On 14 August 2013 10:07, Teck Kwang Choo <teck.kwang.choo@monash.edu> wrote:

Thanks Matthew for the spectra.

Is it correct to use the spectra that was taken in transmission mode (the one you did) to fit those taken in fluorescence mode (my case)?

Teck Kwang

On 14 August 2013 01:37, Matthew Marcus <mamarcus@lbl.gov> wrote:

Here are reference spectra. The calibration is defined with the Fe metal edge at 7110.75eV. The maghemite spectrum has been corrected for mild
overabsorption by reference to magnetite, which is very similar. The magnetite is synthetic Fe3O4 from Aldrich, and done in TEY, so no overabsorption.
The maghemite is from oxidation of Fe oxide nanoparticles and has been verified by XRD and comparison with the ETH group's maghemite spectrum.
mam

On 8/13/2013 1:33 AM, Teck Kwang Choo wrote:

Hi all,

@Drew Latta: I was wondering why the end members should be magnetite and maghemite. Is it because they are both of inverse-spinel structure, the difference only being that the latter has all Fe completely oxidized into Fe(III)? Would you be able to provide the standard spectra to me if that is the case? Thanks very much!

Previously I have only thought of using hematite (alpha-Fe2O3) and FeO as end-members, both representing Fe(III) and Fe(II) respectively without giving much thought to the structure Fe takes. I also had my doubts using magnetite (Fe3O4) as a standard as it is a mixture of both Fe (II) and Fe (III). But thanks to the insights Drew has given, I now think I should take the Fe-coordination environment into account with the use of magnetite and maghemite as standards.

@Alexandre and Matthew: I have obtained Mossbauer spectra of some of my samples but like Drew said, it is not straightforward at this point in time. Will see what I can do with the data I have!

Thanks for all your responses! It is greatly appreciated! This forum has been more helpful than I thought!

Teck Kwang

On 13 August 2013 01:34, Matthew Marcus <mamarcus@lbl.gov <mailto:mamarcus@lbl.gov>> wrote:

While it's true that Mossbauer is the gold standard for Fe valence determination, access to the technique isn't all that common, and I don't know
of any facility that can do it on a micro scale. Is there one?
mam

On 8/12/2013 7:01 AM, Alexandre dos Santos Anastacio wrote:

Hello,

maybe that fingerprinting technique would be Mossbauer spectroscopy. The Fe(II)/Fe(III) ratio comes easily and also there are lots of papers about Mg-ferrite, an example:

10.1109/TMAG.2009.2018880 <http://dx.doi.org/10.1109/__TMAG.2009.2018880 <http://dx.doi.org/10.1109/TMAG.2009.2018880>>

Alexandre.

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Teck Kwang Choo
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Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904

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--
Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904

--
Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904