Direct Realization of Near-Ideal Carbyne in Ultrathin Boron Nitride Nanotubes
Abstract
Carbyne, the sp-hybridized one-dimensional allotrope of carbon, is predicted to be the stiffest known material, with electronic and optical properties set by a single structural parameter, the bond length alternation. However, its intrinsic properties have never been measured: chains synthesized through molecular chemistry carry endgroup and finite-length perturbations that persist even in the longest molecules available, while chains grown inside carbon nanotubes strongly couple to the host, which renormalizes their vibrational frequency by up to 110 cm−1 in a diameter-dependent manner. Here, we show that encapsulating and thermally converting hydrogen-capped polyynes inside ultrathin boron nitride nanotubes, structural analogues of carbon nanotubes but electrically insulating, yields carbyne chains in a near-ideal regime, where endgroup, finite length, and host-guest perturbations are reduced to secondary effects. Statistical Raman spectroscopy across 245 locations returns a vibrational frequency distribution an order of magnitude narrower than in carbon nanotubes, an anharmonicity consistent with the universal law for carbyne-like materials, and a bond length alternation matching correlated calculations for the free chain. No photoluminescence is detected, despite the transparent host, as expected for the dipole-forbidden emission of an unperturbed carbyne chain. Boron nitride nanotubes give experimental access to carbyne in its near-ideal form.
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BibTeX
@misc{ivanenko2026direct,
title = {{Direct Realization of Near-Ideal Carbyne in Ultrathin Boron Nitride Nanotubes}},
author = {Iryna Ivanenko and Pietro Marabotti and Yifan Zhang and Getulio Silva e Souza Júnior and Johannes M. A. Lechner and Pablo Hernández López and Martin Magg and Shivani Shivaprakash and Carlo Spartaco Casari and Sebastian Heeg and Benjamin S. Flavel},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.07443},
eprint = {2609.07443},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.07443},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Direct Realization of Near-Ideal Carbyne in Ultrathin Boron Nitride Nanotubes
AU - Iryna Ivanenko
AU - Pietro Marabotti
AU - Yifan Zhang
AU - Getulio Silva e Souza Júnior
AU - Johannes M. A. Lechner
AU - Pablo Hernández López
AU - Martin Magg
AU - Shivani Shivaprakash
AU - Carlo Spartaco Casari
AU - Sebastian Heeg
AU - Benjamin S. Flavel
PY - 2026
DA - 2026/09/07
PB - arXiv
DO - 10.48550/arxiv.2609.07443
UR - https://arxiv.org/abs/2609.07443
AB - Carbyne, the sp-hybridized one-dimensional allotrope of carbon, is predicted to be the stiffest known material, with electronic and optical properties set by a single structural parameter, the bond length alternation. However, its intrinsic properties have never been measured: chains synthesized through molecular chemistry carry endgroup and finite-length perturbations that persist even in the longest molecules available, while chains grown inside carbon nanotubes strongly couple to the host, which renormalizes their vibrational frequency by up to 110 cm^−1 in a diameter-dependent manner. Here, we show that encapsulating and thermally converting hydrogen-capped polyynes inside ultrathin boron nitride nanotubes, structural analogues of carbon nanotubes but electrically insulating, yields carbyne chains in a near-ideal regime, where endgroup, finite length, and host-guest perturbations are reduced to secondary effects. Statistical Raman spectroscopy across 245 locations returns a vibrational frequency distribution an order of magnitude narrower than in carbon nanotubes, an anharmonicity consistent with the universal law for carbyne-like materials, and a bond length alternation matching correlated calculations for the free chain. No photoluminescence is detected, despite the transparent host, as expected for the dipole-forbidden emission of an unperturbed carbyne chain. Boron nitride nanotubes give experimental access to carbyne in its near-ideal form.
ER -