I use the 1 ml of water extract of dried Spirulina (1gm/5ml),added to 25 ml of 1 mM AgNO3 then left in light shaking to get a purple solution instead of the brown one of the AgNPs.
Hello Yassmine,
Synthesis of AgNPs depends on many conditions like, time, temperature concentration of plant extract and AgNO3 etc... try to use different concentration and different time exposure, and confirm for AgNPs synthesis by UV-Visible spectrophotometry.
following papers may useful for your research.
All well wishes for your endeavor.
Article Green Synthesis of Silver Nanoparticles Using Water Extract ...
Poster Green Synthesis of Silver Nanoparticles by using Plant Extra...
Brown normally means silver oxide Ag2O. A purple sol may simply be silver of a small (nano) size. Is the suspension transparent as well as being purple? Have you measured the size of this purple suspension by any route (DLS, UV-VIS, SEM/TEM)? See also:
September 2nd, 2015 Silver colloids and invisible ink
https://www.brainshark.com/malvern/vu?pi=560497681&b=1&tx=120486&c1=22
and: February 18th, 2016 Metal colloids - their preparation, application and characterization
https://www.brainshark.com/malvern/vu?pi=529368070&b=1&tx=120486&c1=22
The problem is that there is a difference between the suspension in the dark and the light shaking ,in the light ,the purple color appears while no color in the dark shaking,the suspension is transparent and I have analyzed it by UV-VIS getting different absorption peaks in the range of 200-350nm
Not sure I quite understand your comment but I would expect to see a difference in the light and in the dark. Silver nanoparticles easily oxidize (indeed the Ag on the surface is only in the +1 oxidation state by ESCA - it's the Ag+ ion that's a bactericide, not Ag metal) and silver nitrate easily decomposes with light (and reducing agents). The particle size changes with oxidation and with aggregation or agglomeration. Different absorption peaks in UV-VIS mean different particles sizes with the general rule being the lower the wavelength then the smaller the size.
So what I got is not silver nanoparticles of the range 400-480 nm,but silver oxide nanoparticles that are too small because of the oxidation,and that is why they gave lower wavelengths of 200-350nm.
Sorry Professor ,I was asking and making sure that I understood well.
Hello Yassmine,
AgNP or Ag2O NPs is can be known by only X-ray Diffraction pattern (XRD), i agreed with Dr. Alan, color changes are characteristic for NPs.
if you analyzed your sample by UV visible spectroscopy and peak is near to 400 nm and peak is sharp then you can say your sample containing small and nearally mono-disperse NPs.
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