Thin film of PANI deposited by CBD on silicon substrate posses no peak from XRD measurement while the bulk sample obtained from the same procedure posses peaks at low 2theta angle (~ 10 - 30 degree). Any theoretical explanation to substantiate these results?
Thank you in anticipation for your helpful contributions.
Dear Balogun,
what is the expected thickness of your 'thin' film?
If your mass coverage of PANI is too small, there might be not enough crystallites being large enough that can produce bulk type peaks. Your 'thin' film then looks quite amorphous.
Sorry, but I havn't got any theoretical explanation.
Dear Gerhard,
Thank you for your helpful tips. I have a PANI film of ~ 300 - 400 nm thick. More so, the XRD measurements I obtained from both thin and bulk PANI are already reported in published journals.
I just wanted to know what could be responsible for such behavior having same PANI composition.
Warmth regards.
Dear Balogun,
thanks for telling the film thickness.
At the film thickness you have, there are about 1500 to 2000 atomic layers. Altough your PANI molecules exhibit a lot atoms (about 60) you can expect about 30 molecular layers. At such relatively large number of molecular layers I think your film should be able to built up crystallites which are large enough to lead to crystalline type of XRD pattern.
For one to e.g. about three molecular layers I would exclude significant crystallite formation due to the lack of sufficient amount of material.
In your case the production conditions and/or the following treatment(s) may be responsible for the observed difference in XRD pattern type.
Is your bulk sample also grown on the same type of substrate and were the surface preparation conditions (cleanliness/cleaning, polishing, etc.) of both substrates the same?
Is the amorphous state of your thin film reproducible?
You see, there are a lot of variables which could affect the type of your film.
Dear Gerhard,
Thank you very much for your very insightful guide.
Again, I have to state here that the same procedures which I used in producing the thin film is also used to obtain the bulk PANI powders as well.
And the obtained samples (both think film and bulk) are highly reproducible. Basically, it involves oxidative polymerization of aniline in an aqueous acidic medium.
May be I think I still need to increase the thickness.
Warmth regards!
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