Morphology Control of Nanoporous Gold Through Selective Dissolution of Au–Ge Eutectic Microstructures

The synthesis of nanoporous gold (np-Au) through the conventional method of dealloying a more reactive element from AuTherma alloys has been extensively studied and applied in various fields, particularly catalysis. Herein, a novel approach to creating droplet-like np-Au through the selective dissolution of Au–Ge eutectic microstructures is explored. This work reveals that adjusting the undercooling of the eutectic melt during solidification allows for the tuning of pore and ligament sizes. It is demonstrated that this undercooling can be modified, either directly or indirectly, by adjusting either the cooling rate or the heterogeneous nucleation site density of the eutectic melt. The findings, aligned with the model based on classical theory for eutectic solidification, elucidate the connection between the tuning of pore and ligament sizes in the eutectic microstructure and the undercooling of the eutectic melt. Importantly, it is established that this phenomenon is applicable across a variety of compositions, including hypereutectic, eutectic, and hypoeutectic. The ability to regulate pore and ligament size in single crystals of np-Au droplets offers a novel approach to synthesizing catalytic np-Au crystals with enhanced mechanical and thermal stability compared to conventional methods.