Pore and ligament size control, thermal stability and mechanical properties of nanoporous single crystals of gold.

Nanoporous gold is widely used in research and nanotechnology because of its diverse properties, including high surface area and catalytic activity. The ligament size is usually considered as one of the main parameters controlling thermal stability and mechanical properties of nanoporous gold. Recently we developed a method for creating nanoporous single crystal gold particles using eutectic decomposition of Au-Ge, followed by selective etching of Ge. Here, we used this novel method to create nanoporous gold particles with controlled ligament sizes by changing the initial sample's relative concentrations of gold and germanium. When investigated over 1-4 h at 250-400 °C the material was thermally stable up to 350 °C, which is higher than the thermal stability of "classical" nanoporous gold prepared by dealloying. Mechanical properties were examined utilizing nanoindentation of nanoporous gold before and after annealing. For smaller ligament sizes, hardness increased with annealing temperature up to 300 °C and then strongly decreased. For larger ligament sizes, hardness decreased with increasing annealing temperature. Young's modulus was unchanged up to 300 °C.