Controlled synthesis of Ag nanowires and nanoparticles in mesoporous silica using supercritical carbon dioxide and co-solvent

Mesoporous silica supported silver nanocomposites have been successfully prepared using supercritical carbon dioxide as solvent and ethanol or ethylene glycol as co-solvent. There are many advantages of using this method compared to conventional impregnation method such as no solvent residue or no big nanoparticle clusters outside the surface of the substrates. Furthermore, it is easy to separate the product from the solvent and easy to control the metal loading by adjusting the deposition time and pressure. The dissolution of AgNO3 in supercritical carbon dioxide with a little co-solvent was observed through a high pressure view cell. TEM study on the nanocomposites showed the silver nanoparticles were uniformly dispersed within the nanoscale channels of mesoporous silica matrix, and the average particle size obtained under different conditions ranged from 1.7 to 3.0 nm for Ag/MCM-41 and 3.0 to 6.0 nm for Ag/SBA-15. Continuous nanowires with high aspect ratio were also found and the morphology of the nanophase was greatly influenced by both the deposition pressure and time.