I am synthesizing ZVI using callus extract of my plants. After addition of extract I am getting somewhat greenish-black solution. Is it ZVI? In one set I am getting the precipitation also and the solution is turbid and z-average is quite large (1500nm particle size). The one which is less turbid and no precipitation occurred, I got 2 kind of particles (Z-average=213nm and peak 1=50nm and peak2 =260nm).
The colour of ZVI should be the completely BLACK and turbid?
Kindly help me.
1st pic= without FeCl3+plant ext; 2nd, 3rd, 4th= FeCl3+Plant ext
I have always heard that metal nanoparticles in water are black, but it was far before the development of nanotechnologies ... I also know that metal nanoparticles in other media (such gold NP in glass) may give different colours, depending on their sizes. In aqueous solution, greenish makes me think of Fe(+II). Do you observe the typical Prussian blue by addition of a solution of K3Fe(CN)3 ?
Alain
Are you synthesizing your nanoparticles under anaerobic or aerobic conditions? nZVI is highly reactive under aerobic conditions and can oxidize very quickly (in a matter of few minutes in some cases) so the greenish color you observed may be related to the partial oxidation of your nZVI (which should be completely black if synthesized properly). Are you using any surface coating to stabilize your particles? Usually polymers are used such as CMC or PAA.
Laura.
Thank you for your valuable suggestion.... I am not using inert atmosphere. Whenever I just add one/two drop of ext it just change colour otherwise it isnt changing colour. My question is if the colour is completely black, then there will a turbidity and I will get max size in DLS??? I got black but it is not turbid (pic no. 2-second one). Ya, i am using a polymer to prevent agglomeration.
I believe you should purge the solutions with nitrogen for a certain time period to remove the dissolved oxygen. then your synthesized solution would approach more to black. It seems reddish to me. and yes I also got greenish black Fe(0) but that wash synthesized by odium borohydride. And when the NPs are washed with ethanol and acetone the NPs were completely black. For me the salt of boron might had masked the ZVI leading to the greenish appearance. So, you may try to wash your sample with ethanol and acetone to make it pure. I am adding one of my images. but it is not the dried one.
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