Topics for bachelor and master theses

  • 1. NMR studies on model Martian soils (Bachelor/Master) Can a mobile NMR sensor on Mars measure the diffusion of water? What is the relationship for deep eutectic salt mixtures? This is a continuation of two bachelor theses in which iron, salt and water concentrations were varied at room temperature. This project is now about measuring liquid water under realistic Martian surface conditions (saturated chlorate solutions, ferruginous sands, T=200 K and above) - relaxation and diffusion. Focus: sample preparation, experiment; documentation
  • 2nd NMR multipulse methods for polymers and ordered systems (Bachelor/Master) How can the mean displacement square of molecules be determined using novel echo methods? What are the possible applications for biological samples and porous media? For dynamics in polymer melts, a robust multi-echo method has been developed which determines the mean displacement square for anomalous diffusion (subdiffusive processes) in a time domain which is not accessible with other methods. The method is now to be applied to new polymers, biomacromolecules and liquids in porous media. The device allows annealing up to about 470 K. Focus: experiment, data analysis, theory
  • 3. rheometer at the low-field sensor NMR-MOUSE (Bachelor/Master) How can an oscillating rheometer for the NMR-MOUSE be constructed and tested? An existing rheology cell (continuous rotation) is currently being optimized at NMR-MOUSE. This has to be tested and used on different material systems (scope of a bachelor thesis). As the next stage of development, we are planning an oscillating rheology cell (SAOS, Small Amplitude Oscillatory Shear), which is precisely adapted to the magnetic field geometry. For this purpose, two comparable systems have been constructed worldwide in 2019. The device is to be calibrated and verified against known test samples (scope of a master thesis from mid 2020). Focal points: Design and construction; measurement, documentation and optimization of measurement parameters; interaction with other working groups.
  • 4. deuterated polymer mixtures in confinement (Bachelor/Master) How does confinement in narrow pores influence the dynamics of polymer melts? In the department we are working on a long-standing project to analyze polymer melts using different isotope diluted mixtures of polyethylene oxide (both 1Hand 2H resonance). One aspect of the DFG project investigates the question which differences in dynamics arise during confinement in rigid porous media (e.g. Vycor glass, 4 nm, as established standard). In the literature, only the measurement of undereuterated PEO has been successful so far. Main focus: Sample preparation, experiment
  • 5 Liquid mixtures in porous media and rocks (Bachelor/Master) How do wetting and non-wetting liquids distribute on surfaces? How can they be separated from each other metrologically? Surfaces are either hydrophilic or hydrophobic, intermediate states are possible. Wettability is of great economic importance in the distribution of water and crude oil in rocks, but also in catalysis research. Simple mixtures of liquids of different polarity (water/alcohol/alkanes/aromatics) in porous glasses or/and in rocks shall be investigated, where the relaxation properties of the pure substances are known. The aim is an experimental determination of the liquid distribution near the surface. The measurements are performed in comparison with and without signal enhancing radicals at the surface. Main focus: Experiment, preparation, data evaluation
  • 6 Multifunctional hydrogels in natural soils (Bachelor/Master) How does the storage capacity for water in soils change when hydrogels are added? Globally, besides precipitation distribution, the availability of water for agriculture is important - in 2019/20 soils in Germany are massively undersaturated, water cannot be adequately retained without active plant components. Hydrogels can store large amounts of water and also release it in interaction with plant roots, their use on a large scale is being prepared. NMR can be used to measure the amount as well as the binding state and the mobility of the water, MRI can additionally be used to visualize the gel distribution (the latter only in the context of a master thesis). Cooperation with FZ Jülich. Main focus: Experiment, literature study, data evaluation.
  • 7. signal amplification with DNP on highly diluted protein solutions (Bachelor/Master) What are the dynamics of proteins in solutions? What is the minimum detectable concentration? In our department we have developed a hardware which allows to increase the sensitivity of measurements of molecular dynamics up to 100-fold by means of magnetic field dependent relaxation. This method (DNP) has so far only been tested on model systems that are accessible without signal amplification. The method is now to be applied to highly dilute protein solutions of which it is known that individual regions of the molecules show strongly different dynamics. Such measurements have so far only been carried out to a very limited extent on highly concentrated solutions, in which, however, the proteins interfere with each other's mobility. Main focus: Experiment, data analysis, preparation
  • 8. ionic liquid (ILs) under confinement (Bachelor/Master) Investigation of the influence of the silica nanoparticles on ILs dynamic behavior, distinguishing different cases, adsorption of ILs molecules on the outer surface of the nanoparticles, and/or restriction/confinement of ILs molecules in the mesoscopic spaces between nanoparticles. For this project diffusion and relaxation times will be measured using NMR techniques. Focus: experimental, literature studies, data analysis, theory
  • 9 Ionic liquid (ILs) as electrolytes (Bachelor/Master) ILs may be used as well in concrete systems like complex non-aqueous electrolytes in different phases, as free liquid or immobilized in matrices forming gels or even in solid state, with application in batteries, capacitors/ supercapacitors. For these applications, it is common to use a mixture of ILs with a specific Li- or Na-containing salts. The aim in this project is to investigate molecular dynamics, charge transport and conductivity by measuring NMR relaxation and diffusion properties in these systems. Focus: experimental, literature studies, data analysis
  • 10. EPR studies about Ionic liquids (Bachelor/Master) In relation with the Project 15, the properties of the electron spin system in the radicals immersed in the ILs will be studied in this project by using electron spin resonance (ESR). This technique allows one to extract spectroscopic and dynamic information of the radical system and infer information as well about ILs molecules. Focus: experiment, literature studies, data analysis
  • 11. construction and application of a pressure cell for defined deformation of tissue and elastomer samples (Master) How should a non-magnetic pressure cell look like, which deforms samples and measures the pressure at the same time? Design, dimensioning and construction (3D printing) of a pressure cell for soft samples (cartilage, tendons, rubber) made of non-metallic material, suitable for installation in low-field magnets, incl. measurement of force and deformation, test measurements Main topics: Construction, literature work
  • 12 Rheology of polymer melts in a magnetic field (Master) Can mechanical stress measurably influence molecular dynamics? Use of an existing apparatus for the systematic analysis of the change in NMR relaxation properties of sheared polymer melts and possibly other complex fluids with spectral resolution. Measurements in either high field or variable field (field-cycling relaxometer). Main focus: Sample preparation, measurement; documentation and optimization of measurement parameters; data analysis and literature.
  • 13. construction of a miniaturized temperature control cell for the NMR-MOUSE (Master) How can the temperature of a thin object be controlled in isolation from the environment? Temper an object about 2 mm thick at a distance of about 2 mm from the permanent magnet, while keeping the magnet temperature constant: Use of microfluidic elements with heating and cooling circuits or/and Peltier elements, construction of a control system with measuring probes in the flow and return (a model from the literature exists). Main focus: Construction, control, electronics
  • 14. construction of routine measuring methods on a Halbach magnet (master) How can existing NMR measuring methods be effectively implemented on a limited homogeneous and field-variable ring magnet? Use of existing measurement and optimization software on a Halbach ring magnet to extend to manually or motorized adjustable field strength by rotation; homogenization of the magnetic field as a function of field strength, optimization of measurement and control routines Focus: Programming, experiment, automated data evaluation.
  • 15. construction of a unit with field modulation coils (master) How to dimension field modulation coils to perform the Integrated Solid Effect? Dynamic Nuclear Polarization (DNP) is one of the techniques currently used for signal enhancement in NMR; it relies on irradiation with microwaves. For many substances with broad absorption lines, however, excitation by MIcrowaves is much too weak; here, the magnetic field must be modulated at high frequency to cover the entire width of the (electron) spectrum. For this purpose, additional coils have to be constructed which are located close to the sample in order to minimize the necessary current strengths and heating effects. The design is based on commercial solutions for field gradient coils. Emphasis: Design, construction - Electronics skills.
  • Ionic liquids (ILs) and radical dynamics (Master) For certain nuclei (7Li, 19F, 2H, 13C) with low sensitivity or low natural abundance, dynamic nuclear polarization (DNP) is used in order to improve signal intensity. A requirement here is to dissolve a small concentration of radicals containing one or more unpaired electrons in the ILs. In this way DNP induces a transfer of high polarization of the electron spin system to the nuclear spin system. However, the presence of radicals modifies the nuclear relaxation properties of the system of interest. In this project, NMR relaxation studies will be performed combined with DNP in ILs+radical systems in order to achieve information about dynamics of the ILs molecules. Additionally, more complex studies may be performed with this technique, like enhancement of the NMR signal in specific sites of the molecules. Focus: experimental, literature studies, data analysis, theory