Self-Assembly of 2D Nematic and Random Arrays of Sterically Stabilized Nanoscale Rods with and without Evaporation.

The adequate manipulation of nanometer-scale building blocks using dispersion systems is regarded as a fundamental technique to fabricate elaborate microstructures. Although a liquid flow with evaporation is generally regarded as an essential factor for the self-assembly of floating blocks, experimental evidence has not been sufficient to clarify the importance of the flow in the dispersion systems. In the present study, 2D nematic layers of sterically stabilized nanoscale calcite rods were achieved in a millimeter-scale region on a solid substrate via the very slow recession of an organic dispersion with evaporation. 2D random arrays of the nanorods were obtained via recession of the liquid in the same system without evaporation. When the nanorods were not sterically stabilized, 3D random arrays were formed even with evaporation. We demonstrated that the evaporation-driven flow of sterically stabilized nanorods to a confined space at the air-liquid-solid interface is essential for the formation of 2D nematic structures on a substrate.