Scalable Method for the Reductive Dissolution, Purification, and Separation of Single-Walled Carbon Nanotubes
Scalable Method for the Reductive Dissolution, Purification, and Separation of Single-Walled Carbon Nanotubes
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DOI：
10.1021/nn2041494
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发表时间：
2012-01-01
期刊：
影响因子：
17.1
通讯作者：
Shaffer, Milo S. P.
中科院分区：
文献类型：
--
作者：
Fogden, Sian;Howard, Christopher A.;Shaffer, Milo S. P.
在合成时，块状单壁碳纳米管（SWNT）样品通常是高度团聚和不均匀的。然而，它们最有前途的应用需要分离出个性化的、纯化的纳米管，这些纳米管通常具有特定的光电特性。已经开发了广泛的分散和分离技术，但是超声处理或超离心的使用对可扩展性施加了严重的限制，并且可能引入损害。在这里，我们展示了一种新的，本质上可扩展的单壁碳纳米管分散和分离的方法，在钠金属-氨溶液中使用还原处理，任选地随后在极性非质子有机溶剂中选择性溶解。原位小角中子散射表明存在溶解的，未捆绑的单壁碳纳米管在溶液中，在浓度达到至少2毫克/毫升，隔离单个纳米管的能力，证实了原子力显微镜。光谱数据表明，可溶性馏分主要含有大的金属纳米管，提出了一个潜在的新的机制，纳米管分离。此外，在溶解过程中观察到的G/D比，作为金属：碳比的函数，证明了一种新的纯化方法，用于从原始的单壁碳纳米管中去除含碳杂质，避免了传统的，破坏性的，竞争性的氧化反应。
As synthesized, bulk single-walled carbon nanotube (SWNT) samples are typically highly agglomerated and heterogeneous. However, their most promising applications require the isolation of individualized, purified nanotubes, often with specific optoelectronic characteristics. A wide range of dispersion and separation techniques have been developed, but the use of sonication or ultracentrifugation imposes severe limits on scalability and may introduce damage. Here, we demonstrate a new, intrinsically scalable method for SWNT dispersion and separation, using reductive treatment in sodium metal-ammonia solutions, optionally followed by selective dissolution in a polar aprotic organic solvent. In situ small-angle neutron scattering demonstrates the presence of dissolved, unbundled SWNTs in solution, at concentrations reaching at least 2 mg/mL; the ability to isolate individual nanotubes is confirmed by atomic force microscopy. Spectroscopy data suggest that the soluble fraction contains predominately large metallic nanotubes; a potential new mechanism for nanotube separation Is proposed. In addition, the G/D ratios observed during the dissolution sequence, as a function of metal: carbon ratio, demonstrate a new purification method for removing carbonaceous impurities from pristine SWNTs, which avoids traditional, damaging, competitive oxidation reactions.