Isotopic labelling of confined carbyne.

Carbyne is by excellence the one-dimensional allotrope of carbon consisting of a linear chain of carbon atoms bonded to each other with exceptional strength. Its outstanding mechanical, optical, and electronic properties have been theoretically predicted, but its stability has only been achieved when grown encapsulated in the hollow core of doublewalled carbon nanotubes. One of the advantages of this confinement is that its properties can be controlled by the chain's length and surrounding environment. We investigated an alternative way of gaining control of its properties is using isotope labelling as tuning mechanism. This approach has been proven successfully in the other allotropes of carbon (diamond, fullerenes, carbon nanotubes and graphene). However, no report on isotopic labelling of 1D sp 1 -hybridized carbon systems is available. A very long basic carbyne structure in pristine form, whose properties can be followed by the Raman spectral response, is the key ingredient to gain real tunability of carbyne. Here, the optimized liquid precursor was first chosen among several options, which can greatly enhance the yield of the long confined carbyne, then isotopic labelled liquid precursors were encapsulated inside carbon nanotubes as carbon source for further synthesis. This allowed us to obtain pioneering results on isotope engineered carbyne with around 11.9% of 13 C-labelling using 13 C-methanol as precursor.