Oral Session II (1:30pm-4:30pm) Chemistry and Materials Setting the Stage for Semiconductor Plasmonics: Nanoscale Control of Axial Carrier Density Profile in Si Nanowires Dmitriy Boyuk / Prof. Michael Filler Spatial control of carrier density is critical for engineering and exploring the interactions of localized surface plasmon resonances (LSPRs) in nanoscale semiconductors. Here, we couple in situ infrared spectral response measurements and discrete dipole approximation (DDA) calculations to show the impact of axially graded carrier density profiles on the optical properties of mid-infrared LSPRs supported by Si nanowires. The region immediately adjacent to each intentionally encoded resonator ( i.e. , doped segment) can exhibit residual carrier densities as high as 10 20 cm -3 , which strongly modifies both near- and far-field behavior. Lowering substrate temperature during the spacer segment growth reduces this residual carrier density and results in a spectral response that is indistinguishable from nanowires with ideal, atomically abrupt carrier density profiles. Our experiments have important implications for the control of near-field plasmonic phenomena in semiconductor nanowires, and demonstrate methods for determining and controlling axial dopant profile in these systems. The Acid-Catalyzed Decomposition of Dicumyl Peroxide In Dodecane Mark Conley / Prof. Charles Liotta Dicumyl peroxide (DCP) is a commonly used radical crosslink initiator in industrial polymer blends. Some industrial blends incorporate acidic media, which cause DCP to undergo an ionic decomposition mechanism. This work presents the novel discovery of the mechanism for the acid-catalyzed decomposition of dicumyl peroxide (DCP) in non-polar, organic media. We propose that upon reaction with acid, DCP forms a hydrogen-bonded complex species. The complex can break down via at least three pathways, leading to a complex product distribution and kinetics. Additionally, we discovered that DCP can generate cumene hydroperoxide upon reaction with acid. Current literature regarding acid-catalyzed decomposition of DCP is far more simplistic and suggests neither the formation of a hydroperoxide, nor a hydrogen-bonded complexation. We provide detailed experimental evidence supporting our mechanism.
Rabies vaccination in dogs using a dissolving microneedle patch Jaya Arya / Prof. Mark Prausnitz Rabies is mainly a disease of animals, whereas humans get rabies primarily when they are bitten by dogs. Vaccinating domestic dogs and other animals has reduced rabies transmission to humans, however thousands of people in developing countries still die of rabies each year. Dissolving microneedle patches are a simple, sharps-free device that can enable mass vaccination of dogs. The purpose of this study is to stabilize rabies DNA vaccine in a dissolving microneedle patch and evaluate immune response and dose- sparing in dogs. Microneedle patches were able to meet the requirements of this study, which were to maintain activity for 3 weeks at 4 0 C storage and were mechanically strong to insert and dissolve in skin within 15 minutes of insertion. The clinical study was carried out in Beagle dogs and neutralizing antibody titers in blood were used as a correlate of immunity. Microneedle patches were safe and produced equivalent antibody titers as compared to conventional hypodermic needle control, thus demonstrating simple, effective, sharps-free rabies vaccination. Effect of Defect Sites in the Hydrolysis of Cellulose and Cellobiose over Sulfonated Activated Carbon Catalysts Guo Shiou Foo / Prof. Carsten Sievers The chemical oxidation of activated carbon by H 2 O 2 and H 2 SO 4 is investigated, structural and chemical modifications are characterized, and the materials are used as catalysts for the hydrolysis for cellulose. Treatment with H 2 SO 4 primarily targets the edges of carbon sheets, and adsorption isotherms demonstrate that the adsorption of oligomers on functionalized carbon is dominated by van der Waals forces. It is proposed that a synergistic effect between defect sites and weak acid sites enhances the activity by inducing a conformational change in the glucan chains when adsorbed on defect sites. The exposed glycosidic bonds interact with in-plane functional groups to be hydrolyzed. In the hydrolysis of cellobiose, the carbon catalyst with a limited fraction of sulfonic acid groups exhibit moderate cellobiose conversion but a high glucose selectivity. The high selectivity can be attributed to the same synergistic effect, which allows weak acid sites to selectively hydrolyze cellobiose into glucose monomers.
Processing Effects on Dispersion and Thermomechanical Properties of Waterborne Epoxy and Cellulose Nanocrystal Composites Natalie Girouard / Prof. Carson Meredith and Prof. Meisha Shofner Cellulose nanocrystals (CNCs) were incorporated into a waterborne epoxy resin following two processing protocols, which varied by order of addition. The processing protocols produced different levels of nanoparticle dispersion. The more homogeneously disperse composite had a higher modulus at temperatures less than the glass transition, as well as a lower value of the glass transition temperature. Some properties related to component interactions, such as thermal degradation and moisture content, were similar for both composites. The mechanism of dispersion was probed with electrophoretic measurements and electron microscopy. Based on those measurements, it was hypothesized that CNC preaddition facilitated the formation of a CNC-coated epoxy droplet, promoting CNC dispersion and forming a physical barrier to crosslinker diffusion. These structural changes resulted in a remarkable extension of the epoxy/crosslinker pot life by three orders of magnitude. This phenomenon could enable one-part epoxies with long shelf life, offering significant processing advantages relative to two-part formulations. Control of Salt Crystallization from Nuclear Waste Daniel Griffin / Prof. Martha Grover, Prof. Yoshiaki Kawajiri and Prof. Ronald Rousseau The Department of Energy is faced with cleaning up 56 million gallons of nuclear waste currently stored at the Hanford site in the state of Washington. Introducing a crystallization-separation operation to remove non-radioactive salts from the nuclear waste can potentially reduce costs and expedite the cleanup effort. However, the viability of such an operation hinges on the ability control the crystallization operation to produce large, separable salt crystals. In our research, we explore new methods for monitoring and controlling salt crystallizations from complex solutions. In this talk, we will discuss the synthesis of dynamic crystallization measurement data to cast crystallization as a trajectory in a 2D phase space. This introduces a visual representation that facilitates the development of new control schemes. We will present one such scheme and demonstrate control over the average sieve diameter of complex salt crystals formed from a multicomponent electrolytic solution.
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