Construction of NiCo2O4/NiCoO2 co-embedded porous bio-carbon with rich heterogeneous interfaces for excellent bacteriostatic microwave radiation protection

To attain the stable protection against electromagnetic radiation pollution in complex bacterial environment, herein the NiCo₂O₄ and NiCoO₂ co-embedded porous bio-carbon (PBC) with outstanding microwave absorption and anti-bacterial ability was successfully obtained via facile carbonization and immersion-annealing route. The component and microstructure of composites are both tightly affected by the synthetic temperature, which also influences the oxygen vacancy content and defect density within them. The strong interface polarizations from plentiful heterogeneous interfaces and dipole polarizations generated by defects and vacancies contribute greatly to the dielectric absorption, while the eddy-current loss and magnetic resonances have a certain effect as well. Under the matched impedance from magnetic-dielectric balance, the optimized absorption strength of prepared composite achieves −38.2 dB at 2.0 mm thickness with broad absorbing bandwidth of 7.01 GHz for only 2.31 mm. Moreover, the plentiful oxygen vacancies induced reactive oxygen species (ROS) together with heavy metal ions from nickel-cobalt ferrites can suppress the reproduction of Gram negative Escherichia coli (E. coli) and Gram positive Staphylococcus aureus (S. aureus) with anti-bacterial rates of 92.4 % and 93.2 %, respectively. The paper offers a novel insight to design dual-functional microwave absorber with excellent bacteriostatic performance for long-term using in complex bacterial environment.