[curious77]

After drying, can synthesized nanoparticles be crushed using mortar and pestle for SEM analysis?

[cth]

Yes. Just be careful to wear a suitable dust mask.
Nanoparticles are so small and light, they can be carried easily away by a bit of wind. And you don't want to breath them.

[408]

Do it under a light solvent.  Like hexane or something.  Then they do not float away and can be transferred to your SEM plate as a quick evaporating slurry.

[cth]

Yes. Just be careful to wear a suitable dust mask.
Nanoparticles are so small and light, they can be carried easily away by a bit of wind. And you don't want to breath them.

will this bring any problem with health especially lung? a bit scared.

Possibly. The fact is that nobody knows for sure. http://en.wikipedia.org/wiki/Nanoparticles#Safety

Remark, although scientific and industrial interests in nanoparticles are recent, nanoparticles have been in our environment for much longer: wood fire, cigarette smoke, car exhaust,... all release various amounts. True enough, the examples I just mentioned are harmful to breath (and not only for the nanoparticles). But no need to be over alarmist, just being reasonably cautious. 

Second remark, I think "nanoparticles" is too general a term, which covers very different compounds that have nothing in common but their small size... For example, carbon nanotubes http://en.wikipedia.org/wiki/Carbon_nanotube and TiO₂ nanoparticles.