Probing the atomically diffuse interfaces in core-shell nanoparticles in three dimensions

TL;DR

This study uses atomic resolution electron tomography to reveal that core-shell interfaces in palladium-platinum nanoparticles are atomically diffuse with a consistent thickness, providing insights into their structure-property relationships.

Contribution

It introduces a method to visualize 3D atomic structures of core-shell nanoparticles and uncovers the diffuse nature of their interfaces at atomic resolution.

Findings

Core-shell interfaces are atomically diffuse with ~4.2 Å thickness.

The interface's Pd concentration relates to electric double layers.

Structural variety includes bond length, coordination, and symmetry.

Abstract

Deciphering the three-dimensional atomic structure of solid-solid interfaces in core-shell nanomaterials is the key to understand their remarkable catalytical, optical and electronic properties. Here, we probe the three-dimensional atomic structures of palladium-platinum core-shell nanoparticles at the single-atom level using atomic resolution electron tomography. We successfully quantify the rich structural variety of core-shell nanoparticles including bond length, coordination number, local bond orientation order, grain boundary, and five-fold symmetry, all in 3D at atomic resolution. Instead of forming an atomically-sharp boundary, the core-shell interface is atomically diffuse with an average thickness of 4.2 A, irrespective of the particle's size, morphology, or crystallographic texture. The high concentration of Pd in the interface is highly related to the electric double layers of the Pd seeds. These results advance our understanding of core-shell structures at the fundamental level, providing potential strategies into nanomaterial manipulation and chemical property regulation.