The unique mechanical, optical, and electrical properties of carbyne, a one-dimensional allotrope of carbon, make it a highly promising material for various applications. It has been demonstrated that carbon nanotubes (CNTs) can serve as an ideal host for the formation of confined carbyne (CC), with the yield being influenced by the quality of the carbon nanotubes for confinement and the carbon source for carbyne growth. In this study, a robust synthesis route of CC within CNTs is proposed. C₇₀ was utilized as a precursor to provide an additional carbon source, based on its ability to supply more carbon atoms than C₆₀ at the same filling ratio. Multi-step transformation processes, including defect creation, were designed to enhance the yield of CC. As a result, the yield of CC was significantly increased for the C₇₀ encapsulated single-walled CNTs by more than an order of magnitude than the empty counterparts, which also surpasses that of the double-walled CNTs, making it the most effective route for synthesizing CC. These findings highlight the importance of the additional carbon source and the optimal pathway for CC formation, offering valuable insights for the application of materials with high yield.

Armchair graphene nanoribbons (AGNRs) with sub-nanometer width are potential materials for the fabrication of novel nanodevices thanks to their moderate direct band gaps. AGNRs are usually synthesized by polymerizing precursor molecules on substrate surface. However, it is time-consuming and not suitable for large-scale production. AGNRs can also be grown by transforming precursor molecules inside single-walled carbon nanotubes (SWCNTs) via furnace annealing, but the obtained AGNRs are normally twisted. In this work, microwave heating is applied for transforming precursor molecules into AGNRs. The fast heating process allows synthesizing the AGNRs in seconds. Several different molecules were successfully transformed into AGNRs, suggesting that it is a universal method. More importantly, as demonstrated by Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy and theoretical calculations, less twisted AGNRs are synthesized by the microwave heating than the furnace annealing. Our results reveal a route for rapid production of AGNRs in large scale, which would benefit future applications in novel AGNRs-based semiconductor devices.