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17O
Published in Guillaume Madelin, X-Nuclei Magnetic Resonance Imaging, 2022
Dynamic nuclear polarization (DNP) is a technique used to enhance signal intensities in NMR experiments by transferring the high polarization of electrons (from a radical) to their surrounding nuclei. This hyperpolarization method is particularly suitable for 17O NMR where the 17O signal in the samples under investigation is generally extremely low due to the very low natural abundance of 17O atoms (0.038%). A schematic diagram of the DNP phenomenon is shown in Fig. 8.12(B).
Comprehensive Array of Ample Analytical Strategies for Characterization of Nanomaterials
Published in Vineet Kumar, Praveen Guleria, Nandita Dasgupta, Shivendu Ranjan, Functionalized Nanomaterials I, 2020
Nitesh Dhiman, Amrita Singh, Aditya K. Kar, Mahaveer P. Purohit, Satyakam Patnaik
Solid-state NMR spectroscopy is a powerful structural elucidation technique for powdered solid samples and provides very detailed structural and dynamics information. This technique has wide applications across both the physical and biological sciences (Nonappa and Kolehmainen, 2016). To overcome the limitations of the conventional 1H NMR technique, an electron source consisting of either stable radicals or transition metals having high-spin ions has been used as source to amplify the solid-state NMR signal by multiple orders of magnitude, known as dynamic nuclear polarization (DNP) (Ni et al., 2017). (Lee et al., 2012) functionalized SiO2 NPs to produce a surface covered with organosilanes and employed 29Si solid-state NMR to find the surface information on whether the organosilanes polymerization proceeded parallelly or perpendicularly. Using solid-state NMR, (Piveteau et al., 2015) defined the structure of different organic- and inorganic-capped quantum dots (CdSe, CdTe, InP, PbSe, PbTe, CsPbBr3) through DNP.
Perspective on long-lived nuclear spin states
Published in Molecular Physics, 2020
In dissolution dynamic nuclear polarisation (D-DNP), hyperpolarised substrates are first prepared by DNP in the solid state, then rapidly dissolved with a hot solvent and transferred to a solution-state NMR spectrometer or an MRI scanner for detection [49]. For the DNP step, the most common approach consists of: i/ mixing the substrates and radical-bearing molecules in a glass-forming solvent, ii/ placing the sample at a temperature of 1.1–4.2 K and a magnetic field of 3 to 10 T; iii/ irradiating the sample with microwave to build up nuclear polarisation [50, 51]. While the combined effects of DNP and a temperature jump can result in signal enhancements of over , the enhanced spin order decays irreversibly after dissolution and the timescales that can be probed with DNP-hyperpolarised substrates are limited by longitudinal relaxation.
Understanding Overhauser Dynamic Nuclear Polarisation through NMR relaxometry
Published in Molecular Physics, 2018
Giacomo Parigi, Enrico Ravera, Marina Bennati, Claudio Luchinat
One of the most severe limitations of NMR is its low sensitivity, resulting from the small difference in the population of the nuclear spin states at room temperature even at magnetic fields as large as 10–20 T [1]. Dynamic nuclear polarisation (DNP) is emerging as a precious tool to enhance the NMR signal by transferring magnetisation from unpaired electrons to nuclei. Overhauser DNP is achieved by transferring magnetisation through stochastic modulation of the magnetic hyperfine interaction between electron and nuclear spins [2–4]. This occurs in the presence of a non-Boltzmann distribution of the populations of electronic and nuclear spin states, which is achieved by microwave irradiation at the electron Larmor frequency [5–10].