CNT Raman ratio of G band to 2D band?

I believe that the G band (~1600 cm-1) shows the stretching mode of the graphene in a carbon nanotube (e.g. chiral, zigzag, armchair) and the 2D band (~2680 cm-1) shows the number of walls in the CNT. I vaguely remember there is some information that can be gleaned from the ratio of the two. Is this the case? 




I think there might be a mistake in your question...


Around $\pu{2680 cm-1}$, there is the $S\_1$ band (attributed to overtone or combination scattering). I think the $2D$ band you are referring to is the band shouldering the $G$ band (also called $D'$) which is around $\pu{1680 cm-1}$.


About the ratio, there are two ratios that are often used to characterise $\mathrm{sp^2}$ carbon based materials such as the CNT.
$$\text{Intensity ratio} = R\_1 = \frac{I(G)}{I(D)}$$
$$\text{Area ratio} = R\_2 = \frac{A(G)}{A(G)+A(D)+A(D')}$$


Both these ratios help characterise the degree of organization of your sample.


For more information or more details, I would recommend checking out [*Spectrochim. Acta, Part A* **2003,** *59* (10), 2267–2276](https://doi.org/10.1016/S1386-1425(03)00070-2)


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