Determining the different oxide states of manganese nano-particles prepared by evaporating bulk manganese sample.
Hello
many techniques are available.
The most simple one is iodometry which works very well with manganites. This will gives you a direct answer for mean Mn oxidation state by measuring the transfer of charges between original Mnx+ and final Mn2+ states. You only need some few chemical procuts , some glass furnitures and Ar gas. you need between 20 mg and 100mg of powder depending on the accuracy required and the quantity of high valence Mn ions.
XPS is only limited to the surface layers so it should be considered with care.
few mg of powder
XANES is also a good way to detect mixed valence state even if less precise than iodometry. It can be used in fluorescence or transission mode. In the first case, you have a surface probe (probbaly less surface than XPS); in the second case, you have an intergation over the whole volume. A good point of XANES is that you can know if the charges are localised or not (polarons). In the first case, you would have for instance a mixture of Mn3+ and Mn4+ states, in the second case (i.e. if the electron jumps faster than the interaction time considered for the XANEs process), astate that would be intermediate in term of oxidation sate but unique.
few tens of mg of powder.
EELS is a very elegant way to have oxidation states on single particles. Now techniques exist that allow you performing 3D reconstructions. not trivial in this last case.
few mg od powder
hoping it helps.
Guilhem
XANES - X-ray absorption near edge spectroscopy may help. The shift of the absorption edge has several eV with increasing chemical valence, and the structure of the edge also changes for the different oxides. XANES can be measured in solution, in solid state, for dilute samples, concentrated samples, no matter. So this may definitely help in your case! Keep me updated, Dirk
X-Ray photoelectron spectroscopy (XPS) may better help in determining the chemical composition and oxidation states
Hello
many techniques are available.
The most simple one is iodometry which works very well with manganites. This will gives you a direct answer for mean Mn oxidation state by measuring the transfer of charges between original Mnx+ and final Mn2+ states. You only need some few chemical procuts , some glass furnitures and Ar gas. you need between 20 mg and 100mg of powder depending on the accuracy required and the quantity of high valence Mn ions.
XPS is only limited to the surface layers so it should be considered with care.
few mg of powder
XANES is also a good way to detect mixed valence state even if less precise than iodometry. It can be used in fluorescence or transission mode. In the first case, you have a surface probe (probbaly less surface than XPS); in the second case, you have an intergation over the whole volume. A good point of XANES is that you can know if the charges are localised or not (polarons). In the first case, you would have for instance a mixture of Mn3+ and Mn4+ states, in the second case (i.e. if the electron jumps faster than the interaction time considered for the XANEs process), astate that would be intermediate in term of oxidation sate but unique.
few tens of mg of powder.
EELS is a very elegant way to have oxidation states on single particles. Now techniques exist that allow you performing 3D reconstructions. not trivial in this last case.
few mg od powder
hoping it helps.
Guilhem
Thank you very much for all the answers.
I have done XPS before on the sample however the resolution of XPS is not good enough to distinguish between Mn2O3 and Mn3O4.
I will look in to XANES, Iodometry, and EELS. G. Dezanneau, do you by any change now the energy windows for the different oxide in Mn ( I just did a quick search, but it doesn't seem to be available online).
Thank you again, everyone!
Using XANES it is possible to distinguish between Mn2O3 and Mn3O4. You can see the reference | Chem. Commun., 2010, 46, 2920–2922
EELS is probably a good solution with very high spatial resolution. For details see: Determination of Manganese oxidation states in solids by EELS, Rask et al., Ultramicr. 21 (1987), 321
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