Three dimensional (3D) atomic structures of materials govern the physical and catalytic properties of materials. As the material dimension becomes nanometer-scale, 3D structures of colloidal nanocrystals typically deviate from the lattice structures measured and expected in their bulk counterparts. This is presumably because of the dominance of surface dangling bonds, defects, and dislocations within the volume of nanocrystals. To understand these unique structural features of nanocrystal, a method that can precisely determine the positions of the individual atoms is required. We introduce our experimental efforts using a combination of new techniques including graphene liquid cell for in situ TEM, aberration-corrected TEM, structure analysis algorithm, and 3D strain measurement. We apply it to determine the 3D atomic arrangements of different types of nanocrystals in solution. Our high-resolution 3D density maps and fitted atomic models show crystal structures of individual nanocrystals with structural degeneracies, including single crystalline, polycrystalline, distorted structures, and a dislocation. We also discuss the extent of this new analytical method regarding types and dimensions of materials systems which require unprecedented structural information in native conditions.

3D structure study of colloidal nanocrystals using liquid phase TEM

2019 Spring National Meeting

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