TEM captures spinning nanoparticles


Rebecca Pool

Thursday, June 23, 2016 - 15:00
Image: 3D structure of nanocrystals in solution determined with near-atomic resolution
Using novel in-situ TEM, US-based researchers have captured near-atomic resolution videos of individual colloidal nanoparticles rotating in solution.
Professor Paul Alivisatos from Lawrence Berkeley National Laboratory and colleagues, went on to determine the 3D atomic structure of these nanocrystals and provide new insight into growth mechanisms of the materials.
The researchers hope their TEM method will shed light onto how molecular structures migrate and grow in solutions, which is critical for the design of more efficient materials for electricity-generating fuel cells, automotive catalytic converters, and other applications.
To investigate the nanocrystal in solution, Alivisatos and colleagues developed the method,  'Three-Dimensional Structure Identification of Nanoparticles by Graphene Liquid Cell', 3D-SINGLE.
They combined a graphene liquid cell, high resolution TEM - FEI Titan 80/300 - and a direct electron detector with an algorithm for single particle 3D reconstruction, originally developed for analysis of biological molecules.
(A) Schematic of individual rotating platinum nanoparticles in a graphene liquid cell. (B and C) Two-dimensional snapshots are used to reconstruct the 3D images of two different particles. Scale bars: 0.5 nm
According to the researchers, the graphene liquid cell only contains a tiny sample to minimise unwanted electron beam scattering.
The structure of the moving, rotating nanocrystals was imaged many times by a direct electron detector to produce movies with millisecond frame-to-frame time resolution. 
Crucially, the method yielded two 3D structures of individual platinum nanocrystals at near-atomic resolution.
Results confirmed that the individual, and surprisingly asymmetric, particles from the same synthesis solution followed different initiation and growth trajectories.
"Because our method derives the 3D structure from images of individual nanoparticles rotating freely in solution, it enables the analysis of heterogeneous populations of potentially unordered nanoparticles that are synthesised in solution," highlights Alivisatos
"This provides a means to understand the structure and stability of defects at the nanoscale," he adds.
A better understanding of synthesis, growth, and properties of individual colloidal nanoparticles could also advance the development of novel materials for applications in catalysis and renewable energy.
Research is published in Science.
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