Feng Ya, Levshov Dmitry I, Sato Yuta, Inoue Taiki, Cambré Sofie, Wenseleers Wim, Xiang Rong, Suenaga Kazu, Maruyama Shigeo
Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China.
Department of Mechanical Engineering, School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
ACS Nano. 2025 Jan 14;19(1):1396-1404. doi: 10.1021/acsnano.4c14078. Epub 2024 Dec 26.
The intrinsic temperature dependence of Raman-active modes in carbon nanotubes (CNTs), particularly the radial breathing mode (RBM), has been a topic of a long-standing controversy. In this study, we prepared suspended individual CNTs to investigate how their Raman spectra depend on temperature and to understand the effects of environmental conditions on this dependency. We analyzed the intrinsic temperature dependence of the main Raman-active modes, including the RBM, the moiré-activated R feature, and the G-band in double-walled carbon nanotubes (DWCNT) and single-walled carbon nanotubes (SWCNTs) after complete desorption of air. The inner tube of the DWCNT, like the desorbed SWCNTs, was free from environmental influences, resulting in minimal temperature-induced RBM frequency shifts. We show that the larger RBM shift of SWCNTs upon initial heating is not intrinsic but is due to air desorption. The R feature, attributed to moiré-activated phonon scattering and nondispersive in nature, demonstrated a quasi-linear temperature dependence, akin to the G-band but with a lower temperature coefficient. The G-band, which was largely unaffected by environmental conditions, exhibited a consistent temperature coefficient across SWCNTs, DWCNTs, and small SWCNT bundles.
碳纳米管（CNT）中拉曼活性模式的本征温度依赖性，尤其是径向呼吸模式（RBM），一直是一个长期存在争议的话题。在本研究中，我们制备了悬浮的单个碳纳米管，以研究其拉曼光谱如何随温度变化，并了解环境条件对这种依赖性的影响。在空气完全解吸后，我们分析了双壁碳纳米管（DWCNT）和单壁碳纳米管（SWCNT）中主要拉曼活性模式的本征温度依赖性，包括RBM、莫尔激活的R特征和G带。DWCNT的内管与解吸后的SWCNT一样，不受环境影响，导致温度引起的RBM频率偏移最小。我们表明，SWCNT在初始加热时较大的RBM偏移并非本征的，而是由于空气解吸。归因于莫尔激活声子散射且本质上非色散的R特征表现出准线性温度依赖性，类似于G带，但温度系数较低。在很大程度上不受环境条件影响的G带，在SWCNT、DWCNT和小的SWCNT束中表现出一致的温度系数。
