Fig. 1

Hydrodynamic diameter distributions of Fe₃O₄ NPs, Fe₃O₄@Au NPs and PEG-b-PAMPImB-Fe₃O₄@Au NPs (a); TEM image of PEG-b-PAMPImB-Fe₃O₄@Au NPs (b); the inserted image is a magnification of the NPs in b; UV–vis spectra of Fe₃O₄ NPs, Au NPs, Fe₃O₄@Au NPs and PEG-b-PAMPImB-Fe₃O₄@Au NPs (c); magnetization measurements as a function of applied field for Fe₃O₄ NPs, Fe₃O₄@Au NPs and PEG-b-PAMPImB-Fe3O4@Au NPs (d). The inserted image in d is a photograph of a solution of PEG-b-PAMPImB-Fe₃O₄@Au NPs before (right bottle) and after (left bottle) applying a NdFeB magnet during 30 min