I would like to know different characterization techniques where we can understand the coating of a metal to a metal oxide nanoparticles. At least I wanted to know that the layer is coated on the surface of metal oxide nanoparticles.
TEM would be the best way to characterize but AFM can also be an alternate indirect way of characterizing the sample. You can compare the AFM image before and after the metal coating. The height and phase profile can be very revealing about the sample.
A cross-sectional SEM view of the sample can also give lots of information about the structure.
XPS analyses can penetrate samples up to 10 nm (but that may be adjustable) and can give you information on the elemental composition and chemical state of your coating. XRD too might work but this depends on thickness of the coating as well.
I think EDX mapping is the best way and I have used this analysis to find out if or not the core has fully covered with the shell. But of course this analysis is a part of HRTEM. You can focus on just one particle or cluster and determine the element mapping of that particle.
How is the size of your NP before and after coating. Nanosight will provide information straightaway. No need for any sample prep. Just ~300 to 400uL is sufficient and you can recover almost all.
Hi Ashwin
I think what my colleagues have said makes a lot of sense. TEM will be very useful to see how conformal your covering is. But again, one of the biggest disadvantage of TEM is the very small sample size that is being studied. I will vote for X-ray photoelectron spectroscopy (XPS), and time of flight-secondary ion mass spectrometry (ToF-SIMS) to make sure if you are putting down the metal layer. These two techniques are complementary to each other, ToF-SIMS being more sensitive than XPS. XRD might be used to see the difference in the spectra after you put your second metal over the metal oxide layer. Material characterization is all about using a bunch of techniques and then making sense out of all the results you have in hand.
Cheers!!
Hello Ashwin,
XPS will give you a certain and direct answer if your coating is successful. Moreover, you can even calculate the shell thickness using a straightforward method developed by Alexander G. Shard, see J. Phys. Chem. C 2012, 116, 16806-16813. Note, that sample preparation for XPS analysis can be an issue (considered shortly in above mentioned paper).
Good luck!
XPS or AES can be fine, both for thin or thicker layers. If done in situ the risk of atmospheric oxidation of the overlayers is avoided.
XPS is appropriate. you can confirm the matal thin layer from the peak.
FESEM, XPS, EDX, AFM and I suggest thickness meter, hardness and EIS
Thanks a lot for all your efforts in giving me valuable ideas... As many friends suggested to do XPS and TEM.. I will try both these techniques to determine the core and shell.
XPS is easier and sample preparation much simpler. Avoiding oxidation is important.
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