Self-Assembly of Nanocrystal Superlattices: puzzles and opportunities*

Nanoparticles of different functional materials can self-assemble from colloidal solutions into long-range ordered periodic structures (superlattices). Such assemblies provide a powerful platform for designing macroscopic solids with tailored electronic, magnetic, optical and catalytic properties. Unlike atomic and molecular crystals where atoms, lattice geometry, and interatomic distances are fixed entities, the arrays of nanocrystals represent solids made of “designer atoms” with potential for continuous tuning their physical and chemical properties.
The self-assembly process is guided by an intricate interplay of entropy-driven crystallization and soft interparticle interactions, such as van der Waals and dipolar forces. The surface ligands also play an important and sometimes counterintuitive role, supporting many-body interactions and stabilizing complex structures.
By using optimized surface chemistries, the electronic coupling between individual nanoparticles can be significantly enhanced, approaching the metal-insulator transition. We will demonstrate the power of “modular” materials fabrication for electronic and optoelectronic devices and the utility of engineered nanomaterials for real-world technologies.