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Van der Waals'force-controlled nano Raman scattering spectroscopy

范德华力控制纳米拉曼散射光谱

基本信息

批准号：
16360034
负责人：
INOUYE Yasushi
金额：
$ 9.66万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16360034/
关键词：
Near-field Raman spectroscopy Surface enhanced Raman Scattering Density functional formalism Carbon nanotube Local plasmon van der Waals'force Near-field optics Nanoscience technology ナノサイエンス・ナノテクノロジー

项目摘要

We found spectral shift of specific Raman band of carbon nanotubes (CNTs) when van der Waals's force is applied onto the CNTs. We measured Raman spectrum of single CNT bundle while applying stress on it with silver coated cantilever tip of atomic force microscope, and observed spectral change of Raman band of CNT in situ. When we apply stress from 0nN to 2.4nN successively, lower peak of G-band (〜1600cm-1) was red-shifted by 18cm-1. G-band reflects electric property of CNT and has two adjacent peaks. On the other hand, no peak shift was observed in higher peak of G-band. This phenomenon originates from the fact that two peaks are corresponding to the vibrational modes of different vibrational direction, and these two vibrational modes have different shearing stresses with respect to each other. Furthermore, we observed peak shift of radial breathing mode (RBM) around 200cm-1〜300cm-1 at most 5cm-1. RBM depends on the diameter of CNT. This peak shift can be attributed to the fact that the cross-section of CNT is deformed into ellipse shape by applied uniaxial stress on the CNT. We also observed intensity of all Raman band are enhanced when applying stress. This suggests that the band gap energy of CNT comes near to the resonance energy(2.33eV) because of the deformation of CNT along the long axis of CNT, thus contribution of resonant Raman effect is increased.We also performed vibrational calculation of molecule-metal cluster including a number of metal atom based on density functional theory. The calculation showed the experimentally observed band shift by complex formation mechanism is well reproduced if the metal cluster contains at least four Ag atoms.

我们发现当范德华力作用在碳纳米管（CNTs）上时，碳纳米管的特定拉曼带发生了光谱位移。利用原子力显微镜的镀银悬臂尖端对单个碳纳米管束施加应力，测量了其拉曼光谱，并观察了原位碳纳米管拉曼光谱的变化。当我们在0 ~ 2.4nN范围内依次施加应力时，g波段（~ 1600cm-1）的下峰红移了18cm-1。g波段反映碳纳米管的电性能，有两个相邻的峰。另一方面，g波段较高的峰没有出现峰移。这一现象源于两个峰值对应不同振动方向的振动模态，且这两种振动模态相对剪应力不同。此外，我们观察到径向呼吸模式（RBM）的峰移在200cm-1 ~ 300cm-1左右，最多5cm-1。RBM取决于碳纳米管的直径。这种峰移可以归因于碳纳米管的横截面变形成椭圆形状施加单轴应力对碳纳米管。我们还观察到当施加应力时，所有拉曼波段的强度都增强了。这说明由于碳纳米管沿碳纳米管长轴的变形，碳纳米管的带隙能量接近共振能（2.33eV），从而增加了共振拉曼效应的贡献。基于密度泛函理论，对含有多个金属原子的分子-金属团簇进行了振动计算。计算表明，当金属团簇中含有至少4个银原子时，可以很好地再现实验观察到的络合物形成机制的能带位移。