Theses and Dissertations at Montana State University (MSU)
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Item Unveiling the photophysics in solid-state organic materials: a study on BODIPY, porphyrin, and PBI based materials(Montana State University - Bozeman, College of Letters & Science, 2024) King, Alexander James; Chairperson, Graduate Committee: Erik Grumstrup; This is a manuscript style paper that includes co-authored chapters.Organic semiconductors have applications in optoelectronics, light harvesting, and sensing as soft matter materials. One of the biggest challenges to overcome with organic-based materials is structural heterogeneity that arises from the self-assembly of monomers upon solid-state deposition. In this work we have investigated solid-state organic semiconductors with three levels of solution-phase processing: i) materials prepared from drop casting with no solution-phase processing on BODIPY systems ii) films prepared from pre-aggregation of the monomers with porphyrin systems iii) films prepared from aggregated monomers that were covalently stapled with perylene bisimide systems. In the BODIPY systems, we found that: i) the electronic states are highly coupled with a major redshift from 583 nm in the solution to 614 nm in the solid. ii) Through interpretation of the broadband transient absorption spectrum, the initial excited state is delocalized and localizes within the first 10 femtoseconds. iii) Using two color pump probe, we measured ultrafast diffusion at 14.37 + or - 2.79 cm 2 s -1 that abruptly halts after 10 ps. In the porphyrin systems with level 2 solution-phase processing, we have also shown that the lifetime of the excited state is correlated with the degree of structural order. The monomer exhibits the longest lifetime with an average lifetime of 1.26 ns, the aggregate is much shorter with a lifetime of 349 ps, and the films show substantially faster relaxation, with the film fabricated from the monomer having a 72.56 ps average lifetime, and the film composed of the aggregate having a 26 ps average lifetime. These results suggest that the lifetime decreases as the order and electronic coupling of the system increases, so much so that the lifetime is two orders of magnitude different. In the perylene bisimide systems, we did a direct spectroscopic comparison between thin films formed from noncovalent assemblies and from covalently tethered molecular assemblies. This indicates that interchromophore coupling is enhanced in the covalently tethered film. We saw a 73% increase in excited state transport compared to the control film, as well as a shorter and more homogenous excited state lifetime. Covalent tethering proves to be the best strategy for generating homogeneous materials.Item Synthesis and characterization of boron-doped graphitic carbon for energy storage applications(Montana State University - Bozeman, College of Letters & Science, 2023) McGlamery, Devin Gray; Chairperson, Graduate Committee: Nicholas P. Stadie; This is a manuscript style paper that includes co-authored chapters.Carbonaceous materials offer great utility as a medium for electrochemical energy storage of ions or for the storage of chemical fuels. The low molecular weight of the second-row element carbon affords access to materials that express remarkably high gravimetric energy densities, and the robust nature of carbon-carbon bonds allow for good cyclability and longevity of carbon-based materials for use in energy storage applications. With the growing popularity and recent advancement of electric vehicles, current battery technologies are pushed to their limits in terms of capacities as well as in minimizing charging times. This has motivated great efforts to discover new lightweight materials that outperform what has traditionally been used in these applications. Alternative energy carriers, such as hydrogen, are also critical for the development of our energy landscape yet are plagued with their own technical challenges; mainly low volumetric energy densities and safety concerns associated with high pressure gas storage systems. Chapter 2 reviews hydrogen storage in today's society as well as provides a review of past synthetic methods to generate high boron content graphite (BC 3'); being a promising metastable material for the storage of alkali metal ions as well as for solid state hydrogen storage at near ambient conditions. Chapter 3 focuses on the discovery of a new lithium storage mechanism within a novel carbon-based material possessing a high hydrogen content that is tolerant of extremely fast charging, yet still expresses high reversible capacities. Chapter 4 presents a systematic investigation for the detection of chemical environments within BC 3' through an examination of unique spectroscopic properties that originate from the materials phonon structure. Chapter 5 explores the generation of boron and carbon binary phases by the co-pyrolysis of molecular precursors and establishes a density functional theory based approach to align the cracking temperatures of molecular feedstocks; affording access to bulk metastable materials that contain a homogeneous distribution of chemical environments. This work is concluded with an assessment of the materials investigated herein from the perspective of energy storage, as well as provides directions for future work.Item Mobility of boron from coal ash in an aqueous system(Montana State University - Bozeman, College of Letters & Science, 1980) Halligan, Anne ShirleyItem A method for the rapid and routine analysis of boron in plants and aqueous soil extracts(Montana State University - Bozeman, College of Letters & Science, 1940) McCormick, Donald R.