Magnetic Fe3O4 MNPs were prepared by a solvothermal method as previously reported [33]. Briefly, FeCl36H2O (1.62 g), NaOAc (4.0 g) andNa3Cit (1.5 g) were dissolved in EG (60 mL), after vigorous
stirring for 1 h, the obtained yellowsolutionwas transferred to Teflonlined stainless-steel autoclave (100 mL), then sealed and heated at 200 C. After reaction for 12 h, the autoclave was cooled to room temperature. The obtained Fe3O4 MNPs were washed several times with water and ethanol. Finally, the products were collected with a magnet and then re-dispersed in 80 mL water for further use.