesion and spreading of cells inside different hydrogels with various geometries were investigated. The encapsulation of NIH 3T3 cells and pancreatic tumor cells (PaTu 8988t) inside chitosan microbeads cross-linked with glycerol phosphate disodium salt (CS + GP) as well as inside alginate — fibrin microbeads were not successful due to the too harsh conditions of the gelling bath and the lack of cell adhesion properties, respectively. However, a hydrogel consisting of alginate dialdehyde (ADA) with a degree of oxidation of 30 % and gelatine modified with carbohydrazide (GelCHD) in a ratio of 1 : 3 were shown to be useful, afford attachment, spreading, and proliferation of encapsulated cells. Finally, the response of encapsulated NIH 3T3 cells, in the above-mentioned hydrogel, to the signalling molecule N-(3-oxododecanoyl)-L-homoserine lactone (HSL) was examined. A pronounced decrease of the cellsˈ viability from 90 % to 71 % and an increase in the intracellular Ca2+ concentration was detected after treatment with HSL, confirming a response of the cells on the signal molecules. Overall, the results reported in this Thesis highlight the potential of polymer brushes, lipid bilayers as well as hydrogel scaffolds for the encapsulation of cells and the investigation of cellular communication processes.

Luminescent lanthanide materials are of great interest not only for biomedical applications due to their tuneable emission wavelengths that extend from the ultra-violet region into the near-infrared region. These materials are known to be non-toxic and resistant to photobleaching unlike traditional organic dyes. In this Thesis, the focus was laid on the synthesis of nanoscale and microscale fluoride containing luminescent lanthanide materials, such as (LaF₃:Ce³⁺Tb³⁺, TiO₂@SiO₂@LaF₃:Ce³⁺Tb³⁺, and KSmF₄:Ln³⁺ (Ln = Ce, Tb, Eu), which promise unique optical properties, as fluoride containing lanthanide materials are recognized for their strong luminescence and good optical stability due to their low phonon energies. To harness these properties for potential bioimaging applications, this Thesis thus focused on developing and optimizing synthetic routes for producing monodisperse lanthanide doped particles that bridge the length scales from the nano- (< 10 nm) to the microscale (> 1 µm). Furthermore, to enhance their scope by exploiting their surface features, these particles were incorporated into hydrogels and were modified with polymer brushes. The results confirm the successful synthesis of monodisperse particles with sizes ranging from < 10 nm to 15 µm with intense red and green luminescence due to Eu3+ and Tb3+ ions. Among the particles studied, the (LaF₃:Ce³⁺Tb³⁺) nanoparticles were investigated in cell toxicity tests, while the MgF2 microbeads were tailor made for application in digital holography microscopy. The toxicity tests indicated that the NPs are non-toxic at concentrations below 0.0023 mg/mL in cell medium. These NPs were also incorporated into a biocompatible sodium alginate hydrogel matrix and the influence on the mechanical properties of the hydrogels was investigated. Rheological measurements revealed that nanoparticle inclusion significantly enhances the hydrogels’ structural stability, supporting their potential use in drug delivery and bioimaging. The tomography phase microscopy results of spherical MgF2 microparticles hinted at a very similar refractive index compared to human cells (1.360 ± 0.004). These particles were shown to provide the structural parameters required for precise calibration in digital holography, which enhances the accuracy and reliability of label-free live cell imaging. In addition, antibacterial tests with E. coli showed enhanced antibacterial activity compared to commercially purchased MgF2. These results suggest that lanthanide-based particles can be further exploited in future biomedical applications.

Measurements of the electronic circular dichroism (CD) are highly sensitive to the absolute configuration and conformation of chiral molecules and supramolecular assemblies and have therefore found widespread application in the chemical and biological sciences. Here, we demonstrate an approach to simultaneously follow changes in the CD and absorption response of photoexcited systems over the ultraviolet−visible spectral range with 100 fs time resolution. We apply the concept to chiral polyfluorene copolymer thin films and track their electronic relaxation in detail. The transient CD signal stems from the supramolecular response of the system and provides information regarding the recovery of the electronic ground state. This allows for a quantification of singlet−singlet annihilation and charge-pair formation processes. Spatial mapping of chiral domains on femtosecond time scales with a resolution of 50 μm and diffraction-limited steady-state imaging of the circular dichroism and the circularly polarised luminescence (CPL) of the films is demonstrated.

Quality communication of learners has become a fundamental part of chemistry ed-ucation as the scientific language of chemistry is both a study goal and a study tool. Therefore, its acquisition inevitably leads to phrasing difficulties and misunderstand-ings. These challenges are even more evident when it comes to speech communi-cation. The speech communication quality of learners in chemistry lessons is indeed con-cerning; in general, learners’ answers consist of fewer than three words. They con-tain neither adequate terminology nor is it possible to draw coherent conclusions about the chemistry content from them. Consequently, it is a clear desideratum of research to analyse the learners’ usage of both the scientific language of chemistry and the wording. In turn, improving speech communication skills among learners has potential to contribute to improved long-term learning performance, considering the fact that chemistry lessons contain a high amount of speech communication. This doctoral thesis generates a survey of obstacles in the scientific language of chemistry. The research focuses on difficulties in speech communication of second-ary school chemistry learners. Little is known so far in this particular field of re-search. The current data has been acquired in two Austrian schools. Guided inter-views were conducted in five classes. A qualitative method has been applied for data acquisition. Results indicate three major areas of concerns: unclear pronoun-antecedent agreement, problematic shifts between chemical concept levels according to Ma-haffy, and an ambiguous application of the term element.