Tip-Enhanced Raman Spectroscopy of Multiwalled Carbon Nanotubes through D-Band Imaging: Implications for Nanoscale Analysis of Interwall Interactions
Tip-Enhanced Raman Spectroscopy of Multiwalled Carbon Nanotubes through D-Band Imaging: Implications for Nanoscale Analysis of Interwall Interactions
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DOI：
10.1021/acsanm.0c01188
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发表时间：
2020-06-26
影响因子：
5.9
通讯作者：
Verma, Prabhat
中科院分区：
文献类型：
--
作者：
Kato, Ryo;Igarashi, Shun;Verma, Prabhat
多壁碳纳米管（MWNTs）的壁间相互作用，这是与壁的数量，甚至可以在纳米级变化，是很重要的调查，因为它们强烈影响MWNTs的光学性能。通过拉曼光谱研究了密切相关的材料多层石墨烯中的层间相互作用，其中2D带拉曼模式被用作调查工具。然而，由于两种材料之间的结构差异，这种模式不能以类似的方式可靠地用于MNATNT。在这里，我们证明，不同于石墨烯，另一个拉曼模式，D-带，这是传统上已知的局部结构缺陷，可以激活的壁间相互作用在MVVNT，因此可以用作一个有效的工具，调查壁间相互作用在MWNT。为了研究纳米尺度下的壁间相互作用，我们采用了尖端增强拉曼光谱（TERS），并通过实验证实了D-带实际上与壁的数量密切相关。我们还解释了这种相关性的起源，通过数值计算，这既考虑到指数衰减的近场光的强度在尖端顶点和样品体积的非线性增加的壁数的增加。我们的研究结果铺平了道路，通过TERS分析在MVVNTs的壁间相互作用，并可以应用于光谱分析的光学信号和纳米材料的形貌之间的相关性。
The interwall interactions in multiwalled carbon nanotubes (MWNTs), which are associated with the number of walls and may vary even at nanoscale, are important to investigate as they strongly influence the optical properties of MWNTs. Interlayer interactions in a closely related material, multilayered graphene, have been studied by Raman spectroscopy, where the 2D-band Raman mode was used as the investigation tool. However, this mode cannot be reliably utilized for MNATNTs in a similar fashion due to the structural difference between the two materials. Here we demonstrate that unlike graphene, another Raman mode, the D-band, which is conventionally known to represent localized structural defects, can be activated by the interwall interactions in a MVVNT and thus can be used as an effective tool to investigate interwall interactions in MWNTs. To study the interwall interactions at nanoscale, we employed tip-enhanced Raman spectroscopy (TERS) and experimentally confirmed that the D-band was actually strongly correlated to the number of walls. We also interpreted the origin of this correlation by numerical calculation, which takes into account both the exponentially decaying intensity of the near-field light at the tip apex and the nonlinear increase of sample volume as the number of walls increases. Our findings pave ways to analyze interwall interactions in MVVNTs through TERS and can be applied for spectroscopic analysis of the correlation between the optical signal and the topography for nanomaterials.