I understand that you have target inside a liquid and you want to control the space between the produced Nps, isn't it? if yes, I suggest (but I am not sure) you can use electrolysis cell (anode and cathode) the uniform electrical field generated between the electrodes will keep the distance between the nanoparticles produced. If I miss understand please reject my answer. 

Dear Dr. Jassim ,

Did you mean to prevent aggregation or clustering  ?

Dears Prof. Dr. Ghaleb Al Dahash , Mr.sam Taheri and Mr. Mohamed S. Mohamed

Thanks for answers.

Kindly Prof. Dr. Al-Dahash

I assume no occur any aggregation in Nps , after this cause I want separation between Nps ( controlling in path or distance between NPs)

Using Magnet

Dear Dr. Zhen

I think this is good idea, if you have paper include this idea kindly, sent this paper to me