Tailoring double‐wall carbon nanotubes? Available to Purchase

Double‐wall carbon nanotubes (DWNTs) are interesting nano‐objects derived from single‐wall nanotubes (SWNTs) whose potentiality for some applications (such as composite reinforcement) are even more promising than for SWNTs. Depending on the respective chirality of the inner and outer SWNTs involved, electronic properties may also vary, with subsequent possible applications in nanotechnology. Up to now, DWNTs were prepared either from catalytically‐enhanced thermal cracking of gaseous hydrocarbons, electric arc, or thermal annealing of C₆₀@SWNTs (peapods). A drawback of the former as opposed to the latter is that DWNTs hardly concern the whole nanotube production as far as they are always mixed with SWNTs and other MWNTs. Whatever, in any DWNT (or MWNT) from the literature so far, the graphene‐graphene distance looks about equal to the d₀₀₂‐spacing in turbostratic, polyaromatic carbon, i.e., ∼0.34 nm. For peapod‐derived DWNTs prepared from regular 1.35 nm wide SWNTs, for instance, it means that the inner diameter is ∼0.7 nm, i.e. that of the former contained C₆₀ molecules before coalescence. We report here the unexpected experimental observation that the inter‐tube distance and/or the inner tube diameter of DWNTs prepared from peapods by combining both electron irradiation and heating may possibly vary. This is likely to interestingly bring variations to the overall electronic properties of DWNTs. On the other hand, it would allow the preparation of SWNTs (the inner tube) with diameters narrower than 0.7 nm, for which no common route exists yet.