Low-Temperature Synthesis of Weakly Confined Carbyne inside Single-Walled Carbon Nanotubes
Abstract
Carbyne, a one-dimensional (1D) carbon allotrope with alternating triple and single bonds, has the highest known mechanical strength but is unstable to bending, limiting synthesis to short linear chains. Encapsulation within carbon nanotubes (CNTs) stabilizes carbyne, forming confined carbyne (CC), thus enabling further research concerning attractive 1D physics and materials properties of carbyne. While CC has been synthesized in multi-walled CNTs (MWCNTs) using the arc-discharge method and in double-walled CNTs (DWCNTs) via high-temperature high-vacuum (HTHV) method, synthesis in single-walled CNTs (SWCNTs) has been challenging due to their fragility under such conditions. In this work, we report a low-temperature method to synthesize CC inside SWCNTs (CC@SWCNT). By annealing SWCNTs containing ammonium deoxycholate (ADC) at 400{\deg}C, ADC is converted into CC without damaging the SWCNTs. Raman spectroscopy revealed a strong CC phonon (CC-mode) peak at 1860-1870 cm^-1, much stronger than the SWCNT G-band peak, confirming a high fraction of CC in the resulting material. The Raman mapping result showed the uniformity of the CC-mode signal across the entire film sample, proving the high efficiency of this method in synthesizing CC in every SWCNT of appropriate size. Notably, the CC-mode peaks of CC@SWCNT (above 1860 cm^-1) are higher than those reported in previous CC@CNT samples (mostly less than 1856 cm^-1). This is attributed to larger SWCNT diameters (over 0.95 nm) used in this study, compared to the typical 0.6-0.8 nm range. Larger diameters result in reduced confinement, allowing carbyne to closely resemble free-standing carbyne while remaining stabilized. This low-temperature synthesis of long-chain, nearly free-standing carbyne within large-diameter SWCNTs offers new opportunities for exploring 1D physics and the unique properties of carbyne for potential applications.
Cite
@article{arxiv.2411.18899,
title = {Low-Temperature Synthesis of Weakly Confined Carbyne inside Single-Walled Carbon Nanotubes},
author = {Bo-Wen Zhang and Xi-Yang Qiu and Yicheng Ma and Qingmei Hu and Aina Fitó-Parera and Ikuma Kohata and Ya Feng and Yongjia Zheng and Chiyu Zhang and Yutaka Matsuo and YuHuang Wang and Shohei Chiashi and Keigo Otsuka and Rong Xiang and Dmitry I. Levshov and Sofie Cambré and Wim Wenseleers and Slava V. Rotkin and Shigeo Maruyama},
journal= {arXiv preprint arXiv:2411.18899},
year = {2024}
}