Nanostructured Materials Synthesized in Supercritical Fluid
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Supercritical fluid (SCF) approach is a novel and emerging technology to generate nanomaterials in small areas, high-aspect-ratio structures, complicated surfaces, and poorly wettable substrates with high uniformity, high homogeneity, and minimum environmental problems.
Through hydrogen reduction of metal-β-diketone complexes in supercritical CO2, a rapid, convenient, and environmentally benign approach has been developed to synthesize a variety of nanostructured materials: 1) metal (Pd, Ni, and Cu) nanowires and nanorods sheathed within multiwalled carbon nanotube (MWCNT) templates; 2) nanoparticles of palladium, rhodium, and ruthenium decorated onto functionalized MWCNTs. These highly dispersed nanoparticles are expected to exhibit promising catalytic properties for a variety of chemical or electrochemical reactions; 3) Cu, Pd, or Cu–Pd nanocrystals deposited onto SiO2 or SiC nanowires (NWs). Different types of nanostructures were achieved, including nanocrystal-NW, spherical aggregation-NW, shell-NW composites, and “mesoporous” metals supported by the framework of NWs.