Controlling chirality in growth of single-walled carbon nanotubes (SWNTs) is important for exploiting their practical applications. For long it has been conceptually conceived that the structural control of SWNTs is potentially achievable by fabricating nanoparticle catalysts with proper structures on crystalline substrates via epitaxial growth techniques. Here, we have accomplished epitaxial formation of monometallic Co nanoparticles with well-defined crystal structure, and its use as a catalyst in the selective growth of SWNTs. Dynamics of Co nanoparticles formation and SWNT growth inside an atomic-resolution environmental transmission electron microscope at a low CO pressure was recorded. We achieved highly preferential growth of semiconducting SWNTs (~90%) with an exceptionally large population of (6, 5) tubes (53%) in an ambient CO atmosphere. Particularly, we also demonstrated high enrichment in (7, 6) and (9, 4) at a low growth temperature. These findings open new perspectives both for structural control of SWNTs and for elucidating the growth mechanisms.

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Single-walled carbon nanotubes (SWCNTs) have unique electronic and optical properties, which are attractive in various applications. These properties can be further improved by functionalization. In this work, it is shown that filling nanotubes with CuCl leads to improvement of their electro-conductive and optical transmission properties up to outstanding level. The improvement is due to the significant p-type doping of the functionalized nanotubes. That leads to a huge increase in nanotubes charge carrier density and the considerable decrease of the nanotubes absorption via Pauli blocking. The functionalization was realized via a gas-phase filling of SWCNTs with CuCl. We demonstrate the effect of huge doping on optical properties of nanotubes with different average diameters. The observed sufficient stability of the CuCl@SWCNT composite is proved to be due to the formation of quasi-one-dimensional (1D) CuCl crystal inside nanotubes.AC-HRTEM image of 1D CuCl crystal formed inside SWCNT.