New NMR Methods for Investigating Structure in Inorganic Oxide Glasses

俄亥俄州立大学的菲利普·J·格兰迪内蒂博士由化学部物理化学项目资助，研究用于研究无机氧化物玻璃结构的新的核磁共振方法。俄亥俄州立大学和其他地方开发的先进魔角旋转(MAS)技术，如转子辅助偏振转移(RAPT)和快速旋转增强了旋转共振(FASH)的传递增强，将被改进用于玻璃的结构测定。将改进APPT四极灵敏度增强方案，以获得大范围自旋耦合和共振偏移的最大增强，并获得动态角度自旋(DAS)和多量子(MQ)-MAS的APPT增强版本。为了更快地与其他MQ-MAS方法进行比较，我们将对更快的旋转共振与核自旋、四极耦合、不对称性和化学位移等参数的关系进行数值和实验研究。DAS和MQ-MAS的灵敏度增强版将用于研究二元(金属氧化物硅酸盐)和三元(双金属氧化物硅酸盐)玻璃的组成，以期量化Si-O-Si键角、配位数以及桥氧和非桥氧周围的几何结构。从这项研究中获得的对无机氧化物玻璃的理解将影响多个领域的研究人员。固体核磁共振方法在结构测定中的潜在重要性长期以来一直受到敏感性问题的阻碍。其中许多问题正在被格兰迪内蒂博士的团队和其他人的成就所克服，并将被俄亥俄州立大学的研究进一步克服。将开发的提高固态核磁共振灵敏度的方法将对希望充分利用四极核作为结构探针的研究人员产生广泛影响。

Dr. Philip J. Grandinetti of Ohio State University is funded for his research on new NMR methods for investigating structure in inorganic oxide glasses by the Physical Chemistry Program of the Chemistry Division. Advanced magic angle spinning (MAS) techniques, such as rotor assisted polarization transfer (RAPT) and fast spinning gives transfer enhancement at rotary resonance (FASTER), developed at Ohio State University and elsewhere will be refined for applications to structural determinations in glasses. RAPT quadrupolar sensitivity enhancement schemes will be refined for obtaining maximal enhancements for a wide range of spin couplings and resonant offsets, and for obtaining RAPT enhanced versions of dynamic-angle spinning (DAS) and multiple-quantum (MQ)-MAS. Numerical and experimental studies of the dependence of the FASTER rotary resonances on parameters such as nuclear spin, quadrupolar coupling, asymmetry, and chemical shifts will be done in order to compare FASTER with other MQ-MAS methods. Sensitivity enhanced versions of DAS and MQ-MAS will be used to study binary (metal oxide silicates ) and ternary (bimetal oxide silicates) glass compositions, with a view towards quantifying Si-O-Si bond angles, coordination numbers, and geometries around bridging and non-bridging oxygens.The understanding of inorganic oxide glasses obtained from this research will impact researchers in several areas. The potential importance of solid-state NMR methods in structure determinations has long been thwarted by sensitivity issues. Many of these issues are being overcome by accomplishments from Dr. Grandinetti's group and by others, and will be further overcome by the the research done at Ohio State University. The methods that will be developed for enhancing solid-state NMR sensitivity will have a broad impact on researchers wanting to take full advantage of quadrupolar nuclei as structural probes.