Hi....
Can any one comment on this?
Actually graphene based materials (graphene, graphene oxide, reduced graphene oxide) shows an exponential decay type absorption from shorter to longer wavelength. Is it related to the Boltzmann distribution of particles or any other mechanism. As we know that graphene is a nearly zero band gap material. It can absorb even a small energy (longer wavelength) of photons . While going to the towards shorter wavelength (high energy) absorption increase rapidly looks like exponential increment.
You have a largely conjugated system that shows absorption peaks related with the transitions in pi bonds. Other absorption peaks could come from the modified structures, ie in decorated graphenes or functional groups in GO (they do indeed). I feel, not being an expert on optics and solid state physics, that the extended absorption with the exponential behavior in the visible and IR ranges would arise from scattering of optical and acoustic phonons in the conjugated, quasiinfinite graphene sheet, more than optical scattering due to particle sizes, as much as the same absorption in single sheet graphene films is observed.
Thank you sir (Roy),
Yes, I observed same thing for SWCNTs also. In case of graphene I went low concentration upto 12 ug/ml. Still I observed the similar trend as the case showed at 1mg/ml of graphene. Also, I have to check the flake size of graphene sheets
The samples we were studying made by the chemical synthesis.
One more point about the scattering at longer wavelength. Actually our spectrometer basically measure the transmittance from there it convert to the absorption spectrum. So instead of absorption we can say the extinction spectra of the graphene.
Extinction = Abs+scattering
If I real measure the absorption spectra and scattering contribution is more at longer wavelength, then absorption may shows exponential decay.
I hope, In my case spectrometer giving the extinction spectra. So it may not change with wavelength!!!
Please comment!!!
Dear Sudhakar
Please check the attached paper. We did some transmittance measurements and calculate the extinction coefficients, I hope it is useful.
Sure....sir, I will come to soon with some feed back...
Thanks,
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