Nitrogen doping of confined carbyne

Low-dimensional carbon allotropes belong to the most revolutionary materials of the last decades. The latest materialization of confined carbyne, a linear chain of sp1-hybridized carbon encapsulated inside a small-diameter carbon nanotube host, is one extraordinary nano-engineering example. Inspired by these hybrid structures, in this work, we demonstrate the feasibility to synthesize nitrogen-doped confined carbyne by using azafullerene (C59N) molecules encapsulated in nanotubes ("peapods") as precursors for the growth of confined carbyne. Resonance Raman spectroscopy as a site selective local probe has served to identify the changes in the spectra of nitrogen-doped versus pristine carbon peapods and confined carbyne. We are able to disentangle the frequency change due to charge transfer from the change due to the difference in mass for both the nanotube and the carbyne chain. We observe that the changes in the nanotube are dominated by the mass effect and the changes for confined carbyne are dominated by charge transfer. This study demonstrates a suitable pathway to achieve controlled doping of carbyne chains via using specifically doped precursors.