G‐mode behaviour of closed ended single wall carbon nanotubes under pressure

Abstract

We have performed high pressure Raman experiments on closed‐ended single wall carbon nanotubes using two different excitation wavelengths: 632.8 nm and 514 nm. We found that the shape of the G‐mode spectrum changes while changing the excitation wavelength at lower pressures, while it becomes similar at 3.5 GPa. In addition we record that the value of the transition pressure, associated with the structural transitions in the tubes, has also changed with changing the excitation wavelength even though we are examining tubes from the same produced sample. We attribute these results to the tubes having different electronic nature (metallic; semi‐conducting) and different diameters in resonance with each excitation wavelength. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Alkane Encapsulation Induces Strain in Small-Diameter Single-Wall Carbon Nanotubes

“…Lebedkin et al report G-band shifts for hydrostatic radial compression with positive slopes of 8.0 ± 0.2, 6.5 ± 0.6, and 8.0 ± 0.5 cm –1 /GPa for small-diameter semiconducting nanotubes dispersed in an aqueous sodium cholate solution at excitation wavelengths of 514, 633, and 785 nm, respectively. G-band shifts for hydrostatic compression have also been reported for dispersed ≈1.4 nm diameter SWCNTs in DOC of 10 ± 0.2 and 7.0 ± 0.2 cm –1 /GPa for empty and water-filled SWCNTs, respectively, and for SWCNT powders of ≈1.4 nm diameter in varying pressure-transmitting media of approximately 6–10 cm –1 /GPa. − The similarity of these results across diameter ranges and pressure-transmitting media imply an apparent expansive pressure on the order of 0.2 GPa from alkane-filling. This value allows for an estimation of the strain through the Young’s modulus ( Y ).…”

From mesoscale to nanoscale mechanics in single-wall carbon nanotubes

“…Experimental difficulties in identifying the collapse transition include the use of samples having wide distributions of diameter, of samples having both open and closed carbon nanotubes which allows partial filling with the pressure transmitting medium [14], of samples consisting of bundles of nanotubes [15], and difficulties due to the evolution of the Raman resonances with pressure [16,17]. Recent experiments on individualized empty (closed) SWCNT [14] showed excellent agreement with improved simulations [5] at an averaged diameter, but were not used for a quantitative experimental determination of the diameter dependence of the collapse pressure.…”

Carbon nanotubes collapse phase diagram with arbitrary number of walls. Collapse modes and macroscopic analog

“…For small tube diameters with a stable circular cross-section at ambient conditions, it has been shown that a high external pressure causes collapse. This was first shown for SWCNT, where the collapse pressure has been demonstrated to be a function of CNT diameter [41,42,43,44,45,16,46,47,48,49,50,51,52,53,54]. Pressure-induced collapse is also observed for doublewall [55,56,57,58], triple-wall [59] and multi-wall carbon nanotubes [60].…”