Adjustable and high-performance microwave absorbing materials of three-dimensional (3D) reduced graphene oxide (RGO)@Fe 3 O 4 structure were realized with different compositions. 100 × 50 nm Fe 3 O 4 nanorods were anchored on both sides of RGO sheets uniformly which stop RGO sheets from re-stacking. Effective absorption bands shifted to higher frequencies and thinner thicknesses in 2–18 GHz due to the precisely controlled complex permittivity caused by the decreased content of RGO. The maximum reflection loss of RGO@Fe 3 O 4 composites was up to −56.25 dB at 12.62 GHz with a small thickness of 2.0 mm, and the absorption bandwidth below −10 dB was 5.40 GHz with only 20 wt% filler loading in the paraffin matrix. The dielectric loss was a primary factor in the superior absorption performance resulting from dipolar polarization, interfacial polarization and associated relaxation phenomena. Hence, the appropriate composition of the RGO@Fe 3 O 4 structure can consider both the microwave absorptivity and the absorption adjustability. This method can be apply to other graphene-based magnetic microwave absorption materials.
Mingyi Ma,Xiajun Zhang,Haoda Zhang,Zhihao Xu,Shasha Li,Ruijiang Liu
Early-stage colorectal cancer (CRC) is often asymptomatic, leading to late diagnoses and impacting treatment outcomes. Timely detection and diagnosis are crucial, with serum carcinoembryonic antigen (CEA) levels playing a key role in CRC diagnosis and prognosis. To enhance precision, a label-free electrochemical nano-biosensor utilizing magnetic self-assembly (MSA) technology was developed for sensitive CEA detection. The biosensor's core was the α-Fe 2 O 3 /Fe 3 O 4 nanorods prepared by the hydrolysis-calcination reduction process. Its unique magnetism was the cornerstone of MSA technology. The biosensor exhibited excellent mechanical strength, ensuring stability during storage at 4 °C for at least one month. The aptamer probe (CEAA) self-assembled on the nanorods' surface via an Au–S bond, creating the magnetic probe (CEAA/α-Fe 2 O 3 /Fe 3 O 4 @Au). Upon capturing CEA, the current response decreased, indicating a “turn-off" nano-biosensor type as observed through differential pulse voltammetry (DPV) monitoring. In this research, the biosensor not only exhibited robust specificity and superior anti-interference ability but also demonstrated successful regeneration. The limit of detection (LOD) was 0.197 pg/mL, the recovery rate for real serum samples was between 94.15 % and 105.08 %, and the relative standard deviation (RSD) ranged from 1.40 % to 2.09 %. This biosensor showed promise in enhancing the accuracy and effectiveness of CRC diagnostic and prognostic protocols, offering a new direction for point-of-care testing.
Huairu Tian,Jun Peng,Qiuzheng Du,Xuanhong Hui,Hua He
A novel, rapid and simple method is described for the synthesis of magnetic MIL-100(Fe) with novel Fe3O4 morphology, which significantly improved the sustainability of conventional fabrication processes in several aspects. The magnetic MOFs were prepared (i) in one pot (instead of multiple steps), (ii) at room temperature (instead of temperatures over 150 °C), (iii) within a few hours with excellent yield (instead of in few days with low productivity) and (iv) in the absence of any corrosive inorganic acid and organic reagent. The materials were tested in the industrially demanded photocatalytic and photo-Fenton degradation of sodium sulfadiazine. The degradation results indicated that the Fe3O4 nanorods could accelerate the catalytic efficiency. The catalyst would be of potential application due to its stable catalytic activity in repeated reaction cycles and no need for regeneration. Therefore, the MIL-100(Fe) and magnetic MIL-100(Fe) proposed in this study are ideal catalysts for the heterogeneous degradation of sodium sulfadiazine.
The discovery of new anode materials and engineering their fine structures are the core elements in the development of new-generation lithium ion batteries (LIBs). To this end, we herein report a novel nanostructured composite consisting of approximately 75% Fe3O4 nanorods and 25% reduced graphene oxide (rGO). Microscopy and spectroscopy analyses have identified that the Fe3O4 nanorods are wrapped (or encapsulated) by the rGO nanosheets via covalent bonding, which further self-assemble into a mesoporous hybrid composite networked by the graphene matrix. The composite has an average pore size around 20 nm and exhibits a high surface area of 152 m2 g−1, which is 76 times as high as that of conventional Fe3O4 powder. We have used the composite as an LIB anode material to fabricate coin-type prototype cells with lithium as the cathode. Systematic half-cell testing evaluations show that the electrochemical performance of the present composite material is amongst the best of the transition metal-oxide based LIB anode materials. The performances are characterized by a high reversible capacity of 1053 mA h g−1 subjected to 250 charge–discharge cycles at 500 mA g−1 and an excellent rate capability with the deliverable energy of 788–541 mA h g−1 upon the application of high current densities of 1000–5000 mA g−1. Overall, we have demonstrated that Fe3O4 nanorod–rGO hybrid composite is an interesting and promising material for the fabrication of LIB anodes.
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