Nanofoam

Nanofoams are a class of nanostructured, porous materials (foams) containing a significant population of pores with diameters less than 100 nm. Aerogels are one example of nanofoam.

Metallic nanofoams are a subcategorization of nanofoams; more specifically, there are nanofoams consisting of metals, often pure, that form interconnected networks of ligaments that make up the structure of the foam. A variety of metals are used, including copper, nickel, gold, and platinum. Metallic nanofoams may offer certain advantages over alternative polymer nanofoams; structurally, they retain the electrical conductivity of metals, offer increased ductility, as well as the higher surface area and nano-architecture properties offered by nanofoams.

Synthesis of metallic nanofoams may be accomplished through a variety of methods. In 2006, researchers produced metal nanofoams by igniting pellets of energetic metal bis(tetrazolato)amine complexes. Nanofoams of iron, cobalt, nickel, copper, silver, and palladium have been prepared through this technique. These materials exhibit densities as low as 11 mg/cm³, and surface areas as high as 258 m²/g. These foams are effective catalysts and electrocatalyst supports. Also, metal nanofoams can be made by electrodeposition of metals inside templates with interconnected pores, such as 3D-porous anodic aluminum oxide (AAO). Such method gives nanofoams with an organized structure and allows to control the surface area and porosity of the fabricated material.

A 2016 study discussed a low temperature/pressure microwave solvothermal method for fabricating pure copper, silver, and nickel metal nanofoams. The process claims to be non-hazardous, novel, as well as facile, with an emphasis on its low-waste and low-cost method of manufacturing.

Additionally, a 2020 publication discussed successful synthesis of nanofoam films from silver, gold, copper, and palladium through the use of a modified vacuum thermal evaporation method.

Metallic nanofoams have seen a broad variety of applications, including catalysts, hydrogen storage, as well as fuel cells. Additionally, applications of metallic nanofoam as an electrocatalyst have been fruitful; a nickel-iron nanofoam catalyst has proven to exhibit exceptional electrocatalytic performance, as well as water-splitting to isolate hydrogen atoms. Applications to the clean energy industry, specifically for lithium-ion batteries and other fuel cells, have been discussed as well.

Through literature discussing the fabrication of a completely porous nanofoam biopolymer is scarce, recent endeavors have resulted in the formation of nanofoam surfaces on biopolymers. In these instances, biopolymers such as collagen and gelatine, chitosan, and pure curcumin have been used to varying degrees.

A 2008 study explored the usage of femtosecond laser irradiation to create permanent spatial arrangements in transparent materials, particularly in its usage to form a singular foamed layer upon biopolymers such as collagen or curcumin. Foaming these surfaces results in a variety of surface modifications that may improve the material's ability for cell adhesion, permeability of fluids due to cell structure, and the formation of nanoscopic fibers.