Comprehensive study of the role of ethylene glycol when preparing Ag@SBA-15 in supercritical CO2

Well-defined Ag nanowires were obtained in SBA-15 at a short deposition time of 5 min in supercritical CO2 when adding a small amount of ethylene glycol as the co-solvent. Ethylene glycol played a key role in dictating the nanowire morphology. Through detailed investigation of the whole deposition process, including the dissolution of precursor assisted by the co-solvent, the diffusion properties of the precursor into the nano-scale channels of the substrate, and the interaction between the precursor and the substrate, we found that a small amount of precursors were reduced into Ag-0 by ethylene glycol at the initial stage of the deposition. The resultant Ag-0 then acted as nuclei leading to a non-equilibrium sorption of the precursor. The rapid adsorption of the precursor onto the substrate resulted in a high loading of Ag in a short deposition time and the formation of nanowire morphology. Furthermore, this method was successfully extended to other porous substrates such as gamma-Al2O3, SiO2 and KIT-6, demonstrating its great potentials in the synthesis of nanocomposites. (C) 2014 Elsevier B.V. All rights reserved