Dear Mr. Helen Kas

I suggest you to encapsulate or coating your powder sample using organic polymer, such as PEG, PAN, PANI, or others depend on your target. I have proved when I synthesized pure ZnFe2O4 nanoparticles and encapsulated ZnFe2O4 by PEG, so the encapsulated nanoparticles become more dispersed then pure nanoparticles. Pure nanoparticles showed agglomeration after 7 days, in other hand, encapsulated nanoparticles was still dispersed. 

 I would suggest synthesise nanopowder in liquid environment like water. And add some coating material in the liquid.

To my knowledge, nano-particles has application such as additive to polymer. And this is the key, not the simple 'state' during storage. So, what for You want to use them? There are many ways to deagglomerate: ultrasound, isopropyl storage, heat, electrostatic charge, etc. Probably, You will find no information about mentioned because it it only from my researches (13 years ago). And another process I proposed for sample preparation (see my posts).

Thank you for the answers but as you mentioned i used polymers also.I used water as solvent but yet it agglomerate soon.i attached file like this i am getting the results.

It depends on the type of particle your prepare and your intended use. Usually the nanoparticle can be stabilized by synthesizing them in a capping agent/stabilizer environment.. like adding PEG during preparation.. another way is it to do with electrostatic stabilization, like using citrate ions etc. .. 

And if you you want to disperse the particles uniformly again, then you might need to use sonication, heat etc as previously mentioned by Janusz Rebis.

I couldnt open the images.. but from the thing what I see, the sample concentration that you used for drop casting for SEM analysis is more.. you need to dilute more and more and then sonicate it , and then drop cast it for SEM analysis, if you want to visualize individual particles.

Which i attached are with PEG only but same agglomeration occurred. And please give some of capping agents that we can use with hydroxyapatite

You can use anionic surfactant (SDS) or cationic surfactants (CTAB) as capping agents to control the morphology of the nHA synthesized through wet chemical precipitation method!!

Use of 'sacrificial' biopolymers such as BSA, silk or synthetic polymers such as PVA could also help to control the size n morphology of the nHA formed, Later you need to sinter the nHA to get rid of the polymeric framework!

Thank you for help

Hi Joseph Christakiran Moses

Im work with poloxamer 407 for encapsulation of BSA but my micelles agglomerate so quickly

what should i do?

You can use PVP as a capping agent to prevent the agglomeration of NPs. Further you can use chemical reduction or plasma treatment to remove the capping agent.