Fak. 2 Mathematik und Naturwissenschaften

1828 Items

Recent Submissions
Speciation of molybdenum- and vanadium-based polyoxometalate species in aqueous medium and gas-phase and its consequences for M1 structured MoV oxide synthesis

Jung, Sabrina (2018)

Polyoxomolybdate and –vanadate speciation has been examined in aqueous solution and in the gas-phase depending on the concentration and pH value. Raman and UV-vis spectroscopy showed the compact and highly charged hepta- and octamolybdate, and decavanadate species to be present, respectively, while mass spectrometric measurements led to a multitude of different species. The structure of these g...

Computational chemistry studies on metallo-enzymes for the splitting of hydrogen and the interconversion between carbon monoxide and carbon dioxide

Tombolelli, Daria (2018)

Carbon monoxide dehydrogenases (CODH) are metallo-enzymes which perform the interconversion between CO and CO2. In particular, in the present work, nickel iron containing CODH from Carboxydothermus hydrogenoformans, is studied. Its catalytic mechanism is still unclear, because of the difficulties at the experimental level to trap substrate-bound intermediates and pure redox states. For this rea...

N-heterocyclic silylenes as tools in coordination chemistry and catalysis

Zhou, Yu-Peng (2018)

Low-valent main-group chemistry, especially the chemistry of N-heterocyclic silylenes (NHSis), is one of the most attractive research topics in contemporary organometallic chemistry. In this dissertation, a series of NHSis and their derivatives were developed and used as ligands to stabilize low-valent germanium compounds as well as in transition metal-mediated homogenous catalysis. The synthe...

Comprehensive snake venomics of the Okinawa Habu pit viper, Protobothrops flavoviridis, by complementary mass spectrometry-guided approaches

Damm, Maik ; Hempel, Benjamin-Florian ; Nalbantsoy, Ayse ; Süßmuth, Roderich D. (2018-07-29)

The Asian world is home to a multitude of venomous and dangerous snakes, which are used to induce various medical effects in the preparation of traditional snake tinctures and alcoholics, like the Japanese snake wine, named Habushu. The aim of this work was to perform the first quantitative proteomic analysis of the Protobothrops flavoviridis pit viper venom. Accordingly, the venom was analyzed...

Scanning tunneling microscopy study of strong metal-support interaction in iron oxide based model catalysts

Zhang, Ke (2018)

The term “strong metal-support interaction” (SMSI) was introduced by S.J. Tauster in late 1970’s to describe drastic changes in the chemisorption properties of metal particles supported on reducible oxides. Although there may be different explanations for SMSI effect, in the great majority of cases, it manifests itself via encapsulation of the supported metal particles by a thin oxide layer ste...

BiVO4-based photoanodes for photoelectrochemical water splitting

Rohloff, Martin (2018)

Global warming refers to the rise in average surface temperatures on Earth and is considered as the major environmental problem humanity is facing today. An overwhelming scientific consensus maintains that climate change is primarily caused by the combustion of fossil fuels, which releases carbon dioxide and other greenhouse gases into the atmosphere. Consequently, this gives rise to a range of...

Grazing incidence X-ray diffraction

Scherzer, Michael (2018)

The interest to study iridium electrocatalysts originates from their use in PEM electrolyzers, which are used to produce hydrogen from water splitting. The need to overcome the exploitation of fossil fuels and to promote the use of sustainable resources makes this a promising alternative. Usage of expensive and rare iridium additionally pushes research to find cost efficient alternatives, proba...

Surface plasmon resonance based sensor for the detection of glycopeptide antibiotics in milk using rationally designed nanoMIPs

Altintas, Zeynep (2017-07-25)

Glycopeptide antibiotics are known as the last resort for the treatment of serious infections caused by Gram-positive bacteria. The use of milk products contaminated with these antibiotic residues leads to allergic reactions and sensitivity in human. Also, long-term consumption of milk products containing low levels of these antibiotics may cause the relevant bacteria to build up resistance to ...

Isotropic and coisotropic subvarieties of Grassmannians

Kohn, Kathlén (2018)

In this thesis, we study subvarieties of Grassmannians which are characterized by certain rank one conditions on their tangent or conormal spaces. Although these concepts seem to be very abstract at first sight, we will see that many of these subvarieties are naturally associated to underlying projective varieties. Typically such varieties consist of linear spaces which meet a projective variet...

Frustrated Lewis pairs embedded into microporous polymer networks

Trunk, Matthias Georg (2018)

Aufgrund ihrer vielseitigen potentiellen Anwendungsmöglichkeiten in Gasspeicherung und –trennung, Sensorik und Katalyse haben mikroporöse organische Materialien innerhalb der letzten 20 Jahre eine rasante Entwicklung erfahren. Neben geordneten Materialien wie metall-organischen Gerüstmaterialien (MOFs) und kovalent organischen Gerüstmaterialien (COFs) haben sich mikroporöse Polymernetzwerke (MP...

Doppler coherence imaging of ion dynamics in the plasma experiments VINETA.II and ASDEX upgrade

Gradic, Dorothea (2018)

In magnetically confining plasma experiments, measurement of ion dynamics is of great importance to study the plasma behaviour in magnetic fields such as the exhaust particle flows in the divertor areas. The plasma exhaust heat flux in a future nuclear power plant is estimated to be too high for the proposed wall materials. This is due to the relatively small areas, where the exhaust plasma int...

Internal electric field manipulation in nanostructures

Schlichting, Sarah Kristina (2018)

Recently, an unconventional approach [the so-called Internal-Field-Guarded-Active-Region Design (IFGARD)] for the elimination of the crystal polarization field induced quantum confined Stark effect (QCSE) in polar semiconductor heterostructures was developed. This thesis demonstrates by means of micro-photoluminescence techniques the successful tuning as well as the elimination of the QCSE in s...

Magnetische und elektronische Eigenschaften von Übergangsmetallkomplexen in der Gasphase

Bülow, Christine (2018)

In dieser Arbeit wurde der Übergang von einem Hochspin- zu einem Niedrigspinzustand in verschiedenen Systemen mit jeweils einem Übergangsmetallatom mittels Röntgenabsorptions- und XMCD-Spektroskopie in der Gasphase untersucht. Im Vordergrund steht die Frage wie dieser magnetische Übergang von der Anzahl der 3d Elektronen, der Struktur und den Liganden abhängt. Dabei wird von in einem früheren P...

Property-performance correlations in the oxidative coupling of methane

Wang, Huan (2018)

The oxidative coupling of methane is a “dream reaction” in heterogeneous catalysis to achieve direct conversion for natural gas towards value-added and easily transportable C2 products with high economic relevance. Although extensive academic papers and patents have been reported over the last three decades, no economically viable industrial-scale application is yet achieved because of the limi...

Enzymes as modular catalysts for redox halfreactions in H2-powered chemical synthesis: from biology to technology

Reeve, Holly A. ; Ash, Philip A. ; Park, HyunSeo ; Huang, Ailun ; Posidias, Michalis ; Tomlinson, Chloe ; Lenz, Oliver ; Vincent, Kylie A. (2017-01-06)

The present study considers the ways in which redox enzyme modules are coupled in living cells for linking reductive and oxidative half-reactions, and then reviews examples in which this concept can be exploited technologically in applications of coupled enzyme pairs. We discuss many examples in which enzymes are interfaced with electronically conductive particles to build up heterogeneous cata...

Facile Control over the Supramolecular Ordering of Selfassembled Peptide Scaffolds by Simultaneous Assembly with a Polysacharride

Li, Rui ; Boyd-Moss, Mitchell ; Long, Benjamin ; Martel, Anne ; Parnell, Andrew ; Dennison, Andrew J. C. ; Barrow, Colin J. ; Nisbet, David R. ; Williams, Richard J. (2017-07-06)

Enabling control over macromolecular ordering and the spatial distribution of structures formed via the mechanisms of molecular self-assembly is a challenge that could yield a range of new functional materials. In particular, using the self-assembly of minimalist peptides, to drive the incorporation of large complex molecules will allow a functionalization strategy for the next generation of bi...

Enantioselektive Reduktionen mit Ru–S-Komplexen und Untersuchung der zugrundeliegenden Mechanismen

Bähr, Susanne (2018)

Die vorliegende Dissertation widmet sich der Synthese und Charakterisierung chiraler, kationischer Ruthenium(II)-Thiolatkomplexe und deren Anwendung in enantioselektiven Reduktionen. Die Aufklärung der Mechanismen dieser katalytischen Umsetzungen ist ein weiterer Schwerpunkt. Der erste Teil der Arbeit besteht in der mechanistischen Aufklärung der zuvor entwickelten 1,4-Hydrosilylierung von Py...

Growth and characterization of antimony-based quantum dots in GaP matrix for nanomemories

Sala, Elisa Maddalena (2018)

Self-assembled Quantum Dots (QDs) have recently attracted great attention for enabling a novel type of non-volatile electronic nanomemory, the QD-Flash. Such a memory architecture represents the ultimate memory cell, exhibiting endurance and fast access times (~ns). To ensure non-volatile operation, the storage time for carriers has to be of the order of 10 years (or longer) at room temperature...

Stable marriage and roommates problems with restricted edges: complexity and approximability

Cseh, Ágnes ; Manlove, David F. (2016-04-16)

In the Stable Marriage and Roommates problems, a set of agents is given, each of them having a strictly ordered preference list over some or all of the other agents. A matching is a set of disjoint pairs of mutually acceptable agents. If any two agents mutually prefer each other to their partner, then they block the matching, otherwise, the matching is said to be stable. We investigate the comp...

Tropicalization of del Pezzo surfaces

Ren, Qingchun ; Shaw, Kristin ; Sturmfels, Bernd (2016-03-30)

We determine the tropicalizations of very affine surfaces over a valued field that are obtained from del Pezzo surfaces of degree 5, 4 and 3 by removing their (-1)-curves. On these tropical surfaces, the boundary divisors are represented by trees at infinity. These trees are glued together according to the Petersen, Clebsch and Schläfli graphs, respectively. There are 27 trees on each tropical ...