Porous Gold with a Nested‐Network Architecture and Ultrafine Structure

Abstract

A preparation strategy is developed for monolithic samples of nanoporous gold with a hierarchical structure comprising two nested networks of solid "ligaments" on distinctly different structural length scales. The electrochemical dealloying protocol achieves a large retention of less noble element in a fi rst corrosion step, thereby allowing an extra corrosion step which forms a separate structural hierarchy level. The benefi cial impact of adding Pt to the Ag-Au master alloys that are more conventionally used in dealloying approaches to nanoporous gold is demonstrated. At ≈6 nm, the lower hierarchy level ligament size emerges extremely small. Furthermore, Pt favors the retention of Ag during the fi rst dealloying step even when the master alloy has a high Au content. The high Au content reduces the corrosion-induced shrinkage, mitigating crack formation during preparation and favoring the formation of high-quality macroscopic (mm-sized) samples. The corrosion effectively carves out the nanoscale hierarchical ligament structure from the parent crystals tens of micrometers in size. This is revealed by X-ray as well as electron backscatter diffraction, which shows that the porous crystallites inherit the highly ordered, macroscopic crystal lattice structure of the master alloy.

Nanoporous-gold-based composites: toward tensile ductility

“…26 Nonetheless the network exhibits a uniform and highly correlated architecture, as evidenced by a pronounced interference peak in small-angle scattering. 27,28 Compression tests As a preliminary to the results obtained with composite samples, Figure 4 shows compression stress-strain curves for monolithic samples of the native NPG reinforcement phase alone. The data are partly from Wang et al, 18 obtained with identical procedures as here.…”

Plasmonic nanosponges

“…The ligaments possess the morphology of coexistent concave and convex with high curvature gradients, which enable the porous structure highly active by the catalytic applications [34]. Porous gold with multilevel porous structures can be also realized by applying a two-step dealloying strategy [35]. Residual Ag can be often detected in the NPG formed from Au-Ag alloy.…”

Nanoporous Metals with Structural Hierarchy: A Review

“…When carefully designed and controlled, solidification strategies can result in highly ordered structures with well-defined structural length scales, see ref. [75,[97][98][99] Hierarchical np-Pd has also been generated by the electrochemical dealloying of a Pd-Ni-P metallic glass. A bimodal porous structure is developed in regions where the microstructure is heterogeneous due to the different chemical activities for Al and PdAl 3 phases.…”

“…[97,152] Function requires high surface area with many active surface sites and, hence, small pores. [97,152] Function requires high surface area with many active surface sites and, hence, small pores.…”