SLIDE 1 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 1020 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
- f 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
- f 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.
SLIDE 2 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 0C storage and were mechanically strong to insert and dissolve in skin within 15 minutes
- f 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 H2O2 and H2SO4 is investigated, structural and chemical modifications are characterized, and the materials are used as catalysts for the hydrolysis for cellulose. Treatment with H2SO4 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.
SLIDE 3 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
- ne such scheme and demonstrate control over the average sieve diameter of complex salt crystals formed
from a multicomponent electrolytic solution.
SLIDE 4
Synergy and Inhibition during Co-Gasification of Biomass-Coal Blends Gautami Newalkar / Prof. Pradeep Agrawal and Prof. Carsten Sievers
With the clean coal power initiative of the US government, technologies such as co-gasification of coal- biomass blends are being investigated because they present numerous advantages: lower emissions of CO2, SOx, and NOx, better H2/CO ratios, etc. Our objective is to examine the synergy and inhibition effects during co-gasification of switchgrass with two coals: Texas lignite and Illinois#6 bituminous coal. Switchgrass is rich in potassium and silica, while the coals contain much lower potassium and a large amount of silica. Alkali and alkaline earth metals are known to catalyze gasification reaction while silica is known to form inactive alkali silicates. The effect of addition of switchgrass-derived char or ash to coal char was explored. Results show that when potassium is added to lignite, irrespective of the source, it is scavenged by the silica in lignite. Significant synergistic effects were observed in case of bituminous coals.
Understanding The Gasification Reactivity Of Different Biomass-derived Chars Mohmed Syed / Prof. Pradeep Agrawal and Prof. Carsten Sievers
Formulating a correlation to predict gasification reactivity of chars from a wide variety of biomass requires an understanding of the fundamental descriptor(s) of char gasification reactivity. However, the major hurdles to achieve this objective are the inherent complexity of biomass and the concurrent variations in many char properties. These factors prevent the deconvolution of the effect of different char properties on its gasification reactivity. To partially overcome these limitations, chars from different biomass feedstocks are used in this study in an effort to segregate the effect of different char properties on its initial reactivity. The physiochemical properties of char (namely, surface area; ash content, ash composition, and H/C atomic ratio) were measured and correlated with gasification reactivity. Results show that none of the aforesaid char property could solely explain the observed char reactivity for different biomasses, while the active surface area of chars quantifies the cumulative effect of the properties above, and therefore it is a better descriptor.
Fabrication of Oleophobic Paper with Tunable Hydrophilicity by Treatment with Non-fluorinated Chemicals
Zhenguan Tang / Prof. Dennis Hess and Prof. Victor Breedveld Surfaces that can simultaneously display hydrophilicity and oleophobicity have attracted great interest due to their potential use in different industrial applications such as oil/water separation membranes, self- cleaning surfaces or anti-fog surfaces. However, most exiting methods to fabricate such surfaces heavily rely on environmental unfriendly fluorinated materials. Also, the majority of such surfaces were fabricated
SLIDE 5
- n flat, non-porous substrates, which fundamentally limits its potential applications. In this presentation, a
novel method to fabricate
paper with tunable hydrophilicity was reported. Methyltrimethoxysilane (MTMS) was used as the coating material. It is shown that by systematically varying hydrolysis time, paper with different wetting properties ranging from hydrophilic/oleophobic to hydrophobic/oleophobic can be fabricated. Compare with existing method, this new material does not contain any fluorine, therefore more environmental friendly. The hydrophilic/oleophobic paper can be potentially used as filter for oil/water separation.
Tuning of Higher Alcohol Selectivity and Productivity in CO Hydrogenation Reactions over K/MoS2 Catalysts Supported on Mesoporous Activated Carbon and Mixed MgAl Oxide Micaela Taborga Claure / Prof. Christopher Jones and Prof. Pradeep Agrawal
A family of mesoporous activated carbon (C) and MgAl oxide (MMO) were used as supports to tune higher alcohol selectivity and productivity for higher alcohol synthesis from syngas over K/MoS2. While C supports yield high ethanol productivities, MMO supports yield high C3+OH selectivity. MoKC-MMO, whereby Mo is initially contained on the carbon support and ground with MMO, yields reactivity trends related with Mo species on both single supported parent catalysts (high C3+OH selectivity-MoKMMO and productivity-MoKC), suggesting that weak Mo-C interactions allow Mo to migrate from C to MMO during reaction. In contrast, MoKMMO-C yields reactivity trends similar to single supported MoKMMO, suggesting that Mo species are parked on the MMO during reaction. Structure-reactivity relationships were investigated, specifically, MoS2 layers were correlated with selectivity through STEM (single layers ~total hydrocarbon selectivity and double MoS2 layers ~ C3+OH selectivity). This study presents a new catalyst composition with desirable reactivity.
Markov Decision Process based Dynamic Programming for Controlling Colloidal Self-Assembly Xun Tang / Prof. Martha Grover
Self-assembly broadly refers to the process of a disordered system converging to a well-arranged state without human intervention. We propose to apply a Markov decision process (MDP) based dynamic programming optimal control algorithm to manipulate a SiO2 colloidal self-assembly process for two- dimensional defect-free crystals. The movement of the particles is manipulated by the dipole-dipole and dipole-field interactions, which are controlled by changing the magnitude of the voltage on the electrodes surrounding the system. Markov state models are developed based on simulations from a Brownian dynamics model which is built to simulate the process dynamics. An infinite-horizon MDP
- ptimization problem is then formulated and the optimal control policy is solved by dynamic
- programming. Our MDP-based dynamic programming control policy is able to improve the yield of
perfect crystals significantly.
