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Full-Text Articles in Engineering
Instrumentation For Dynamic Nuclear Polarization And Application Of Electron Decoupling For Electron Relaxation Measurement, Nicholas Howard Alaniva
Instrumentation For Dynamic Nuclear Polarization And Application Of Electron Decoupling For Electron Relaxation Measurement, Nicholas Howard Alaniva
Arts & Sciences Electronic Theses and Dissertations
Dynamic nuclear polarization nuclear magnetic resonance (DNP NMR) exploits internal electron spin and nuclear spin interactions to increase sensitivity and uncover valuable information regarding structure and dynamics of a system. To manipulate these interactions, instrumentation is developed to combine high-power microwave and radiofrequency irradiation with the ability to spin samples at the magic angle (MAS) at temperatures from 90 K to 4.2 K. Electron decoupling uses frequency-modulated microwaves to mitigate the electron-nuclear dipolar interaction, improving signal intensity and resolution in DNP NMR experiments. Electron decoupling is combined with short DNP periods to encode electron spin information in polarized nuclear signal. …
Magic Angle Spinning Spheres And Improved Microwave Coupling For Magnetic Resonance, Pin-Hui Chen
Magic Angle Spinning Spheres And Improved Microwave Coupling For Magnetic Resonance, Pin-Hui Chen
Arts & Sciences Electronic Theses and Dissertations
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 …
Wave Function Engineering In Cdse/Pbs Core/Shell Nanocrystal Heterostructures, Brian Matthew Wieliczka
Wave Function Engineering In Cdse/Pbs Core/Shell Nanocrystal Heterostructures, Brian Matthew Wieliczka
Arts & Sciences Electronic Theses and Dissertations
Colloidal semiconducting nanocrystals hold significant potential for third generation photovoltaics as solution processable materials that can surpass the Shockley-Queisser limit through multiexciton generation. In pursuit of this goal, the synthesis and optical characterization of CdSe/PbS core/shell quantum dots is reported. The spectroscopic behavior of these particles demonstrates their potential for use in optoelectronic devices, taking advantage of wave function engineering of the electron and hole. The rock salt PbS shell grows on all sides of the underlying zinc blende CdSe quantum dot, creating a core/shell structure. With increasing shell thickness, the band edge absorption and photoluminescence transitions decrease in energy …