Well, the bulk complement for XPS would be XANES/NEXAFS, but of course that requires a synchrotron.

If the potential oxidation states have differing paramagnetism, you could try EPR spectroscopy.

Also, the fluorescence behaviour may change so fluorescence spectrsoscopy would be an option; the evaluation of that is not totally straightforward, however, so better first check if there is info available for your system.

Jürgen Weippert

How we can determine the oxidation states using EPR spectroscopy?

Dear Yasir,

As pointed out before, XPS can be used to determine the oxidation state of Co in ZnS, which is certainly 2+ according to the reductive chemical surrounding. At RG there is an open paper, which shows a dedicated XPS analysis. Moreover, you can use optical spectroscopy, since a. [Ar]3d7 h.s. ion (Co2+) can be easily diminished from a [Ar]3d6 ion (Co3+) by tha absorption spectrum and may also by the luminescence. Other useful techniques are EPR and SQUID.

Hope this helps a bit.

Thomas

Article Electronic structure of ZnS:Co and ZnSe:Co crystals

Asif Ali Haider The simplest differentiation would be if one oxidation state would form a diamagnetic complex and the other one a paramagnetic complex, although I would not expect this in this case. In Co-doped CdS I would expect the Co to replace a Cd atom, so it would be a tetraedral high-spin complex since the tetraedral ligand field splitting is not that strong. The occupations going along with the oxidation level should then result in different multiplicities to which EPR should be sensitive. Also, you could compare it to a simulation as it was done in

Article EPR Spectra of Low-Symmetry Tetrahedral High-Spin Cobalt(II)...

• Jürgen Weippert Thank you sir for explaining the fact.

Dear Yasir,

in addition to the expert answers provided by Thomas and Jürgen I would like to mention that it is often helpful to search the "Publications" and "Questions" sections of RG fo find and access helpful literature references and closely related technical questions. For example, please have a look at the answers given to the following closely related RG questions:

Is there any technique available to know the oxidation state of metal ion other than XPS?

https://www.researchgate.net/post/Is-there-any-technique-available-to-know-the-oxidation-state-of-metal-ion-other-than-XPS

(15 answers)

and

How can we identify the oxidation state of a doped element?

https://www.researchgate.net/post/How_can_we_identify_the_oxidation_state_of_a_doped_element

(6 answers)

I hope this helps. Good luck with your work!

Dear Yasir Javed

Jürgen Weippert is right.

XANES /NEAFS will do the job.

However due to the low concentration of the dopand (such as Co here), combined with highly absorbing matrix (Cd!), it is advised to do XANES (at the Co K-edge) in fluorescence mode at grazing incidence.

A Co(III) doped in a solid matrix would be relatively simple to deduce because this oxidation state is EPR silent (3d6 a singlet state),

Co(II) (triplet state S=3/2) actually exist as tetrahedral (small Ligand Field gap) that gives usually two signals (4000 Gauss one octet and another octet at higher field) when magnetically diluted in a diamagnetic solid. See this free article:

Epub 2015 Jan 20.. 2015 Feb;71(Pt 1):20-4.Acta Crystallogr B Struct Sci Cryst Eng Mater

(C4H12N2)[CoCl4]: tetrahedrally coordinated Co2+ without tComputational Studies

of Quantum Spin Systems

Sandvikle works on solid state, it may be useful for you:

Anders W. Sandvikhe orbital degeneracy

• DOI: 10.1107/S2052520614024809

The problems come in when there are two or more Co(II) bounded like 3 Angstroems away, where magnetic exchange between high spin Co(II) ions in pseudooctahedral are exchanged coupled, you have to use High Field-EPR:

Inorg Chem, 2014 Mar 3;53(5):2535-44. doi: 10.1021/ic402797t.

The other very common symmetry of Co(II) is square planar, as in Co-porfiirines

whis has a weak signal at low field near a strong signal at higher field. Both broad and poorly resolved Fine structure, whit characteristic strtucture:

In short, here you get a very simplified Chapter with pictures;:

Chapter EPR Interactions - Zero-Field Splittings

Also look at this xcelent Review;

Article EPR Everywhere

I do work with Organometallic tetrameric clusters of Co(0)

that have a typical EPR sample according to the number of Co(0) bound:

Jn Inorg. Chem. 1996, 35, 7289-7294

TI Clusters as Ligands. 4. Synthesis, Structure, and Characterization of the

Tungsten(II)-Tungsten(III) Cluster Carboxylate

{[Na][W 2{OOCCCo 3(CO)9}2 (OOCCF3 )4 (THF)2 ]} 2

From the difference in binding energy we can find out oxidation state of a doped metal. If suppose metal is in elemental state meaning its in 0 oxidation state then number of electron is more so they are less tightly held by the nucleus compared to metal in 2+ state. In that case the number of electron present is less and they are more tightly held so more energy is needed to remove electrons.