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dc.contributor.advisor Bennati, Marina Prof. Dr.
dc.contributor.author Enkin, Nikolay
dc.date.accessioned 2016-09-12T08:33:13Z
dc.date.available 2016-09-12T08:33:13Z
dc.date.issued 2016-09-12
dc.identifier.uri http://hdl.handle.net/11858/00-1735-0000-0028-882E-8
dc.language.iso eng de
dc.relation.uri http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc 571.4 de
dc.title Fullerene-Nitroxide Derivatives as Potential Polarizers for Dynamic Nuclear Polarization (DNP) in Liquid State de
dc.type doctoralThesis de
dc.contributor.referee Bennati, Marina Prof. Dr.
dc.date.examination 2015-09-21
dc.description.abstracteng Nuclear magnetic resonance spectroscopy and imaging (NMR/MRI) are widely applied methods for non-destructive analysis of biological systems, materials and medical applications. Dynamic nuclear polarization (DNP) is a method to enhance NMR signal by means of polarization transfer from unpaired electrons to nuclei through saturation the electron spin transition by microwave (MW). DNP in liquids is governed by Overhauser mechanism which results from the simultaneous flipping of electron and nuclear spins. The DNP efficiency decreases with increasing an external magnetic field. Since many organic molecules, which are potentially interesting for DNP as polarizers, are not soluble in water, the Overhauser DNP analysis has been done for toluene solutions. Also nonpolar solvents, in contrast to water, suffer less from dielectric losses and this allows using larger volume of the investigated samples. These experiments have demonstrated higher DNP efficiency of nitroxide radicals in toluene solution than in aqueous solution at low radical concentration. The reason is higher Heisenberg spin exchange rate between different hyperfine EPR transitions due to lower viscosity of toluene. The theoretical model of the relaxation dynamic for the electron-nuclear hyperfine coupled system with S=1/2 and I=1 has been analytically solved and the analytical expressions for the saturation factors of the individual hyperfine lines have been obtained. The electron-electron double resonance (ELDOR) method has been extended for the experimental measurements of the saturation factors and the polarization recoveries for radicals with more than 2 hyperfine lines. The series of experiments have demonstrated that the DNP enhancement increases with increasing of molecular size and does not depend on the nitroxide radical concentration in the case of dominant nitrogen nuclear relaxation between hyperfine EPR transitions. Several nitroxide derivatives with the covalently linked fullerene C60, as the dye with high quantum yield of the triplet state, have been synthetized. The transient EPR experiments of the photoexcited fullerene-nitroxide derivatives have demonstrated the feasibility to generate high non-equilibrium electron spin polarization by light. The photoexcited electron polarization, if successfully transferred to solvent nuclei, may provide a new method to perform DNP in liquids without MW irradiation. de
dc.contributor.coReferee Zweckstetter, Markus Prof. Dr.
dc.contributor.thirdReferee Enderlein, Jörg Prof. Dr.
dc.subject.eng Dynamic nuclear polarization de
dc.subject.eng Dynamic electron polarization de
dc.subject.eng Radical-dye system de
dc.subject.eng DNP in liquid state de
dc.subject.eng Overhauser mechanism de
dc.subject.eng Fullerene-nitroxide de
dc.identifier.urn urn:nbn:de:gbv:7-11858/00-1735-0000-0028-882E-8-4
dc.affiliation.institute Göttinger Graduiertenschule für Neurowissenschaften, Biophysik und molekulare Biowissenschaften (GGNB) de
dc.subject.gokfull Biologie (PPN619462639) de
dc.identifier.ppn 869469908

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