Pressure-induced structural transformations on linear carbon chains encapsulated in carbon nanotubes: A potential route for obtaining longer chains and ultra-hard composites

Anti-Stokes Raman Scattering of the Smallest Carbon Nanowires Made of Long Linear Carbon Chains Inserted inside Single-Walled Carbon Nanotubes

“…While, the L S band that belongs to LLCCs had a significant variation in its peak position, with a total variation of 28 cm –1 when the temperature changed from 80 to 850 K. This kind of peak position variation of L S bands with the temperature should be mainly due to changing the carbon atom distance of linear carbon chains (the bond length alternation, BLA) and a lower temperature means a smaller BLA and will lead to a lower Raman peak position. A similar result had been found for LLCCs@DWCNTs under high pressures, a higher pressure could generate a smaller BLA, resulting in a downshift of L bands. − The effect of a lower temperature on the BLA of LLCCs is comparable to that of higher pressure, which can also make LLCCs to have a smaller BLA. In addition, the iTOLA band, which were only seen in Stokes of LLCCs@SWCNTs, also showed a shift from 1936 to 1920 cm –1 .…”

“…Even though MWCNWs (LLCCs@MWCNTs) were first discovered in 2003, until now the means of characterization are only the Raman scattering and HRTEM. The purpose of research studies has still been the preparation and confirmation of LLCCs@MWCNT samples, as well as some of high-pressure research studies on LLCCs@MWCNT samples have been carried out. , Compared with MWCNWs (LLCCs@MWCNTs), the studies of DWCNWs (LLCCs@DWCNTs) encapsulating LLCCs have made great progress in the research studies on preparation, structure, and physical properties due to the high purity of samples and two layers of graphene encapsulating LLCCs; even though, DWCNW (LLCCs@DWCNTs) samples were first synthesized and affirmed in 2011, , and LLCCs@DWCNTs containing the LLCCs with >6000 carbon atoms were successfully obtained in 2016. The L-band of LLCCs inside DWCNTs has been proved to possess the highest resonant Raman scattering cross section per atom, exceeding that of any other known material or molecule, and the anti-Stokes Raman spectra of L-band from single LLCCs have been successfully observed by the TERS setup for the first time .…”

Raman spectroscopy of isolated carbyne chains confined in carbon nanotubes: Progress and prospects

“…Adapted from Ref. [51]. (e) Depiction of a mechanically stable 3D structure of confined carbyne under compressing pressure suggested by Argaman and Makov.…”

“…[50] The fact that several competing models of the mechanics of carbyne are being put forward in the literature highlights the need to generate experimental data to test the predictions of the corresponding models. So far, the main source of experimental data on the mechanical properties of confined carbyne has focused on the compression of encapsulated chains with hydrostatic pressure, [36,51,54] see Section 4.2.3. In these works, carbyne's Raman active C-mode tracks the structural changes in the chain, while the G-band of carbon nanotubes reports structural changes in the tubes.…”

“…A series of works on the change of the Raman signatures of LCCs encapsulated in DW-and MWCNTs under hydrostatic pressure represent the first experimental realization of external tuning of confined carbyne's electronic and vibrational properties. [16,18,36,51,54] In these experiments, confined carbyne samples are placed inside a diamond anvil cell (DAC) filled with a pressure-transmitting fluid, typically Nujol mineral oil, that transforms the uniaxial pressure from the DAC in uniform hydrostatic pressure. A ruby sensor placed inside the cell allows to calibrate the pressure by tracking the variation of ruby's luminescence lines.…”