I have recorded FTIR for reduced graphene oxide and graphite flakes it shows both transmittance and absorption peaks. Whether transmittance peaks are enough, what is the reason for the presence of absorption ?
The spectra are shown as transmission spectra. The numbers say a lot. On one spectrum the scale is approx 52 - 67 percent T. In the second the scale is 90 - 130 T. The main bands going up at 3400 and 1640 cm-1 are consistent with liquid water. However they are going up because they are present in the background spectrum and not in the sample. The effects of these and the water vapour (very sharp bands) are exaggerated by the the spectra being expanded to fit the chart. This also exaggerates the size of the interference fringes which are relatively minuscule. The sloping background is possibly due to scatter from carbon particles. As Gyorgy says we need to know about the sampling technique to give a full answer.
If people are going to ask questions like this they should give details of sample prep, sample presentation, the number of scans and the instrument resolution. All affect the spectrum. Any less information and you will get some well meaning but incomplete answers
What were the test conditions? Film, KBr pellet, reflection or what? The background seems to be awful. What was your background aganst which you measured the spectra? Did you dry and purge well enough the beam path?
I would assume this is a background problem. Make sure the background spectrum is exactly the same matrix/ambient as the actual sample.
The spectra are shown as transmission spectra. The numbers say a lot. On one spectrum the scale is approx 52 - 67 percent T. In the second the scale is 90 - 130 T. The main bands going up at 3400 and 1640 cm-1 are consistent with liquid water. However they are going up because they are present in the background spectrum and not in the sample. The effects of these and the water vapour (very sharp bands) are exaggerated by the the spectra being expanded to fit the chart. This also exaggerates the size of the interference fringes which are relatively minuscule. The sloping background is possibly due to scatter from carbon particles. As Gyorgy says we need to know about the sampling technique to give a full answer.
If people are going to ask questions like this they should give details of sample prep, sample presentation, the number of scans and the instrument resolution. All affect the spectrum. Any less information and you will get some well meaning but incomplete answers
It may be due to a background problem due to some moisture in KBr. Make sure the background spectrum is of Pure KBr matrix and cross matching with their reported one. Even though if their is an appearance of same features then decrease the concentration of your compound. Some time i also faced same problem with carbon based nanostructures because of their intense color.
Dear Prakash,
I observed your result and, apparently, you have problems wiht the blank brackground. The spectrometer, usually, collect a blank brackground to be subtracted/divided by the sample spectrum. When you have problems in blank background, this will be reflected in the sample spectrum. I suggest you improve your purge gas inside the spectrometer in order to smooth the blank background. This will extract the peaks (in a transmittance spectrum) or the valleys (in an absorbance spectrum). Also, you can optimize the number of scans/velocity to maximize the sample spectrum! Finally, independently what sample techinique you using, you need have a good sample! Roughness, particulates, low transparency, scatter centers and other let your sample spectrum poor.
thanks every body for your valuable comments, i have also recorded spectra for Graphite oxide with the same KBr at the same time but it seems to be good. I have attached that data also please, explain whether that data is good or not?
This spectrum seems to a normal absoprtion spectrum. The strong, frequency dependent background frequently appears in carbon based systems, but the abosrption peaks are well discernible.
This is much better spectrum. The background slope indicates a lack of dispersion. With some materials no matter how well ground you cannot achieve a perfectly flat background. However the broad 3400 and 1640 cm-1 bands indicate a trace water. The bands are very strong so a minor amount will show. KBr is hygroscopic and can pick up water during the grinding process. It may be worth running a blank disc just to check the purity of the KBr and the method.
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