Fig. 1

(a) Hydrophobic Fe3O4 NPs coated with oleic acid, and (b) hydrophilic Fe3O4 NPs coated with oleic acid and a layer of CTAB
(a) Hydrophobic Fe3O4 NPs coated with oleic acid, and (b) hydrophilic Fe3O4 NPs coated with oleic acid and a layer of CTAB