How can i calculate the peak shift of a material if there are two different lasers being used to study the same material.
It depends upon the vibrational modes/characteristics of the material under laser illumination. The dispersive features were similar in the case of graphite and shift was in the range of 1 - 3 cm-1.
#Ram Krishna Sir:---According to A.C.Ferrari group , namely Raman Spectrum of Graphene and Graphene Layers (PRL, 2006) a shift of even 50 cm-1 can be seen in case of graphene if one switch laser from 514 to 633 nm.
#Albert Kh. Kuptsov Sir:---If possible sir can you explain it in more details or any reference to it.
The behavior of graphite is completely different from graphene and both behave differently under the laser source, and their interpretions are also different, so I think it is not appreciable comparing the two. Are you working on graphene?
In GO probably give substantial shift, better you check it or send me it I'll check for you
Hi guys!
As a general rule the position of Raman bands does not depend on the laser energy. Although as already mentioned above, for carbon based materials, specially with sp2 hybridization, there're some bands that change position with laser energy. These dispersive bands i.e.: the D and 2D that have coefficients of 50 and 90 cm-1/eV, respectively, for single layer graphene.
In carbon nanotubes the position of the peaks is also related to the tube diameter. This is partly why Raman spectroscopy is such a powerful method to characterize carbon-based nanomaterials.
#Albert Kh. Kuptsov:--- Sir I am working on graphene oxide and I would like to ask one more question if my GO is thick then in raman spectroscopy is it possible that I will not get GO 2D peak or what possible reason can lead to suppressing of GO peak.
#Raul D. Rodriguez: Sir can you relate it to graphene oxide. I am exploring Raman spectroscopy of graphene oxide also if you can add what peak in Raman i will get in 633nm laser then it would be very useful to me
#Ram Krishna: Thanks for the support sir. Can you give some more ideas about graphene oxide peak by 633nm laser in Raman spectroscopy
It depends on dispersion of quasi-particle on which the Raman scattering is take place. For example, for phonons in crystals, the frequency depends on wave number (reversal wavelength). 514.5 nm is 19436 reversal centimeters (in vacuum), 633 nm is 15798 reversal centimeters (in vacuum). Refractive index is also depends on wavelength, so in media wavenumbers for 514.5 and 633 nm are different. Because of dispersion, frequency of a quasi-particle is also little different. But usually this differense is less than 1 reversed centimeter.
If you represent your peak in terms of Raman shift, the same Raman shift value applies to both 514.5 nm and 633 nm lasers. To calculate the absolute wavenumber, first of all you need to calculate the wavenumber of the laser: (1/laser wavelength)*10^7=laser wavenumber (in cm^-1). Then, simply subtract the Raman shift of your peak from the laser wavenumber. If you repeat the procedure for both lasers you'll end up with two values of absolute wavenumber for your material peak, from which you can calculate the difference.
Pranay, from GO you can obtain the D and G Raman bands, around 1350 and 1585 cm-1, respectively. Contrary to the case of carbon based materials with purely sp2 bonding, in GO these bands are much broader. Remember my comment above, the D band will appear at different positions depending on the laser energy.
In addition to defect concentration, sp2/sp3 ratio, and oxygen content, I just found a paper reporting the layer thickness determination in GO using also Raman! See this link.
http://onlinelibrary.wiley.com/doi/10.1002/jrs.4843/full
#Raul D. Rodriguez: Sir the link is not functioning . Can you again share it or upload the contents of it.
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