Nearest-neighbour nanocrystal bonding dictates framework stability or collapse in colloidal nanocrystal frameworks

Abstract

Block copolymers serve as architecture-directing agents for the assembly of colloidal nanocrystals into a variety of mesoporous solids. Here we report the fundamental order–disorder transition in such assemblies, which yield, on one hand, ordered colloidal nanocrystals frameworks or, alternatively, disordered mesoporous nanocrystal films. Our determination of the order–disorder transition is based on extensive image analysis of films after thermal processing. The number of nearest-nanocrystal neighbours emerges as a critical parameter dictating assembly outcomes, which is in turn determined by the nanocrystal volume fraction (f_NC). We also identify the minimum f_NC needed to support the structure against collapse.