Towards New Synthetic Methodologies for the Preparation of Well-Defined Carbon Nanomaterials

点击翻译按钮获取中文摘要

Carbon nanomaterials such as fullerenes, carbon nanotubes, and graphene, have outstanding electronic and optical properties. However, many potential applications require carbon nanomaterials with well-defined structures and properties that still cannot be reached through conventional synthetic methods, which are based on high-temperature transformations of basic carbon feedstock. During the last funding period, we undertook an innovative research program for the preparation of carbon nanomaterials using mild conditions, allowing better control over their sizes, shapes, functions, and chemical natures. The new approach, called the “hybrid method,” allowed us to prepare carbon nanomaterials from reactive, self-assembled oligoyne-containing building blocks such as linear oligomers, macrocycles, and star-shaped molecules. In this proposal, we intend to use the tools we have recently developed to push the hybrid strategy further with the aim to develop carbon nanomaterials, more precisely graphene nanoribbons and carbon-rich nanotubes, whose structural properties (size, shape, width, length, aspect ratio, etc.) and chemical nature can be precisely modulated. Our strategies will provide novel carbon nanomaterials with customized optical and electronic properties that cannot be acquired using known synthetic methods. Our strategy to prepare graphene nanoribbons with different widths relies on the preparation of aryl-appended polydiacetylenes (PDAs) as reactive precursors that will undergo multiple cycloaromatization reactions using physical stimuli (light, gentle heat) under mild conditions to give the desired materials. The initial PDAs with carefully chosen functional groups will be prepared using either the topochemical polymerization of self-assembled oligoynes, or more traditional solution chemistry involving C-C coupling reactions. Using these methods, asymmetric graphene nanoribbons with different width will also be prepared. The carbon-rich nanotubes will be prepared using the topochemical polymerization of self-assembled butadiyne-containing macrocycles. Macrocycles with different sizes and chemical functions will be prepared using the recently developed conjugated diynes metathesis reaction that will be adapted for the preparation of conjugated macrocycles. All the new carbon nanomaterials will be rigorously characterized using optical and vibrational spectroscopy, thermal analysis, electronic microscopy, electrochemistry and X-ray diffraction to study their optical, electronic and morphological properties. The best materials will be tested as semiconducting materials in solar cells and field-effect transistors. The synthetic strategies we propose for both graphene nanoribbons and nanotubes will lead to carbon nanomaterials that cannot be accessed by any other synthetic methods reported so far. Moreover, “on-demand” variations of structural parameters in both graphene nanoribbons and carbon-rich nanotubes through subtle chemical modifications could have a tremendous impact, especially in the electronics industry where "close-to-perfect" materials are required. Nonetheless, a lot of fundamental research work needs to be done before these methods can be used on a regular basis by materials scientists in academia and industry. This grant will be an excellent opportunity for us to make significant contributions in the area of carbon nanomaterials. Because of their multidisciplinary nature, these projects will also strongly contribute to the training of HQP whose skills will benefit private and public research laboratories later on.