Li Shilong, Wei Xiaojun, Li Linhai, Cui Jiaming, Yang Dehua, Wang Yanchun, Zhou Weiya, Xie Sishen, Hirano Atsushi, Tanaka Takeshi, Kataura Hiromichi, Liu Huaping
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
Beijing Key Laboratory for Advanced Functional Materials and Structure Research, Beijing 100190, China.
Anal Methods. 2020 May 14;12(18):2376-2384. doi: 10.1039/d0ay00356e.
We quantitatively analyze the effect of reabsorption on the Raman spectroscopy of (10, 3) and (8, 3) single-chirality single-wall carbon nanotube (SWCNT) solutions by varying the detection depth in confocal micro-Raman measurements and SWCNT concentration the in sample solution. The increase of the detection depth and concentration of SWCNTs enhances the reabsorption effect and decreases the intensities of the Raman features. More importantly, reabsorption exhibits different effects on different Raman features such as the radial breathing mode (RBM) and G+ band, strongly depending on the resonance degree of the scattered light energy and the interband transition of SWCNTs. When (10, 3) SWCNTs are excited with a 633 nm laser, the scattered light from RBM has stronger resonance with the interband transition of the SWCNTs than that from the G+ band, leading to a faster reduction in the RBM intensity and a lower intensity ratio of RBM to the G+ band. In contrast, when (8, 3) SWCNTs are excited with a 633 nm laser, reabsorption has the same effect on the RBM and G+ band intensities and thus maintains a constant intensity ratio of RBM to the G+ band. Furthermore, we precisely establish a quantitative relationship of the intensities of the Raman features such as RBM, the G+ band and their intensity ratio as a function of the focal depth and SWCNT concentration by theoretical calculations and numerical simulation, which reproduces the experimental results well. These results are very useful in the precise analysis of the Raman spectroscopy of SWCNTs and thus their applications in molecular detection and imaging.
我们通过在共聚焦显微拉曼测量中改变检测深度以及样品溶液中单壁碳纳米管（SWCNT）的浓度，定量分析了重吸收对（10, 3）和（8, 3）单手性单壁碳纳米管溶液拉曼光谱的影响。检测深度的增加和SWCNT浓度的提高增强了重吸收效应，并降低了拉曼特征峰的强度。更重要的是，重吸收对不同的拉曼特征（如径向呼吸模式（RBM）和G + 带）表现出不同的影响，这很大程度上取决于散射光能量的共振程度以及SWCNT的带间跃迁。当用633 nm激光激发（10, 3）SWCNT时，RBM的散射光与SWCNT的带间跃迁的共振比G + 带的散射光更强，导致RBM强度下降更快，且RBM与G + 带的强度比更低。相比之下，当用633 nm激光激发（8, 3）SWCNT时，重吸收对RBM和G + 带强度的影响相同，因此RBM与G + 带的强度比保持恒定。此外，我们通过理论计算和数值模拟精确建立了拉曼特征（如RBM、G + 带）的强度及其强度比与焦深和SWCNT浓度的定量关系，该关系很好地再现了实验结果。这些结果对于精确分析SWCNT的拉曼光谱及其在分子检测和成像中的应用非常有用。
