I'm trying to analyse my Raman spectra of reaggregated graphene samples for any signs of functionalisation, and I know this can normally be deduced from the ratio of the D to the G peaks and the change in intensity of the D peak and the shoulder of the G peak (G'?).
What I want to ask for help with is what changes in the small peak at ~2440 cm-1, before the 2D peak mean? The intensity increased relative to the other peaks in a couple of my spectra but I can't find anything about it in the literature other than it being labelled D+G'' or something similar.
I haven't looked past 3100 cm-1 in my spectra either but is there any other information about the small peak at 3300 cm-1 too? Or should these only change with whichever of the main peaks its related to?
In basic terms Raman spectroscopy gives you and idea of vibrational modes within your material. So when a peak is labeled D+G' it means it comes from a coupling of the 2 vibrational modes, with a Raman shift that is generally the sum of the other two peaks.
I've also found that the published Raman data on graphene and graphene based materials is not always the best and often comes with a lot of contradicting claims. Although this seems to be getting better with newer publications, so I would take any explanation and claims found in publications with a grain of salt and an objective eye.
Ratios between the D and G peak only really tell you about the amount of disorder and defects within the graphene lattice. Functionalization groups will ofcourse introduce defects within the lattice, however it can be hard to figure out if your D/G ratio comes from these functionalized groups or just from an increase in other defects, especially from a reaggregated sample as I imagine will consist of many graphene flakes with a lot of edge effects.
The 2440cm-1 peak seems to be a combination of the D and D" peaks, so it should be affected by whatever affects the D and the D" peaks. (not necessarily in the same manner)
If you want to quantify the amount of functionalization on your sample, I would try to directly measure your fonctionalized groups. Depending, on what those functionalized groups are and the amount of functionalization , you can most likely find a weak Raman peak associated with these groups. G/D peak ratios are probably a crapshoot unless you have functionalized prestine monolayered graphene. (I know a lot of people use the D/G ratio to quantify their functionalization, but I have come to not trust these results in most cases for the reason stated above). Think about it this way: what is the variation of the amount of edges in your graphene sample compared to the amount of functionalization?
I hope this helps you a bit even tho this looks more like a non-answer.
In basic terms Raman spectroscopy gives you and idea of vibrational modes within your material. So when a peak is labeled D+G' it means it comes from a coupling of the 2 vibrational modes, with a Raman shift that is generally the sum of the other two peaks.
I've also found that the published Raman data on graphene and graphene based materials is not always the best and often comes with a lot of contradicting claims. Although this seems to be getting better with newer publications, so I would take any explanation and claims found in publications with a grain of salt and an objective eye.
Ratios between the D and G peak only really tell you about the amount of disorder and defects within the graphene lattice. Functionalization groups will ofcourse introduce defects within the lattice, however it can be hard to figure out if your D/G ratio comes from these functionalized groups or just from an increase in other defects, especially from a reaggregated sample as I imagine will consist of many graphene flakes with a lot of edge effects.
The 2440cm-1 peak seems to be a combination of the D and D" peaks, so it should be affected by whatever affects the D and the D" peaks. (not necessarily in the same manner)
If you want to quantify the amount of functionalization on your sample, I would try to directly measure your fonctionalized groups. Depending, on what those functionalized groups are and the amount of functionalization , you can most likely find a weak Raman peak associated with these groups. G/D peak ratios are probably a crapshoot unless you have functionalized prestine monolayered graphene. (I know a lot of people use the D/G ratio to quantify their functionalization, but I have come to not trust these results in most cases for the reason stated above). Think about it this way: what is the variation of the amount of edges in your graphene sample compared to the amount of functionalization?
I hope this helps you a bit even tho this looks more like a non-answer.
If the detector works above 3,000 cm-1 there is not a reason to stop there. There are references for Raman lines of defected graphene above 3,000 cm-1.
This link is really useful,
http://www.instanano.com/characterization/experimental/raman-graphene/
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Carbon Materials
- Graphite
- Graphene