Environmental Molecular Sciences Laboratory

A DOE Office of Science User Facility

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In situ TEM study of branched nanocrystal growth mechanism

Date: 
Thursday, October 1, 2020
Principal Investigator: 
Dongsheng Li
Lead Institution: 
Pacific Northwest National Laboratory
Project ID: 
51625
Abstract: 

The long-term goal of this project is to understand the growth of complex crystalline structures by aggregation and oriented attachment (OA) of primary nanoparticles and thus to tune crystal structures with desired properties. The formation of materials through this process both leads to branched structures of interest for photovoltaics, energy storage devices and catalysis, and appears to be important in biomineral formation by living organisms, as well as non-biogenic geochemical systems. Recently, we made a major breakthrough in understanding the process of OA by demonstrating the ability to directly observe this process in the iron oxyhydroxide system at lattice resolution in situ. Analysis of OA processes allowed us to produce the first estimate of the force that drives OA and show that electrostatics is the most likely source of OA in this system. Successful application of this capability to branched nanowire structures will lead to a new understanding of the underlying mechanisms and controls on the morphology that promise to significantly advance our ability to utilize branching to create functional materials.
The purpose of this project is to now apply in situ TEM to oxides and metals (TiO2, ZnO, Pt, and Au) systems, where the growth is highly anisotropic along different crystallographic directions resulting in tree-like structures which we believe are ones in which we can isolate the key factors controlling nucleation, interaction and OA of primary particles, and eventual formation of branched nanowires.