Dynamic Nuclear Polarization Solid-state Nuclear Magnetic Resonance Spectroscopy of Insensitive Nuclear Spins.

点击翻译按钮获取中文摘要

The physical properties of molecules or materials are a direct consequence of the intimate arrangement of the atoms together. Therefore, the availability of scientific methods to directly see the connectivity between these atoms is essential. Atoms are extremely small objects, in the order of 10-10 meter or equivalent to try to see a single house on the Earth from the Sun. They are smaller than the wavelength of visible light and therefore too small to be seen by the naked eye. Scientists rely on the use of indirect methods to observe these atoms. Nuclear Magnetic Resonance (NMR) spectroscopy is the most powerful technique to see these atoms. NMR is commonly related to Magnetic Resonance Imaging, often abbreviated to MRI, and is a medical imaging technique used in radiology to investigate the anatomy of a body. The power of NMR spectroscopy relies on its sensitivity of the atomic length scale, and is used in addition to medicine, across the sciences, and especially in biology, chemistry and physics to determine the structure of matter. In particular, solid-state NMR spectroscopy, or NMR spectroscopy of solid-state samples, is becoming increasingly powerful to determine the structure of materials involved in a very wide range of applications, such as batteries, pharmaceuticals drugs and proteins responsible for diseases. However, the main limitation of the NMR technique in general, and solid-state NMR in particular, is the sensitivity, i.e. the intensity of signals with respect to the noise level, preventing fast acquisition of the NMR signals in seconds. One very important method to dramatically enhance the NMR signals is dynamic nuclear polarization. This technique permits a sensitivity enhancement factor of several hundred leading to reduction in experimental times of up to five orders of magnitude. For example, an NMR experiment lasting 10 min with dynamic nuclear polarization will require more than 1 year without dynamic nuclear polarization to obtain identical signal to noise ratio. This changes completely the type of atomic solid-state structures that could be determined and studied by NMR. Dynamic nuclear polarization relies on a transfer of polarization from the highly sensitive electron spins to the low sensitive nuclear spins at cryogenic temperatures. Dynamic nuclear polarization instruments capable of performing these experiments have only been available commercially since 2010. There are none in the United Kingdom today. Hence, this proposal aims at funding overseas travel to countries (such as France and the United States) to access a range of dynamic nuclear polarization hardware with various capabilities, and investigate some fundamental aspects of dynamic nuclear polarization enhanced solid-state NMR spectroscopy. Of particular interest to this proposal is that the work will exclusively target nuclei that are difficult (or nearly impossible) to detect by normal solid-state NMR, either due to a low natural abundance (e.g. 17O, 43Ca) or a low resonance frequency (25Mg, 39K, 107Ag, 183W) or a combination of both, and is therefore a clear and natural application of a dramatic sensitive enhancement technique such as dynamic nuclear polarization. This will be the source of immediate innovations in a very wide range of areas across science such as in materials science, catalysis and nanotechnology. It has the potential to completely revolutionize approaches to the determination of the atomic scale structure of materials, thereby driving the development of new high performance materials.