Optical Properties of 3a-Graphene Nanoribbons in Single-Wall Carbon Nanotubes

Narrow graphene nanoribbons with the width of three carbon atoms and the edge structure of the armchair type (3a-GNRs) are synthesized in inner channels of single-wall carbon nanotubes (SWCNTs) about 1.8 nm in diameter. The method used involves gas-phase filling of nanotubes with 4,4-dibromo-p-terphenyl molecules and subsequent polymerization of individual molecules into graphene nanoribbons inside the tubes. We have established that 3a-GNRs encapsulated in single-wall carbon nanotubes retain their optical and electronic properties. Investigation by the Raman scattering method confirms the structure and high quality of the resulting hybrid systems—3a-GNR@SWCNTs. Like free 3a-GNRs, encapsulated graphene nanoribbons show bright luminescence in the UV/blue and green spectral regions with characteristic features with maxima at the wavelengths of 385 and 555 nm in films and 410 nm in aqueous suspensions of 3a-GNR@SWCNTs. Carbon nanotubes used as containers of graphene nanoribbons allow not only protecting the GNR structure but also individualizing GNRs for subsequent optical measurements. The results are important for further investigations of optical properties of narrow GNR@SWCNTs and practical applications of GNRs in development of photosensitive optoelectronics elements.