title: 1H relaxation enhancement induced by nanoparticles in solutions: influence of magnetic properties and diffusion.
abstract: Magnetic nanoparticles that induce nuclear relaxation are the most promising materials to enhance the sensitivity in Magnetic Resonance Imaging. In order to provide a comprehensive understanding of the magnetic field dependence of the relaxation enhancement in solutions, Nuclear Magnetic Resonance (1)H spin-lattice relaxation for decalin and toluene solutions of various Fe2O3 nanoparticles was investigated. The relaxation experiments were performed in a frequency range of 10 kHz-20 MHz by applying Field Cycling method, and in the temperature range of 257-298 K, using nanoparticles differing in size and shape: spherical--5 nm diameter, cubic--6.5 nm diameter, and cubic--9 nm diameter. The relaxation dispersion data were interpreted in terms of a theory of nuclear relaxation induced by magnetic crystals in solution. The approach was tested with respect to its applicability depending on the magnetic characteristics of the nanocrystals and the time-scale of translational diffusion of the solvent. The role of Curie relaxation and the contributions to the overall (1)H spin-lattice relaxation associated with the electronic spin-lattice and spin-spin relaxation was thoroughly discussed. It was demonstrated that the approach leads to consistent results providing information on the magnetic (electronic) properties of the nanocrystals, i.e., effective electron spin and relaxation times. In addition, features of the (1)H spin-lattice relaxation resulting from the electronic properties of the crystals and the solvent diffusion were explained.
authors.affiliation: Faculty of Mathematics and Computer Science, University of Warmia and Mazury in Olsztyn, Słoneczna 54, 10-710 Olsztyn, Poland.
authors.forename: D
authors.initials: D
authors.lastname: Kruk
authors.affiliation: Department of Biophysics, Jagiellonian University Medical College, Łazarza 16, 31-530 Kraków, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Korpała
authors.affiliation: Department of Physical Chemistry I, Universität Bayreuth, 95440 Bayreuth, Germany.
authors.forename: S Mehdizadeh
authors.initials: SM
authors.lastname: Taheri
authors.affiliation: NU-MED Group Inc., Center of Radiotherapy and Improvements in Elbląg, Królewiecka 146, 82-300 Elbląg, Poland.
authors.forename: A
authors.initials: A
authors.lastname: Kozłowski
authors.affiliation: Department of Physical Chemistry I, Universität Bayreuth, 95440 Bayreuth, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Förster
authors.affiliation: Experimentalphysik II, Universität Bayreuth, 95440 Bayreuth, Germany.
authors.forename: E A
authors.initials: EA
authors.lastname: Rössler
mesh_terms: D004058:Diffusion; D005290:Ferric Compounds / Q000737:chemistry; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D055585:Physical Phenomena; D011522:Protons; D012996:Solutions / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; D011522:Protons; D012996:Solutions; D012997:Solvents