Saito Yuika, Kondo Takahiro, Harada Sora, Kitaura Ryo, Balois-Oguchi Maria Vanessa, Hayazawa Norihiko
Department of Chemistry, Faculty of Science, Gakushuin University, 1-5-1 Mejiro, Toshima, Tokyo 171-0031, Japan.
Department of Chemistry, Nagoya University, Furo-Cho, Nagoya, Aichi 464-8602, Japan.
J Phys Chem B. 2023 Aug 3;127(30):6726-6733. doi: 10.1021/acs.jpcb.3c00586. Epub 2023 Jul 20.
In the present study, we investigated the intermolecular interactions between single-walled carbon nanotubes (SWCNTs) and encapsulated molecules by polarization resonance Raman microscopy. C encapsulated in SWCNTs is investigated under incident laser polarization parallel and perpendicular to the tube axis. We employed two excitation laser wavelengths 442 and 532 nm, which are in resonance with different electronic states of C. Under 532 nm excitation, no distinct polarization dependence is found in the Raman spectral pattern, while under 442 nm excitation, a peak not previously seen for this excitation wavelength was clearly observed for parallel excitation. This result can be explained by the modulation of the resonance Raman process via a charge transfer contribution between C and the SWCNTs, which is sensitive to the incident polarization as well as the excitation wavelength. The intensity of the local electronic field inside a SWCNT is higher for the parallel excitation than the perpendicular excitation when the nanotubes are in a bundle. The results can be explained by field localization effects at the nanotube walls, qualitatively supported by finite-difference time-domain simulations.
在本研究中，我们通过偏振共振拉曼显微镜研究了单壁碳纳米管（SWCNT）与包封分子之间的分子间相互作用。对封装在SWCNT中的C在与管轴平行和垂直的入射激光偏振下进行了研究。我们采用了442和532 nm这两种激发激光波长，它们与C的不同电子态共振。在532 nm激发下，拉曼光谱图案中未发现明显的偏振依赖性，而在442 nm激发下，对于平行激发，清楚地观察到了该激发波长之前未见的一个峰。该结果可以通过C与SWCNT之间的电荷转移贡献对共振拉曼过程的调制来解释，这对入射偏振以及激发波长敏感。当纳米管成束时，平行激发时SWCNT内部局部电场的强度高于垂直激发时。该结果可以通过纳米管壁处的场局域化效应来解释，有限时域差分模拟定性地支持了这一点。
