X-Ray Studies of Nanoporous Gold: Powder Diffraction by Large Crystals with Small Holes

TL;DR

This study investigates how nanoscale holes in large crystalline nanoporous gold affect X-ray diffraction, revealing that ligament size influences scattering and microstrain, with implications for understanding its structural properties.

Contribution

It provides a theoretical and experimental analysis of diffraction in nanoporous gold, highlighting the impact of ligament size and thermal effects on scattering and microstrain.

Findings

Ligament size correlates with coherent scattering domain size.

Samples with ligament sizes below 10 nm exhibit high microstrains.

Thermal relaxation causes loss of long-range coherence and microstrain.

Abstract

X-ray diffraction studies of nanoporous gold face the poorly understood diffraction scenario where large coherent crystals are riddled with nanoscale holes. Theoretical considerations derived in this study show that the ligament size of the porous network influences the scattering despite being quasi single crystalline. Virtual diffraction of artificially generated samples confirms the results but also shows a loss of long-range coherency and the appearance of microstrain due to thermal relaxation. Subsequently, a large set of laboratory X-ray investigations of nanoporous gold fabricated by different approaches and synthesis parameters reveal a clear correlation between ligament size and size of the coherent scattering domains as well as extremely high microstrains in samples with ligament sizes below 10 nm.