Browsing by Author "Sivapragasam, Nilushni"

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    Adsorption Kinetics and Dynamics of Small Molecules on Graphene and Graphene oxide
    (North Dakota State University, 2018) Sivapragasam, Nilushni
    Graphene is an allotrope of carbon composed of sp2 hybridized carbon and arranged into a honeycomb lattice. Graphene is a mechanically strong material (200 times stronger than steel) and has high carrier mobility, high thermal conductivity, and high optical transparency. Owing to these outstanding properties graphene is used in many applications; often graphene is used on a support instead as a free-standing graphene. When graphene is utilized it can adsorb many molecules and this adsorption could be influenced by the support. Furthermore, comparing the adsorption of such molecules on the support alone and on the supported graphene (graphene on the support) could provide details on the transparency of graphene; transparency can be defined as the identical interactions of a molecule on a supported graphene and the respective support. Therefore, this dissertation focused on studying the adsorption kinetics and dynamics of selected molecules (water, benzene, n-alkane, and carbon dioxide) on two different types of graphene: chemical vapor deposited (CVD) and physical vapor deposited (PVD) graphene. In addition, the chemically inert graphene was functionalized with oxygen to produce graphene oxide and the reactivity of graphene oxide on carbon dioxide adsorption was studied. All the experiments were carried at ultrahigh vacuum conditions to ensure an atomically clean environment. The PVD graphene was synthesized on Ru(0001) and was further functionalized with oxygen to produce graphene oxide. The surface characterizations were carried out by various surface analytical techniques: Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). The adsorption kinetics and dynamics were studied by thermal desorption spectroscopy (TDS) and molecular beam scattering techniques, respectively. Transparency of graphene, support effects, and the reactivity of graphene oxide were mapped. The studies clearly showed that the transparency of graphene depends on the polarizability of the molecule and the supports; the supports indeed influenced the adsorption of molecules on graphene. In addition, graphene oxide did not react with CO2 to produce any reaction products but it enhanced the CO2 adsorption.
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    Carbohydrate-Based Micro and Nano Scale Materials from Soybean Meal, Distillers Dried Grains, and Sugar Beet Pulp for Food and other Applications
    (North Dakota State University, 2013) Sivapragasam, Nilushni
    Study 1 was carried out to isolate and produce enzyme resistant micro and nano scale carbohydrates from soybean meal (SBM), distillers dried grains (DDG), and sugar beet pulp (SBP). All materials produced were in micro and nano scales, and the yields were different depending on the starting material. Study 2 determined the physiological stability of study 1 materials for potential encapsulation applications. Both SBM and SBP were stable under simulated physiological conditions; the stability of the SBM was higher than SBP. In study 3 the SBM nanomaterial from buffer extraction was used for in vitro fermentation by Bifidobacterium brevis. The B. brevis showed a good growth in the presence of SBM nanomaterial. Study 4 characterized the SBM- resistant starch thin films produced with pectin and carboxymethylcelllulose. The films formed with SBM-resistant starch and pectin at 3:1 and 1:3 provided good barrier and viscoelastic properties.