Role of the Pressure Transmitting Medium for the Pressure Effects in Single-Walled Carbon Nanotubes

Abstract

We present the pressure-dependent infrared absorbance spectra of unoriented single-walled carbon nanotube films for pressures up to 8 GPa. Various pressure transmitting media (helium, argon, CsI, and alcohol mixture) were employed to verify the influence of the pressure medium on the observed pressure effects. For all pressure transmitting media, a pressure-induced redshift of the absorption bands is observed, with an anomaly at the critical pressure P c = 2−3 GPa. This anomaly can be attributed to the circular-to-oval structural phase transition. The pressure transmitting medium only affects the results quantitatively, namely, the value of P c and the broadening of the bands.

Exploring the possible interlinked structures in single‐wall carbon nanotubes under pressure by Raman spectroscopy

“…In all cases, we observed a sudden increase of the RBM linewidth at around 2 GPa, where an obvious slope change of G‐band wavenumber and linewidth occurred. This observation is consistent with other previous experimental observations and theoretical simulation, which can be safely attributed to a structural phase transition in the nanotube cross‐section from circle to an oval shape. The second transition in nanotubes takes place at around 5 GPa, such as the RBM linewidth shows the second anomaly by using 830‐nm laser excitation, or the RBM signals disappear by using 514‐nm laser.…”

“…[3][4][5][6] Extensive efforts have been carried out to understand the behavior of SWNTs under high pressure. Raman spectroscopy, [7][8][9][10][11][12][13][14][15][16][17][18] x-ray diffraction, [19,20] neutron-diffraction, [21] and infrared spectroscopy [22][23][24] have been used and provided evidence for the pressure-induced structural phase of SWNTs. With the pressure increasing, it is suggested that the nanotube cross-section changes from circular to oval, elliptical, polygonized, or flattened shape.…”

Pressure‐induced phenomena in single‐walled carbon nanotubes: Structural phase transitions and the role of pressure transmitting medium

“…The background‐subtracted absorbance spectra as a function of pressure are presented in Fig. 2 for different pressure transmitting media 5. The absorption bands labeled S 11 , S 22 , and M 11 correspond to interband transitions between the Van Hove singularities in the density of states.…”

“…Recently, it was shown that also infrared spectroscopy is a very useful experimental technique to observe the signatures of the pressure‐induced deformation of SWCNTs 4–8: The optical transitions between the Van Hove singularities in the density of states exhibit an anomaly in the pressure‐induced shift at around 2 GPa, where the nanotubes change their shape from circular to oval or ellipse‐like. Pressure‐dependent infrared transmission studies for various pressure transmitting media 5 could also clarify that the pressure‐induced anomaly is qualitatively independent of the pressure transmitting medium used.…”

Raman and IR spectroscopic characterization of molybdenum disulfide under quasi‐hydrostatic and non‐hydrostatic conditions

“…Figure c and d show the evolution of Raman spectra under quasi‐hydrostatic and non‐hydrostatic conditions at different pressures. Similar to analogous materials, the () modes of both the 2 H c and 2 H a phases are well known to increase with pressure . Three prominent vibrational modes () accessible in MoS 2 were investigated under quasi‐hydrostatic and non‐hydrostatic pressure conditions.…”