Typically we start from the bottom and build up the particles. You begin by reacting the molecules to form a mixture in which solid particles are suspended in a liquid. Then you pour this mixture into a mold, where it becomes a soft, jelly-like material. Finally, you carefully apply heat and drying treatments to produce the nanoparticles. This technique is great because it produces a very even distribution of nanoparticle sizes.
It's very difficult to take bulk materials and just grind them up to make nanoparticles; this method usually creates a broad particle size distribution of both nanoparticles and larger particles. One can isolate the nanosized particles by setting up a fluid flow in which the small particles get carried along and the larger ones fall out due to gravity, but it's a very tedious and slow process.
Was this article helpful?