固态动态核极化在9.4和18.8T从100K到室温
Moreno Lelli1, Sachin R Chaudhari1, David Gajan1
1Institut de Sciences Analytiques, Centre de RMN à Très Hauts Champs, Université de Lyon (CNRS/ENS Lyon/UCB Lyon 1) , 69100 Villeurbanne, France.
Journal of the American Chemical Society
|November 12, 2015
概括
使用动态核极化 (DNP) 的高灵敏核磁共振 (NMR) 实验现在可以在更高的温度下进行. 研究人员使用特定的溶剂在240K时取得了显著的 (1) H DNP增强,从而实现了新的应用.
科学领域:
- 固态核磁共振 (NMR) 光谱
- 动态核极化 (DNP) 技术
- 材料科学和物理化学
背景情况:
- 动态核极化 (DNP) 显著提高了NMR信号的灵敏度.
- 目前的DNP方法通常仅限于低温 (≤100K).
- 更高温度的DNP对于更广泛的应用至关重要,特别是在生物和材料科学中.
研究的目的:
- 研究在高温下实现有效的动态核极化 (DNP) 的可行性.
- 探索用于高温DNP的特定溶剂和二基.
- 应用高温DNP来监测固体药物化合物的分子动力学.
主要方法:
- 作为一种溶剂系统,使用溶解在正极 (OTP) 的二基TEKPol.
- 在100300K的温度范围内进行了 (1) H交叉效应的DNP实验.
- 在9.4和18.8特斯拉的磁场强度进行实验.
- 应用DNP来研究Ambroxol和Ibuprofen固体中的分子动态转换.
主要成果:
- 在240K时获得超过80的 (1) H交叉效应DNP增强.
- 在OTP的玻璃过渡温度 (Tg = 243 K) 上,DNP增强的速度相对缓慢.
- (1) 在环境温度下得到1520的H DNP增强.
- 通过使用DNP方法成功监测了Ambroxol和Ibuprofen的分子动态转变.
结论:
- 通过选择合适的溶剂系统,如ortho-terphenyl (OTP),可以实现高温DNP的效率.
- 开发的方法允许在明显高于常规极限的温度下进行DNP增强的NMR研究.
- 该技术为在近环境条件下研究药物相关固态材料的分子动力学提供了有价值的工具.
相关概念视频
Atomic Nuclei: Nuclear Spin State Population Distribution
2.6K
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
2.6K
Atomic Nuclei: Nuclear Relaxation Processes
1.4K
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.
1.4K
Nuclear Stability
24.2K
Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10−15 meters, a nucleus is quite small compared to the radius of the entire atom, which is about 10−10 meters. Nuclei are extremely dense compared to bulk matter, averaging 1.8 × 1014 grams per cubic centimeter. If the earth’s density were equal to the average nuclear density, the earth’s radius would be only about 200 meters.
To hold positively charged protons together...
To hold positively charged protons together...
24.2K
Atomic Nuclei: Nuclear Spin State Overview
2.2K
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 one, the...
2.2K
Nuclear Fission
12.9K
Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger binding energies per nucleon—that is, mass numbers and binding energies per nucleon that are closer to the “peak” of the binding energy graph near 56. Sometimes neutrons are also produced. This decomposition of a large nucleus into smaller pieces is called fission. The breaking is rather random with the formation of a large...
12.9K
Nuclear Binding Energy
15.2K
The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect indicates a “loss” in mass of 4.0331 amu – 4.0026 amu = 0.0305 amu. The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms. The nuclear binding energy is the energy produced when the atoms’ nucleons are bound...
15.2K


