Self-assembled patterns of nanospheres with symmetries from submicrons to centimeters.

We report pattern formations during the drying of a sheet of an aqueous suspension of nanospheres. The structures self-assembled by nanospheres span several centimeters and exhibit order at scales ranging from nanometers to centimeters, although the substrate has no predefined pattern. Within these structures, several regular patterns can be identified, including two-dimensional periodic gratings generated by crack networks with a characteristic spatial frequency linearly depending on the evaporation speed, and three-dimensional flower-like structures. This phenomenon potentially provides a simple and inexpensive method to grow structures having unique electromagnetic and/or biological properties. [ABSTRACT FROM AUTHOR]