Yao, Haiqing (2015-05). Surface Functionalization of 1-D and 2-D Carbon-Based Nanomaterials and Their Applications. Doctoral Dissertation.
Carbon nanotubes (CNTs) and graphene are dominant and emerging carbon-based materials that have attracted extensive attention for potential applications in advanced nanotechnology. The attractiveness of these materials originates from their excellent mechanical, thermal, and electrical properties. However, their insolubility and difficult processability in solvents have significantly limited their use. To solve these problems, surface functionalization is used to increase their solubility, enhance their processability in solvents, and integrate these materials into nanodevices. Conventional methods are being challenged due to their ineffective and insufficient control of the functionalization of CNTs or graphene, which is critical to realize tailored structures with unprecedented optical, electrical and catalytic properties. Further development in this field requires a fundamental understanding of the steps involved in surface functionalization, namely the reaction mechanism(s) and controlled kinetics, to yield tailored structures. The overall objective of my dissertation is to develop new approaches to functionalizing CNTs and graphene, study the functionalization mechanism and kinetics, and fabricate tailored structures with unprecedented properties. The study begins with developing new covalent functionalization methods for CNTs and graphene based on the defect chemistry method. This method is less destructive and more reactive compared to the conjugate structure method. Amination of MWCNTs with octadecylamine on the mutual position of pyracyclene units in the closed caps and pentagons on the MWCNT sidewalls is developed. The functionalized MWCNTs possess controllable surface wettability. For covalent functionalization of GO, dual-function silane agents were reacted with GO through oxygen containing groups. The exposed amine groups of the functionalized GO could effectively template the assembly of Au nanoparticles on the graphene surface with high density and good dispersity. The GO-Au composites exhibit improved surface-enhanced Raman scattering and enhanced efficiency in catalytic applications. For the noncovalent method, ZnO-CNT and ZnO-GO composites were prepared. Due to the electronegative nature of CNTs and GO, ZnO nanoparticles with positive charges can anchor on their surfaces through electrostatic attraction. The creative combination of CNTs or graphene and ZnO leads to higher efficiency and stability for photocatalytic applications than the corresponding components, which makes them a new class of functional materials to advance nanotechnology.