  We describe briefly a possible coagulation mechanism for unipolar nanodust
clouds of 3 nm single charged metal nanoparticles. A theoretical dependence of
the critical cloud concentration vs the Hamaker constant is derived and
compared with available experimental data for Au, Ag, and Cu. Curious empty 1-3
um spheres, precipitated from the clouds in the result of coagulation, are
discussed. The work may be interesting for nanoprinting and initial planetary
formation mechanisms as establishing a bridge between nano and micro solids.
