A Glass Hook Allows Fishing of Hexa‐peri‐hexabenzocoronene Graphitic Nanotubes: Fabrication of a Macroscopic Fiber with Anisotropic Electrical Conduction
A Glass Hook Allows Fishing of Hexa‐peri‐hexabenzocoronene Graphitic Nanotubes: Fabrication of a Macroscopic Fiber with Anisotropic Electrical Conduction
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DOI：
10.1002/adma.200502116
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发表时间：
2006-05
影响因子：
29.4
通讯作者：
Y. Yamamoto;T. Fukushima;W. Jin;A. Kosaka;T. Hara;T. Nakamura;A. Saeki;S. Seki;S. Tagawa;T. Aida
中科院分区：
文献类型：
--
作者：
Y. Yamamoto;T. Fukushima;W. Jin;A. Kosaka;T. Hara;T. Nakamura;A. Saeki;S. Seki;S. Tagawa;T. Aida
π电子有机分子的可控自组装在制备具有电子和光电子功能的纳米结构材料方面具有潜在的应用价值，因而受到越来越多的关注。[1]特别是，多环芳烃（PAH）被认为是分子电子学的有前途的组分之一[2]，因为它们强烈倾向于通过π堆积相互作用形成一维柱状结构。[3]一些单向组装的多环芳烃已被证明表现出各向异性的电荷和能量传输活动。[4]多环芳烃的代表性实例包括六-正-六苯并蔻（HBC），其由十三个稠合苯环组成。Müllen及其同事在HBC衍生物自组装方面的开创性工作表明，具有对称取代的石蜡侧链的HBC形成分散的液晶材料，显示出有趣的电学性质，如高电荷载流子迁移率。[3b最近，我们已经开发了一类新的Gemini形状的HBC两亲物，例如1（图1a），其带有亲水性氧化烯（OA）链和亲脂性十二烷基链，其可以自组装以形成具有大量π堆叠HBC单元的螺旋阵列的明确定义的纳米管物体（图1b）。[5]如通过使用纳米间隙电极所研究的，氧化后的纳米管是半导电的，具有半导体行为。[5a]最近，我们还成功地通过在每个氧化烯链中引入立体中心来制造具有单手螺旋手性的纳米管（2，图1a）。[5c]在这些研究的过程中，我们碰巧注意到这种单手螺旋纳米管可以很容易地加工成宏观纤维，其中大多数纳米管沿着纤维轴沿着单向排列。通常，将（S）-2（1.5 mg mL-1）的热2-甲基四氢呋喃（MeTHF）溶液（50 ℃）冷却至25 ℃，并将所得悬浮液老化三周，使得最初形成的纳米管[5c]进一步生长并缠结，形成大束。然后，将玻璃钩浸入该悬浮液中（图2a）以收集纳米管束，然后拉起以拉伸捕获的聚集体（图2b）。这种简单的方法允许加工直径为0.05-0.5 mm的5-30 mm长的宏观纤维。与此形成鲜明对比的是，由非手性1形成的纳米管和由外消旋2形成的纳米管都没有得到宏观纤维。（S）-2的宏观纤维的偏振光学显微镜表明，大多数纳米管束沿纤维轴沿着单向取向（图1A和1B）。3a，B）。宏观纤维的小角X射线衍射分析显示出2θ= 0.40-2.7范围内的多个衍射峰，这些峰可归因于纳米管束（图1 - 3）。4a，B）。虽然衍射图案不是完全周期性的，可能是因为纳米管的非均匀堆积，但观察到的16.3nm的d-间距（其可以被索引为（100）衍射）大致对应于通过透射电子显微镜评估的纳米管的直径。[5c]非常有趣的是，这些特征衍射仅在垂直于纤维轴的方向上观察到（图4a），其中例如2θ= 0.54处的衍射强度显示出β角依赖性，其中最强的衍射间隔为174（图4 b，插图）。因此，由于纳米管束的宏观取向，所包含的纳米管中的大多数是…
Controlled self-assembly of π-electronic organic molecules has attracted increasing attention in view of their potential utility for the fabrication of nanostructured materials with electronic and optoelectronic functions.[1] In particular, polycyclic aromatic hydrocarbons (PAHs) are considered as one of the promising components for molecular electronics [2] because of their strong tendency to form one-dimensional columnar structures via π-stacking interactions.[3] Some unidirectionally assembled PAHs have been shown to exhibit anisotropic charge-and energy-transport activities.[4] A representative example of PAHs includes hexa-peri-hexabenzocoronene (HBC), which consists of thirteen fused benzene rings. Pioneering works by Müllen and co-workers on the self-assembly of HBC derivatives have revealed that HBCs with symmetrically substituted paraffinic side chains form discotic liquid-crystalline materials that display interesting electrical properties such as high charge-carrier mobility.[3b, 4] Recently, we have developed a new class of Gemini-shaped HBC amphiphiles such as 1 (Fig. 1a) bearing hydrophilic oxyalkylene (OA) chains and lipophilic dodecyl chains, which can self-assemble to form well-defined nanotubular objects with a helical array of a large number of π-stacked HBC units (Fig. 1b).[5] As investigated by using a nanometer-gap electrode, the nanotube upon oxidation is electroconductive, with semiconducting behavior.[5a] More recently, we have also succeeded in the fabrication of nanotubes with one-handed helical chirality via the introduction of a stereogenic center into each oxyalkylene chain (2, Fig. 1a).[5c] In the course of these studies, we happened to notice that such one-handed helical nanotubes can readily be processed into a macroscopic fiber, where the majority of the nanotubes are aligned unidirectionally along the fiber axis. Here, we report details of this bottom–up processing and electrical-transport properties of the resulting fiber.Typically, a hot 2-methyltetrahydrofuran (MeTHF) solution (50 C) of (S)-2 (1.5 mg mL–1) was allowed to cool to 25 C, and the resultant suspension was aged for three weeks so that the initially formed nanotubes [5c] grew further and became entangled, forming large bundles. Then, a glass hook was dipped into this suspension (Fig. 2a) to collect the nanotube bundles and then pulled up to stretch the captured aggregate (Fig. 2b). This simple method allowed processing of 5–30 mm long macroscopic fibers with a diameter of 0.05–0.5 mm. In sharp contrast, neither the nanotubes formed from achiral 1 nor those from racemic 2 gave macroscopic fibers. Polarized optical microscopy of a macroscopic fiber of (S)-2 suggested that the majority of the nanotube bundles are oriented unidirectionally along the fiber axis (Figs. 3a, b). Smallangle X-ray diffraction analysis of the macroscopic fiber showed several diffraction peaks in a range of 2θ= 0.40–2.7 that are assignable to the bundles of the nanotubes (Figs. 4a, b). While the diffraction pattern was not fully periodic, possibly because of a non-uniform packing of the nanotubes, the observed d-spacing of 16.3 nm, which can be indexed as the (100) diffraction, roughly corresponds to the diameter of the nanotube evaluated by transmission electron microscopy.[5c] Quite interestingly, these characteristic diffractions were observed only in a direction perpendicular to the fiber axis (Fig. 4a), where the diffraction intensity at, for example 2θ= 0.54 showed a β-angle dependency with the most intensive diffractions being separated by 174 (Fig. 4b, inset). Therefore, thanks to the macroscopic orientation of the nanotube bundles, the majority of the included nanotubes are …