Nanoparticles are defined as < 100 nm. If you're wanting a powder then you have a collection of fused and post-micron aggregates, so I doubt you'll be able to get material of this type.. Much of the surface may be available for gas absorption, dissolution, reactivity etc and this scale (< 100 nm) may be specified by, say, BET (> 60 ms/g for unit density). If you want to preserve material at this size then it's best generated by a bottom-up process keeping the material in colloidal suspension for stability.

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Hello, the 0.5um scale is not nano scale... in general the nano scale is started from 1 nm to 100 nm.

Dear all, thanks for the answers! Ok, not nano particles, half micron size particles (200-500nm). The question is about this type of scales.

Dmitry