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What is the world's finest powder substance that has the smallest granules but remains solid?

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  • $\begingroup$ Welcome to Chemistry SE! Please define, in your terms, what finest is. $\endgroup$ – Asker123 May 10 '15 at 12:27
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Clusters of just a few atoms, such as gold atomic clusters, and quantum dot nanoparticles could be considered very fine powders, though they usually are suspended in another substance to keep the clusters from agglomerating. Particles this tiny have different properties from the bulk material, both because of quantum effects (there are few particles, so there is not a continuous valence band) and because more atoms are at the surface interface than are surrounded by similar atoms in the interior.

See Quantum dot for more information.

I hope this fits your definition of a "fine powder". You might also be interested in pyrophoric iron.

BTW, ruby glass is made using colloidal, i.e. super-finely divided, gold.

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    $\begingroup$ While not quantum dots, there are some pretty small nanoparticles which can be bought in bulk as a powder. The type that come to mind the most are titanium dioxide nanoparticles, which are regularly sold in kilogram bags with particle diameters as small as $\rm{21\ nm}$. $\endgroup$ – Nicolau Saker Neto May 10 '15 at 23:48
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    $\begingroup$ Maybe fullerens and similar nanocarbons qualify as one of the finest powder stable without any solubilizer. $\endgroup$ – Greg May 11 '15 at 5:38
  • $\begingroup$ @Greg this is interesting question, can a substance consisting of individual molecules be a powder rather than a liquid or gas? $\endgroup$ – Anixx May 11 '15 at 5:59
  • $\begingroup$ @Anixx There is no substantial difference between large single molecules and nanparticles/fine powders. If you take a look at C60 or nanotubes, there is nothing in there physical appearance that would make them gas or liquid. see commons.wikimedia.org/wiki/File:C60_powder.jpg $\endgroup$ – Greg May 11 '15 at 7:55
  • $\begingroup$ @Greg the powder on the photo may be composed of particles greater than single molecules $\endgroup$ – Anixx May 11 '15 at 8:15

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