Building 3D-organaized Nanocrystallites to Harness Grain-boundary Defects

Topological defects (i.e. dislocation, grain-boundaries) play an essential role in the properties of crystalline materials. When the size of the crystallite or functional domain of the materials decreases to the nanometer scale, the defects predominantly determine those properties. To date, however, neither bottom-up nor top-down methods for synthesizing nanocrystalline materials have been able to find a reliable way of controlling these defects. Herein, we demonstrate the delicate control of 3D heteroepitaxy using a lipid membrane-like synthetic system to grow various nanocrystallites, 3D organized with uniform grain-boundaries and related defects. In the resulting structures, the 3D-patterned strain field, which exists in the form of disclinations and dislocations, can be determined with atomic precision and even tailored. Through nano-to-macro crystallography and spectroscopy, we have also confirmed that the uniformity and dicreteness of the defects allow us to find a reliable correlation between the local strains/defects and collective electrochemical properties (i.e. catalytic activities for oxygen reduction reactions). These middle-entropy nanomaterials give us an opportunity to conduct nano-mechanics of 3D organizations of interconnected and symmetry-related functional domains and explore novel electronic states emerging from 3D coherent lattice and topological defects. Lastly, the current research focus to build next-generation functional nanomaterials for energy nanotechnology using 3D nano-mechanics will be discussed.