If you got black color in solution then may be it is oxide. Pure AgNPs are dark red color. On dilution they gave red color

It could be if high pH conditions are maintained in the plant extract. Anyway you can expect to have silver nanoparticles at regular pH but with some silver oxide on the surface.

Thank you so much Omar. Yes, many of those researchers have reported synthesizing black AgNPs in basic medium by adding NaOH solution.

You can see whether the dark precipitate is Ag NPs or Ag2O. Take a small amount of the solid put in a test tube and add few drops of NH3. If the solid completely dissolved and gave a clear solution, then the sample is Ag2O, because Ag2O is solvable in NH3 but Ag NPs are not.

Thank you so much Mohammad. Yes, that will confirm the formation of silver oxide.

If you got black color in solution then may be it is oxide. Pure AgNPs are dark red color. On dilution they gave red color

Mohammad Kooti also explain best

Thank you Muhammad Ismail

Abdounasser Omar Please see the below link. You can calculate the concentration from UV using this site online

http://instanano.com/characterization/theoretical/concentration-calculation-from-uv-vis-absorbance/

Cheers

M. Ismail

Thanks Muhammad Ismail

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