Functionalization and Characterization of Carbon Based Nanomaterials for Electronics, Composite and Biomedical Applications

Abstract: Surface functionalization of nanomaterials to combine different material’s properties together opens up unlimited possibilities for both academic research and industrial applications. In this thesis, flexible and scalable chemical approaches to functionalize carbon nanomaterials (CNMs) are developed for different applications, including electronics, composite and biomedical applications. According to the bonding difference between CNMs and functional components, these approaches can be divided into two groups, including covalent functionalization and non-covalent functionalization.

Covalent functionalization of CNMs surface is based on reactions of different components with the oxygen-containing groups of CNMs. The first part in this section introduced the covalent functionalization of carbon nanotubes for biomedical application. The surface of CNTs was modify by a multi-oxidation process and coated by silver nanoparticles to improve CNT’s antibacterial property. The developed silver/CNT composites show strong antibacterial property to bacteria. The second part presents covalent functionalization of graphene oxide for cement reinforcement. The developed surface functionalized GO (FGO) can improve both the early and ultimate strength of the Portland cement mortar efficiently. The key benefit of FGO lies in its ability to form covalent bonds with C-S-H whilst having minimum effect on the workability of mortar paste. The third part introduced the covalent functionalization of graphene based films (GBFs) that act as heat spreaders for hotspot cooling. The applied covalent bonding between GBF and the substrate can significantly reduce the thermal interface resistance, showing great advantages on cooling of high-power density devices.

Non-covalent functionalization utilizes various functional molecules or active species as assembly mediators to functionalize the surface of CNMs via non-covalent interactions. The first part of this section presents a method of non-covalent self-assembly of high-thermal-conductivity of graphene films (GFs). The fabricated smooth, large-grain and turbostratic-stacking GFs shows excellent thermal and mechanical properties, which is superior to most of currently existing thermally conductive materials. The second part introduced the non-covalent functionalization of graphene for high thermal conductive adhesive. Liquid exfoliated few-layer graphene was utilized as fillers to improve the thermal conductivity of the thermal conductive adhesive which showed an improvement of 400 %. The third part presents a non-covalent functionalization process for synthesizing intrinsically flexible multi-functionalized CNT based hybrid nanowires. The synthesized multi-functionalized CNT based hybrid nanowires possess many excellent properties, such as good dispersability and stability in various polar solvents, large flexibility and high electrical conductivity. These extraordinary properties facilitate the application of hybrid nanowires in the fabrication of flexible and stretchable circuits (FSCs) with high resolution.