High-Resolution Solid-State NMR in St Andrews: Development and Applications

该提案旨在圣安德鲁斯提供现代设备，这将使新的核磁共振(核磁共振)实验得以开发，以深入了解固体的结构。核磁共振光谱学利用原子核的固有磁性来探测材料的局部结构和动态环境。然而，对于固体来说，影响核磁共振光谱的许多相互作用的取向相关性(以及液体中通过快速分子翻滚而平均的相互作用)导致了较大的展宽和没有信息的光谱。许多工作都集中在通过魔角旋转(MAS)和多量子MAS(MQMAS)等技术消除这种展宽。最近在磁铁技术、硬件和方法发展方面的进步使固态核磁共振发展到现在可以用来提供关于工业、生物和地质相关的复杂化学系统的详细信息的阶段。我们的目标是使用新的设备来开发新的实验和改进现有的技术来获得这两个高分辨率光谱，并通过实验提供不同原子核的结构信息(例如，证明两个物种的空间接近或提供关于它们的化学键的性质的信息)。这种类型的信息是将材料的原子尺度结构与其宏观性质联系起来的关键一步。此外，我们将扩大这些方法的适用性，使其适用于许多具有工业和商业价值的材料中存在的更具挑战性和不寻常的原子核。这些包括低灵敏度(89Y，39K)、低自然丰度(17O，25 mg)、长弛豫时间(89Y)和较大的四极耦合(45Sc，71Ga，93Nb)的核，例如，在这些材料中，结构无序、显著的动力学行为或顺磁离子的存在是一个问题。使用现代探头硬件和增加磁场强度将是实现这些目标的关键。我们将在一系列领域使用这些最先进的实验，包括地球内层的高压硅酸盐矿物的17O和25毫克的核磁共振，其中核磁共振的灵敏度受到高压合成中产生的少量样品(通常为3-15毫克)的限制。此外，我们还将用89Y、17O和119Sn核磁共振研究烧绿石陶瓷材料的局域结构和有序性，这些材料被认为是核废料的包覆和长期储存的主体相。另一个令人感兴趣的领域是微孔骨架材料的局部结构和几何形状的表征(通过27Al、31P、45Sc和71Ga核磁共振)，这些材料可用作催化剂和气体存储介质。

The proposal aims to provide modern equipment in St Andrews which will enable the development of new Nuclear Magnetic Resonance (NMR) experiments to provide insight into structure of solids. NMR spectroscopy utilises the inherent magnetism of atomic nuclei to probe the local structural and dynamic environment of a material. However, for solids the orientational dependence of many of the interactions which affect NMR spectra (and which are averaged in liquids by rapid molecular tumbling) results in large broadenings and uninformative spectra. Much work has focussed on the removal of this broadening through techniques such as magic-angle spinning (MAS) and multiple-quantum MAS (MQMAS). Recent improvements in magnet technology, hardware and methodological development have advanced solid-state NMR to the stage where it can now be employed to provide detailed information on chemically-complex systems of industrial, biological and geological relevance.We aim to use the new equipment to develop new experiments and improve existing techniques to acquire both high-resolution spectra, and provide structural information through experiments which correlate different nuclei (demonstrating, for example, the spatial proximity of two species or providing information on the nature of their chemical bonding). This type of information is a crucial step in linking the atomic scale structure of a material to its macroscopic properties. Furthermore, we will widen the applicability of these approaches to the more challenging and unusual nuclei present in many materials of industrial and commercial interest. These include nuclei with low sensitivity (89Y, 39K), low natural abundances (17O, 25Mg), long relaxation times (89Y), and larger quadrupolar couplings (45Sc, 71Ga, 93Nb) in materials where structural disorder, significant dynamic behaviour, or the presence of paramagnetic ions, for example, are a problem. The use of modern probe hardware and increased magnetic field strength will be crucial in achieving these goals.We will utilise these state-of-the-art experiments in a range of areas including 17O and 25Mg NMR of the high-pressure silicate minerals in the inner layers of the Earth, where NMR sensitivity is limited by the small amount of sample produced (typically 3-15 mg) in the high-pressure synthesis. Also we will study the local structure and ordering by 89Y, 17O and 119Sn NMR in pyrochlore ceramic materials, which have been proposed as host phases for the encapsulation and long-term storage of nuclear waste. A further area of interest is the characterisation of the local structure and geometry of microporous framework materials (through 27Al, 31P, 45Sc and 71Ga NMR), which have applications as catalysts and gas storage media.