I prepared my silver nanoparticles by adding silver nitrate into sodium borohydride solution. And then NaCl solution was added, suspension turn darker yellow then gray as nanoparticles aggregate. Next, 0.3% PVP solution was added to prevent aggregation.
My question is, how would I know whether almost all of the aggregates were completely dissociated?
And based on the picture, it shows that there is some layer on top of the particles, what is those layer?How I can eliminate those top layer?
Dear Risalinda,
First, I want to thank you for your patience.Second, however attached image has spherical nanopartcles but still there are large plates shapes and seems to cover aggregates of nanoparticles.
So, let me give some observations,
- appearance of yellowish color is the primary indicator of nano-silver, and you can get benefit from this characteristic property through UV-vis spectrum to predict the homogeneity of size and shapes of your colloid. The sharper peak you have, the smaller variation in size and shapes. If you have more than one peak, it would be due to presence different nano-shapes. The attached file can help to identify the sharpness and boarding in the difference in UV-Vis spectra.
- purification of your colloid may be using centrifuge or filter membranes. But in your case, you would lose a lot of silver because, you have large plates.
If I wre you, I would:
- add PVP (anti-aggregating agent) once yellow color appears.
- use sonicator to improve dispersion.
- add sodium borohydride solution at low temperature (ice bath).
Finally, I hope my answer can help you. For any inquiry please contact me .
Good Luck
Diana
http://www.rjpbcs.com/pdf/2015_6(1)/[15].pdf
Hi,
As it was described earlier the attached image doesn't look like well prepared homogenous nanoparticles. During the synthesis of nanoparticles (Here, about Ag NPs), one should look for many things together. One set of experiment or observation could not justify the quality of the prepared nanostructures. In case of spherical NPs as expected from your experiment, after visual observation of colour change you need to go for UV-visible spectroscopy to find out the characteristics peaks for the associated size and shape of Ag NPs. The chances of impurity from foreign or unreacted residues and Ag+ ions are always there, which need to be removed as much possible by washing with a suitable organic solvent (ethanol) and repeated centrifugation. The quality of a sample can also be improved by varying the reaction time and keeping reaction mixture in an inert atmosphere and possibly in dark (silver goes for photoreduction). XRD and EDS analysis can bring more light to the purity of the sample which will also help to understand morphology changes and a shift in UV peaks. There are many stabilizing and capping agents available (PVP, citrates, polysaccharides and amides) based one's need they can be used, but unreacted agents need to be removed. Finally before going for electron microscopy, a short duration of sonication would always give the quality result if performed properly without much heating.
Hope this may help.
All the best.
Roslinda
Firstly conferm by UV-vis spectra that whether your AgNPs are forming or not and for this you have to do wavelength scan from 300 to 700nm. if your peak come across 420nm or near by that means your nanoparticles are forming. You can use sonication for avoiding aggregation before going any kind of characterisation.
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