Supercritical fluids have high diffusivity, low viscosity and controllable solubility. They are not condensed in the liquid phase. Thus, they are expected to overcome the limitation of diffusivity and mass transfer of conventional solvents and can carry effective amounts of substances into fine spaces.

We demonstrated a novel method to synthesize porous materials using supercritical fluids, called the Nanoscale Casting (NC) process. The precursors of the metals or metal oxides are dissolved in supercritical fluids and are attached to activated carbon templates. After removal of the activated carbon templates, nanoporous metals or metal oxides replicating the morphology of the activated carbon over a wide range from nanometers to centimeters can be produced. Supercritical fluids are shown to be effective solvents for chemical reactions (e.g., sol-gel) in nanospaces.