Examinations Conducted, Their Assessment by the Person Conducting Them and the Literature

Of a small portion of the product, Raman pictures were taken at a department of Budapest University of Technology and Economics (BMGE). On the basis of the pictures and the referred-to literature, staff at the department claim the product is not FLG but graphite, and in the case of two samples, it is also so-called pyrolitic coal.

The reason for this is that in the pictures peak 2D is at a higher position than, according to the literature referred to, in the case of graphene and also where in the case of graphite peak 2D is too low compared to peak G, which means the same thing.
The height of peak D, which is typical of structural faults, gave contradictory results, as on some curves it is very low, while on others it is high.    However, compared with substance Nature to be seen here,

Rate

Number of layer G / D Evaluation G / 2D Evaluation
1 2.75 0.53
2 5 1.15
3 16.5 2.55
> 4 112 14
1, 3 3.34 1- 2 1.8 2 – 3
2.27 1 2.11 2 – 3
0.85 1 2.37 2 – 3
2, 4 3.37 1- 2 2.15 2 – 3
4.55 1- 2 2.27 2 – 3
1.25 1 2.2 2 – 3

Thus, even in the most unfavorable case the result is FLG of two or three layers. The reason for the difference is supposed to be that our samples were examined at a wavelength of 532 mm, similarly to substance Nature, while in the other case a wavelength of 633 mm was applied.

Another portion of the product was examined at Szeged University in southern Hungary. Here, the product of a different kind of production was also examined, with the product called “rest”.

These results are the following:

1, 3 185 192 114
2, 4 * 201 164   62
2, 4 191 182 105
Rest 126 155   44
Rate
Name G / D Evaluation G / 2D Evaluation
1, 3 1,04 1 1,68 2 – 3
2, 4 * 0.82 1 2,65 3
2, 4 0.95 1,73 2 – 3
Rest 1.23 3,52 3 – 4

Data considerably differing from those above have also been published by the literature.

For example, Sci Rep. 2013; 3: 1195. Visualization of arrangements of carbon atoms in graphene layers by Raman mapping and atomic-resolution TEM

According to the article written by Chunxiao CongKun LiXi Xiang Zhang, and Ting Yu:

Number of layer D G 2D
2   8 133 145
3 31 133 135
Rate
Number of layer G/D G/2D Evaluation
2 16.6 3 0.92
3 4.29 1 – 2 !!

In the article Spatially resolved Raman spectroscopy on single- and few-layer graphene, by D. Graf, F. Molitor, and K. Ensslin, published in Solid State Physics (Zurich):

Number of layer D G 2D
graphite 1 194 84
1   35 53
2 102 38
Rate
Number of layer G/D G/2D Evaluation
graphite 194  > 4 2.31 2 – 3 !!
1 0.66 1
2 2.68 3

Raman Imaging of Single-layer and Multilayer Graphene

mlg_flg11

Number of layer D G 2D
1   33 96
2   67 62
3   91 54
4 116 59
Rate
Number of layer G/D G/2D Evaluation
1 0.34 1
2 1.08 2
3 1.65 2 – 3
4 1.97 2 – 3 !!
  1. Phys. Chem. C 2008, 112, 10637-10640.
Number of layer D G 2D
1   18 41
2   29 24
3   41 27
4   60 33
Rate
Number of layer G/D G/2D Evaluation
1 0.44 1
2 1.21 2
3 1.52 2 – 3
4 1.82 2 – 3 !!

Thus, these are completely different from the referred-to substance Nature, and in some cases contradict even each other.

Is it possible at all to establish on the basis of the peak proportion of G / 2D whether

  • the carbon sample examined contains single-layer or multilayer grapheme or not,
  • and if yes, how many layers it has?

Is it certain that the type of carbon whose peak is where G and 2D are is graphene or graphite?

Endre Simonyi