Browsing by Author "Carter, Marcus"
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Item POLYMER ASSISTED ASSEMBLY OF INORGANIC MATERIALS FOR NEXT GENERATION BATTERIES(2019) Carter, Marcus; Rodriguez, Efrain; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Nanoscale materials have desirable electronic features (e.g. high surface areas, reduced mass and transport paths) that can be harnessed for a variety of technological applications. In most storage devices, there is a particular interest in nanostructured electrodes and solid-state electrolytes. A key challenge is the reproducible fabrication of these nanostructured materials. Polymers are nanoscale materials that could be used for nanoscale fabrication with improved reproducibility. In this thesis I explored two nanostructured systems using novel polymer assisted assembly methods. I fabricate a nano-structured MoS2 electrode and a nano-structured Li7La3Zr2O12 solid-state electrolyte with a garnet-type structure. A clear redox mechanism for MoS2 is currently being sought. Using our electrode, we propose a mechanism to understand the total or partial decomposition of the electrode and the formation of long soluble polysulfides. We complete a fundamental study to determine the peaks on a cyclic voltammetry curve of nanostructured MoS2. We resolve these peaks by building a novel but simple system of restacked MoS2 with a conformal polyaniline (PANI) coating. We propose that the novel coating functions by absorbing, capturing, and promoting charge transfer (oxidization and reduction) of sulfur atoms remaining at the surface. Our data suggests that PANI acts as redox mediator. Redox mediators can be molecules or solid surfaces that aid in the charge transfer to redox species, traditionally oxide species. Our findings suggest that sulfur behavior dominates the redox chemistry at 0.7 V even earlier than the proposed deep discharge. We propose that longer chain polysulfides are formed through surface mediated interactions with persistent lattice planes of MoS2. Solid-state electrolytes like cubic garnet type Li7La3Zr2O12 offer safety advantages over flammable liquid electrolytes, which is especially significant to the advancement of high energy density battery devices. Garnet however is unstable in air, suffers from low preparation efficiency and degradation into a two competitive phases, tetragonal type garnet and lithium carbonate phases, which have low conductivity. For two polymers systems, poly(styrene)-block-poly(acrylic acid), PS(0.3)-b-PAA(0.7) and PS(0.8)-b-PAA(0.2), we synthesize cubic Li7La3Zr2O12 garnet. We systematically investigate the effect of growth parameters, temperature and excess lithium content, to find the optimized synthesis conditions of 750 °C for ~5 h with 60 wt.% and 65 wt.% excess lithium salt, for the polymer systems.Item Two-Photon Characterization of Substituted (T8) Cage Silesequioxanes(2011) Carter, Marcus; Goodson, Theodore, III; Clark, Travis; Zhang, JinAn efficient source of alternative energy has yet to be developed. Solar energy, the most viable and sustainable source of renewable energy, remains less effective due to limitations in absorbing materials to convert direct sunlight into useful solar cell devices. However, this flaw can be circumvented if solar panels had the capability to convert infrared radiation into useable energy. The focus of this study is the evaluation of the non-linear optical properties of silsesquioxane (caged {T8}) molecules through ultrafast two-photon spectroscopy to determine their applicability in creating more effective solar energy devices (Laine et al, 2010; Sulaiman et al, 2008). The two photon absorption measurements were carried out using 770 to 830nm, 30 femto-second pulses. The results revealed that there are maxima for the cross sections near 800nm for the different caged molecules studied. The increase in cross section is correlated with increasing substitution of electron donating groups on the cage. This data provides further support for these materials to be used in applications of near infrared solar absorption devices.Item Visualizing Amine Groups Tethered to a Glass Surface(2010) Carter, Marcus; Kumi, George; Fourkas, JohnThis study determined the viability of a new technique for visualizing micron (or smaller) sized areas of amines tethered to a glass substrate. The experiment utilized a methodology that requires the use of amine functionalization, plasma cleaning, and an elastomeric mold to pattern amines on a glass surface. Electro-less copper metallization was used to verify that the patterned amine region was indeed present on the surface of the glass. The results suggest that metallization can be used to detect amine groups on glass; however, more experimentation is needed to attain maximum selectivity in the devised visualization technique.