I recently read an article published in Nature Protocols (http://www.nature.com/nprot/journal/v7/n9/full/nprot.2012.082.html) regarding the preparation of functionalised magnetic nanoparticles. I have succeded in reproducing the first steps with magnetite nanoparticles using this excellent protocol. Being not an expert in the field, I was wandering if there was a simple influence of the nature of the ferrite on most important properties of the nanoparticles : facility of the synthesis, resistance to oxidation, ease of magnetic separation etc..?
Each of these materials will have different magnetic properties, since the oxidation state of the Fe ion will be different in each case. This will lead to different saturation magnetization, permeability, coercivity, etc.
I suggest you clarify/refine somewhat further what is your list of most important properties since the range of opinions might be large in the community. Even within the more narrow range of magnetic properties Steven addresses, what you consider important might well differ from what I do.
Dear Kai, thank you for your answer, which unfortunately I did not notice before.
I am interested in synthesis of magnetic nanoparticles in order modify the covalently for catalytic purposes. I am especially interested in the stability over long durations of magnetic nanoparticles, either coated with silica or not. As far as oxidation is concerned, the 3 types of particles I mentioned in the question differ by the nature of the metal(II) ion, iron(III) being present in all cases. I expect that cobalt(II) ions are more difficult to oxidise thant iron(II) and that consequently cobalt ferrite nanoparticles are more stable over long times than Fe3O4 particles. Does this sound correct?
Hi, I think the main difference between your question NPs is their magnetic properties. For example if we use Ni ferrite Np in spite of Fe3O4, they will have more powerful attraction & cause gathering. another important magnetic property of Fe2O3 is paramagnetic behave of it .
Federico, I am not terribly familiar with the details of the ferrites particularly concerning their chemistry. I have previously worked with oxidized Fe nanoparticles. From those days I remember that there is a continuous transition between maghemite (Fe3O4) and magnetite (gamma-Fe2O3, both spinels (and all intermediates) being ferrimagnetic). To what extent this applies to Co and Ni ferrites, too, I don't actually know.
I have very recently talked to a colleague working on Co and Ni ferrite thin films, though, thickness ranging from about 2 to about 20 nm. They observe deviations in saturation magnetization from the corresponding bulk ferrites, and the 2nm films are markedly different from the 20 nm films (no reference, unfortunately, the work is unpublished. There should be, however, some published stoff on ferrite films). One idea for interpreting the results is the possibility of a thickness dependent change of cation site occupation (inversion).
If true then its not an unlikely expectation that growing some protectiective shell and/or functionalizing the particles may induce changes in ferrite particles. Once this modifications done, the resultinng state may well be very stable. Again I cannot comment on stability variations between different kinds of ferrites.
The difference is only that in case of Co and Mn, they are replacing the Fe sites in the iron oxide crystals. That will off course the their magnetic as well as crystalline properties.
from my prior experiences in nano ferrite synthesis, MnFe2O4 is more sensible to heating treatments than Co and Ni ferrite and simply decomposed to sub-phases as Mn and Fe oxides.
I hope be helpful
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