I tried synthesizing silver nanoparticles using plant extract. 1mM has not changed any colour. i then tried using 10mM and colour changed from green brown. i was monitoring the biosynthesis using UV-vis but then my peak remains at 328nm even after 72hours. i have no idea on how to explain the peak with the image i received from SEM. anyone to help on this please
The band you are observing in UV-Vis is not a plasmon resonance from Ag NPs. Instead it is likely due to free Ag+ ions (near 300-310 nm wavelength) and some contribution from the organic matrix. plasmon peak for spherical Ag NPs should appear in the 400-450 nm wavelength range, depending on NPs diameter and interaction of the same NP with organic environment of the same NP.
Therefore, you have not got any significant Ag NP dispersion. I suggest you to further increase the used Ag nitrate concentration.
Moreover, the SEM iimages you report are useless because of the too large scale (500 um). Single NPs are expected to have a size not larger than about 100 nm, so you can not resolve with SEM unless you paerform measurements with much higher magnification... a FESEM could be required.The rough deposits you are observing in youe SEM images are likely to be generated by the organic components of your solution.
Mariah Muhongo
The UV absorbance peaks show, very very low conversion of Ag+ to AgNPs. I can see a mild AgNP resonance peak at around 400 nm. I think the choice of green agent can be changed by studying its chemistry and knowing if it can reduce the metal ions or not. FESEM images can be generated at low scales like 0.1-0.5 um to see a good results.
Thank you very much. i tried different concentration of silver nitrate 1mM, 5mM and 19mM. I also tried different concentration of extract to silver nitrate, like 1:1, 1:2, 1:3, 1:4, 1:9, 1:18. The color changed from green to dark brown but then for all, i am getting my peak at 328.
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