The rational structural design and compositional merits as well as the synergistic coupling effect can break the properties of single material and broaden the microwave absorption band. Herein, the unique lightweight Fe-doped MnO 2 @C hollow nanocubes are rationally designed and successfully synthesized via a scalable wet chemical process and polydopamine coating followed by high-temperature calcination . By virtue of the unique structure and compositional merits, the as-obtained Fe-doped MnO 2 @C hollow nanocubes (Fe–MnO 2 @C-HNBs) displayed notable microwave absorption performance (MAP), simultaneously achieving ultra-broad absorption bandwidth and strong absorption characteristics at a low thickness of 2.3 mm (the reflection loss of −41.02 dB and the effective absorption bandwidth of 5.86 GHz). Surprisingly, the effective absorption bandwidth (RL < −10 dB) could reach up to 8.08 GHz and the minimum reflection loss (RLmin) was −38.20 dB at the thickness of 2.7 mm. The results further confirmed that the excellent microwave attenuation ability of the as-prepared Fe–MnO 2 @C-HNBs composites benefitted from the special “air@core-shell” structure and multiple heterointerfaces as well as multi-component recombination. These results demonstrated that the as-obtained Fe–MnO 2 @C-HNBs composites could be attractive candidates for broadband microwave absorption materials .
Zhenda Liang,Zhiquan Chen,Yongtao Xu,Haiqing Wang,Li Zhou,Bing Yan
Manganese dioxide (MnO 2 ) has been recognized as one of the natural systems' most active mineral oxidants. However, when it comes to catalytic oxidation of antibiotic applications, pure MnO 2 falls short in delivering satisfactory performance. Hence, a set of Fe 3+ -doped porous MnO 2 (0.02Fe–MnO 2 , 0.1Fe–MnO 2 , and 0.14Fe–MnO 2 ) nanoparticles were synthesized here via a convenient and energy-efficient one-step reaction method. A series of experiments revealed that Fe-doping strategy enhances the properties of MnO 2 host by suppressing the crystalline structure, increasing the amount of surface oxygen defects, and modifying the Mn 3+ /Mn 4+ ratio. Specifically, the tetracycline (TC) removal efficiency of 0.14Fe–MnO 2 reaches 92% without the need for any additional co-oxidant, representing a 20% improvement over pristine MnO 2 nanoparticles . Moreover, this process shows a fast dynamic (achieving 70% of TC removal in just 5 min) and demonstrates pH-resistance, maintaining high TC removal efficiency (≥90%) over a wide pH range of 3.0–9.0. Mechanical studies reveal that the degradation of TC can be attributed to the oxidation by reactive oxygen radicals and Mn 3+ , with 1 O 2 being the primary radical involved in the reaction, accounting for 55% of TC removal. Importantly, cytotoxicity testing indicates that the biotoxicity of TC toward organisms can be effectively mitigated using 0.14Fe–MnO 2 nanomaterial . This study presents a readily applicable candidate for economically and conveniently eliminating of environmental TC pollution, thereby reducing the threat posed by TC pollution to the ecosystem.
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