This question was already asked (and answered):

https://www.researchgate.net/post/Why_is_in_Raman_is_laser_of_wavelength_785_nm_not_compatible_with_graphene

Actually, there are two main peaks in the Raman spectra of Graphene, G band and G' band. The G band is not sensitive to the laser energy, but the G' band is sensitive. Please read our paper , https://ac.els-cdn.com/S0008622314009907/1-s2.0-S0008622314009907-main.pdf?_tid=aa91de38-2e34-440e-8f25-043e2f5a4ddf&acdnat=1525663161_ebcb2406eeafa7c438570caff75f7a90

Thank you

Theoretically, Raman is not wavelength dependent. You should see the same Raman signal at all wavelengths. However, if the incident light energy matches with the electronic excitation energy of the material, one can get a better signal (Resonance Raman).

thank you very much everyone for all your kind help

Hi,

Please check attached papers for clear understanding. It was observed that the relative peak intensities of the G′ mode to the G mode increase with decreasing laser excitation energy. The shift in peak values was also noticed on excitation with different wavelength laser.

Article Deep-ultraviolet Raman scattering studies of monolayer graph...

Article The SERS study of graphene deposited by gold nanoparticles w...

https://www.nature.com/articles/nnano.2013.46

Good Luck

very useful question and answers. Thank you

Thank you all for your kind help