Even though ultrasonication is considered to be an effective method to disperse carbon nanotubes (CNTs), its devastating effects on the nanotubes are often neglected. Here, even mild ultrasonication is found to rapidly extract the inner single-wall CNTs (SWCNTs) from the outer shells of the double-wall CNTs (DWCNTs). As-synthesized DWCNTs are gently solubilized in a surfactant solution, strictly avoiding any ultrasonication, followed by two consecutive density gradient ultracentrifugation (DGU) steps to obtain a purified colloidal solution of isolated DWCNTs. The latter is carefully selected based on in situ resonant Raman (RRS) and fluorescence (PL) spectroscopy, measured as a function of depth directly in the ultracentrifuge tube after DGU. These purified DWCNTs are ultrasonicated in successive time steps while intermittently probing the sample via RRS and PL spectroscopy. These results unravel the very fast increasing, yet saturating extraction mechanism that leads to the formation of fluorescing SWCNTs. A statistical high-resolution transmission electron microscopy study confirms the drastic increase in SWCNTs after ultrasonication, and evidences that ultrasonication forms SWCNTs from both the inner and outer shells of the DWCNTs. This study demonstrates how easily ultrasonication extracts SWCNTs from individually solubilized DWCNTs, unavoidably complicating any further spectroscopic studies on DWCNTs severely.

尽管超声波处理被认为是分散碳纳米管 (CNT) 的有效方法，但其对纳米管的破坏性影响往往被忽视。在这里，发现即使是温和的超声波处理也能从双壁碳纳米管 (DWCNT) 的外壳中快速提取内部单壁碳纳米管 (SWCNT)。合成后的 DWCNTs 在表面活性剂溶液中轻轻溶解，严格避免任何超声处理，然后进行两次连续的密度梯度超速离心 (DGU) 步骤，以获得分离的 DWCNTs 的纯化胶体溶液。后者是根据原位精心挑选的共振拉曼 (RRS) 和荧光 (PL) 光谱，在 DGU 后直接在超速离心管中测量为深度的函数。这些纯化的 DWCNT 在连续的时间步长中被超声处理，同时通过以下方式间歇性地探测样品RRS 和 PL 光谱。这些结果揭示了导致形成荧光单壁碳纳米管的快速增加但饱和的提取机制。统计高分辨率透射电子显微镜研究证实了超声处理后 SWCNT 的急剧增加，并证明超声处理从 DWCNT 的内壳和外壳形成 SWCNT。这项研究证明了超声处理从单独溶解的 DWCNT 中提取 SWCNT 是多么容易，不可避免地使对 DWCNT 的任何进一步光谱研究严重复杂化。