I carried FTIR analysis on walnut shell treated with Zn and Fe salt, and found out the FTIR result such as peak 3500 cm-1 and 1075 cm-1 pointing upward instead of downwards as in most previous literature, I need to explain this. Any ideas would help. Thank you.
It depends on the parameter that is shown on y axis. In your case you plotted the absorbance, but it is most common to plot the transmittance, with the peaks pointing down. You can choose the parameter in the software of data collection
Marcella Bini is right, except I disagree that the major number of publications favors the transmittance (downwards peaks) over the absorbance (upwards peaks). Both are quite common, at least in my field.
Dear Osondu Ugochukwu, that's indeed a very interesting question.
That is easy and interesting. Don’t worry about this problem. Transmission was originally used because it was measured by the instrument. In this spectrum, the Y- axis shows vibrational stretching in absorbance unit (% absorbance). If you know:
-Absorbance -: it can be said that the electrons absorb photons with certain energies.
-Transmittance-: It is the opposite of absorbance. There is a measurement of the light that has passed through the sample.
This has two advantages:
-Humans are better at interpreting upward-facing peaks than downward-facing peaks.
-Absorbance is a logarithmic scale. This enables to detection of weak signals next to very strong signals.
Here I am also sharing a presentation related to absorbance and transmittance, I hope this will help you.
Presentation Introduction to Fourier Transform Infrared Spectrometry
Good luck with your research and best wishes!
Dear Osondu Ugochukwu
Take transmittance on y axis rather than absorbance, then you will get peaks pointed downward.
Regards
These comments are right but the small thing that you must do is to inverse the Absorbance values (T=1/A)
The vibrations of the crystal binding. will be as a resute of absorbtion (peake downward) or translation. (Peak upward) that mean the same discreption of the charts
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