A rapid, convenient and environmentally benign method has been developed for the fabrication of metal nanoparticle–multiwall carbon nanotube (MWCNT) composites. Nanoparticles of palladium, rhodium and ruthenium are deposited onto functionalized MWCNTs through a simple hydrogen reduction of metal–β-diketone precursors in supercritical carbon dioxide, and are characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) analyses. These highly dispersed nanoparticles, with a narrow range of size distribution and good adhesion on MWCNT surfaces, are expected to exhibit promising catalytic properties for a variety of chemical reactions. Preliminary experiments demonstrate that Pd nanoparticles supported on MWCNTs are effective catalysts for hydrogenation of olefins in carbon dioxide. The Pd nanoparticle–MWCNT composite also shows a high electrocatalytic activity in oxygen reduction for potential fuel cell application.

Hydrogen reduction of a Pd(II)-β-diketone precursor in supercritical carbon dioxide produces palladium nanoparticles on multi-walled carbon nanotubes that exhibit promising catalytic properties for hydrogenation of olefins in carbon dioxide as well as electro-reduction of oxygen in fuel cell applications.

Uranium adsorbed on amidoxime (AO)-based polyethylene fiber in simulated seawater can be quantitatively eluted at room temperature using 1 M Na₂CO₃ containing 0.1 M H₂O₂ without significant damage to fiber.

Ionic species can be stabilized in the water core of a water-in-CO₂ microemulsion in supercritical fluid CO₂; by mixing two microemulsions containing Ag⁺ and X⁻ ions separately, silver halide (AgX) nanoparticles were synthesized in supercritical CO₂; the water-in-CO₂ microemulsion may provide a reaction system for a wide range of nanoparticle syntheses involving ionic species in supercritical CO₂.