Controlled isotope arrangement in 13C enriched carbon nanotubes

We report the synthesis of a novel isotope engineered $^{13}{\rm C}$--$^{12}{\rm C}$ heteronuclear nanostructure: single-wall carbon nanotubes made of ${}^{13}\mathrm{C}$ enriched clusters which are embedded in natural carbon regions. The material is synthesized with a high temperature annealing from ${}^{13}\mathrm{C}$ enriched benzene and natural ${\mathrm{C}}_{60}$, which are co-encapsulated inside host SWCNTs in an alternating fashion. The Raman 2D line indicates that the ${}^{13}\mathrm{C}$ isotopes are not distributed uniformly in the inner tubes. A semi-empirical method based modeling of the Raman modes under ${}^{13}\mathrm{C}$ isotope enrichment shows that experimental data is compatible with the presence of ${}^{13}\mathrm{C}$ rich clusters which are embedded in a natural carbon containing matrix. This material may find applications in quantum information processing and storage using nuclear spins as qubits.