Doctor of Philosophy (PhD)
Interfaces are systems that contain two or more condensed phases existing together, which makes the study of such systems challenging. However, the study of interfaces is critical in fields such as catalysis, energy storage, separations, drug discovery etc. Various experimental methods have been discovered to study these systems. However, atomistic investigations of these systems are important to understand and improve the uses and properties of such interface systems. Hence computer simulations, with the capability to gain molecular-level information of the interfacial systems, are used to gain information which are not accessible to the experiments. This dissertation is composed of computational investigations performed on several aqueous interfacial systems that are composed of important applications. The main aqueous interfacial system that has been studied is the Graphene Oxide (GO)-water system. This study was focused on the structuring and various interaction of the aqueous interface at this solid-liquid interface. Different computational approaches such as ab-initio molecular dynamics (MD), MD simulations with conventional force fields (OPLS-AA) as well as with polarizable force fields and MD simulations with the inclusion of many-body interactions were used to study the interfacial region. The orientation of water molecules and the local structure of water at different regions of the interface has been examined and compared with different potentials/force fields. These studies have provided vital information on the development of a novel force field to study the GO-water interface. Furthermore, using the GO-water system, the adsorption of an organic contaminant molecule on to the GO surface was investigated. The effects of the ionic strength and interactions that govern this adsorption processed was studied. xvii The lipid bilayer-water aqueous system was also studied with atomistic MD simulations accompanied with enhanced sampling methods. The adsorption processes of small drug-like molecules through the interfacial region of this system were investigated in an atomistic-level. The effects of factors such as the critical interactions and temperatures on the adsorption processes were examined. The results from these studies will be beneficial for the development of a liposome-based drug delivery system in the future. Finally, computational investigations of the influence of sulfur on acid-mediated enamide formation were performed. Electronic structure calculations were used to verify and optimize an organic synthesis scheme proposed by an experimental group. Furthermore, the computational investigations were used to explain the stereoselectivity in the synthesis scheme as well. This novel synthesis scheme will be useful to the synthesis of enamides which are important in the fields of antibiotics and cancer treatments.
Subasinhege Don, Visal Kavinda Subasinghe, "Computational Investigations of Aqueous Interfaces" (2021). LSU Doctoral Dissertations. 5386.
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