My polymer shows symmetric and asymmetric peaks at 1421 and 1605 cm-1. The polymer was able to reduce palladium nanoparticle. If carboxylate is responsible for reduction then Which direction should the band shift and why?
First of all, palladium nanoparticles are something I would expect as a product of reduction rather than something undergoing reduction. Please confirm if that is correct in your case.
Secondly, if the carboxyl group was the product of the redox process (with some alcohol or aldehyde being oxidised to form the carboxyl system), then typically a signal should appear in the range of 1700-1800cm-1 (C=O). If the unoxidised system was an aldehyde, it should have a carbonyl group signal in the 1650-1750cm-1 range. As such, the carbonyl band *should* move towards higher values.
Please bear in mind, though, that these ranges (as found in any kind of IR signal tables) are for *typical* organic compounds and your compounds may not be all that typical, so their signals may be found a bit beyond those rnages (such as the 1605cm-1 signal, which may possibly be a carbonyl group signal).
Now, assuming that the carboxyllic acid formed through oxidation is not particularly strong and that the environment is not strongly alkaline, you should also have some non-dissociated acid molecules (i.e. COOH groups), which should give a broad signal in the 2500-3000cm-1 range.
Thirdly, if the carboxyllic acid is the species that is being oxidised, I would expect the carbonyl signal at (supposedly) 1605cm-1 to lose intensity or even devolve to the baseline.
For a detailed study of COOH/COO- IR spectral features, you might want to read through the following paper: Article Infrared Spectroscopy of Aqueous Carboxylic Acids: Compariso...
Dear Sarkar,
FTIR interpretation is essential to rationalize the interaction between metal ion and carboxylate (-COO-) during adsorption. In fact, different types of attachments, like ionic and coordination bonds (monodentate, bidentate bridging and bidentate chelating), can be interpreted by observing antisymmetric stretching of -COO- and the difference of symmetric and antisymmetric stretching of -COO-. You can find the details from my publications.
Thanking you very much.
I agree with Tomasz Jarosz and Mrinmoy Karmakar. The position of the vibrational absorption of COO- depends on the kind of interaction between this group and the metal.
Regards,
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructured Materials
- Nanoparticles