I need an accurate and precise technique to detect silica coated iron oxide nanoprticles.
Dr Baraa tq
1. we don't have HRTEM
2. I need a technique to confirm the result of TEM.
Better to go for cheap and effective tool i.e. FT-IR analysis...
Your question isn't specific enough. What exactly are you trying to determine? That you have iron oxide? How much iron? That silica has coated the iron oxide? The size? The magnetization?
@ DR Robert Taylor, i need to determine beyond reasonable doubt that my silica NP really coat on the Iron Oxide NP. tq
OK. Then, 2 things... 1) you can prepare a negatively-stained TEM image. Coat your sample on a grid, as usual, and then stain it with a 2% Uranyl acetate (UA) solution. In simple terms, the UA stains the grid anywhere where there isn't a sample. So, if coated with silica, you will see a light "halo" around your particles. Here is a link to a paper where I have negative stained images to see if the particles are coated with phospholipid. (Its also on my page)...
https://www.researchgate.net/publication/230723340_Paclitaxel-loaded_iron_platinum_stealth_immunomicelles_are_potent_MRI_imaging_agents_that_prevent_prostate_cancer_growth_in_a_PSMA-dependent_manner
2) ICP: Digest the sample in strong acid (aqua regia) and then perform ICP. The ICP is very sensitive and will tell you exactly how much iron and silica are in your sample.
Hope that helps. Good luck.
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...Actually, my article in the Journal of Nanoparticle Research has more negative-stained TEM images than the one I listed before.
FTIR is good enough to provide bonding information between Silica and Iron. HRTEM can provide you crystal structure, alternatively you can use XRD. But it is necessary to use EDX for chemical composition of Silica.
If the coating is required to be a closed shell (for protective and/or functionalization purposes) then I see little room besides doing microscopy and chemical experiments.
If you have some reaction that ruins, for example, the magnetic properties of the iron oxide core then subject the core shell particle to that reaction and watch our for the magnetic response. Alternatively, use methods that probe Fe valence etc.
Microscpoy-wise stick with the recommendatons of Robert above.
@Dr. Kai Fauth the coating is meant for protective and functionalization purpose.
Then I stick with what I wrote before. Try to find some reagent that changes the Fe oxide chemically and/or magnetically in a way that you can control and/or detect, but which cannot penetrate the silica shell. Then, if your shell is fully enclosing the Fe oxide core, the chemical state and/or magnetic response of the core should remain unaltered.
Merely detecting Fe - silica bonding does not prove the shell to be closed.
But then again, TEM and SEM might be the easier way to show your case, if core and shell dimensions are appropriate. I have seen this previously in silica coated CoO particles and have taken some SEM pictures on them. I'll try to spot the reference and one of my micrographs.
So, if SEM/TEM are not available at your lab, you might try to find someone nearby whom you can collaborate with.
tq chuka, is clear that FTIR will do it but i just want to ascertain that it is coated but not assembled or any other form cluster.
Probably YOU will find some similarity with here presented approach?
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