If particles are aggregated on SEM sample holder it doesn't mean they are aggregated in the solution. Just do DLS of your particles to see if they are aggregated or not.

If they are indeed aggregated and you want to separate them, then try to find out conditions for centrifugation, where you will have only desired size in supernatant solution.

Are you starting with a powder or a colloidal suspension?

Try to disperse your powdered sample in acetone and after 30-45 min of ultrasonic treatment put a small drop of the liquid on a cover slip. Cut down the cover slip according to your required dimensions and coat it with Au/Pt to observe the sem micrographs.

ultrasonic bath can re disperse the particles

If particles are aggregated on SEM sample holder it doesn't mean they are aggregated in the solution. Just do DLS of your particles to see if they are aggregated or not.

If they are indeed aggregated and you want to separate them, then try to find out conditions for centrifugation, where you will have only desired size in supernatant solution.

Thanks all for your valuable suggestions.

I took my powder sample and added in acetone and the mixture is sonicated about 40 minutes.But still I get only particle agglomerates and also got some particles of approx 40nm size.By centrifugation is it possible to seperate these particles?

Hi Manish, Best option is to mix your sample in suitable solvent (acetone as you are using it already I assume it is suitable or you can use distilled water also if it is suitable) then perform high shear homogenization for 5 minutes at high rpm ( as high as possible).Then mount your sample over small silicon wafer slides(just a drop to cover whole slide) and allow them to dry completely to evaporate the liquid. Then place this slide for SEM.

If high shear homogeniser is not available , then go for prop-sonicator. If

prop- sonicator is not available then only go for ultrasonication as ability to segregate decreases in above mentioned order. You can find these setups in chemistry or chemical engineering department. If you have further cunfusion please feel free to ask here.

Thank you Rishabh sir