I did not use high resolution TEM but a 120 kv Technai TEM. Please explain the information which can be drawn from SAED image.
Thank you.
Unfortunately, your SAED doesn't show any crystalline information - it is just an amorphous background pattern. Try to use a smaller aperture and confine the SAED to an area with many crystallites in it.
The cobalt nanoparticles are highly crystalline nature but in your TEM images the SAED pattren doesn't show any diffraction spots so yu have do high resolution TEM analysis and also you may calculate d spacing of cobalt nanoparticles using image J software
Hi Shiva..Thanks. Peter has raised the similar point and I'm going to do TEM again.
Have you focused you sample properly? There seems to be a big fuzzy ring at the very edge area. Still, no sharp diffraction is present, which means probably no crystals.
Hi Huaping!
The TEM of NPs was done by the facility technologists and i doubt as he might not be accurate in doing so.
my query is that "
1. Is type OF TEM (viz. 120kv Technai here) responsible for not showing the actual crystalline nature of NPs?
2. OR- NPs are mostly elemental form of Co-NPs thats why it is showing amorphous SAED?
plz have a light on above queries.
thank you,
Hi Manoj,
TEM type should not be responsible for this. But if the operation condition is far away from focus (either objective focus or diffraction focus), sharp crystal features in the DPs can be very fuzzy and not recognizable, because it looks like amorphous. I suppose your NPs are really nano-particles.
However, in you case, it was likely to be caused by too less crystal structures compared to the carbon background on the supporting grid.
As suggested by Peter and Shivanada, try smaller Selected Area Aperture when doing diffraction, or doing nano-beam diffraction, or just taking HREM images.
Ask your technologist to make picture of your nanoparticles first (with diffraction aperture already inserted), then you can be sure you have NP in analyzed area.
Only 2 things to suspect:
1. Technologist error (most probable)
2. Amorphous particles (much less propable).
Do not blame TEM, it's innocent.
It looks like a very weak Debeye Scherrer polycrystalline diffraction pattern to me on a huge background. The camera length is chosen far from optimum. you should use something like 500-700mm to have good sampling on film or a bottom mounted camera. I think most of the diffraction rings are masked by the beam stopper of the primary beam, because the camera length was chosen too small.
The background can mean two things, a lot of amorphous material in the area illuminated or the support film of the sample is quite thick and gives a lot of inelastic scattering as background. Since it is only a 120kV tool thickness of the support film plays a role here.
How was the sample prepared? Did you use a commercial Quantifoil or Lacey film or something else? As well contamination can cause the background signal with the growth of amorphous carbon under the beam, when `dirty` solvants were used to disperse the particles.....
Hi!
Dear Bert sir,
FORMVAR/CARBON, 300 CU TEM grid was used and TEM imaging was done by TEM operator. And, he used the NPs as they were initially that is synthesised in o-dichlorobenzene solvent.
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