Figure 3.

Making of hierarchical nanoporous gold by dealloying. (A) Schematic illustration of the preparation steps: (i) first dealloying of a Ag-rich precursor alloy leaves a nanoporous network with high amount of residual Ag; (ii) coarsening of the ligament structure by thermal annealing; (iii) second dealloying forms the lower level nanoporous microstructure. (B–D) Scanning electron micrographs of the microstructure after the first dealloying (B), coarsening (C), and second dealloying steps (D). Reproduced with permission from ref (177). Copyright 2021 American Association for the Advancement of Science.