Sonochemical formation of iron oxide nanoparticles in ionic liquids for magnetic liquid marble

Ionic liquids (ILs)-stabilized iron oxide (Fe2O3) nanoparticles were synthesized by the ultrasonic decomposition of iron carbonyl precursors in [EMIm][BF4] without any stabilizing or capping agents. The Fe2O3 nanoparticles were isolated and characterized by X-ray powder diffraction, transmission electron microscopy and susceptibility measurements. The physicochemical properties of ILs containing magnetic Fe2O3 nanoparticles (denoted as Fe2O3@[EMIm][BF4]), including surface properties, density, viscosity and stability, were investigated in detail and compared with that of [EMIm][BF4]. The Fe2O3@[EMIm][BF4] can be directly used as magnetic ionic liquid marble by coating with hydrophobic and unreactive polytetrafluoroethylene (PTFE), for which the effective surface tension was determined by the puddle height method. The resulting magnetic ionic liquid marble can be transported under external magnetic actuation, without detachment of magnetic particles from the marble surface that is usually observed in water marble.