单壁碳纳米管的溶液相手性选择性分离及其高密度阵列组装研究

As the most promising building block for the integrated circuits (ICs) to replace single crystal Si, semiconducting single-walled carbon nanotubes (s-SWNTs) have faced major challenge during their eventual integration into practical electronics: control over the type of carbon nanotubes and placement of high density SWNT array. Two main kinds of approaches have been developed to control these disparate aspects, which are preferential growth of horizontal array of semiconducting or single-chirality SWNTs by chemical vapor deposition (CVD) method and assembly of pre-sorted s-SWNTs into highly aligned arrays on substrates. Here we propose that, by rationally combining these two approaches, preparation of high-density uniformly distributed single-chirality SWNT arrays will be effectively realized. Firstly, s-SWNTs with different band gap are separated sequentially by employing overloading effect in conjugated polymer sorting system; then solution of enriched SWNTs with specific chirality was subjected to assembling process, with the CVD grown SWNT array fluorinated to be insulating and used as template to provide size confinement and proper interaction to drive the alignment, the sorted SWNTs are going to be assembled into high density arrays composed of individual SWNT. Additionally, the relationship between the selectivity and the chirality of the nanotubes will be investigated comprehensively, as well as the aligning mechanism of the nanotube array template. We believe that accomplishment of this project including the preparation of high density single chirality SWNT array, understanding on the chirality selective sorting by new strategy in conjugated polymer sorting system and the novel concept of using SWNT array as a template to align sorted SWNTs is going to largely benefit the progress towards the integration of carbon nanotube based transistors in real electronic devices.

碳纳米管是CMOS集成电路中替代传统单晶硅的理想材料，当今面临的瓶颈问题是难以获得均一半导体性的碳纳米管高密度阵列。目前已发展的制备半导体性碳纳米管阵列的方法主要分两种：第一种是运用化学气相沉积（CVD）法在单晶基底表面直接选择性生长半导体性碳纳米管阵列，该方法能获得高准直性高密度阵列；第二种是溶液相分离和自组装的组合技术，该方法可获得高纯度单手性碳纳米管，但组装后的阵列有序度和密度均不够理想。本项目拟结合这两类技术的特点，将凝胶色谱中的“过载效应”引入有机相分离体系实现高选择性的手性分离，再以CVD生长的碳纳米管阵列绝缘化后作为诱导溶液中碳纳米管定向排列的模板，获得高密度均匀排布的单手性碳纳米管阵列，深入开展不同手性碳纳米管的高效顺序分离及其高密度阵列的定向沉积研究，阐明定向沉积机制，揭示碳纳米管能带带隙与手性选择性的关系，为推进碳纳米管在CMOS器件中的应用进程提供科学依据。

项目以碳纳米管的结构控制制备及其在电子器件当中的应用为目标开展研究，在特定导电属性碳纳米管制备、精确表征及其在电子器件应用方面都取得了一定成果和技术突破。首先在高密度碳纳米管水平阵列制备方面取得了进展，所获得的碳纳米管阵列密度从每微米10根到每10微米1根连续可控可调。通过改变生长气氛引入杂原子掺杂，使得所获得碳纳米管的管径大小进一步可调，进而影响纳米管的精细原子排布和包括导电属性在内的性质。碳纳米管结构的精确表征对导电属性控制极为关键，共振拉曼光谱高通量精确表征方面依赖于其他表征技术。本项目利用碳纳米管样品区分于体相碳纳米管的高度定向的特征，不仅实现了在单根纳米管尺度上的精细结构表征，还首次获得了在大量表征样品范围内杂原子掺杂碳纳米管的 “掺杂浓度-管径-导电属性”关系的准确对应。研究同时实现了不同基底上高密度碳纳米管阵列的制备及相关机理研究。本项目实现将特定导电属性碳纳米管应用于电子器件，制备成高效线状及薄膜状柔性超级电容器，可作为柔性可编织电子/传感器件的电源，促进其发展与实际应用。利用碳纳米管独特的一维线性结构和优异导电性将其与非导电纤维基底复合，兼顾了结构的机械稳定性、电子传导能力、离子扩散性能，保证了电解液在复合电极内部的扩散。借助碳纳米管自组装结构的均一可控等结构特点，对基于碳纳米材料的复合超级电容器电极的构效关系进行了深入探讨，明确了其中的关键影响因素，进一步开拓了碳纳米管在电子器件中的应用。