Preparation and Characterization of Hydrophobic Graphene-Based Thin Films
Since the ``Scotch tape" discovery of graphene synthesis over a decade ago there has been significant interest in the industrial scale-up of graphene production, with the understanding that the material's exceptional physical and electrical properties could be used to enhance finished products. One remarkable property of graphene is the degree to which it, an atomically-thin material, can impart hydrophobicity to a surface. Liquid-phase surface treatments are familiar to many industrial engineering practices and it is well-known that graphene oxide, a graphene derivative which can be modified to achieve graphene-like material qualities, disperses well in many solvents. Although graphene oxide is hydrophilic, it can be made hydrophobic by reduction, and perhaps even superhydrophobic with the inclusion of surface topography. Therefore, the reduction of graphene oxide films offers one possible route to graphene's entry to industry as a hydrophobic surface coating treatment. This thesis begins with an experimental investigation into graphene oxide's dispersibility in different solvents. The influence of these solvents on the physico-chemical characteristics of the resulting graphene oxide and reduced graphene oxide thin films cast on a silicon substrate is studied. It is found that the choice of dispersing medium determines the degree of surface coverage and therefore the degree of film wettability. Subsequently, the chemical nature and hydrophobicity increase that is imparted by a new photoreduction process applied to the graphene oxide-based films is researched. From this, it was observed that the chemistry of the photoreduced films greatly differs from that of the thermally reduced films, including larger quantities of oxygen. The thesis concludes with a brief examination of the degree to which substrate topography can enhance the hydrophobicity of graphene oxide-based films deposited on chemically etched glass. It is found that with the addition of a roughened surface topography the water contact angle can be improved by up to 45°.