Self-assembled superlattices of size-and shape-selected nanocrystals: Interdigitative and gear molecular assembling models

摘要

Size and shape selected nanocrystals behave asfundamental building blocks that can be used to constructnanocrystal assembled superlattices. This is a new state ofmaterials that has orders in atomistic and nanocrystal length-scales.The nanocrystals are passivated with organic molecules (callthiolates) that not only protect them from coalescing but act as themolecular bonds for forming the superlattice structure. Theinterparticle distance is adjustable, possibly resulting in tunableelectric, optical, and transport properties. In this article,nanocrystal superlattices (NCSs) constructed by truncatedoctahedral Ag particles are studied to illustrate the bundling andinterdigitation of the passivation thiolates in forming thedirectional molecular bonds in NCSs. The {111}S facets observedin the NCSs suggest the key roles played by the molecular bondingenergy in forming the surfaces of NCSs. The formation of twins inthe NCSs supports the "gear" assembling model of the nanocrystals.The gear assembling is likely to have higher energy than theinterdigitative assembling.