Date of Award
Doctor of Philosophy (PhD)
Nuclear magnetic resonance (NMR) is a nondestructive technique used to characterize molecular structure and dynamics with atomic resolution. In solid-state NMR, magic angle spinning (MAS) is commonly implemented to improve spectral resolution by partially averaging anisotropic interactions. To further improve NMR sensitivity, dynamic nuclear polarization (DNP) is utilized to transfer the polarization from electron spins to nuclei of interest using microwaves. Advanced MAS DNP NMR instrumentation, such as spherical rotors for stable and fast spinning, dielectric lenses to effectively couple the microwaves into the sample, and the separation of receiving and transmitting circuits to decrease measurement noise, are developed to improve NMR resolution and sensitivity in different aspects. The stable spinning of 9.5 mm outer diameter (OD) spherical rotors is demonstrated at 10.6 kHz with helium gas. 240 µm OD spherical rotors and stators can be fabricated by three-dimensional direct laser writing (3D-DLW) for ultra-fast MAS. Moreover, dielectric lenses for cylindrical and spherical rotors are analyzed to increase electron Rabi frequencies. A double-lens insert and 0.5 mm diamond spheres are proposed as potential strategies to improve microwave coupling. To effectively decrease NMR measurement noise, the receiving and transmitting circuits of the probe are separated along with placing the pre-amplifier in close proximity to the receive coil. This design can lead to an improved signal-to-noise ratio. The improved MAS DNP NMR instrumentation will allow for sufficient sensitivity to investigate complicated biological systems.
Chair and Committee
Alexander B. Barnes Kater Murch
Anders E. Carlsson, Sophia E. Hayes, Erik Henriksen,
Chen, Pin-Hui, "Magic Angle Spinning Spheres and Improved Microwave Coupling for Magnetic Resonance" (2019). Arts & Sciences Electronic Theses and Dissertations. 1893.