Development of methods and theory of DNP enhanced NMR relaxometry for the study of complex fluids and porous media

• Applicant: Professor Dr. Siegfried Stapf
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Analytical Chemistry ; Experimental Condensed Matter Physics ; Experimental and Theoretical Physics of Polymers
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 384109209

Field Cycling Relaxometry is a particular variant of NMR which studies slow molecular dynamics by measurement of relaxation times at different magnetic field strength. Due to the low detection fields, the method remains fundamentally insensitive, so that many systems such as diluted solutions or low-sensitivity isotopes cannot be studied. During the first funding period we have demonstrated that combination with Dynamic Nuclear Polarization (DNP) generates signal enhancement up to 100fold and thus brings many of these systems within reach of field-cycling relaxometry. More important, however, was acquiring knowledge about the nature of interaction processes of the radicals with the target molecules, and how the isotope-specific relaxation rates can be reconstructed from experimental data. During the extension period we are planning the further increase of signal intensities by at least one order of magnitude, the improvement of stability and the enabling of temperature-dependent measurements required for a theoretical description of the different DNP processes – these optimizations require the use of commercial components. At the same time we will apply our findings from experimental work within the first period and will concentrate on surfaces (immobilization of radicals for analyzing molecular dynamics of adsorbates in bicomponent systems) and complex fluids (ionic liquids, polymers) with two or more components that can be addressed selectively by signal enhancement.

• DFG Programme: Research Grants
• Major Instrumentation: Wide-Bore-Magnet (Upgrade) für DNP-NMR
• Instrumentation Group: 1741 Festkörper-NMR-Spektrometer