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.

Ziel der vorliegenden Arbeit war zum einen die Entwicklung einer Synthesestrategie und deren praktischen Umsetzung zur Verwirklichung der Idee eines organometallischen Koordinationspolymers, in dem das verknüpfende Bindungsmotiv Metall-Kohlenstoff-Bindungen sind. Der zweite und größere Teil der Arbeit beschäftigte sich mit der Synthese von neuen metallorganischen Gerüstverbindungen auf der Basis von Carboxylatliganden. Diese sollten Eigenschaften besitzen, die sie als Gasspeichermaterialien, vor allem für Methan und Wasserstoff, geeignet erscheinen lassen. Durch Kombination von H3BTB und Co(NO3)2•6H2O wurde ein strukturell hochkomplexes MOF, DUT-28, erhalten, dessen hohe theoretisch, geometrisch berechnete Oberfläche (3875 m2/g) gute Gasspeichereigenschaften hätte erwarten lassen. Leider schlugen sämtliche Versuche, die metallorganische Gerüstverbindung in lösungsmittelfreier Form zu erzeugen, fehl. Es konnte gezeigt werden, dass sich die Raumgruppe, in der DUT-28 kristallisiert, bei Verringerung der Temperatur (298 K auf 100 K) von C2/m zu C2/c ändert. Die durch dieses Faktum implizierte strukturelle Flexibilität könnte ein Grund für das Scheitern aller Bemühungen, DUT-28 unter Erhalt der Struktur zu aktivieren, sein. Die Entdeckung eines metallorganischen Polyeders, bestehend aus sechs Kupferschaufelradeinheiten und 12 Carbazol-3,6-dicarbonsäuren, regte eine Änderung der Synthesestrategie für die Darstellung weiterer MOFs an. Im Gegensatz zu der explorativen Vorgehensweise bei der Synthese von DUT-28 wurden im Folgenden durch Anwendung des sogenannten SBB Konzepts vergleichsweise kontrolliert weitere hochporöse MOFs dargestellt. Das SBB Konzept beschreibt im Kern den Aufbau dreidimensionaler Strukturen durch geeignete Verknüpfung von metallorganischen Polyedern und wurde vor allem durch ZAWOROTKO und EDDAOUDI bekannt. Die Verknüpfung der MOPs kann dabei sowohl über koordinative als auch kovalente Bindungen erfolgen. Ausgehend von dem beschriebenen Carbazol-MOP wurden zwei verschiedene Strukturen generiert, die sich durch Reduktion der SBBs auf 12-konnektive Knoten, als fcu bzw. ftw-a beschreiben lassen. Beide Strukturen wurden jeweils einmal isoretikular erweitert. Im Fall des fcu Netzes wurden die Carbazole über ihren Stickstoff mit einer starren Phenylen (DUT-48) bzw. Biphenylen (DUT-49) verbunden. Zur Erzeugung des ftw-a Netzwerks wurde eine Carboxyphenyl- (DUT 75) bzw. Carboxybiphenyleinheit (DUT 76) an den Carbazolstickstoff gebunden (Abbildung 1). Alle vier Verbindungen müssen überkritisch mit Kohlendioxid getrocknet werden. Alle Verbindungen zeigen hohe bis sehr hohe Oberflächen und Porenvolumina und sehr gute bis herausragende Wasserstoffspeicher- und Methanspeicherkapazitäten. DUT-76 besitzt mit rund 6400 m2/g eine herausragende spezifische Oberfläche und mit 3,25 cm3/g ein sehr großes spezifisches Porenvolumen. Alle vier Verbindungen zeigen hohe bis sehr hohe gravimetrische Speicherkapazitäten für Wasserstoff und Methan. Dabei ragt DUT-49 mit einer Rekordkapazität für Methan von 308 mg/g, und DUT-76 mit einer Wasserstoffkapazität von 82 mg/g, heraus. Zusammenfassend ist festzuhalten, dass es gelungen ist, eine Reihe metallorganischer Gerüstverbindungen zu synthetisieren, die sehr hohe bzw. rekordbrechende Gasspeicherkapazitäten für die alternativen Energieträger Wasserstoff und Methan aufweisen. Zur Synthese eines organometallischen Koordinationspolymers wurde ein besonders stabiler Übergangsmetallolefinkomplex als Bindungsmotiv gewählt (Abbildung 2a). Dieser Komplex ist nur ein lineares Verknüpfungsmotiv. Zur Herstellung von Dreidimensionalität wurden vier 7-norbornadienylreste, in jeweils 4-Position an ein Tetraphenylsilangerüst geknüpft. Die Synthese des Liganden (TNPS, vgl. Abbildung 2b) gelang in einer kurzen Sequenz von 3 Stufen ausgehend von reinem Norbornadien. Der TNPS-Ligand wurde in einer Ligandenaustauschreaktion mit dem oben genannten Rhodium-Norbornadienkomplex umgesetzt. Dabei wurde eine amorphe, gelartige Substanz erhalten (DUT-37) (vgl. Abbildung 2c und 3a). Durch Röntgenabsorptionspektroskopie, NMR-Experimente und Elementaranalyse konnte gezeigt werden, dass tatsächlich ein Ligandenaustausch stattgefunden hat, und die Bindungsverhältnisse innerhalb des Festkörpers denen im monomeren Komplex entsprechen. DUT-37 konnte ebenfalls nur durch überkritische Trocknung als permanent poröses Material erhalten werden. In diesen Zustand besitzt es eine spezifische Oberfläche von 470 m2/g und ein spezifisches Porenvolumen von 0,38 cm3/g. Es zeigt eine für poröse Polymere charakteristische Hysterese über den gesamten Relativdruckbereich und ist im aktivierten Zustand über mehrere Wochen stabil gegenüber atmosphärischen Bedingungen. DUT-37 zeigt eine merkliche Kapazität für Kohlenstoffmonoxid bei Raumtemperatur. Ein großer Anteil der CO-Moleküle wird allerdings chemisorbiert, was durch IR-Messungen gezeigt werden konnte. Durch Wasserdampfphysisorption konnte eine relativ hohe Hydrophobizität des Materials gezeigt werden, die möglicherweise eine Ursache für die überraschende Stabilität von DUT-37 ist. Abschließend, ist DUT-37 katalytisch aktiv in der Transferhydrierung von Cyclohexanon mit 2-Propanol (Abbildung 3b). Zusammenfassend ist es gelungen, im Rahmen dieser Arbeit erstmals ein poröses organometallisches Koordinationspolymer zu synthetisieren. Dieses zeigte interessante Adsorptionseigenschaften, eine unerwartete Stabilität und katalytische Aktivität.

New materials can be fabricated using small scaled building blocks as a repetition unit. Nanoparticles with their unique size-tuneable properties from quantum confinement can especially be utilised to form two- and three-dimensional ordered assemblies to introduce them into what would normally be considered to be incompatible matrices. Furthermore, new collective properties that derive from the ordered arrangement of the building blocks, are accomplished. Additionally, different materials can be combined by mixing different building blocks during self-assembly, so that size ranges and material combinations that are difficult to achieve by other means can be formed. The arrangement of small particles into highly ordered arrangements can be realised via self-assembly. To achieve such assemblies, highly monodisperse nanoparticular building blocks with a size distribution below 5 % have to be synthesised. The production and variation in the size of both lead chalcogenide and noble metal nanoparticles is presented in this work. Moreover, the syntheses of multicomponential nanoparticles (PbSe/PbS and Au/PbS) are investigated. Non-classical crystallisation methodologies with their varyious self-assembly mechanisms are used for the formation of highly symmetrical mesocrystals and supracrystals. Analogous to classical crystallisation methods and their formation processes the interparticle interactions, attractive as well as repulsive, determine the resulting crystalline structure. Variation of the environmental parameters consequently leads to structural variation due to the changing interparticle interactions. In contrast to classical crystallisation the length scale of the interparticle forces stays constant as the size dimension of the self-assembled building unit is changed. Two different non-classical crystallisation pathways are investigated in this work. One pathway focuses on the slow destabilisation of nanoparticles in organic media by the addition of a non-solvent. In this approach optimisation of parameters for the formation of highly symmetrical three-dimensional mesostructures are studied. Furthermore, to shine some light onto the mechanism of self-assembly, the intrinsic arrangement of the building units in a mesocrystal and the steps of non-solvent addition are analysed. The mechanistic investigations explain the differences observed in mesocrystal formation between metal and semiconductor nanoparticles. The lower homogeneity of the building units of the metal nanoparticles leads to smaller and less defined superstructures in comparison to semiconductor building blocks. Another pathway of non-classical crystallisation is the usage of electrostatic interactions as the driving force for self-assembly and supracrystal formation. Therefore, the building blocks are transferred into aqueous media and stabilised with oppositely charged ligands. The well-know procedure for metal nanoparticles was adapted for semiconductor materials. The lower stability of these nanoparticles in aqueous solution induces an agglomeration of the semiconductor nanoparticles without including oppositely charged metal nanoparticles. The destabilisation effect can be increased by the addition of equally charged metal nanoparticles in a salting out type process. In comparison to the slow formation of mesocrystals achieved via destabilisation in an organic media (up to 4 weeks), the salting out procedure takes place within two hours, but the faster agglomeration causes a less well defined assembly of the building units in the mesocrystals. Moreover, the arrangement of semiconductor nanoparticles with organic molecules such as polymers and proteins was investigated in order to use the nanoparticles as a light harvesting component. In combination with the directly bound polymer the charge carrier may be directly transferred to the conductive thiophene-based polymer, so that infrared light can be transformed into an electrical signal for use in further applications such as solar cells. The advantage of the nanoparticle-protein system is the self-assembly across a liquid-liquid interface and additionally a Förster resonance energy transfer can occur at this phase boundary. Hence, it is possible to transfer highly energetic photons directly to biological samples without destroying the biological material.

Using X-ray photoelectron (XPS) and X-ray absorbtion spectroscopy (XAS) we demonstrate charge transfer at an interface between two transition metal phthalocyanines, MnPc and F16CoPc, resulting in charged MnPc + and F16CoPc -, species. Density functional theory calculations reveal that a hybrid state is formed between the two types of phthalocyanines, which causes this charge transfer. For the hybrid state the Mn3dxz interacts with the Co 3dz2 orbital leading to a two-level system. Moreover, we have prepared mixed films out of this pair, which were characterized also by means of electron energy-loss spectroscopy. Our data reveal the formation of MnPc/F16CoPc charge transfer dimers in analogy to the heterojunction. The electronic excitation spectrum of these blends is characterized by a new low energy excitation at 0.6 eV.

By means of advanced molecular dynamic techniques, we predict the stability of novel materials based on carbon, germanium and PbSe. This topological solutions have been studied and characterised at a DFT/DFTB level of theory and interesting optical, mechanical, electronic and heat transport properties have been pointed out.

In the recent years, interest in TM oxides with 5d valence electrons has grown immensely due to the realization of novel spin-orbit coupled ground states. In these compounds, e.g., iridates and osmates, the intriguing situation arises where the spin-orbit and electron-electron interactions meet on the same energy scale. This has created a new window of interest in these compounds since the interplay of crystal field effects, local multiplet physics, spin-orbit couplings, and intersite hopping can offer novel types of correlated ground states and excitations. In 5d5 iridates, a spin-orbit entangled j = 1/2 Mott insulating state has been realized recently. A remarkable feature of such a ground state is that it gives rise to anisotropic magnetic interactions. The 2D honeycomb-lattice 213 iridium oxides, A2IrO3 (A=Li,Na), have been put forward to host highly anisotropic bond-dependent spin-spin interactions that resemble the Kitaev spin model, which supports various types of topological phases relevant in quantum computing. The 2D square-lattice 214 iridates Sr2IrO4 and Ba2IrO4 are, on the other hand, appealing because of their perceived structural and magnetic simi- larity to La2CuO4, the mother compound of the cuprate high-Tc superconductors. This has promoted the latter iridium oxide compounds as novel platforms for the search of high-Tc superconductivity. To put such considerations on a firm footing, it is essential to quantify the different coupling strengths and energy scales, as they for instance appear in effective Hamiltonian descriptions of these correlated systems. Moreover, it is important to correctly describe their effects. In this thesis, the electronic structure and magnetic properties of 5d5 (mainly 214 and 213) iridates are studied using wave-function-based quantum chemistry methods. These methods are fully ab initio and are capable of accurately treating the electron-electron interactions without using any ad hoc parameters. The spin-orbit entangled j = 1/2 ground state in 214, 213 and other lower symmetry Sr3CuIrO6 and Na4Ir3O8 iridates is first analyzed in detail, by studying the local electronic structure of the 5d5 Ir4+ ion. We establish that the longer-range crystal anisotropy, i.e., low-symmetry fields related to ionic sites beyond the nearest neighbor oxygen cage, strongly influence the energies of Ir d levels. The ground state in all the compounds studied is j = 1/2 like with admixture from j ≃ 3/2 states ranging from 1 – 15 %. Further, the average j ≃ 1/2 → j ≃ 3/2 excitation energy we find is around 0.6 eV. The NN magnetic exchange interactions we computed for 214 iridates are predominantly isotropic Heisenberg-like with J ~ 60 meV, 3 – 4 times smaller than found in isostructural copper oxides. However, the anisotropic interactions are an order of magnitude larger than those in cuprates. Our estimates are in excellent agreement with those extracted from experiments, e.g., resonant inelastic x-ray scattering measurements. For the 213 honeycomb-lattice Na2IrO3 our calculations show that the relevant spin Hamiltonian contains further anisotropic terms beyond the Kitaev-Heisenberg model. Nevertheless, we predict that the largest energy scale is the Kitaev interaction, 10 to 20 meV, while the Heisenberg superexchange and off-diagonal symmetric anisotropic couplings are significantly weaker. In the sister compound Li2IrO3, we find that the structural inequivalence between the two types of Ir-Ir links has a striking influence on the effective spin Hamiltonian, leading in particular to two very different NN superexchange pathways, one weakly AF (~ 1 meV) and another strongly FM (−19 meV). The latter gives rise to rigid spin-1 triplets on a triangular lattice.

The ability to tune the electronic band gap of semiconductor nanoparticles or “quantum dots” by controlling their size simply by variation of the synthetic conditions has opened many possibilities for applications across a wide range of fields. Many of these applications, such as solar cells, catalysis, sensing and light emitting diodes involve charge transfer processes between the nanoparticles and an adjacent phase. In order to make that charge transfer as efficient as possible, knowledge pertaining to the absolute energy positions of the electronic levels of such nanoparticulate materials is of primary relevance. The determination of these values and the important parameters that influence them was therefore the central issue of the present work. An electrochemical approach was chosen so that the data obtained could be referred to an absolute energy scale.The ability to tune the electronic band gap of semiconductor nanoparticles or “quantum dots” by controlling their size simply by variation of the synthetic conditions has opened many possibilities for applications across a wide range of fields. Many of these applications, such as solar cells, catalysis, sensing and light emitting diodes involve charge transfer processes between the nanoparticles and an adjacent phase. In order to make that charge transfer as efficient as possible, knowledge pertaining to the absolute energy positions of the electronic levels of such nanoparticulate materials is of primary relevance. The determination of these values and the important parameters that influence them was therefore the central issue of the present work. An electrochemical approach was chosen so that the data obtained could be referred to an absolute energy scale. To achieve reliable measurements a new strategy was developed so that dense and homogeneous monolayers of semiconductor particles could be deposited onto transparent electrodes. The films were obtained by exchanging the original bulky ligand shell of the nanocrystals with a reactive alkoxysilane species and subsequent immersion of the substrate into a solution of the modified nanocrystals. SEM and electrochemical investigations have shown a much higher coverage efficiency in comparison with other methods presently established in the literature, which are based on the approach of prefunctionalizing of the substrates prior to coating. Fractional coverages of 80 % were obtained within 24 h while avoiding the time consuming and complicated step of functionalizing the substrates before deposition. Films of CdSe and CdS nanoparticles deposited on fluorine doped tin oxide (FTO) electrodes were characterized by means of potential modulated absorption spectro-scopy (EMAS). Employing this special spectroelectrochemical technique, bleach signatures in the absorption spectra of the quantum dots induced by electron injection into their respective conduction band states were investigated. The features observed in the spectra and the evaluation of the potential dependence of the signal intensity revealed that only the lowest conduction band state, namely the 1Se state, is populated. The occupancy follows a quasi Fermi-Dirac distribution whose distributional width, in addition to the temperature, also depends on the size distribution of the particle ensemble investigated. On that basis a model was developed to extract the electrochemical potentials of the respective populated lowest conduction band states. For CdSe quantum dots the four energetically lowest excitonic transitions were found to become bleached as the 1Se state is populated, indicating that these transitions promote electrons from different states in the valence band to the same conduction band state. These findings are in excellent agreement with results obtained from ultra fast optical pump probe experiments, which are methods that usually demand much more experimental efforts than the technique presented in these studies. The determination of the potential of the 1Se state versus a known reference potential allows one to map the top valence band states with respect to an absolute energy scale. This provides the opportunity to compare the energy positions obtained for different samples. Determination of the electrochemical band edge potential clearly features a size dependent shift of the conduction band edge and the valence band edge for both CdSe and CdS quantum dots, which is in excellent agreement with the expected behavior due to the quantum confinement effect. Investigations in different electrolytes have shown that the immediate environment has a major impact on the electrochemical potentials of the energy levels of the nanoparticles. This observation is particularly important from a technological point of view, as in many applications the semiconductor material is in direct contact with an electrolyte as for example in quantum dot sensitized solar cells, electrochemical sensors and catalysis. In contrast to other “purely physical” methods such as photoelectron spectroscopy or scanning tunneling spectroscopy, potential-modulated absorption spectroscopy provides the ability to probe the materials under their most likely “working” conditions where such environmental influences can be directly taken into account. Further, it has been shown that potential modulated absorption spectroscopy can be applied to bulk semiconductor electrodes, as long as they are thin enough to allow adequate amounts of light to pass through. The features observed in the EMAS spectra of these samples clearly differ from those obtained for nanoparticle films, as in such materials a continuum of states is progressively filled rather than a single state. Besides band-filling the potential modulation additionally induces changes in the absorption, which can be attributed to the Franz-Keldysh effect resulting from the modulation of the electric field across the space charge layer. The resolution and sensitivity that one can obtain with this comparatively simple and cost-effective setup is quite remarkable. As has been demonstrated it was possible to achieve clearly resolved bleach spectra of submonolayers of quantum dots attached to FTO with optical densities below 0.001. Recently it has been reported that cyclic voltammetry (CV) can be used to study the size dependent positions of the electronic levels of quantum dots. The intention of the last part of this thesis was to reproduce this work for the nanoparticles investigated within this thesis in order to compare the results with those obtained by EMAS. However, the experiments undertaken here reveal that the anodic and cathodic peaks observed in the cyclic voltammograms cannot automatically be assigned to the absolute band edge positions of the particles as the size dependent peak positions and their potential differences do not show any evidence for a correlation with respect to the quantum size effect. Rather the voltammetric responses reflect the solid state electrochemical characteristics of CdSe. Theoretical considerations concerning the response expected in a CV due to band filling of semiconductor nanoparticles confined to an electrode surface revealed that the expected currents are quite similar to that of a pseudo-capacitance. However, pronounced signals are only obtained if appropriate amounts of deposited nanoparticles are present which are electronically addressable without hampering the charge transfer. Hence a clear assignment of the peaks obtained in a cyclic voltammogram to the electronic band edges without employing a complementary technique to confirm ones findings therefore seems to be at best questionable.

We report controllable synthesis of Pd aerogels with high surface area and porosity by destabilizing colloidal solutions of Pd nanoparticles with variable concentrations of calcium ions. Enzyme electrodes based on Pd aerogels co-immobilized with glucose oxidase show high activity toward glucose oxidation and are promising materials for applications in bioelectronics.

Das NZK ist nach dem Prostata- und Harnblasenkarzinom der dritthäufigste urologische Tumor. Die Prognoseaussichten hängen beim NZK vom Metastasenstatus der Patienten ab. Die Heilungschancen für das lokal begrenzte NZK sind im Vergleich zum metastasierten NZK deutlich besser. Durch den Einsatz von TKI und mTOR-Inhibitoren wurde die Therapie des metastasierten NZK revolutioniert und das Überleben von Patienten signifikant verbessert. Nichtsdestotrotz profitiert ein Teil dieser Patienten aufgrund von Resistenzmechanismen nicht von solch einer anti-VEGF-Therapie. Bisher gibt es keine geeigneten Biomarker, die das Ansprechen auf eine solche Therapie vorhersagen könnten. Daher bestand das primäre Ziel dieser Arbeit darin, molekulare Marker für die Abschätzung der Prognose beim lokal begrenzten und metastasierten NZK sowie die Vorherage für das Ansprechen auf eine Sunitinib-Therapie beim metastasierten NZK zu identifizieren. Für das Prognosemodell am lokal begrenzten NZK konnten auf mRNA-Ebene signifikante Assoziationen der Marker HIF-2α, VEGFR3 und sVEGFR1 mit dem PFS, TSS und OS der Patienten identifiziert werden. Da bisher nur klinische Parameter für Prognosemodelle des lokal begrenzten NZK genutzt werden, könnten die hier untersuchten molekularen Marker nach einer unabhängigen Validierung zur Vorhersage der Prognose herangezogen werden. Patienten mit einem metastasierten NZK wiesen VHL-Mutationen (50%) und -Kopienzahlverluste (60 %) auf, die jedoch nicht mit dem Ansprechen auf Sunitinib assoziiert waren und nur geringfügige Auswirkungen auf die Proteinlevel von VHL und dessen Targetgene HIF-1α, CA9 und VEGFA zeigten. Bei den Untersuchungen zur VHL-Promotormethylierung wurde im tumorfreien Gewebe eine hohe Grundmethylierung festgestellt. Aufgrund der geringen Patientenzahl und der weitgehend unbekannten komplexen Methylierungsstruktur des VHL-Promotors konnten keine Assoziationen mit der Prognose und dem Ansprechen der metastasierten NZK-Patienten auf Sunitinib bestimmt werden. Für die Proteinlevel potenzieller prädiktiver Marker wie CA9, HIF-1α, VEGFR1 und -2, pVEGFR1, pPDGFRα und -β, CD31, pAkt sowie Ki67 wurden signifikante Assoziationen mit dem Ansprechen auf die Sunitinib-Behandlung beobachtet. Die CA9-Membranfärbung und das Ansprechen nach 9 Monaten wurden in der multivariaten Analyse als unabhängige prognostische Marker für das OS bei Patienten mit metastasiertem NZK identifiziert. In anderen Arbeiten wurde CA9 bereits mehrfach als potenzieller Biomarker beschrieben und könnte daher eine Anwendung in der Prognosevorhersage und Patienten-Selektion für eine Target-Therapie finden. Polymorphismen in Angiogenese-assoziierten Genen gelten ebenfalls als potenzielle Marker für das Ansprechen auf eine Therapie mit Sunitinib. Die Überlebensanalysen deckten signifikante Assoziationen zwischen dem VEGFA-SNP -2578 und dem PFS und für die SNPs VEGFR1 B sowie VEGFR2 +1191 mit dem OS auf. Das kombinierte Auftreten der Varianten-Allele der VEGFA-SNPs -2578, -1154 und +405 wirkte sich ebenfalls signifikant auf ein verlängertes OS der mit Sunitinib behandelten Patienten aus. Bei eindeutiger Bestätigung dieser Ergebnisse in prospektiven Studien könnten einfache SNP-Analysen an Blutproben die Therapieentscheidung und das Überleben der NZK-Patienten maßgeblich beeinflussen. Die künstlich erzeugte Sunitinib-Resistenz in den NZK-Zelllinien A498, Caki-1 und KTCTL-26 offenbarte nur begrenzt veränderte Proteinniveaus potenzieller Marker wie HIF-1α, Akt und pAkt zwischen den resistenten und sensitiven Zellen. Ein besseres Verständnis der molekularen Grundlagen der Resistenzentwicklung könnte zusammen mit einem wirkungsvollen, prädiktiven Biomarker für das Ansprechen die Therapie beim metastasierten NZK erheblich verbessern. In dieser Arbeit konnten letztlich verschiedenste Biomarker identifiziert und evaluiert sowie deren Bedeutung für die Prognosevorhersage und Prädiktion von Patienten mit metastasiertem NZK unter Sunitinib-Therapie herausgearbeitet werden. Diese Daten stellen damit einen weiteren Grundstein für mögliche prospektive klinische Studien dar, die den therapeutischen Nutzen der Biomarker eindeutiger definieren könnten.