Janus-like Fe3O4/PDA vesicles with broadening microwave absorption bandwidth

Microstructural design of the magnetic composites with ultra-wide microwave absorption bandwidth has been attracting extensive attention in the fields of both electromagnetic shielding and radar stealth, but it still remains a great challenge. Herein, asymmetric Janus nanocomposites of Fe3O4/PDA vesicles were successfully prepared, and they exhibited strong absorption intensity (−50.0 dB) and ultra-wide bandwidth (6.4 to 18 GHz) covering 73% of the frequency range of 2–18 GHz with a film thickness of only 2.5 mm. The excellent absorption properties could be due to the asymmetric polarization and magnetic coupling effects, which allow most incident microwaves propagating from the nonmagnetic PDA shell into the magnetic core to be exhausted (−50.0 dB). Electron holography analysis confirmed the intense magnetic coupling of the high-density flux lines within the adjacent Fe3O4-derived core@shell network. Our findings suggest that the anisotropic Janus absorber effectively possesses a broad bandwidth, which might be extended to other asymmetric nanomaterials for electromagnetic interference applications.