Bottom-up fabrication of three-dimensional nanoporous gold from Au nanoparticles using nanowelding

Abstract

Three-dimensional (3D) nanoporous gold (NPG) shows promising applications in various fields. However, its most common fabrication strategy (i.e., dealloying) faces the problems of high energy consumption, resource waste, the use of corrosive solvent, and residue of the sacrificial component. Here, we report a general bottom-up nanowelding strategy to fabricate high-purity NPG from Au nanoparticles (NPs), accomplished via interfacial self-assembly of the Au NPs into monolayer Au NP film, its subsequent layer-by-layer transfer onto a solid substrate, and direct current (DC) nanowelding. We show that the DC nanowelding process can gradually evolve the layered Au NP film into NPG at low temperatures within 10 s, while not damaging their spherical structure. This is because during the nanowelding, electrons are preferred to be localized at the high-resistance NP/NP junctions, whose electrostatic repulsion in turn strengthens their surface atom diffusion to initiate a mild solid-state diffusion nanowelding. Furthermore, when using differently sized Au NPs as the starting building blocks, this strategy allows readily tuning the thickness, ligament size, and pore size, thereby offering great flexibility to create functional porous nanomaterials, e.g., electrocatalyst for methanol electrooxidation. Surely, low-temperature nanowelding can play a role for the production of diverse nanoporous materials from other NPs beyond Au NPs.