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.

Sub-nanometer armchair graphene nanoribbons (GNRs) with moderate band gap have great potential towards novel nanodevices. GNRs can be synthesized in the confined tubular space of single-walled carbon nanotubes (SWCNTs), in which precursor molecules have been specifically designed to form the GNRs with certain width and edge. However, it is still unexplored how the diameter and metallicity of SWCNTs influence the synthesis of the GNRs. Herein, we applied a series of SWCNTs with different average diameters to study the diameter-dependent synthesis of GNRs. By using Raman spectroscopy and transmission electron microscopy, we found that the width of the GNRs can be tailored by the diameter of the SWCNTs. Especially, the SWCNTs with average diameter of 1.3 nm produced 6 and 7 armchair GNRs with the highest yield, which can be well explained by considering the width of the GNRs and van der Waals radius of hydrogen and carbon atoms. In addition, semiconducting and metallic SWCNTs produced GNRs with different yields, which could attribute to different diameter distributions and density of defects. These results enable the possibility of a high-yield production of certain armchair graphene nanoribbons in large scale, which would benefit future applications as semiconductor with sub-nanometer in width.