Synthesis of stable dispersion of copper nanoparticles in a water-in-supercritical carbon dioxide using polydimethylsiloxane as the stabiliser

This study reportes the synthesis of stable dispersion copper nanoparticles by chemical reduction of copper chloride (CuCl2) in a water-in-supercritical carbon dioxide medium using sodium borohydrate (NaBH4) as a reducing agent, polydimethylsiloxane as the stabiliser and sodium bis(2-ethylhexyl)sulphosuccinate (AOT) as co-surfactant at temperature 40°C and pressure in the range 2000–2400 psi. UV–visible spectroscopy exhibits a typical emission peak at 560–590 nm for Cu nanoparticles. By changing the reaction pressure and the stabiliser concentration, the size and the shape of the copper nanoparticles could be easily controlled. The X-ray diffraction pattern reveals that the Cu nanoparticles are formed in the range 4–8 nm, which is consistent with the transmission electron microscopy images.