I have several nanopowder samples synthesized in our lab and I would like to compare their absorbances as a function of the various treatments. We have a uv-vis spectrophotometer, so please advise on how to prepare the nanopowders and measure the absorbance spectra.
Secondly, I need to measure the morphology of the nanopowders by SEM. How should i prepare the sample before measurement? Is there a special sample holder for powders or they need some special handling/preparation?
Thanks
Hello,
The best way to measure would be in an aqueous dispersion with constant concentration (if interested in the relative extinction coefficients). This will give the most homogeneous and reliable results. If H2O does not yield stable dispersions or modifies the properties you are interested in, you can use solvents, but some start absorbing in the UV regime. I would measure the dispersion in a quartz cuvette. Dispersions can be tricky if you have not prepared them before, you might need some surfactants and ultrasound treatement.
The second part entirely depends on your SEM. We have used some relatively new SEMs just casting dispersions on an Si or metal substrate to look at them. We found it relatively useless, because we were interested in morphologies around 10-20 nm, which is very tricky if not impossible with most SEMs. Older SEMs "push" non conducting things out of the way. In that case, I would evaporate a very thing (5-10 nm) film of metal on top, but this can change the picture a bit. This would also immobilize the nanoparticles
Hello,
The best way to measure would be in an aqueous dispersion with constant concentration (if interested in the relative extinction coefficients). This will give the most homogeneous and reliable results. If H2O does not yield stable dispersions or modifies the properties you are interested in, you can use solvents, but some start absorbing in the UV regime. I would measure the dispersion in a quartz cuvette. Dispersions can be tricky if you have not prepared them before, you might need some surfactants and ultrasound treatement.
The second part entirely depends on your SEM. We have used some relatively new SEMs just casting dispersions on an Si or metal substrate to look at them. We found it relatively useless, because we were interested in morphologies around 10-20 nm, which is very tricky if not impossible with most SEMs. Older SEMs "push" non conducting things out of the way. In that case, I would evaporate a very thing (5-10 nm) film of metal on top, but this can change the picture a bit. This would also immobilize the nanoparticles
Hello,
dependent of the quantity which do you have from the powder, do you can thing about to press the powder together. The keyword here is KBr pellet.
Hi,
Dr. Raoul give you a complete picture.. Thank you Dr. Raoul
I would say you can take the measurements from UV-VIS spectroscopy by dissolving your materials (i.e. powder) form in appropriate amount of solvent and then take measurement, but if you're interest to find out band-gap of the material then I'd suggest you to go for Diffuse Reflectance Spectroscopy that would give you better results..but it will give reflectance percentage rather than absorption spectra
While in order to obtain the results from SEM you can either use carbon substrate or gold substrate, and preparing sample for SEM would not take any time neither special handling but for sure you do need some knowledge in order to use SEM
Good luck!
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