Array formation in nano-colloids: Theory and experiment in 2D

We discuss theoretical and experimental aspects of the array formation of nano-colloids in two-dimensional (2D) situations. In particular, we treat metal nanocrystals which have been passivated by surfactant monolayers and then deposited on the free surface of water. Their self-organization properties follow from the fact that the relevant interparticle attractions do not greatly exceed thermal energies, thereby allowing for equilibrium structures to form and to evolve reversibly as a function of temperature and concentration. In the case of large enough metal cores, spatially-modulated phases arise because of long-range repulsions between particles; for smaller cores, the interactions are highly directional, giving rise to linear chain structures at low concentrations and to extended networks at higher densities.