Formation of low-dimensional close-packed arrays of nanoparticles in a dewetting water layer

We report on self-assembly of CoPt3 particles (diameter 6 nm) into low-dimensional close-packed arrays. This was achieved on substrates coated with a nitrocellulose (NC) thin layer by spreading of a hexane solution containing CoPt3 particles, hexadecylamine, and water. In a first step, the solution film transforms into a bilayer containing a hexane layer located onto a water film. The hexane layer dewets the water layer and the latter dewets the NC covered substrate. Dewetting of the water layer leads to the formation of water droplets. Finally, the particles follow the motion of the contact line of the dewetting water layer and thus assemble into close-packed arrays at the periphery of the water droplets.