Functionalization and Characteization of Carbon-based Nanomaterials
Licentiate thesis, 2015
Surface functionalization of nanomaterials opens up unlimited possibilities to combine the distinct properties of inorganic, organic, or even bioactive components in a single material and bring novel functionalities in a wide range of applications ranging from electronics to catalysts and medicine carriers. So far, a variety of organic and inorganic nanomaterials have been explored to construct different functionalized nanomaterials. Among them, carbon nanomaterials (CNMs), such as carbon nanotubes (CNTs) carbon nanofibers (CNFs) and graphene, are believed to be promising building blocks for constructing nanoscale functionalized materials, owing primarily to their large surface area and extraordinary electrical and mechanical properties. In this thesis, flexible and scalable chemical approaches to functionalize CNMs are developed for different applications. According to the bonding difference between CNMs and the functional components, these approaches can be divided into two groups, including covalent functionalization and non-covalent functionalization. In addition, a variety of characterization methods are utilized to characterize the structures and properties of the as-fabricated functionalized CNMs.
Covalent functionalization of CNMs surface is based on reactions with the oxygen-containing groups of CNMs which are bonded directly to the π-conjugated skeleton of the CNMs. The first part of the work in the thesis is to functionalize CNTs surface via simultaneously oxidation and ultrasonication treatments and fabricate metal nanoparticle decorated CNT hybrid. As a result, finely grained and uniform silver nanoparticles were successfully deposited on the surface of activated CNTs. The other part of covalent functionalization of CNMs is about the fabrication of free-standing graphene based films (GBFs) via self-assembly and functionalization to improve GBF’s heat spreading performance. The results show efficient cooling performance of the functionalized GBF which could offer potential solutions for the thermal management of high power devices.
Non-covalent functionalization utilizes various functional molecules or active species as assembly mediators to functionalize the surface of CNMs via non-covalent interactions. In the thesis, non-covalent functionalization of CNTs was realized through polymer wrapping. The targeted wrapping of APTES and silica layers on the surface of CNTs enabled homogeneous CNT dispersion in various polar solvents, and also facilitated the silver nanoparticle’s deposition. The synthesized multi-functionalized CNT based hybrid nanowires demonstrated superior mechanical and electrical performance in the application of flexible and stretchable circuits (FSCs) due to a highly conductive and flexible structure, which show great potential in the field of wearable and portable electronics.