Behaviors of ionic liquids in the phase transfer of aqueous metal nanoparticles

To understand why ionic liquids are efficient solvents for the phase transfer of metal nanoparticles, we added a small amount of ILs to dichloromethane and studied the behaviors of ILs in the phase transfer. The proposed mechanism of phase transfer is the formation of a hydrophobic ion-pair between the cation of the stabilizer on the particle surface and the anion of the ILs, which cause the change in the surface hydrophilic properties and facilitate the phase transfer of aqueous nanoparticles into an organic phase. This mechanism was supported by NMR, FT-IR, XPS and ESI-MS. Furthermore, we investigated the effects of parameters on the phase transfer and found that phase-transferring efficiency increases with the extraction time and the concentration and hydrophobicity of the ILs. The results indicate that ILs play the roles of phase-transfer agents and solvents in the phase transfer of aqueous metal nanoparticles with ILs.