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Ptychography provides detailed look at challenging nanoparticles

JUN 14, 2024
Ptychography can capture signals from light elements in a dose-effective manner in 3D, providing a more complete understanding of upconverting core-shell nanoparticles than conventional methods.
Ptychography provides detailed look at challenging nanoparticles internal name

Ptychography provides detailed look at challenging nanoparticles lead image

Upconverting nanoparticles can convert infrared light to visible light, making them useful for bio-imaging, patterning, and other optical applications. Understanding the structure of these particles can help researchers looking to improve their function or design better materials. While scanning transmission electron microscopy (STEM) can often be used to image nanostructures, electron beam-sensitive structures like upconverting nanoparticles are challenging to image with this approach.

Ribet et al. addressed this problem by employing multislice electron ptychography, a phase imaging method that collects more data using a lower electron dose.

Conventional STEM involves measuring a single data point from an annular detector at each position across a two-dimensional sample area.

“Instead, we did a 4D-STEM experiment, where we recorded a full diffraction pattern at each position in real space,” said author Stephanie Ribet. “The 4D-dataset tells us a lot more structural information about our sample.”

This ptychography approach is also more sensitive to light elements, allowing the team to capture the positions of fluorine atoms in their sample, and employing multislice imaging let them study how the particles changed with depth. Using this method, the team evaluated nanoparticles with and without defects to determine their structural properties.

The researchers are excited to continue to employ this method to study materials that are otherwise challenging to image due to their weak scattering or dose sensitivity.

“This was a great example of how multislice ptychography can be used in materials characterization,” said Ribet. “We’re excited about applying this to different structures and characterizing their 3D morphology at high resolutions.”

Source: “Uncovering the three-dimensional structure of upconverting core-shell nanoparticles with multislice electron ptychography,” by Stephanie M. Ribet, Georgios Varnavides, Cassio C. S. Pedroso, Bruce E. Cohen, Peter Ercius, Mary C. Scott, and Colin Ophus, Applied Physics Letters (2024). The article can be accessed at https://doi.org/10.1063/5.0206814 .

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