Coalescence of carbon nanotubes while preserving the chiral angles.

Takakura, Akira; Nishihara, Taishi; Harano, Koji; Cretu, Ovidiu; Tanaka, Takeshi; Kataura, Hiromichi; Miyauchi, Yuhei · Nat Commun · 2025

basic_science · Level V

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Abstract

Atomically precise coalescence of graphitic nanocarbon molecules is one of the most challenging reactions in sp<sup>2</sup> carbon chemistry. Here, we demonstrate that two carbon nanotubes with the same chiral indices (n, m) are efficiently coalesced into a single (2n, 2 m) nanotube with preserved chiral angles via heat treatment at less than 1000 °C. The (2n, 2 m) nanotubes constitute up to ≈ 20%-40% of the final sample in the most efficient case. Additional optical absorption peaks of the (2n, 2 m) nanotubes emerge, indicating that the reaction occurs over the entire sample. The reaction efficiency strongly depends on the chiral angle, implying that C-C bond cleavage and recombination occurs sequentially. Furthermore, the reaction occurs efficiently even at 600 °C in an atmosphere containing trace amounts of oxygen. These findings offer routes for the structure-selective synthesis of large-diameter nanotubes and modification of the properties of nanotube assemblies via postprocessing.