Nano- to micrometer-scale surface roughness contributes to the hydrophobicity of materials as discussed often in terms of superhydrophobicity. We report here that as little as 1 wt% of α, β, and γ-cyclodextrins (CDs) can disperse carbon nanohorn aggregates (CNHa) as surfactants in water by binding on their pointed tips. The binding mode was visually demonstrated using single-molecule atomic resolution real-time electron microscopy (SMART-EM). The SMART-EM data provided an estimation of the equilibrium constant of the CD binding to be close to that of adamantane ammonium chloride to β-CD. A qualitative study on the rate of decomplexation of α, β, and γ-CDs from CNHa suggests a substantial mechanistic difference in their binding mode to the CNH tips. A sequence of α-CD complexation and decomplexation allows us to purify CNHa by selectively removing graphitic ball-shaped impurity (GB). Upon treatment with NaNH2 , the purified CNHa produce GB-free amino-CNHa where the tips are functionalized with NH2 groups.

中文翻译：

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环糊精作为表面活性剂，用于增溶和纯化碳纳米角聚集体。

纳米级至微米级的表面粗糙度有助于材料的疏水性，正如经常在超疏水性方面讨论的那样。我们在这里报告说，低至1 wt％的α，β和γ-环糊精（CDs）可以通过在其尖端上结合而将碳纳米角聚集体（CNHa）作为表面活性剂分散在水中。使用单分子原子分辨率实时电子显微镜（SMART-EM）在视觉上证明了结合模式。SMART-EM数据提供了CD结合平衡常数的估计值，该平衡常数接近于金刚烷氯化铵与β-CD的结合常数。对来自CNHa的α，β和γ-CD分解的速率的定性研究表明，它们与CNH尖端的结合方式存在很大的机械差异。一系列的α-CD络合和分解过程使我们能够通过选择性地去除石墨球形杂质（GB）来纯化CNHa。用NaNH2处理后，纯化的CNHa会产生不含GB的氨基CNHa，其中的末端会被NH2基团官能化。