Water Response at Graphitic Interfaces

Graphitic nanoscale allotropes such as graphene and carbon nanotubes have inspired science and engineering towards innovative nanotechnological applications since their discovery. Their interesting physical properties have allowed them to be considered as primary components of nanocomposites, energy storage devices, biosensory systems and filtration and purification assemblages. For the latter applications, the interface of graphitic molecular structures with water is of crucial importance. Understanding the interplay of intramolecular forces at the interfaces of water with graphitic carbon will provide insights to the origin of experimental observations which have perplexed the scientific community for years, such as the apparent excellent osmotic capabilities of nanochannels, and consequently assist in the design of novel and efficient membrane-based nanodevices for precise drug delivery, biological sensing and nanofiltration. Despite the continuous strive for advancements of lab equipment and construction methodology of carbon-based nanomaterials, there is a long way to the conduction of error-free and inexpensive experiments of nanofluidic phenomena. On the contrary, advancements in algorithms and computing allow for inexpensive computational experiments that can shed light into the underlying physics governing the response of water at graphitic interfaces. In this thesis, the Molecular Dynamics methodology is employed to conduct computational investigations of the static and dynamic response of water in the proximity of graphitic interfaces and confinements. To start with, the structure and static properties of water, like tetrahedrality and dielectric permittivity, are found to vary immensely in graphitic confinement, whereas tunability of solvent response is achieved with tuned surface properties. In turn, the interplay between water and graphitic carbon is shown to affect the dynamics of water transport through graphitic nanostructures, as diffusion and transport of water are found to depend on simulation protocol and the excitation of the graphitic wall. Furthermore, local interfacial phenomena at carbon nanotube junctions are shown to alter the permeation profiles of complex nanotube structures. Subsequent studies exploit interfacial phenomena imposed by surface energy patterns on graphene surfaces and in carbon nanotubes to design efficient nanodevices for ultra-fast unidirectional water motion