Institute of Nanotechnology, Karlsruhe Institute of Technology, P.O. Box 3640, 76021 Karlsruhe, Germany.
Institute of Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
ACS Nano. 2021 Mar 23;15(3):4699-4709. doi: 10.1021/acsnano.0c09235. Epub 2021 Feb 24.
Helical wrapping by conjugated polymer has been demonstrated as a powerful tool for the sorting of single-walled carbon nanotubes (SWCNTs) according to their electronic type, chiral index, and even handedness. However, a method of one-step extraction of left-handed () and right-handed () semiconducting SWCNTs (s-SWCNTs) with subsequent cleavage of the polymer has not yet been published. In this work, we designed and synthesized one pair of acid cleavable polyfluorenes with defined chirality for handedness separation of s-SWCNTs from as-produced nanotubes. Each monomer contains a chiral center on the fluorene backbone in the 9-position, and the amino and carbonyl groups in the 2- and 7-positions maintain the head-to-tail regioselective polymerization resulting in polyimines with strictly all-() or all-() configuration. The obtained chiral polymers exhibit a strong recognition ability toward left- or right-handed s-SWCNTs from commercially available CoMoCAT SWCNTs with a sorting process requiring only bath sonication and centrifugation. Interestingly, the remaining polymer on each single nanotube, which helps to prevent aggregation, does not interfere with the circular dichroism signals from the nanotube at all. Therefore, we observed all four interband transition peaks (E, E, E, E) in the circular dichroism (CD) spectra of the still wrapped optically enriched left-handed and right-handed (6,5) SWCNTs in toluene. Binding energies obtained from molecular dynamics simulations were consistent with our experimental results and showed a significant preference for one specific handedness from each chiral polymer. Moreover, the imine bonds along the polymer chains enable the release of the nanotubes upon acid treatment. After s-SWNT separation, the polymer can be decomposed into monomers and be cleanly removed under mild acidic conditions, yielding dispersant-free handedness sorted s-SWNTs. The monomers can be almost quantitatively recovered to resynthesize the chiral polymer. This approach enables high selective isolation of polymer-free s-SWNT enantiomers for their further applications in carbon nanotube (CNT) devices.
手性聚合物螺旋缠绕已被证明是一种强大的工具，可根据单壁碳纳米管（SWCNT）的电子类型、手性指数甚至手性对其进行分类。然而，尚未有报道一种将左手性（）和右手性（）半导体 SWCNT（s-SWCNT）一步提取并随后切断聚合物的方法。在这项工作中，我们设计并合成了一对具有确定手性的酸可裂解聚芴，用于从所生产的纳米管中分离 s-SWCNT 的手性。每个单体在芴骨架的 9 位上含有一个手性中心，而 2 位和 7 位上的氨基和羰基基团保持头对头区域选择性聚合，得到严格全（）或全（）构型的聚亚胺。所得手性聚合物对来自市售 CoMoCAT SWCNT 的左手或右手 s-SWCNT 具有很强的识别能力，仅需浴超声和离心即可完成分离过程。有趣的是，每个单根纳米管上残留的聚合物有助于防止聚集，但完全不干扰纳米管的圆二色信号。因此，我们在甲苯中观察到仍被光学富集的左手和右手（6,5）SWCNT 的圆二色（CD）光谱中出现了所有四个带间跃迁峰（E、E、E、E）。从分子动力学模拟得到的结合能与我们的实验结果一致，表明每个手性聚合物对手性的一种特定手性具有明显的偏好。此外，聚合物链上的亚胺键可在酸处理时释放纳米管。在 s-SWNT 分离后，聚合物可在温和酸性条件下分解成单体并被干净地去除，从而得到无分散剂的手性分离 s-SWNTs。单体可以几乎定量回收以重新合成手性聚合物。该方法可实现对聚合物自由的 s-SWNT 对映体的高选择性分离，以便在碳纳米管（CNT）器件中进一步应用。
