Friedrich Giesel entdeckte im Jahre 1902 das Actinium nach Fällung mit Lanthan aus einer Pechblendelösung. Er hatte den Namen Emanium vorgeschlagen, da es stark emanierte. Lange Zeit wurde nur Andre-Louis Debierne als Entdecker des Actiniums akzeptiert, da er 1904 behauptet hatte, dass die von ihm im Jahr 1900 gefundene von ihm Actinium genannte radioaktive Substanz mit den chemischen Eigenschaften des Thoriums, die hauptsächlich das Thoriumisotop 230Th enthielt, mit dem Emanium von Giesel identisch gewesen sei. In dem Beitrag werden die Entdeckungen von Debierne und Giesel und der Weg bis zur Anerkennung von Giesel als Entdecker vorgestellt. / Friedrich Giesel discovered actinium in 1902 after co precipitation with lanthanum from a solution of pitchblende. He had suggested to name it emanium, because of its emanating properties. But for a long time only Andre-Louis Debierne was accepted as discoverer of actinium, because in 1904 he has explained, that the radioactive substance found by him in 1900, with chemical properties of thorium, named actinium, and mainly consisting of the thorium isotope 230Th, has been identical with the emanium of Giesel. The discoveries of Giesel and Debierne are explained as well as the steps on the way of acceptance of Giesel as discoverer of actinium.

The investigation of the physical properties of deoxyribonucleic acid under confinement is an essential step for the all-embracing understanding of the replication and transcription in living cells as well as for the development of the biomimetic nanotechnology. The following report addresses the measure-ment and interpretation of the intramolecular diffusion along stretched λ-DNA-molecules. This work comprises the fabrication of submicroscopic channels via softlithography, the integration of the chan-nels in an experimental setup with a fluorescence microscope and a source-measurement unit, and the experiments with the DNA-stretching in electrical field. The important results are the development of a measuring assembly with stable, softlithographic structures in Ormostamp, the direct imaging and measurement of the intermolecular diffusion along stretched DNA-molecules in channels with cross sections down to 100 x 300 nm2, and the qualitative and quantitative analysis on the basis of models of polymer physics.

By the combination of 9a-azaphenalene and a perpendicularly oriented acene, we have synthesized three derivatives of a series of novel, fully-conjugated nitrogen-containing polycyclic aromatic hydrocarbons (PAHs), namely [7,8]naphtho[2′,3′:1,2]indolizino[6,5,4,3-def]phenanthridine, with an acetylene triisopropylsilyl (TIPS), phenyl or benzothiophenyl substituent. Their optoelectronic properties were studied via UV-Vis-NIR absorption, fluorescence spectroscopy and cyclic voltammetry. In addition, in situ spectroelectrochemistry was performed to investigate the optical and magnetic properties of the mono-radical cation and anion by quasi-reversible oxidation and reduction of 11-(tert-butyl)-5,17-bis((triisopropylsilyl)ethynyl)[7,8]naphtho[2′,3′:1,2]indolizino[6,5,4,3-def]phenanthridine (1a). Theoretical modelling confirmed the predominately closed-shell electronic ground state with a weak diradical character depending on the geometry.

This work aims to investigate the vapor sensing behavior of conductive polymer composites (CPCs). In connection with the protection of the environment and human beings, sensing of different kinds of chemical vapors is of increasing importance. At the moment, four kinds of vapor sensors are widely investigated and reported, namely semiconducting metal oxide sensors (MO), conjugated polymer sensors, carbonaceous nanomaterial based sensors, and CPC based sensors. Due to their unique component systems, the different sensor types are based on different sensing mechanisms resulting in different potential application ranges. In consideration of cost and processability, CPC based vapor sensors are promising owning to their low cost, excellent processability, and designable compositions. In terms of vapor sensing behavior of CPC sensors, the interaction between the polymer and the organic vapor is a decisive factor in determining the sensing performance of CPCs. Ideally, the chosen polymer matrix should be able to swell without dissolving during vapor exposure so that the conductive network within the matrix can be disconnected, giving rise to the resistance change of CPCs. In some reported cases, polymers such as PLA and polycaprolactone (PCL) are degradable polymers, which are not durable when being exposed to environmental conditions for a long time. Therefore, it is necessary to make sure whether the selected polymers are resistive to vapors or not. There are two options for the polymer selection. One is to select a polymer that is only swellable in a specific or few organic solvents; another one is to select a polymer that is swellable to a variety of solvents. Since CPC sensors are used for detecting as many as possible hazardous chemicals to human beings or environment, the second case is more desired because of its broader window of detection. The solubility parameter is effective to characterize the interaction of polymers and organic solvents/vapors, which was firstly proposed by Charles Hansen. Initially, the Hansen solubility parameter (HSP) was used to predict the compatibility between polymer partners, chemical resistance, permeation rates, and even to characterize the surface of fillers. Liquids with similar solubility parameter (δ) are miscible, and polymers will dissolve in solvents whose δ is similar to their own value. This behavior is recognized as “like dissolves like”. Based on the description above, CPCs that can be used as liquid/vapor sensor materials should meet the following two requirements: 1) the chosen polymer should be swellable to vapors; 2) the CPCs as sensor materials have to be electrically conductive. Therefore, the relationship between conductive network and vapor sensing behavior of CPCs was investigated from the following aspects: 1) According to the previous studies, CB/polymer composites exhibit poor reversibility in cyclic vapor sensing tests because of the susceptible conductive network formed by CB particles. Thus, there is a need to improve the reversibility and increase the relative resistance change (Rrel) of CPCs. MWCNTs, as 1-dimensional carbon fillers with high aspect ratio, have excellent electrical and mechanical properties. Therefore, a hybrid filler system (MWCNT and CB) was utilized and incorporated in polycarbonate (PC) via melt compounding. PC was selected as the polymer matrix of CPCs because it showed high affinity with many commercial organic solvents/vapors as well as high and fast volume change upon organic solvents/vapors. In order to discuss the effect of conductive network formation on the vapor sensing behavior of PC/MWCNT/CB composites, two MWCNT contents were selected, which were lower and higher than the electrical percolation threshold of the PC/MWCNT composites. In the following, three CB contents were selected for the mixtures with MWCNT. The conductive networks composed of either MWCNT or hybrid CB/MWCNT are compared. The morphology of CPCs with different hybrid filler ratios was observed and investigated using SEM and OM. Moreover, to quantify the vapor sensing behavior of CPCs, some organic solvents were chosen and characterized by Flory-Huggins interaction parameter to demonstrate the polymer-vapor interaction. Afterwards, the cyclic vapor sensing was applied to illustrate the vapor sensing behavior of CPCs with different conductive network formations. 2) At moment, the filler dispersion is still a big challenge for MWCNT filled polymer composites due to the fact that the strong Van der Waals force among nanotubes makes them easily to entangle with each other resulting in the formation of agglomerates. A good filler dispersion state is desirable to achieve CPCs with low φc and. In order to reduce the φc of CPCs, immiscible polymer blend systems are introduced, which can have different blend microstructures by adjusting the polymer component ratios. In the second section, an immiscible polymer blend system based on two amorphous component, namely PC and polystyrene (PS), was chosen aiming to explain the influence of the blend morphology on the sensing performance of CPCs. PC/PS blends with different compositions filled with MWCNT were fabricated by melt mixing. The selective localization of MWCNTs in the blends was predicted using the Young’s equation. Moreover, the composite morphology, filler dispersion, and distribution were characterized by SEM and TEM. In the following, three kinds of CPCs ranging from sea-island structure to co-continuous structure were selected for the cyclic sensing measurement. The relationship between composite microstructure and resulting vapor sensing behavior was evaluated and discussed. 3) The poor reversibility of CPCs towards good solvent vapors is still a problem that hinders the cyclic use of CPC sensor materials. As an important class of polymer, crystalline polymers are rigid and less affected by solvent penetration because of the well-arranged polymer chains. Therefore, the effect of polymer crystallinity on the vapor sensing behavior of CPCs is imperative to be studied. In the third section, poly(lactic acid) (PLA), a semi-crystalline polymer, was selected to melt-mixed with PS and MWCNTs with the aim to improve the sensing reversibility of CPCs towards organic vapors, especially good solvent vapors. Thermal annealing was utilized to tune the PLA crystallinity and the polymer blend microstructure of CPCs. The electrical, morphological, and thermal behavior of CPCs after different thermal annealing times is discussed. In the following, the effect of crystallinity on the vapor sensing behavior of the CPCs was studied in detail. Besides, the different sensing performances of the CPCs towards different vapors resulted from the selective localization of MWCNTs and increased polymer matrix crystallinity were investigated and compared. 4) As discussed for the amorphous polymer blends and crystalline polymer blends and their vapor sensing behavior. The comparison of compact and porous structure of CPCs is going to be studied. In the fourth section, studies to further improve the sensing performance and to find out the exact sensing mechanism of CPCs were performed. Therefore, poly(vinylidene fluoride) (PVDF), a solvent resistive polymer, was chosen to be melt-mixed with PC and MWCNTs. In order to compare the MWCNT dispersion and localization in the blends, three kinds of PCs with different molecular weights were selected; hence, the viscosity ratio of immiscible blends was varied. Rheological, morphological, and electrical properties of CPCs were characterized. After that, the cyclic sensing and long-term immersion tests of CPCs towards different vapors were carried out to evaluate the vapor sensing behavior of compact CPCs with different blend viscosity ratios. Moreover, porous CPC sensors were prepared by extracting the PC component. The same sensing protocols were also applied to these porous sensor materials. The sensing mechanisms between compact CPC sensor and porous CPC sensor were compared and investigated.

Polymer brushes can be used to tailor the physical and chemical properties of materials on demand to meet potential applications. Therefore, fabrication of polymer brushes with well-defined structure and functional groups enables the engineering of new materials with diverse functions. In addition, two-dimensional (2D) materials have their unique physical/chemical properties and potential applications in (opt)electronics, catalysis, energy storage, sensing, and other related fields. However, the dispersibility, chemical stability, charge transport behavior, mechanical properties of the 2D materials hinder their further applications. Therefore, combining polymer brushes and 2D materials may bring in new properties which are not available by either of them alone. This thesis focuses on brushing up 2D materials (from inorganic to organic) with universal photografting techniques. (1) The first chapter introduces the outline and research content of the thesis. (2) The second chapter describes the background of 2D materials and polymer brushes. In particular, this chapter analyzes mechanisms, drawbacks and benefits of different polymerization methods, and also summarizes the general approaches to grow polymer brushes on 2D material surfaces, coupling with potential applications of polymer functionalized 2D materials. (3) The third chapter shows the motivation and aim of this thesis. (4) The fourth chapter discusses the results of the functionalization of hexagonal boron nitride (hBN), MoS2, graphitic-carbon nitride (gCN), alkyl-polydopamine (alkyl-PDA), and conjugated 2D polymers (2DPs) with polymer brushes by the same self-initiated photografting and photopolymerization (SIPGP) method and their related applications in detail, respectively. First, the direct photopolymerization of vinyl monomers results in the formation of thick and homogeneous polymer brushes covalently bounded to hBN. The brush layer mechanically and chemically stabilizes the material and allows facile handling as well as long-term use in water splitting hydrogen evolution reactions. Second, the chapter demonstrates the MoS2 can be directly modified with polymer brushes by SIPGP. After modifying MoS2 with polymer brushes, the dispersibility of polymer brushes-modified MoS2 was obviously improved. Third, the polymer brushes functionalized gCN significantly improves the dispersibility. Application of polymer brush functionalized gCN as excellent recyclable substrates for an outstanding SERS as well as photocatalytic degradation of dyes is demonstrated. Fourth, to directly obtain the 2D materials with functional groups, the chapter proposes a facile method to prepare amphiphilic polymeric Janus nanosheets with hydrophilic PDA and hydrophobic alkyl chains at both sides. Benefiting from the Janus property of the alkyl-PDA nanosheets, the nanosheets can be grafted polymer brushes through photografting and be conjugated Fe3O4 nanoparticles selectively onto the PDA side. Finally, the chapter shows that various polymer brushes can be directly grafted onto 2DPs and freestanding system is also obtained. Moreover, it is found that the morphology of freestanding system quickly and reversibly responds to solvent quality by shrinking/stretching. (5) The fifth chapter addresses the general conclusion and future prospective of the whole work. (6) The sixth chapter describes the experiment part of the whole thesis.

Clays are considered as potential host rocks and backfill material for deep geological repositories for radioactive waste. Therefore, profound understanding of radionuclide retention processes at clay mineral surfaces is essential for a long-term safety assessment. This understanding has already been generated in the past for simple chemical systems, in which experiments are easy to conduct and interpretation is straightforward. However, there is still a lack of molecular process understanding when considering complex natural systems (low radionuclide concentrations, high ionic strength, high pH values, multi-mineral solid phases, complex solution composition). This thesis aims to close some of these knowledge gaps, focusing on U(VI) and Np(VI) sorption on clays at (hyper)alkaline conditions. pH values between 10 and 13 can prevail in the near-field of a radioactive waste repository as a result of the degradation of concrete, which is part of the geo-engineered barrier. Existing studies on radionuclide sorption on clays do not exceed pH 10. Therefore, within this work, a comprehensive investigation in the pH range 8-13 was conducted. This included the quantification of radionuclide retention in batch sorption experiments as well as spectroscopic investigations to generate understanding about the underlying retention mechanisms on a molecular level. Beside the pH, additional focus was on the influence of dissolved carbonate and calcium on radionuclide sorption at (hyper)alkaline conditions. Next to two small chapters dealing with the stability and surface charge of Ca-bentonite at (hyper)alkaline conditions (chapter 4.1) and the influence of ISA on U(VI) sorption at high pH values (chapter 4.3), the thesis can be subdivided in two major parts. The first part (chapter 4.2) is a detailed investigation of U(VI) sorption on Ca-bentonite at (hyper)alkaline conditions in mixed electrolyte solutions. Batch sorption experiments were conducted, varying a number of experimental parameters (sorption time, S/L ratio, U(VI) concentration, pH value, carbonate concentration) and assessing their effect on U(VI) sorption. In order to be able to explain the observed sorption behavior, next to U(VI) solubility tests, spectroscopic techniques were applied. The aqueous speciation of U(VI) was investigated with TRLFS, while its surface speciation was probed with ATR FT-IR, site-selective TRLFS, EXAFS and CTR/RAXR. Since the results of this chapter indicated a great importance of the presence of calcium (see below), the second major part of the thesis (chapter 4.4) was dedicated to a careful evaluation of the influence of calcium on An(VI) sorption on clay minerals at (hyper)alkaline conditions. This encompasses the sorption of Ca(II) on Ca-bentonite and its effect on the bentonite surface charge. Furthermore, U(VI) batch sorption experiments with Na-montmorillonite, synthetic kaolinite and muscovite were conducted in 0.1 M NaCl as well as in 0.1 M NaCl + 0.02 M CaCl2 at pH 8-13, in order to quantify the influence of calcium on U(VI) sorption on supposedly Ca-free mineral phases. Site-selective TRLFS was applied with the aim to observe U(VI) sorption species involving calcium. Finally, complementary sorption experiments Np(VI) on muscovite were performed in order to check whether its sorption behavior is analogous to U(VI) under the given conditions. Batch sorption experiments demonstrate that U(VI) retention on Ca-bentonite can be very effective at pH > 10, even in the presence of carbonate and despite the prevalence of anionic aqueous species. Above a certain pH, depending on the concentration of carbonate in solution, carbonate does not play a role in the aqueous U(VI) speciation anymore due to the predominance of hydrolysis. TRLFS measurements revealed a clear correlation between sorption behavior and aqueous U(VI) speciation, showing that retention reaches a maximum at pH 10-12, where UO2(OH)3− is the predominant aqueous species. This raised the question whether the strong retention can be achieved by adsorption of an anionic species to the negatively charged mineral surface or rather by precipitation of uranates. By in situ ATR FT-IR and CTR/RAXR experiments the formation of U(VI) precipitates on the mineral surface was observed at U(VI) concentrations of 2×10-5 M and 5×10-5 M, respectively. However, solubility tests at sub-micromolar U(VI) concentrations, which were also applied in the batch sorption experiments, showed that the observed complete U(VI) removal at pH 10-12 cannot be attributed to precipitation of (earth) alkali-uranates from the solution. In order to unambiguously distinguish between surface precipitation and surface complexation, direct spectroscopic investigations of the U(VI) complexes on the Ca-bentonite surface were performed with site-selective TRLFS and EXAFS. The occurrence of luminescence line-narrowing and the frequency of the total symmetric stretch vibration obtained from the site-selective TRLFS emission spectra, indicate the presence of two U(VI) surface complexes. Also EXAFS spectroscopy confirmed the presence of two independent U(VI) sorption species on Ca-bentonite at pH 8-13. With increasing pH, the nature of the retained U(VI) complexes shifts from bidentate inner-sphere surface complexes with an overall equatorial coordination of five adsorbed on aluminol or silanol edge sites to surface complexes with a 4-fold equatorial coordination, resembling the aqueous species UO2(OH)42−. For the first time, a 4-fold coordination in the equatorial plane of U(VI) was univocally proven with the help of a multiple-scattering feature originating from the strong symmetry of the complexes, and without the need for error-prone shell fitting. The lack of scattering paths from the substrate and the comparatively high value for the total symmetric stretch vibration indicate that the high-pH-component is an outer-sphere complex. Concerning the character of the second sorption species at very high pH it was hypothesized that the anionic uranyl hydroxide complexes are mediated to the surface by calcium cations. It was found that calcium sorbs strongly on Ca-bentonite between pH 8 and 13. Also zeta potential measurements showed a partial compensation of the strongly negative surface charge of Ca-bentonite due to adsorption of calcium. U(VI) sorption on kaolinite and muscovite was strongly reduced in the absence of calcium at pH > 10. An increased retention upon addition of calcium proved the sorption enhancing effect of calcium at pH 10-12. Site-selective TRLFS allowed the spectroscopic observation and identification of calcium-induced U(VI) sorption complexes on muscovite. The obtained spectra correspond to the outer-sphere species found on Ca-bentonite. Combining the findings from batch sorption, zeta potential, TRLFS and EXAFS suggests that calcium adsorbs to the mineral surface in the first place, displaying locally positively charged sites which enable an electrostatically driven attachment of anionic uranyl hydroxides. The same effect could also be demonstrated for Np(VI) sorption on muscovite, which was also strongly enhanced in the presence of calcium at pH 9-12. ISA leads to a mobilization of U(VI) at (hyper)alkaline conditions only when present in very high excess of U(VI). A reduction of sorption on Ca-bentonite and the formation of aqueous U(VI)-ISA complexes, detected with TRLFS, occurred at an U:ISA ratio of 1:100,000. Such conditions are not likely to be found in deep geological repository environments. Based on these findings it can be concluded that under certain alkaline repository conditions, where precipitation does not occur (due to very low concentrations or kinetic restraints), U(VI) and Np(VI) are still effectively retained in argillaceous minerals and rocks by adsorption despite the anionic character of prevailing aqueous species. Repulsive forces between the actinide species and the mineral surfaces are overcome by mediating Ca2+. This finding is of great relevance, as also the migration of very small amounts of uranium or neptunium out of waste repositories could lead to a hazardous accumulation in the long term. The achieved knowledge gain concerning radionuclide retention at environmental conditions helps to take the next step towards realistic long-term safety assessment of nuclear waste repositories.

In the framework of this thesis, a study was conducted dealing with a strategy to change the mechanical properties of microgel particles using inwards-interweaving self-assembly post-synthesis. This technique was invented by my cooperation partners of the Trau group, and they prepared all particles studied. Exemplarily, agarose microparticles were used to interweave a defined shell of complexed poly(allylamine) (PA) and poly(styrenesulfonic acid) (PSS) into such particles. Thereby, the shell thickness can be well-defined. Adjusting the concentration of PA and the incubation time, the filling of the particles can be readily controlled up to complete filling. By adding excessive PSS, the diffusion-controlled shell formation stops by complexation. The shell thickness of individual particles was determined through fluorescence-labeled PA and confocal laser scanning microscopy. The mechanical properties of single particles were inferred by AFM with an attached colloidal probe (CP). Here, a non-linear increase of the elastic modulus (E-modulus) from 10 to 190 kPa was determined while the shell thickness increased from 10 to 24 µm. After adding a second shell, a further gain to 520 kPa on average can be realized. Furthermore, a new concept was developed by Mr. Fery and me to change the surface mechanical properties of mircogel particles by applying a thermal trigger. Meanwhile, a particular focus was laid to maintain constant adhesive properties at every temperature. First, crosslinked poly(N-isopropyl acrylamide) (PNIPAM) particles are prepared by droplet microfluidics. These gelled particles are injected into a second microfluidic device and surrounded by an aqueous solution of uncrosslinked poly(acrylamide) (PAAM). At a second junction, droplets are formed via the cut-off effect of the continuous organic solvent. The droplets now contain the crosslinked PNIPAM core and a thin uncrosslinked PAAM liquid shell. After a short diffusion of PAAM polymers into the core they are crosslinked by UV-light. These experiments were performed by our cooperation partners of the Seiffert group. I applied temperature-controlled CP-AFM to obtain the resulting adhesive and mechanical properties of individual particles. Here, the core-shell particles behaved similarly to plain PNIPAM particles displaying the typical increase in E-modulus at temperatures above 34°C, however lower in magnitude. Further, no temperature effect on the interfacial interaction for these core-shell particles was detected. While one focus of the study above was on constant adhesion, in the following section, a new synthetic approach for mussel inspired underwater adhesives, and their characterization is presented. Based on a peptide sequence of ten amino acids, which is found frequently in natural mussel foot proteins, a new polymerization route was developed by my cooperation partners of the Börner group. Possible reaction pathways were investigated with specifically designed model reaction and analyzed using mass spectroscopy and gel permeation chromatography. The resulting polymers were further characterized using high-performance liquid chromatography and SDS-page. Nanometer thick coatings of these synthetic polymers revealed an excellent persistence even against highly concentrated salt solutions measured by quartz crystal microbalance with dissipation experiments. My contribution was the investigation of the work of adhesion necessary to detach a microparticle from such a coating by CP-AFM in an aqueous environment. Here, the newly developed synthetic polymer provided higher adhesive strength, up to 10.9 mJ m- 2, compared to comparable natural mussel foot proteins. / Im Rahmen dieser Arbeit, wurde eine Studie durchgeführt, welche die Möglichkei¬ten der nachträglichen Elastizitätsveränderung von Mikrogelpartikeln mittels „nach Innen gerichteter, verwebender Selbstassemblierung“ (engl. inwards-interweaving self-as¬sembly) beleuchtet. Diese Technik wurde von meinen Kooperationspartnern aus der Gruppe von Herrn Trau entwickelt. Am Bespiel von Agarose Mikropartikeln, kann mittels dieser Technik eine definierte Schale aus Polyallylamin (PA) und Polystyrolsulfonsäure (PSS) in das Partikel verwoben werden. Die Schalendicke kann dabei kontrolliert variiert werden, bis hin zur vollständigen Ausfüllung des Partikels, in dem die Konzentration von PA und die Inkubationszeit angepasst werden. Durch Zugabe eines Überschusses an PSS wird der diffusionsgesteuerte Schalenaufbau durch Komplexierung beendet. Die Schalendicke der individuellen Partikel wurde mittels Fluoreszenzmarkierung und konfokaler Laser Raster¬mikroskopie (engl. confocal laser scanning microscopy) ermittelt. Die mechanische Cha¬rakterisierung einzelner Partikel durch AFM und kolloidaler Sonde (engl. colloidal probe, CP) ergab eine nicht lineare Erhöhung des Elastizitätsmoduls (E-Modul) von 10 auf 190 kPa bei einem Schalendicken Zuwachs von 10 auf 24 µm. Durch eine zweite Schale, in der Ersten, konnte der E-Modul auf im Mittel 520 kPa gesteigert werden. Weiterführend, wurde von mir und Herrn Fery ein neues Konzept entwickelt, um eine mechanische, oberflächliche Verhärtung von Mikrogelpartikel durch Temperaturver¬änderung zu induzieren mit einem Augenmerk, dass sich die Adhäsionseigenschaften nicht verändern. Zunächst wurden von meinen Kooperationspartnern aus der Gruppe von Herrn Seiffert vernetzte Poly-N-isopropylacrylamid (PNIPAM) Partikel mittels Tropfenmikroflu¬idik hergestellt. In einem zweiten Mikrofluidik Experiment wurde diese Partikel mit einer wässrigen Lösung von Polyacrylamid (PAAM, unvernetzt) umgeben bevor es zu einer Tropfenbildung in der organischen Phase kommt. Nach kurzer Diffusionszeit der PAAM Polymerketten in die Kernpartikel, wurde die PAAM Schale mittels UV-Licht querver-netzt. In temperaturkontrollierten CP-AFM Untersuchungen habe ich die resultierenden Adhäsions- und mechanischen Eigenschaften auf der Einzelpartikel Ebene bestimmt. Hier¬bei konnte bei den Kern-Schale Partikeln der für bloße PNIPAM Partikel typische E-Modul anstieg oberhalb von 34°C nachgewiesen werden, jedoch mit verminderten Absolutwerten. Eine begleitende Veränderung der adhäsiven Eigenschaften der Kern-Schale Partikel konnte dabei nicht beobachtet werden. Lag ein Fokus der vorherigen Arbeit auf konstanten Wechselwirkungen, behandelt der dritte Teil der Ergebnisse, einen neuen Synthese Ansatz zur Herstellung Muschel in¬spirierter Unterwasser Adhäsiva und deren Charakterisierung. Basierend auf einer natürli¬chen Peptidsequenz, wurde eine enzymatische Polymerisationsroute von meinen Koopera¬tionspartner aus der Börner Gruppe entwickelt. Der Reaktionsverlauf wurde durch neu de¬signte Modelreaktion untersucht und mittels Massenspektroskopie und GPC analysiert, das resultierende Polymer zusätzlich mit HPLC und SDS-page. Nanometer dicke Beschichtun¬gen dieser Muschel inspirierten Polymer wiesen eine sehr gute Beständigkeit gegen hoch konzentrierten Salzlösung in QCM-D Experimenten auf. Die Adhäsionsarbeit, welche nö¬tig ist um eine Mikropartikel von diesen in wässeriger Lösung zu entfernen, wurde von mir mittels CP-AFM bestimmt. Nach meiner Erweiterung einer bekannten Adhäsionstheorie, konnten für das synthetische Polymer höhere Werte als für vergleichbare Natürliche von bis zu 10.9 mJ m-2 bestimmt werden.

Der unselektive Kationenkanal TRPC6 (transient receptor potential canonical 6) wird durch den second messenger Diacylglycerol (DAG) aktiviert und spielt eine wichtige Rolle bei einer Vielzahl physiologischer und pathophysiologischer Prozesse. Um neuartige Therapien zu ermöglichen, ist die Identifizierung potenter und selektiver Kanalmodulatoren von großem Interesse. Die vorliegende Dissertation widmet sich der Identifizierung, Optimierung und Charakterisierung neuer Inhibitoren sowie Aktivatoren des TRPC6-Ionenkanals. Im ersten Teil der Arbeit werden aufbauend auf früheren Studien diverse Modifikationen am Grundgerüst des TRPC6-selektiven terpenoiden Naturstoffs (+)-Larixol vorgenommen, um eine umfassende Struktur-Wirkungsbeziehung zu erstellen. Die Derivate werden durch fluorometrische Ca2+-Influx-Analysen sowie elektrophysiologische patch clamp-Untersuchungen in HEK293-Zellen mit stabiler Überexpression der Kanäle TRPC6, TRPC3 und TRPC7 charakterisiert. Die potenteste Verbindung Larixyl-N-methylcarbamat Lab-19 weist eine 16-fach höhere TRPC6-Affinität als die Leitstruktur (+)-Larixol und 4-fache bzw. 13-fache Selektivität gegenüber den nah verwandten Ionenkanälen TRPC7 und TRPC3 auf. Die Inhibition von nativ exprimierten TRPC6-Kanalkomplexen wird durch die Anwendung von Lab-19 in pulmonalen glatten Gefäßmuskelzellen der Ratte demonstriert. Weiterhin führt die Behandlung von isolierten, perfundierten Mauslungen mit Lab-19 zu einer Reduktion des Ischämie-Reperfusionsödems, einer lebensbedrohlichen Komplikation bei Lungentransplantationen. Der zweite Teil beschreibt das Screening einer 16.671 Substanzen umfassenden Wirkstoffbibliothek nach potentiellen Kanalaktivatoren und deren Charakterisierung. Die Beschreibung und Synthese der vielversprechendsten Verbindung C20 aus dieser Studie erfolgt in einem dritten Teil der Arbeit. C20 wirkt selektiv auf TRPC6, was die Substanz von bisherigen Aktivatoren wie OAG (1-Oleoyl-2-acetyl-sn-glycerol) unterscheidet, welche auch die Ionenkanäle TRPC3 und TRPC7 aktivieren. Eingehende Untersuchungen mithilfe von Ca2+-Assays und elektrophysiologischen Experimenten zeigen, dass C20 als positiv allosterischer Modulator agiert und eine Kanalaktivierung verstärkt. Die Verbindung C20 wird schließlich in humanen Thrombozyten getestet, für welche eine Expression von TRPC6 beschrieben ist. Die Kombination von OAG und C20 führt zu einem signifikant höheren Anstieg des intrazellulären Calciums in Thrombozyten verglichen mit einer gewöhnlichen Antwort auf OAG-induzierte Aktivierung. Diese Beobachtungen unterstreichen die Eignung des identifizierten positiven Modulators C20 als zukünftiges selektives Demaskierungswerkzeug für TRPC6-Signale in nativen Geweben.:Inhaltsverzeichnis Abbildungsverzeichnis III Schemataverzeichnis IV Tabellenverzeichnis V Abkürzungen VI 1 EINLEITUNG 1 1.1 DIE FAMILIE DER TRP-IONENKANÄLE 2 1.2 DER TRPC6-KATIONENKANAL 7 1.2.1 Struktur und Regulation 7 1.2.2 Physiologische Relevanz 8 1.3 MODULATOREN DES TRPC6-IONENKANALS 9 1.3.1 Aktivatoren 11 1.3.2 Inhibitoren 14 1.3.3 TRPC6-Inhibition durch Larixolderivate 16 2 ZIELSTELLUNG 19 3 EXPERIMENTELLER TEIL 21 3.1 CHEMISCHE SYNTHESEN 21 3.1.1 Reagenzien und Lösungsmittel 21 3.1.2 Analytische Methoden 21 3.1.3 Synthesen 23 3.2 BIOLOGISCHE METHODEN 43 3.2.1 Reagenzien, Lösungsmittel und Puffer 43 3.2.2 Aktivatoren, Inhibitoren, Pharmaka 44 3.2.3 Verbrauchsmaterialien 44 3.2.4 Zellkultur 45 3.2.5 Transiente Transfektion 45 3.2.6 Bestimmung der Zellviabilität 46 3.2.7 Fluoreszenz-Imaging 47 3.2.8 Elektrophysiologie 51 3.2.9 Analyse des Ischämie-Reperfusions-Ödem in isolierten Mauslungen 53 3.2.10 Isolierung humaner Thrombozyten 54 3.2.11 Aggregometrie 54 3.2.12 Datenanalyse 53 4 ERGEBNISSE 55 4.1 SAR-STUDIE NATURSTOFFBASIERTER TRPC6-KANAL-INHIBITOREN 55 4.1.1 Isolierung des Naturstoffes Larixol aus dem Lärchenharz 55 4.1.2 Erstellung einer labdanbasierten Substanzbibliothek 56 4.1.3 SAR-Daten der Inhibition von TRPC3, TRPC6 und TRPC6 60 4.1.4 Auswirkung der Larixolderivate auf die Zellviabilität 69 4.1.5 Subtypspezifität von Larixylmethylcarbamat 69 4.1.6 Elektrophysiologische Charakterisierung der TRPC3/6/7-Inhibition durch Lab-19 73 4.1.7 Wirkung von Larixylmethylcarbamat auf Zellen mit endogener TRPC6-Expression 75 4.1.8 Diskussion 76 4.2 IDENTIFIZIERUNG POSITIVER TRPC6-IONENKANALMODULATOREN 82 4.2.1 Hochdurchsatz-Screening der ChemBioNet-Bibliothek 82 4.2.2 Funktionelle Charakterisierung von 46-J17 88 4.2.3 Diskussion 90 4.3 CHARAKTERISIERUNG DES POSITIVEN ALLOSTERISCHEN TRPC6-MODULATORS 93 4.3.1 C20 induziert transienten Ca2+-Einstrom in HEKhTRPC6-YFP-Zellen 93 4.3.2 C20 – ein positiver TRPC6-Modulator 97 4.3.3 Untersuchung mechanistischer Aspekte der TRPC6-Potenzierung 100 4.3.4 Aktivierung des TRPC6 im physiologischen System 103 4.3.5 Diskussion 106 5 ZUSAMMENFASSUNG UND AUSBLICK 111 6 LITERATUR 115 Appendix

The replacement of the conventional field effect transistor (FET) by single electron transistors (SET) would lead to high energy savings and to devices with significantly longer battery life. There are many production approaches, but mostly for specimens in the laboratory. Most of them suffer from the fact that they either only work at cryogenic temperatures, have a low production yield or are not reproducible and each unit works in a unique way. A room temperature (RT) operating SET can be configured by inserting a small (few nm diameters) Si-Nanocrystal (NC) into a thin (<10 nm) SiO2 interlayer in Si. Industrial production has so far been excluded due to a lack of manufacturing processes. Classical technologies such as lithography fail to produce structures in this small scale. Even electron beam lithography or extreme ultraviolet lithography are far from being able to realize these structures in mass production. However, self-organization processes enable structures to be produced in any order of magnitude down to atomic sizes. Earlier studies realized similar systems using a layer of Si-NCs to fabricate a non-volatile memory by using the charge of the NCs for data storage. Based on this, it is very promising to use it for the realization of the SET. The self-organization depends only on the start configuration of the system and the boundary conditions during the process. These macroscopic conditions control the self-formed structures. In this work, ion beam irradiation is used to form the initial configuration, and thermal annealing is used to drive self-organization. A Si/SiO2/Si stack is irradiated and transforms the stack into Si/SiOx/Si by ion beam mixing (IBM) of the two Si/SiO2 interfaces. The oxide becomes metastable and the subsequent thermal treatment induces selforganization, which might leave a single Si-NC in the SiO2 layer for a sufficiently small mixing volume. The transformation of the planar SiOx layer (restriction only in one dimension) into a small SiOx volume (restriction in all three dimensions) is done by etching nanopillars with a diameter of less than 10nm. This forms a small SiOx plate embedded between two Si layers. The challenge is to control the self-organization process. In this work, simulation was used to investigate dependencies and parameter optimization. The ion mixing simulations were performed using binary collision approximation (BCA), followed by kinetic Monte Carlo (KMC) simulations of the decomposition process, which gave good qualitative agreement with the structures observed in related experiments. Quantitatively, however, the BCA simulation seemed to overestimate the mixing effect. This is due to the neglect of the positive entropy of the Si-SiO2 system mixing, i.e. the immiscibility counteracts the collisional mixing. The influence of this mechanism increases with increasing ion fluence. Compared to the combined BCA and KMC simulations, a larger ion mixing fluence has to be applied experimentally to obtain the predicted nanocluster morphology. To model the ion beam mixing of the Si/SiO2 interface, phase field methods have been applied to describe the influence of chemical effects during the irradiation of buried SiO2 layers by 60 keV Si+ ions at RT and thermal annealing at 1050°C. The ballistic collisional mixing was modeled by an approach using Fick’s diffusion equation, and the chemical effects and the annealing were described by the Cahn Hilliard equation. By that, it is now possible to predict composition profiles of Si/SiO2 interfaces during irradiation. The results are in good agreement with the experiment and are used for the predictions of the NCs formation in the nanopillar. For the thermal treatment model extensions were also necessary. The KMC simulations of Si-SiO2 systems in the past were based on normed time and temperature, so that the diffusion velocity of the components was not considered. However, the diffusion of Si in SiO2 and SiO2 in Si differs by several orders of magnitude. This cannot be neglected in the thermal treatment of the Si/SiO2 interface, because the processes that differ in speed in this order of magnitude are only a few nanometers apart. The KMC method was extended to include the different diffusion coefficients of the Si-SiO2 system. This allows to extensively investigate the influence of the diffusion. The phase diagram over temperature and composition was examined regarding decomposition (nucleation as well as spinodal decomposition) and growing of NCs. Using the methods and the knowledge gained about the system, basic simulations for the individual NC formation in the nanopillar were carried out. The influence of temperature, diameter, and radiation fluence was discussed in detail on the basis of simulation results.

Comprehensive understanding of chirality has played a crucial role for ensuring safety and efficacy of drug products. In many cases, two optical configurations of a chiral molecule exhibit substantially different physiological behaviour, and thus the preparation of single enantiomers has become as an essential topic in the pharmaceutical industry.1-2 Enantiomerically pure compounds could generally be achieved by separation from racemic mixtures or direct synthesis of enantiopure molecules. Either way, chiral materials which are employed as stationary phase in chiral columns or chiral catalysis, are a basic condition to decide to enantiomeric excess of resulting mixtures. Despite obtaining high enantiomeric purity, the chiral separation of racemic mixtures is considered as an expensive and inefficient approach due to undesired enantiomers, while asymmetric synthesis, which enables dominant formation of the single enantiomers, is an atom-economical method. However, the development of efficient heterogeneous chiral catalysts has been still required further investigations to provide more potential options for asymmetric organic reactions, especially carbon-carbon bond formations, which are key steps in organic synthesis.1-3 In recent years, metal-organic frameworks have emerged as one of the most intriguing solid porous materials. Together with the highly active catalytic centers, wide structural and functional variations, MOFs have been successfully employed as heterogeneous catalysts for a variety of organic transformations.4-5 However, very few achievements relating to MOFs as asymmetric catalysts have been reported to date because of their low thermal and chemical stabilities. Such solid stable frameworks, the Zr-MOFs offers great opportunities for designing novel effective asymmetric catalysts.1, 6-9 This is an interesting, but also challenging topic with many open issues: • How can we introduce effectively enantiopure active sites into Zr-MOFs? • Are there any positive or negative impacts of Zr-nets on the performance of chiral catalytic sites? • If any, is it possible to control these effects during the reaction phase? • How is the recyclability of these chiral Zr-MOFs? Finding answers for these questions are the core of this thesis. In Chapter 3, DUT-67, an 8-connected zirconium and 2,5-thiophenedicarboxylate based MOF, was post synthetically functionalized by L-proline via solvent assisted linker incorporation to obtain a chiral base catalyst. The parent monocarboxylate could be almost completely exchanged by L-proline after 5 days of treatment. The resulting chiral DUT-67, DUT-67-Pro, was demonstrated to be a promising heterogeneous catalyst for the asymmetric Michael addition of cyclohexanone to trans-β-nitrostyrene with excellent yield (up to 96%) and enantioselectivity comparable to that of L-proline in homogeneous reaction (ee approximately 38%). The Zr-MOF could be reused at least 5 times without substantial degradation in crystallinity or catalytic activity. No leaching of catalytically active species into the liquid phase was detected over 5 cycles. A further understanding regarding the role of catalytic active sites, including Zr-clusters and L-proline, in asymmetric aldol addition of cyclohexanone and 4-nitro-benzaldehyde is investigated in Chapter 4 to clarify the predominant formation of syn-products as well as the absence of enantioselectivity in previous catalytic systems. The presence and location of L-proline into DUT-67 was confirmed by Solid-state MAS and DNP NMR data. The chiral DUT-67-Pro catalyst exhibits an excellent catalytic activity at low temperature (298 K) with an unprecedented syn-(S,S)-product selectivity in an asymmetric aldol addition reaction of cyclohexanone to 4-nitrobenzaldehyde (yield = 95%, ee = 96%). Comparative catalytic studies using a molecular Zr6-cluster model compound indicate the Zr6-moiety to be responsible for this inverse diastereoselectivity compared to well-established L-proline organocatalysis and a mechanism is proposed to explain the Zr6-cluster-mediated syn-selectivity. Masking residual acidic active sites in the cluster of the framework was found to be a key prerequisite to achieve the high enantioselectivity. The purely heterogeneous catalytic system based on DUT-67-Pro is highly stable and can be recycled several times. Lastly, a novel chiral diimine Zr-MOF, namely DUT-136, synthesized from one-pot reaction of ZrCl4 with 4-formylbenzoic acid, and (R,R)-1, 2-diphenylethylenediamine as an enantiopure core will be described in Chapter 5. Inspired from the versatile transformation of the C=N double bonds, a variety of post-synthetic methods, including oxidation, reduction, and metalation, was employed to modify DUT-136 for formation of the chiral amide-, amine-, and Ni-DUT-136, respectively. The catalytic behaviour of these post-synthetically modified materials was then evaluated in a wide range of asymmetric organic transformations, including the Friedel Craft alkylation, the Michael addition, the aldol reaction and the Ni-catalyzed C-C coupling. The research on synthesis of chiral Zr-MOFs and their catalytic behavior in this work are expected to provide a better understanding or at least give to other scientists open ideas for further deeper studies regarding this topic in the future.