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 using supercritical CO2 as solvent.
• The deposition time was only 5 min when using the mixture of ethylene glycol and ethanol as co-solvent.
• A non-equilibrium sorption occurred due to the reduction of a small amount of precursors.

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 Ag0 by ethylene glycol at the initial stage of the deposition. The resultant Ag0 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 γ-Al2O3, SiO2 and KIT-6, demonstrating its great potentials in the synthesis of nanocomposites.

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