Probing Charge Transfer between Shells of Double‐Walled Carbon Nanotubes Sorted by Outer‐Wall Electronic Type

Abstract

Double-walled carbon nanotubes (DWCNTs) with outer metallic (M) or semiconducting (S) shells were sorted by density-gradient ultracentrifugation and examined by Raman spectroscopy and in situ Raman spectroelectrochemistry. The combination of sorting and the selection of appropriate laser excitation energies allowed the disentanglement of the effects of different variations of the electronic type (M or S) of the inner and outer tubes in DWCNTs on the doping behavior and charge transfer between the inner and outer walls. Charge transfer from the outer tube to the inner tube occurs only if the electronic states of the outer tube are filled with electrons or holes, and if these filled states are higher in energy than those of the inner tube. Therefore, each combination of inner and outer tube (i.e., inner@outer: M@M, M@S, S@M, and S@S) exhibits a distinct behavior. The potential needed to observe the effects of charge transfer between the inner and outer tubes is found to increase in the following order: M@M < S@M < M@S < S@S.

Mass-related inversion symmetry breaking and phonon self-energy renormalization in isotopically labeled AB-stacked bilayer graphene

“…This is consistent with previous calculations by Das17 and experiments by Fang et al 22. We also note that a similar situation happens in the case of double wall carbon nanotubes where both outer and inner tubes are metallic and only the outer tube is contacted by the electrode31. The in-situ Raman spectroelectrochemical measurements on the latter samples also demonstrated that there is more charge located on the outer tube than on inner tube31.…”

“…2 and 4(b) is, indeed, a S and AS mixing of the E g and E u modes distinctly observed only when the inversion symmetry exists, like is the case for 12/12 C AB-2LG. This mixing of the E g and E u modes has also been observed for 12/12 C AB-2LG when the latter is under the effect of an electric field31. Indeed, this mass-related symmetry breaking is confirmed by the electrochemistry measurements.…”

Intra- and Interlayer Electron-Phonon Interactions in 12/12C and 12/13C BiLayer Graphene

“…This is consistent with previous calculations by Das et al [80] and experiments by Fang et al [11]. We also note that a similar situation happens in the case of double wall carbon nanotubes where both outer and inner tubes are metallic and only the outer tube is contacted by the electrode [87]. In order to understand the results obtained here for the LG and HG modes in 12/13 C AB-2LG, we must, as stated earlier in the text, recall that the inversion symmetry in 12/13 C AB-2LG is naturally broken due to the different 12 C and Based on Gava et al [10] and noting that due to conventions related to electrochemistry experiments, positive (negative) electrode potentials means that the E F is decreasing (increasing), Araujo et al [75] concluded that n bottom > n top .…”

Double-Wall Carbon Nanotubes for Wide-Band, Ultrafast Pulse Generation

“…58 With a semiconducting outer tube for s - s and s - m combinations, optical absorption from excitonic transition energies of both the inner and outer walls is expected to contribute to the overall optical absorption of the resultant DWNT structure, making them suitable as wide-band SAs. Conversely, with metallic outer wall for the m - s and m - m combinations, the outer wall has zero band gap with wide absorption range and may create a screening effect, 59 suppressing optical absorption from the inner s - or m -nanotubes.…”