Ultrafine Nanoporous Gold via Thiol Compound-Mediated Chemical Dealloying

Nanoporous gold (NPG), whose chemical and physical properties largely depend on its ligament size and pore size, is attractive for many applications. However, it is difficult to achieve NPG with ultrasmall structural features. Here, we report a convenient thiol compound-mediated dealloying method for fabricating NPG with feature size down to 4 nm (one of the smallest values reported to date) at an ambient air condition. It is unraveled that the ultrafine ligament and pore sizes were mainly due to the lowered diffusion rate of the Au atoms at the alloy/electrolyte interface upon forming complexes with the thiol compounds in the etchant. This work opens a new route for conveniently controlling the structural features of dealloyed nanoporous materials.