Review Reports

Round 1

Reviewer 1 Report

The paper presents a comprehensive study of various carbon (sp2) materials by Raman spectroscopy, in particular the potential of D band analysis. In my opinion the work is very useful for many material science researchers, especially by means of giving various scenarios possible after a complex sample treatment. There are some point, which needs to be addressed prior publication:

English - the style is somewhat plain, but one can understand the text without a serious problem, however separating long sentences would help the readability of the text. There are few cases, where the interpretation of the results is not clear, i.e.:  'It could be due to an average effect due to the addition on crystallite domains of graphene layers with very small La originating
 from elastomer carbonisation. Another origin could be the surfacic functionalisation of the crystallite  by the elastomer functional groups during decomposition. On the other hand, Lc has increased after
 the post-treatments, but it is believed that this is due to the contribution of the carbonised remanants of the elastomer which was not fully eliminated by the treatments and ended by coating the carbon
black nanoparticles.' In this case, additional method or reference to literature would help to identify the most probable scenario (like for the discussion on fitting strategies of kerogens). Why the fit of Raman spectra is not given for Fig 2, 3 c, d; Fig 6, 8, 9, 10?  The XRD results should be checked in context of the work of Rafaja group, which gives much more detailed description for complex shape (i.e.: https://onlinelibrary.wiley.com/doi/full/10.1002/adem.201300157) Typos should be carefully checked, i.e. using automated spell check.

Author Response

We thanks the referee for the valuable comment about carbon blacks (3.2) and consequently, we have changed this paragraph, by simplifying the discussion using the suggested reference (now ref 28) for keeping the most plausible explanation for La and Lc changes.

The paragraph (line 299 to line 306) is now:

“The most probable origin is the surface functionalisation of the crystallite by the elastomer functional groups while being decomposed. L_c has increased after the post-treatments. We have corrected the value by taking into account the new value of L_a [20]. At a constant number of carbon atoms, Dopita et al [28] showed that the shape of the crystalite does not play a role in the linewidth of 002. It is believed that this is due to the contribution of the carbonised remnants of the elastomer which was not fully eliminated by the treatments and ended by coating the carbon black nanoparticles, thereby adding atoms to the crystallite and so leading to the increase of L_c [28].”

For the fits, we are very happy with this remark, because the fits were actually there! But they were so good that they could not discriminate from the experimental lines on fig 6, 8, 9. So, to improve this, we have changed both the markers and the colors. We have also added the decomposition when necessary. In figures 2 and 3, we have changed the color code for avoiding misunderstanding as both figures c and d correspond to figures a and b where the fits are already presented. For figure 10, we have added the fitting of the G+ and G-. Anyway, we prefer not to fit the D band by a sum of asymmetric Lorentzians because discussing in details the exact wavenumbers values is well beyond the scope of this article. Some typos were corrected.

Reviewer 2 Report

In this paper, the Authors discuss the information that can be extracted from the analysis of the Raman spectra of different graphenic carbon materials. Experimental results related to both poorly ordered (gas-shale samples, carbon black, cokes) and highly ordered (carbon cones and isolated single-walled carbon nanotubes) graphenic carbon materials are considered.

The paper is well written and arranged, presenting rigorous analyses and interesting results. In particular, it should be appreciated that the Raman spectra of very different structures among themselves have been studied.

The only gap of this paper, which must be carefully taken into account by the Authors, is related to the single-walled carbon nanotubes (SWCNTs), and in particular to the fact that, for these nano-structures, the Raman spectra can be used also to determine the value of the radial breathing (axisymmetric) modes (RBMs, as only quickly reported on page 14).

Actually, resonant Raman spectroscopy is an experimental technique which allows both the determination of the atomic configuration of SWCNTs (i.e. chirality indices) and the measure of the natural frequencies of RBMs (i.e. frequency of the Raman peaks detected by means of transmission electron microscopes).

Therefore, in order to describe this additional information that can be extracted from the Raman spectra of graphenic carbon materials, the Authors are invited to insert and adequately discuss in the part devoted to SWCNTs the following relevant papers on the RBM oscillations:

1) Rao A.M., Richter E., Bandow S., Chase B., Eklund P.C., Williams K.A. Diameter selective Raman scattering from vibrational modes in carbon nanotubes. Science 275 (1997) 187–91.

2) Strozzi M., Smirnov V.V., Manevitch L.I., Pellicano F. Nonlinear vibrations and energy exchange of single-walled carbon nanotubes. Radial breathing modes. Composite Structures 184 (2018) 613–632.

3) Araujo P.T., Pesce P.B.C., Dresselhaus M.S., Sato K., Saito R., Jorio A. Resonance Raman spectroscopy of the radial breathing modes in carbon nanotubes. Physica E 42 (2010) 1251–61.

4) Jorio A., Saito R., Hafner J.H., Lieber C.M., Hunter M., McClure T. Structural (n,m) determination of isolated single-wall carbon nanotubes by resonant Raman scattering. Physical Review Letters 86 (2001) 1118–1121.

To conclude, in the opinion of the Reviewer, this paper should be accepted for publication by minor revision.

Author Response

Following the referee request, we added a paragraph on the RBMs including the suggested references (refs 36, 37 and 38 in the text). Only the reference 2, which is too much specialized, is withheld. This paragraph is as follows:

Line 457 to line 465 :

"The low wavenumber range is usually used to determine the diameter as the radial breathing mode (RBM) wavenumber is roughly proportional to the inverse to the diameter [36]. When the laser energy meets optical transition energies (incoming resonance) or optical transition energies with, in addition, the phonon energy (outcoming resonance), the intensity of the RBM becomes large. Thus, from the couple of these two parameters (RBM wavenumber and photon energy), we can deduce the chirality (n,m) (which characterizes how the graphene sheet roll-up to form the nanotube). [37] With the amount of observations reported over years, accuracy was improved and the effects from the surrounding have been taken into account [38]."