Hi Chandra Your question hints at some potential problems if you use TEM. TEM requires a thin section, typically < 100 nm. What information are you trying to get from visualization of your system? You state your particles are in the 500 nm range. Thus you'd have to prepare your samples usually by microtoming a thin section of your material in, say, an epoxy resin (and thus you'd need an organic solvent to disperse the particles). Imagine that all your particles are monodisperse (absolutely identical in size), identical in shape and you slice sections from them. If they're spherical to start you'll have a collection of discs ranging from virtually 0 nm up to the true diameter of the sphere (500 nm in your case). If they're cubes then you'll end up with anything from triangles to hexagons. Thus you'll see an apparent distribution from a monodisperse starting material! See attached for an example.

At the sizes (500 nm) you quote, I'd be looking at laser diffraction for a quantitative particle size distribution and SEM for some guidance as to shape, degree of agglomeration etc.

The 3 stages in making a stable dispersion are wetting, separation (the critical step), and stabilization. They're the same steps one takes in the BDAS regime for diffraction size measurement. See:

PST and BDAS - an acronym approach to laser diffraction method development

https://www.brainshark.com/malvern/vu?pi=478888057&text=M021507&r3f1=

Thank you very much Dr. Rawle. My main aim is find out SAED image and to get superlattice .

You may try SAED measurement. However, relatively bigger size particles (500 nm) means combination of several smaller particles, where multiple planes and surfaces combined. Therefore, it is difficult to select the area which remain of single lattice plane for saed measurement to obtain information about the fine structure of the corresponding superlattice.

Thank you very much Dr. Md. Abdur Rahman .

Transmission electron microscopy and selected area diffraction requires the sample to be thin enough to allow the electron beam to pass through it. Since your sample contains heavy elements the thickness limitations are still more stringent. Since the sample is not soluble in water, you have to use a mechanical method to reduce the size of the particles. Of course, you can use a colloidal solution of these fine grain particles to prepare the sample for electron microscopic observation. You may put a drop of this colloidal solution on a microscopic grid with a carbon film to support the particles. A 200 kV microscope may be needed to observe a nanometer size sample. Sometimes, the edges of the particle may be thin enough to provide some useful data.

Shivakumar G.K

colloidal dispersions or not colloidal solutions - latter are solutions of polymers or solutions containing micelles.

see also

https://www.researchgate.net/project/nanoparticle-solutions-search-for-a-perpetuum-mobile-there-are-no-particle-solutions-only-particle-dispersions