The modification of surfaces : from fundamentals to applications

Abstract

You’re surrounded by surfaces. Viewed from a macro perspective they might appear soft, brightly colored, or textured. Maybe you don’t think anything of them at all. But what happens when we take a closer look? Here, down at the nanoscale, chemical reactions at surfaces play a hugely important role in the world in which we live. Whether it’s preventing metal corrosion, or developing the latest fuel cell, the state of surface being investigated is crucial. Indeed, by intentionally modifying surfaces we can introduce desirable properties, all because we’re controlling what goes on at the molecular level. The first part of this thesis discusses the use of model surfaces to probe fundamental properties and processes. Firstly, model surfaces displaying well-defined chemical functionality are created using self-assembled monolayers (SAMs), and are subsequently used as a means to understand the primary interactions that occur between carbonaceous soot contaminants, and surfactant-like molecules in engine oils. The quartz-crystal microbalance (QCM) is employed as a means to determine minute levels of surface adsorption, and a structure-activity relationship for these molecules is suggested. Next, a new approach for profiling the activity of molecular adsorbates at carbon surfaces is introduced, which allows for the impact of individual surface features on resulting electrochemical activity to be determined. It is used to study the case of quinone adsorption at graphite electrodes, a currently debated topic, and it is revealed that current literature models regarding the activity of the basal surface need revision, with significant implications for carbon electrochemistry as a whole. The second part of this thesis turns to understanding and controlling surface modification processes. Through a range of complementary techniques, the ability of scanning electrochemical cell microscopy (SECCM) to control the extent of the aryl diazonium grafting process at sp2 carbon surfaces is demonstrated. Aryl diazonium chemistry as been identified as a route to band-gap generation in graphene electronics, and as such, controlled routes to localized surface modification are of great interest. Next, the versatility of SECCM for controlled surface modification is further demonstrated, where it is used as a method to draw intricate patterns of defined surface chemistry in graphene, with a strong focus on the production of integrated graphene circuits, a prospect often promised. Finally, a new methodology for the transfer of graphene synthesized via chemical vapor deposition (CVD) is introduced. Crucially, it yields graphene surfaces with distinctly low levels of contamination, an area that currently poses a problem in graphene research