Abstract: Organization of nanocrystals (NCs) into larger scale superstructures is a promising approach for integrating the useful properties of single NCs into macroscopic forms relevant in technology. These NC superstructural metamaterials possess order on two length scales: the atomic lattice of the NCs and the interparticle spacing of the superstructure. Preparing such highly organized superstructural materials requires exquisite control in the assemblies from the atomic, nano-, to macroscopic levels. While building assemblies from isotropic NCs has been well studied and documented, creating novel and complex superstructures from anisotropic building blocks still lags significantly behind.

In this talk, I will discuss how we design anisotropic NC building blocks by developing colloidal syntheses of size or shape, composition, and surface-tailored quantum-dot-based NCs and exploring methods for their assembly into atomically precise, superstructural architectures. Through fine-tuning the anisotropic interactions between NC building blocks and assembly environment, not only periodic crystalline superlattices and supercrystals, but also aperiodic quasicrystalline NC films, can be fabricated. Both translational periodicities and orientational orderings of the final constructs are decoded through characterization techniques in real and reciprocal spaces. The dictating driving forces and new tiling rules (for the quasi-crystalline order) that lead to the obtained architectures are identified through experimental explorations, structural reconstructions, and molecular dynamics computer simulations. Our study provides insightful information about the packing of anisotropic NCs into complex superstructural metamaterials and may further enhance their potential in practical applications.

Bio: Ou Chen is an assistant professor in the chemistry department of Brown University. He completed his Ph.D. in chemistry at the University of Florida.