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Articles 1 - 6 of 6
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. …
Self-Assembly Of Conducting Polymer Nano- And Microstructures For Energy Storage, Luciano Matteo Santino
Self-Assembly Of Conducting Polymer Nano- And Microstructures For Energy Storage, Luciano Matteo Santino
Arts & Sciences Electronic Theses and Dissertations
Plastics are materials composed of many long chains of molecules with repeating subunits; strong interactions between neighboring molecules lead to the material used throughout the world. Plastics are commonly thought to be insulating, in stark contrast to the conductivity of metals. However, certain polymer structures were discovered to exhibit semiconducting properties, the subject of the Nobel Prize in Chemistry in 2000. Conducting polymers have a unique molecular structure with an electronically conjugated backbone, allowing electrons to freely travel both across the chain and in between chains. This work focuses on controlling the kinetics of the reaction between the vapors of …
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 …
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 …
Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias
Electronic Transport Behavior Of Adatom- And Nanoparticle-Decorated Graphene, Jamie Anne Elias
Arts & Sciences Electronic Theses and Dissertations
To induce a non-negligible spin-orbit coupling in monolayer graphene, for the purposes of realizing the Kane-Mele Hamiltonian, transition metal adatoms have been deposited in dilute amounts by thermal evaporation in situ while holding the device temperature near 4K. Electronic transport studies including measurements such as gate voltage dependent conductivity and mobility, weak localization, high field magnetoresistance (Shubnikov de Haas oscillations), quantum Hall, and nonlocal voltage were performed at low temperature before and after sequential evaporations. Studies of tungsten adatoms are consistent with literature regarding other metal adatoms on graphene but were unsuccessful in producing a spin-orbit signature, at least partially …
Isotopically-Resolved Neutron Cross Sections As Probe Of The Nuclear Optical Potential, Cole Davis Pruitt
Isotopically-Resolved Neutron Cross Sections As Probe Of The Nuclear Optical Potential, Cole Davis Pruitt
Arts & Sciences Electronic Theses and Dissertations
Neutron scattering experiments provide direct access to the forces experienced by nucleons in the nuclear environment. Due to the experimental difficulty of cross section measurements with neutrons, isotopically-resolved neutron scattering cross sections are sorely needed as inputs for many nuclear models. This dissertation presents the results from a campaign of isotope-specific neutron total cross section measurements on 16,18O, 58,64Ni, 112,124Sn, and 103Rh from 3-450 MeV and elastic scattering differential cross section measurements on 112,nat,124Sn at 11 and 17 MeV. Equipped with these new data and with computational improvements to the Dispersive Optical Model (DOM), we present DOM treatments of 16,18O, …