Self-assembly of gold nanowire networks into gold foams: Production, ultrastructure and applications

Fine-tuning the shape of nanostructured materials through easy and sustainable methods is a challenging task for green nanotechnology. In this contribution, we propose a cheap and green method capable of generating nanoporous gold (gold foam). The proposed gold foams are fabricated by the self-assembly of gold nanowire networks in an eco-friendly solvent (water) and at room temperature. Our strategy allows a controlled growth process able to scale down the morphology of gold nanowire networks and the ultra-structure of the corresponding gold foams. The internal ultra-structure could be observed by conventional transmission electron microscopy by developing a method to embed a polymer resin in gold foam giving a composite material which can be cut into very thin slices (50 nm). We also demonstrate the potential applications and versatility of our method in terms of catalysis and very uniquely in terms of physical entrapment of materials (magnetic nanoparticles, thermo-labile molecules) without altering the ultrastructure of the gold-foam or the entrapped material.