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Related Concept Videos

Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic Nuclei: Nuclear Relaxation Processes

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In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis,  the precessing magnetic moments are randomly oriented around the z-axis.
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All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...
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NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of...
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Atomic Nuclei: Magnetic Resonance01:05

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The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
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In the AX proton spin system, proton A can sense the two spin states of a coupled proton X, resulting in a doublet NMR signal with two peaks of equal (1:1) intensity. When proton A is coupled to two equivalent protons (AX2 spin system), the spin states of each X can be aligned with or against the external field, creating three possible scenarios. This results in a 1:2:1  triplet signal, where the central peak corresponds to the chemical shift of A and is twice as large or intense as the...
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Tetrahedral Complexes
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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
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Triplet-DNP in magnetically oriented microcrystal arrays.

Akinori Kagawa1, Ryosuke Kusumi2, Rintarou Nagase3

  • 1Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan; Center for Quantum Information and Quantum Biology, Osaka University, Japan.

Journal of Magnetic Resonance (San Diego, Calif. : 1997)
|April 21, 2023
PubMed
Summary

We developed a new method for dynamic nuclear polarization using electron spins in photo-excited triplet states (Triplet-DNP). This technique significantly enhances nuclear polarization in magnetically oriented microcrystal arrays (MOMAs).

Keywords:
Dynamic nuclear polarization (DNP)Magnetically oriented microcrystal array (MOMA)Photo-excited triplet stateTriplet-DNP

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Area of Science:

  • Solid-state chemistry
  • Quantum chemistry
  • Spectroscopy

Background:

  • Dynamic nuclear polarization (DNP) enhances NMR sensitivity.
  • Conventional Triplet-DNP in powders faces limitations like reduced polarization and broadened electron-spin resonance (ESR).
  • Magnetically oriented microcrystal arrays (MOMAs) offer a promising platform for improved DNP.

Purpose of the Study:

  • To investigate Triplet-DNP in MOMAs of pentacene-doped p-terphenyl.
  • To compare the polarization efficiency of Triplet-DNP in MOMAs with conventional powder samples and single crystals.
  • To explore potential applications of Triplet-DNP in MOMAs.

Main Methods:

  • Preparation of magnetically oriented microcrystal arrays (MOMAs) of pentacene-doped p-terphenyl.
  • UV curing of the MOMA suspension in a stationary magnetic field.
  • Measurement of nuclear polarization enhancement using Triplet-DNP.

Main Results:

  • Triplet-DNP in MOMAs achieves high dynamic polarization comparable to single crystals.
  • Enhanced 1H polarization in 1D MOMAs is an order of magnitude higher than in powder samples.
  • Polarization levels in MOMAs rival those in 3D MOMAs prepared with a modulational rotating field.

Conclusions:

  • Triplet-DNP in MOMAs provides a significant improvement over conventional powder methods.
  • MOMAs offer a simple and effective route to high nuclear polarization.
  • This technique holds potential for polarizing co-doped molecules and in dissolution experiments.