Metallic nano-foams – properties and perspectives

Metal nanofoams are ancient materials: the first patent was filed by Raney in 1927, on nickel, for an application in heterogeneous catalysis. They are also very recent materials, with intensive studies since the 2000s and the development of unexpected behaviors such as the catalytic properties of nanometric gold, chemical and biological selectivity, and plasmonics. The need for innovation in the field of materials is permanent, and is even intensifying in the face of the challenges that societies are setting themselves, stemming from natural evolution (improving living conditions: health, industry, transport, building, etc.) and environmental necessities (energy, ecology). This context calls for the creation of new functions, which will in fact mainly rely on new materials, new architectures or new concepts.

Metal foams (micrometric) are mass-produced, and are mainly used for their mechanical properties and in the metallurgical industry, for example. Their smaller siblings, metal nanofoams, have catalytic applications but are more confidential, mainly due to the small quantities produced. However, the niche sectors in which they are used are significant. Applications discussed in this article include actuators, sensors (especially biosensors), plasmonics-based Raman and fluorescence spectroscopy, microelectronics interconnection, catalysis and electro-catalysis, batteries and supercapacitors.

Nano-foams are cellular materials with a bi-continuous structure. In this article, the nano-foams described are mainly those resulting from the dealloying process, as they are the most widespread. They are made up of disordered, connected ligaments of nanometric dimensions, developing a porosity of the order of 50%. The application prospects developed are based on a review of the optical, mechanical and chemical properties of metallic nanofoams, with systematic emphasis on their nanometric nature and high specific surface area.