Engineering external and internal precursors to boost the synthesis of confined carbyne

Single-walled carbon nanotubes (SWCNTs) serve as ideal templates for synthesizing inner tubes with engineered diameters, resulting in the formation of double-walled carbon nanotubes (DWCNTs). This approach enables the synthesis of confined carbyne (CC) with tailored properties through the newly formed inner tubes. The formation of CC primarily relies on carbon sources derived from the SWCNTs themselves via structure reconstruction under high-temperature annealing, leading to inherently low yield of CC due to insufficient carbon supply. To enhance the yield of CC, we explored the introduction of internal carbon sources, which are small enough to be inserted inside the SWCNTs, such as organic solvents or fullerene molecules; however, further improvements remain challenging. In this study, we demonstrate that incorporating external carbon sources via surfactants on the walls of SWCNTs significantly increases the yield of CC. The surfactants decompose at high temperatures, releasing carbon atoms that integrate into both the DWCNT structure and the CC; thus, the Raman intensity of CC increased by approximately 2.1 times compared to the empty counterpart. Moreover, combination of external surfactants and internal C 70 results in an ultrahigh Raman intensity of CC, exhibiting value approximately 30 times greater than that of the pristine SWCNTs. These findings underscore the potential of engineered both external and internal precursors to boost the synthesis of CC, benefiting their applications.