Structural Study of a Self-Assembled Gold Mesocrystal Grain by Coherent X-ray Diffraction Imaging

TL;DR

This study uses coherent X-ray diffraction imaging to reveal detailed internal structures and heterogeneity of a gold mesocrystal, advancing understanding of self-assembled nanostructured materials.

Contribution

It provides the first high-resolution structural characterization of a gold mesocrystal, including internal defects and strain distribution, using coherent X-ray diffraction imaging.

Findings

Resolved individual gold nanoparticles within the mesocrystal.

Identified local deviations in lattice parameters and internal defects.

Found that the superlattice and multidomain structure are closely aligned.

Abstract

Mesocrystals are nanostructured materials consisting of individual nanocrystals having a preferred crystallographic orientation. On mesoscopic length scales, the properties of mesocrystals are strongly affected by structural heterogeneity. Here, we report the detailed structural characterization of a faceted mesocrystal grain self-assembled from 60 nm sized gold nanocubes. Using coherent X-ray diffraction imaging, we determined the structure of the mesocrystal with the resolution sufficient to resolve each gold nanoparticle. The reconstructed electron density of the gold mesocrystal reveals its intrinsic structural heterogeneity, including local deviations of lattice parameters, and the presence of internal defects. The strain distribution shows that the average superlattice obtained by angular X-ray cross-correlation analysis and the real, multidomain structure of a mesocrystal are very close to each other, with a deviation less than 10 percent. These results will provide an important impact to understanding of the fundamental principles of structuring and self-assembly including ensuing properties of mesocrystals.