Optical Microspectroscopy Study of the Mechanical Stability of Empty and Filled Carbon Nanotubes under Hydrostatic Pressure

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• 作者：Badawi Anis ; F. B枚rrnert ; M. H. R眉mmeli ; and C. A. Kuntscher
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：November 20, 2014
• 年：2014
• 卷：118
• 期：46
• 页码：27048-27062
• 全文大小：795K
• ISSN：1932-7455

文摘

We present a high-pressure optical and infrared spectroscopy study on the mechanical stability of single-walled carbon nanotubes (SWCNTs) filled with C₆₀ and C₇₀ fullerene molecules (C₆₀- and C₇₀-peapods), double-walled carbon nanotubes (DWCNTs) derived from the C₆₀- and C₇₀-peapods (DWCNTs/C₆₀ and DWCNTs/C₇₀), and iodine-filled SWCNTs (I-SWCNTs). High-resolution transmission electron microscopy, Raman, and optical spectroscopy were used to characterize all prepared samples. For the C₆₀- and C₇₀-peapods, we find an anomaly in the pressure-induced shifts of the optical transitions at the critical pressures P_c1 鈮?6.5 and 7.0 GPa, respectively, compared to P_c1 鈮?3 GPa in the case of empty SWCNTs. The shift of the anomaly to higher pressure signals the stabilization of the nanotubes by the C₆₀ and C₇₀ filling. The value of P_c1 is in good agreement with theoretical predictions of the pressure-induced deformation for highly filled peapods with similar average diameter. In comparison to SWCNTs, the pressure-induced red shifts of the optical transitions in DWCNTs/C₆₀ are extremely small below 鈭?0 GPa, demonstrating the enhanced mechanical stability due to the inner tube. The anomaly at the critical pressure P_d 鈮?12 GPa in DWCNTs/C₆₀ signals the onset of the pressure-induced deformation of the tubular cross sections or the collapse of the DWCNTs. For the DWCNTs/C₇₀, the anomaly in the pressure-induced shift is lowered to P_d 鈮?9 GPa compared to 12 GPa in the case of DWCNTs/C₆₀. This behavior signals that the stabilization of the outer tube by the inner tube in DWCNTs/C₇₀ is lower compared to the DWCNTs/C₆₀. Interestingly, the iodine filling shows a stabilization for the outer tubes up to 10 GPa in contrast with the previously published Raman results. For all samples, except I-SWCNTs, the low energy absorbance decreases rapidly with increasing pressure, suggesting the destruction of the SWCNT electronic band structure and hence an increasing carrier localization. In the I-SWCNTs the pressure-induced free carriers localization is partially compensated by the metallization of the iodine chains under pressure.