Hello,
I have taken raman spectra from my nanocomposite comprising Active carbon , graphene oxide and nano zero-valent iron (nZVI). The concentration of nZVI is fixed in all the samples attached in the plot. The level of active carbon and graphene oxide is variable in the samples. In the attached graph, the legend part the first number indicates the active carbon and the second number indicates graphene oxide. I am not an expert in the interpretation of raman spectra and would appreciate it if somebody can suggest what has happened with the increase of graphene oxide as the intensity of D & G bands are decreased with the addition of graphene oxide content. Also, in the sample WS:400/400 the D & G bands demonstrate two sharp peaks compared to the other samples.
Thanks.
Considering the complexity of the carbon-based materials and their impact on the Raman spectra, the interpretation of the Raman spectra can be more reliable when it is combined with other relevant information such as EDX data, XPS, AFM, etc. A simple & incomplete analysis of the Raman spectra you have shared may include: (I) Graphene: show two major Raman peaks G-band at 1580 (cm-1) and 2D-band at 2690 (cm-1). (II) Disordered graphene: enhanced Raman intensity for disorder peaks D-band at ~1350 (cm-1), D´-band at ~1620 (cm-1) & D+G at ~2940 (cm-1). The intensity ratio of D-Band to G-band represent the degree of disorder.
(III) the first order Raman peaks for Graphite, Graphene oxide and reduced Graphene oxide are different (e.g., see Fig 5 in https://www.physics.purdue.edu/quantum/files/Raman_Spectroscopy_of_Graphene_NOVA_Childres.pdf). The intensity ratios in your spectra may suggest the presence of GO in case of WS 300/600 sample (when intensity of 1587 is greater than that for the 1350 line) while WS 440/400 and WS 600/300 may suggest the presence of reduced GO (considering the intensity of 1350 being greater than the higher energy peak)
(IV) you may also look at the 2D and D+G bands that are closer to 2700 cm-1 region. The shape of those lines (especially if you can deconvolute them) can provide additional information about the materials such as number of layers of graphene, degree of disorder, etc. The number of Graphene layers impact both the G-band and the 2D-band, and I think the difference in the Raman peak at 1587 cm-1 vs. 1592 cm-1 suggest differences in the number of graphene layers present in your sample. (e.g., see https://www.intechopen.com/books/raman-spectroscopy/graphene-nanocomposites-studied-by-raman-spectroscopy
(V) Also, the excitation line you use (e.g. 488 nm, 532 nm, 632.8 nm, etc.) impact the shape and intensity of the Raman peaks measure. (e.g., see https://pubs.rsc.org/en/content/articlehtml/2018/cs/c6cs00915h
I am not sure why you see a peak at 1571 cm-1, and I have not seen a Raman peak at that frequency for these materials.
Hi Iman Katouzian,
I agree with Bahram Roughani. According to the results of Raman spectroscopy, it may be wrong to interpret the structure alone. Therefore, I think that EDX, XRD and FTIR tests should be done.
In Raman spectroscopy, the first peak represents irregular regions (D band) and the second peak refers to regular regions (G band). By proportioning the regions (ID / IG), we can hypothesize about which particular structures the materials belong to. For carbon-based materials, for example, this ratio is considered to be 0.95-1.22 (https://doi.org/10.1016/j.ssc.2007.03.052 and https://doi.org/10.1021/jp107131v ).
You can make an inference by proportioning the intensity of D and G band of your samples. The intensity (a.u.) of the graph is not exactly seen, but to measure sloppy.
GO, ID/IG: 625/640 = 0,977
WS600/300, ID/IG: 247/221 = 1,118
WS400/400, ID/IG: 455/410 = 1,110
WS300/600, ID/IG: 100/105 = 0,952
Your GO sample is a carbon-based material, which can be compared to the ID/IG ratios of GO in different studies.
The increase of the ID/IG ratio can be interpreted as the increase of irregular regions. Therefore, irregular regions of the material decreased as the amount of GO increased. It could be said otherwise. In other words, as the amount of GO increased, the degree of disorder of the material decreased.
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