3D core-shell Fe3O4@SiO2@MoS2 composites with enhanced microwave absorption performance

Assembly of core-shell Fe3O4 @CD-MOFs derived hollow magnetic microcubes for efficient extraction of hazardous substances: Plausible mechanisms for selective adsorption

Hazardous heavy metals and organic substances removal is of great significance for ensuring the safety of aquatic-ecosystem, yet the highly effective and selective extraction always remains challenging. To address this problem, magnetic hollow microcubes were fabricated through thermal carbonization of Fe3O4-COOH@ γ-CD-MOFs, and core-shell structured precursors were in-situ greenly constructed on a large scale via microwave-assisted self-assembly strategy. As noted, the development of secondary crystallization was utilized to achieve uniform dispersion of cores within MOFs frameworks and thus improved magnetic and adsorption ability of composites. Acquired magnetic Fe3O4 @HC not only can harvest excellent extraction of heavy metals (Cd, Pb, and Cu of 129.87, 151.05, and 106.98 mg·g-1) but also exhibit highly selective adsorption ability for cationic organics (separation efficiency higher than 95.0 %). Impressively, Fe3O4 @HC achieved outstanding adsorption (60-80 %) of Cd in realistic mussel cooking broth with no obvious loss in amino acid. Characterizations better offer mechanistic insight into the enhanced selectivity of positively charged pollutants can be attributed to synergistic effect of ions exchange and electrostatic interaction of abundant oxygen-containing functional groups. Our study provides a feasible route by rationally developing core-shell structured composites to promote the practical applications of sustainable water treatment and value-added utilization of processing by-products.

Hierarchical-Bioinspired MOFs Enhanced Electromagnetic Wave Absorption

Proteins exhibit complex and diverse multi-dimensional structures, along with a wide range of functional groups capable of binding metal ions. By harnessing the unique characteristics of proteins, it is possible to enhance the synthesis of metal-organic frameworks (MOFs) and modify their morphology. Here, the utilization of biomineralized bovine serum albumin (BSA) protein as a template for synthesizing Mil-100 with superior microwave absorption (MA) properties is investigated. The multi-dimensional structure and abundant functional groups of biomineralized BSA protein make it an ideal candidate for guiding the synthesis of Mil-100 with intricate network structures. The BSA@Mil-100 synthesized using this method exhibits exceptional uniformity and monodispersity of nanocrystals. The findings suggest that the BSA protein template significantly influences the regulation of nanocrystal and microstructure formation of Mil-100, resulting in a highly uniform and monodisperse structure. Notably, the synthesized 2-BSA@Mil-100 demonstrates a high reflection loss value of -58 dB at 8.85 GHz, along with a maximum effective absorption bandwidth value of 6.79 GHz, spanning from 6.01 to 12.8 GHz. Overall, this study highlights the potential of utilizing BSA protein as a template for MOF synthesis, offering an effective strategy for the design and development of high-performance MA materials.

A smartphone-based fluorescent sensor for rapid detection of multiple pathogenic bacteria

In this study, we developed a fluorescent sensor for the sensitive detection of multiple pathogenic bacteria based on magnetic separation, fluorescent probes, and smartphone image processing. A microchannel device was assembled using high-transparency resin and 3D printing technology. This device was combined with a smartphone and an external lens to develop a fluorescent sensor for autonomous detection of multiple pathogenic bacteria. Three fluorescence probes with different fluorescence were synthesized from highly specific aptamers and tetraphenylethylene derivatives. These fluorescent probes can make Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa emit different colors of fluorescence. Using the enrichment performance of molecularly imprinted materials, separation and detection of bacteria can be achieved simultaneously. Finally, with the Red-Green-Blue (RGB) analysis functionality of a smartphone, real-time field detection was realized with a sensitivity of 102 CFU/mL and a detection time of 40 min. This work provides a simple, inexpensive, and real-time sensor for the detection of multiple pathogens in medical diagnostics, food testing, and environmental analyses.

Dual Resonance Behavior and Enhanced Microwave Absorption Performance of Fe3O4@C@MoS2 Composites with Shape Magnetic Anisotropy

Ternary hierarchical Fe3O4@C@MoS2 composites and binary hierarchical Fe3O4@C composites were successfully fabricated by a modified mixed solvothermal method, a self-oxidation polymerization method, and a hydrothermal process. Their magnetic properties and microwave absorption performance were investigated. Dual resonance behavior was observed in the Fe3O4@C@MoS2 composites. One of the resonances was attributed to natural resonance with a resonance frequency of 2.58 GHz, which was much higher than that for Fe3O4 bulk (1.5 GHz). The other originated from the superparamagnetic/ferromagnetic relaxation with a resonance frequency of 12.45 GHz. The minimum reflection loss (RLmin) reached -64.30 dB with a matched thickness of 2.24 mm at 11.64 GHz, and the maximum effective absorption bandwidth (EABmax) covered 6.39 GHz with a matched thickness of 1.89 mm. In addition, the maximum Radar cross section (RCS) reduction value reached 31.90 dB m2 at a scattering angle of 0°. Electron holography analysis confirmed a dense magnetic absorption network in the Fe3O4@C@MoS2 composites. The boost in microwave absorption performance was caused by the synergistic effects of magnetic and dielectric properties owing to the ternary hierarchical structure, shape magnetic anisotropy, and incorporation of 1T/2H MoS2. Besides, the binary hierarchical Fe3O4@C composites also exhibited good absorbing performance caused by natural resonance, with an RLmin of -52.90 dB at 5.80 mm, an EABmax of 5.98 GHz at 3.38 mm, and a relatively high RCS reduction value of 13.04 dB m2 at θ = 20°. This work paves the way for designing multicomponent hierarchical absorbers with broadband and intensive microwave absorption.

Enhanced photocatalytic degradation of amoxicillin using a spinning disc photocatalytic reactor (SDPR) with a novel Fe3O4@void@CuO/ZnO yolk-shell thin film nanostructure

Antibiotics are resistant compounds with low biological degradation that generally cannot be removed by conventional wastewater treatment processes. The use of yolk-shell nanostructures in spinning disc photocatalytic reactor (SDPR) enhances the removal efficiency due to their high surface-to-volume ratio and increased interaction between catalyst particles and reactants. The purpose of this study is to investigate the SDPR equipped to Fe3O4@void@CuO/ZnO yolk-shell thin film nanostructure (FCZ YS) in the presence of visible light illumination in the photocatalytic degradation of amoxicillin (AMX) from aqueous solutions. Stober, co-precipitation, and self-transformation methods were used for the synthesis of FCZ YS thin film nanostructure and the physical and chemical characteristics of the catalyst were analyzed by XRD, VSM,, EDX, FESEM, TEM, AFM, BET, contact angle (CA), and DRS. Then, the effect of different parameters including pH (3-11), initial concentration of AMX (10-50 mg/L), flow rate (10-25 mL/s) and rotational speed (100-400 rpm) at different times in the photocatalytic degradation of AMX were studied. The obtained results indicated that the highest degradation efficiency of 97.6% and constant reaction rate of AMX were obtained under LED visible light illumination and optimal conditions of pH = 5, initial AMX concentration of 30 mg/L, solution flow rate of 15 mL/s, rotational speed of 300 rpm and illumination time of 80 min. The durability and reusability of the nanostructure were tested, that after 5 runs had a suitable degradation rate. Considering the appropriate efficiency of amoxicillin degradation by FCZ YS nanostructure, the use of Fe3O4@void@CuO/ZnO thin film in SDPR is suggested in water and wastewater treatment processes.

High-performance microwave absorption by optimizing hydrothermal synthesis of BaFe12O19@MnO2 core-shell composites

Stealth technology advances in radar-absorbing materials (RAMs) continue to grow rapidly. Barium hexaferrite is the best candidate for RAMs applications. Manganese dioxide (MnO2) is a transition metal with high dielectric loss and can be used as a booster for changing polarization and reducing reflection loss. The advantages of BaFe12O19 and MnO2 can be combined in a core-shell BaFe12O19@MnO2 composite to improve the material's performance. MnO2 composition, temperature, hydrothermal holding time, and sample thickness all have an impact on the core-shell structure. In this study, a core-shell BaFe12O19@MnO2 composite is synthesized in two stages: molten salt synthesis to produce BaFe12O19 as the core and hydrothermal synthesis to synthesize MnO2 as the shell. In the hydrothermal synthesis, BaFe12O19 and KMnO4 were mixed in deionized water using different mass ratios of BaFe12O19 to KMnO4 (1 : 0.25, 1 : 0.5, 1 : 0.75, and 1 : 1). The main goal of the analysis was to figure out how well the hydrothermal synthesis method worked at different temperatures (140 °C, 160 °C, and 180 °C) and holding times (9 h, 12 h, and 15 h). The composite material was subjected to characterization using a vector network analyzer, specifically at thicknesses of 1.5 mm, 2 mm, 2.5 mm, and 3 mm. The hydrothermal temperature and composition ratio of BaFe12O19 : MnO2 are the most influential parameters in reducing reflection loss. Accurate control of the parameters makes a BaFe12O19@MnO2 core-shell composite structure with a lot of sheets. The structure is capable of absorbing 99.99% of electromagnetic waves up to a sample thickness of 1.5 mm. The novelty of this study is its ability to achieve maximal absorptions on a sample with minimal thickness through precise parametric control. This characteristic makes it highly suitable for practical applications, such as performing as an anti-radar coating material. BaFe12O19@MnO2 demonstrates performance as a reliable electromagnetic wave absorber material with simple fabrication, producing absorption at C and X band frequencies.

Lightweight Chain-Typed Magnetic Fe3O4@rGO Composites with Enhanced Microwave-Absorption Properties

A lightweight microwave-absorbing material with a strong electromagnetic-absorption capability of practical significance in the field of electromagnetic compatibility was obtained by adjusting the ratio of Fe₃O₄ and rGO. A nanoparticle material with a chain-typed structure consisting of a combination of Fe₃O₄ and rGO was produced by a hydrothermal method under an applied magnetic field. The electromagnetic loss property of the Fe₃O₄@rGO composites is studied in the frequency range from 2 to 18 GHz. In addition, the reflection loss and the mechanism of microwave absorption are explored. By changing the amounts of rGO, the electromagnetic loss of the Fe₃O₄@rGO composites can be effectively regulated, which obtain better reflection loss. The minimum reflection loss of the Fe₃O₄@rGO composites is -49.4 dB at 16.2 GHz only with a thickness of 1.75 mm. Thus, the Fe₃O₄@rGO composites have an extremely thin thickness and a strong electromagnetic wave absorption capacity, which is a candidate for the development of lightweight magnetic absorbing materials.

Magnetic Composite Rapidly Treats Staphylococcus aureus-Infected Osteomyelitis through Microwave Strengthened Thermal Effects and Reactive Oxygen Species

It is difficult to effectively treat bacterial osteomyelitis using photothermal therapy or photodynamic therapy due to poor penetration of light. Here, a microwave (MW)-excited magnetic composite of molybdenum disulfide (MoS₂ ) / iron oxide (Fe₃ O₄ ) is reported for the treatment of bacteria-infected osteomyelitis. In in vitro and in vivo experiments, MoS₂ /Fe₃ O₄ is shown to effectively eradicate bacteria-infected mouse tibia osteomyelitis, due to MW thermal enhancement and reactive oxygen species (ROS) (¹ O₂ and ·O₂ ^- ) production under MW radiation. In addition, the mechanism of MW heat generation is proposed by MW network vector analysis. By the density functional theory and finite element method, the ROS generation mechanism is proposed. The synergy or conductive network between dielectric MoS₂ and magnetic Fe₃ O₄ can reach both enhancement of the dielectric and magnetic attenuation capability. In addition, abundant interfaces are generated to enhance the attenuation of electromagnetic waves by MoS₂ and Fe₃ O_4, introducing multiple reflections and interfacial polarization. Therefore, MoS₂ /Fe₃ O₄ has excellent MW absorption ability based on the synergy or conductive network between MoS₂ and magnetic Fe₃ O₄ as well as multiple dielectric reflections and interfacial polarization.

Magnetic modulation of core@shell MoS2-based flower-like multicomponent nanocomposites to improve microwave attenuation

Nanocomposites with a three-dimensional (3D) flower-like geometrical morphology were considered as excellent microwave absorbers (MAs) because of the numerous effective sites for the multiple reflections of electromagnetic (EM) wave. Herein, for optimizing the EM matching characteristic and taking full advantage of interface polarization, a strategy of magnetic modulation was proposed to further improve the EM wave absorption performances (EMWAPs) of MoS₂-based nanocomposites. We adopted a simple hydrothermal route and a combined method of hydrothermal treatment/hydrogen reduction to synthesize core@shell CoFe₂O₄@MoS₂ and CoFe@MoO₂/MoS₂ flower-like nanocomposites, respectively. The obtained results indicated that the hydrogen reduction effectively improved their magnetic properties and magnetic loss capabilities, and their 3D flower-like geometrical morphologies were well maintained during the hydrogen reduction process. The obtained core@shell CoFe@MoO₂/MoS₂ flower-like nanocomposites presented the extraordinary comprehensive EMWAPs including the optimal reflection loss value of -54.83 dB with the matching thicknesses (d_m) value of 2.05 mm and effective absorption bandwidth value of 6.40 GHz with the d_m value of 2.59 mm, which were evidently superior to the properties of CoFe₂O₄@MoS₂. Therefore, the findings provided an effective pathway to further improve EMWAPs of MoS₂-based core@shell nanocomposites and the as-prepared core@shell CoFe@MoO₂/MoS₂ flower-like nanocomposites could be utilized as the novel high-efficient MAs.

Preparation of magnetic silica supported Brönsted acidic ionic liquids for the depolymerization of lignin to aromatic monomers

Lignin, the most abundant renewable resource of aromatics in nature, is recognized as an alternative for fossil-based fuels and chemicals. Herein, we proposed an efficient method to obtain aromatic monomers...

3D porous coral-like Co1.29Ni1.71O4 microspheres embedded into reduced graphene oxide aerogels with lightweight and broadband microwave absorption

In this work, three-dimensional (3D) porous coral-like Co_1.29Ni_1.71O₄ microspheres were successfully combined with reduced graphene oxide (rGO) to form Co_1.29Ni_1.71O₄/rGO aerogels as an efficient microwave absorber by a facile calcination and hydrothermal method. The elemental composition, microstructure, and morphology of the as-synthesized composites were characterized, and the electromagnetic wave absorption performance were analyzed in the frequency range of 2.0-18.0 GHz. The results show that adjusting the mass ratio of Co_1.29Ni_1.71O₄ microspheres and rGO in the composites can effectively tune the electromagnetic parameters, which in turn improves their microwave absorption performance. Here, the minimum reflection loss (RL_min) of the Co_1.29Ni_1.71O₄/rGO aerogels is -51.76 dB with an effective absorption bandwidth (RL < -10 dB) of 7.04 GHz (10.96-18 GHZ) at the thickness of 2.66 mm and a low filling ratio of 15 wt%. It can be demonstrated that the superior microwave absorption performance is attributed to the synergistic effect of impedance matching and dielectric loss, the unique 3D porous structure as well as the abundant interface of the composites. In brief, this study provides a new strategy for the design of magnetic/dielectric high-performance microwave absorbing materials.