基于sp-sp2杂化结构的碳纳米线的可控制备及生长机理研究

A linear carbon chain (C-chain) based on sp hybrid has attracted theorists and experimentalists for more than one hundred years. The linear C-chains are a truly one-dimentional nanomaterial with only one carbon atom diameter. Generally, C-chains can not survive in air at room temperature. One of the methods for fabricating C-chains is to encapsulate them into carbon nanotubes (CNTs), and the final products are called carbon nanowires (CNWs, C-chain@CNT). Carbon nanowires are a new-type sp-sp2 hybridized carbon nanomaterial. There are two types of methods to fabricate CNWs. One is to grow C-chains in the innermost tubes of multiwalled carbon nanotubes (MWCNTs) by arc discharge method or laser ablation. The other is to insert atomic and molecular carbon species into the inner tubes of open-ended double-walled carbon nanotubes (DWCNTs) and heat-treat them at high temperature to form C-chains inside, or to grow C-chains in DWCNTs/MWCNTs by high-temperature heat treatment. In this project, we use the simple method based on high-temperature heat treatment of purified DWCNTs/MWCNTs to realize the controllable growth of CNWs. To improve the content of DWCNTs/MWCNTs with small-diameter innermost tubes by optimizing the synthesis and purification conditions, then to improve the content of CNWs in the samples. The structures of CNWs will be observed and confirmed by high-resolution transmission electron microscopy. The growth mechanism of C-chains in CNTs will be explained by analyzing the origin of carbon atoms forming C-chains and the Raman peaks in L-band. In addition, the simplest CNWs, i.e. C-chains in the single-wall carbon nanotubes, will be attempted to fabricate. These results will facilitate the study of one-dimensional C-chains.

线型碳原子链是基于sp杂化轨道成键的真正的一维材料，它只有一个原子尺寸的直径，具有非常奇异的结构，是纳米材料家族的新秀，但由于在室温空气中的稳定性差限制了对它的研究，使我们对其了解甚少。碳纳米线，即在最内层管里包裹有线型碳链的碳纳米管，是一种新型的基于sp-sp2杂化结构的碳纳米材料，也是间接制备和了解碳链性能的最佳途径式之一。本项目将运用简单的高温热处理方法在提纯后的含小内径管的双壁/多壁碳纳米管中制备线型碳原子链，进而形成碳纳米线结构。通过改进制备及提纯条件提高小内径双壁/多壁碳纳米管的含量，进而提高碳纳米线的纯度；获得碳纳米线结构的HRTEM观察证据；讨论形成碳链的碳原子的来源，结合拉曼散射技术、高分辨透射电子显微镜等手段，了解高温热处理方法中碳纳米线的生长机理。本项目将为碳纳米线的研究提供样品以及实验支持。

碳纳米线是在碳纳米管中心空洞里插入直线状长碳原子链形成的一种新型的基于sp-sp2杂化结构的一维碳纳米材料。理论计算表明，碳纳米线拥有优异的机械强度、导电性和导热性，并可用于制造世界最小的纳米器件。 .本项目研究了电弧放电法中小直径双壁碳纳米管径的制备条件，寻找到了制备最佳的催化剂制备及气氛条件。通过有机溶剂液相电弧法制备出高浓度的具有线性结构的polyyne（C2nH2, n=3, 4, 5…）溶液，并获得了单分离的polyyne分子溶液，研究了其拉曼光谱。利用超临界流体法成功地向开口的单/双壁碳纳米管中填充入了polyyne分子，经过后续的高温热处理成功观察到了碳纳米线的特征拉曼光谱线。此外，通过凝胶色谱法对具有高分离难度的氢电弧法制备的单壁碳纳米管样品进行了首次单手性分离，为制备单壁碳纳米管型的碳纳米线提供了样品支持。.本项目的研究结果，将促进碳纳米线及一维碳原子链的各项研究开展，也为一维碳基纳米器件的开发奠定基础。