3D Nest-Like Architecture of Core-Shell CoFe2O4@1T/2H-MoS2 Composites with Tunable Microwave Absorption Performance

Ultrasensitive and selective nanomolar detection of quercetin in 12 complex food matrices via 3D hierarchical SiO₂@MoS₂/MXenes heterostructured sensor

Quercetin (Que) is a ubiquitous flavonoid and polyphenol antioxidant. Negatively charged MoS2 was self-assembled onto the surface of positively charged SiO2 nanospheres to form SiO2@MoS2 core-shell materials. Subsequently, the materials were embedded into the interlayer of MXenes to form an effectively conductive three-dimensional heterostructured composite. The MoS2 shell formed on SiO2 not only retained the intrinsic properties of SiO2 but also improved its conductivity and specific surface area. In addition, the addition of SiO2@MoS2 to the interlayer of MXenes effectively alleviated the interference within the potential window and promoted the accurate electrical signal detection of Que. The detection range of the SiO2@MoS2/MXenes electrochemical sensor was 20 nM ∼ 30 μM, and the detection limit was 2 nM. The sensor can be effectively applied to the detection of Que. in 12 kinds of fruits, vegetables and agricultural products, and the results were comparable to those of UV spectrophotometry with satisfactory recovery.

1T/2H-MoS2-Decorated Carbon Felts as Excellent Co-Catalysts in Advanced Oxidation Processes for the Degradation of Organic Pollutants

The Fenton reaction is restricted by the sluggish Fe(II)/Fe(III) cycle and the low activation efficiency of oxidants. Herein, 1T/2H MoS2 nanoflowers with abundant defects and a multiphase structure, loaded on carbon felts (denoted as THMC), have been prepared to boost catalytic activity in Fenton-like oxidation. The defects and ultrathin nanosheets promote the adsorption of iron ions and pollutants, while the unsaturated S atoms and exposed Mo(IV) sites facilitate the conversion of Fe(III) to Fe(II). Additionally, the 1T phase accelerates electron transfer in Fe(II)/Fe(III) cycling, thereby synergistically enhancing catalytic activity in Fenton-like oxidation and improving the efficiency of pollutant elimination. Moreover, the loading of MoS2 nanoflowers on carbon felts not only overcomes the limitations of powder in separation and recycling but also offers robust stability for long-term applications. Thanks to these structural characteristics, the degradation efficiencies of rhodamine B and bisphenol A in the THMC cocatalyzed system reach 99.3% and 98.1%, respectively, and the corresponding rate constants (kobs) are 10.3 and 10.1 times higher than those of the traditional Fe2+-catalyzed system. Impressively, THMC still maintains excellent cocatalytic performance after 5 cycles and exhibits high degradation efficiencies across wide pH ranges. The cocatalytic system can efficiently eliminate a variety of organic pollutants and adapt to natural water samples. Furthermore, the performance of several MoS2 nanoflowers with varied phase structures and phase ratios has been investigated to probe the effect of phase structure. Interestingly, the kobs value of MoS2 with 52.4% 1T phase was 5.9 and 3.4 times higher than that of 5.6%-1T MoS2 in the degradation of RhB and BPA, respectively. Moreover, the cocatalytic performance of MoS2 could be further improved with an increase in the 1T phase to 66.6%. These observations reveal the significant role of phase effects on the cocatalytic activity of MoS2 in AOPs.

Optimized design, fabrication, and enhanced performance of honeycomb sandwich structure for excellent impact resistance and broadband microwave absorption

Lightweight microwave absorbing structures have wide applications in aerospace and military equipment. In general, honeycomb sandwich structure is regarded as an ideal choice. However, traditional honeycomb sandwich structure designs have limitations in improving absorption bandwidth, and their impact resistance remains unremarkable. Herein, a novel microwave absorbing honeycomb sandwich structure (MAHSS) has been thoroughly investigated through both theoretical and experimental validations. The MAHSS is crafted using a glass fiber (GF)/epoxy composite that is coated with reduced graphene oxide (RGO) for enhanced performance. The middle honeycomb layer of MAHSS is arranged transversely to add more interface. When the honeycomb core has 2 layers and a wall thickness of 2.4 mm in MAHSS, the maximum achievable bandwidth is 13.6 GHz, while the minimum reflection loss (RLmin) reaches -24.02 dB under TE mode. The mechanical properties of the MAHSS were evaluated by compression test and drop weight impact testing. The MAHSS exhibits excellent compression and impact resistance, accompanied by self-recovery performance post-unloading. It still did not penetrate under an impact energy of 150 J, absorbing up to 123 J of energy. This work provides theoretical guidance and technical support for designing and preparing structural and functional integration microwave absorption materials.

MoS2-Coated MOF-Derived Hollow Heterostructures for Electromagnetic Wave Absorption

Structural design constitutes one of the crucial approaches for augmenting the wave-absorbing capacity of electromagnetic wave (EMW) absorbers, and the incorporation of cavity structures represents a typical methodology therein. In this work, the MoS2-coated metal-organic framework (MOF)-derived Hollow-MoS2@CNS@CoS2 composite materials (HCNSs) were prepared by combining tannic acid-protected etching, carbonization, and hydrothermal methods. Especially, HCNS700, which possessed both a hollow structure and a layered heterogeneous structure, demonstrated excellent EMW absorption properties. It attained an optimal reflection loss of -63.63 dB at 16.4 GHz and -58.97 dB at 10.4 GHz, along with an extremely low thickness. In addition, the radar cross section simulation demonstrated that HCNS700 possessed excellent electromagnetic stealth capabilities. Its excellent performance is put down to the multiple loss mechanisms brought by the special structure, including multiple scattering of EMW caused by the hollow structure, interface polarization caused by the heterogeneous interfaces of MoS2, CoS2, and the carbon matrix, dipole polarization caused by element doping and defects, and optimization of impedance matching by MoS2. This research offers a novel concept for the design of EMW-absorbing materials with hollow heterogeneous layered structures.

Heterogeneous interfaces in 3D interconnected networks of flower-like 1T/2H Molybdenum disulfide nanosheets and carbon-fibers boosts superior EM wave absorption

With the wide application of electromagnetic waves in national defense, communication, navigation and home appliances, the electromagnetic pollution problem is becoming more and more prominent. Therefore, high-performance, and low-density composite wave-absorbing materials have attracted much attention. In this paper, three-dimensional (3D) network structures of flower-like 1T/2H Molybdenum disulfide nanosheets anchored to carbon fibers (1T/2H MoS2/CNFs) were prepared by electrostatic spinning technique and calcination process. The morphology and electromagnetic wave absorption properties were tuned by changing the content of flower-like MoS2. The optimized 1T/2H MoS2/CNFs composite exhibits superior electromagnetic wave absorption with minimum reflection (RLmin) of -42.26 dB and effective absorption bandwidth (EAB) of 6.48 GHz at 2.5 mm. Multi-facts contribute to the super performance. First, the uniquely designed nanosheet and 3D interconnected networks leads to multiple reflection and scattering of electromagnetic waves, which promotes the attenuation of electromagnetic waves. Second, the propriate content of CNFs and MoS2 with different phase regulates its impedance matching characteristic. Third, Numerous heterogeneous interfaces existed between CNFs and MoS2, 1T and 2H MoS2 phase results in interface polarization. Besides, the 1T/2H MoS2 rich in defects induces defect polarization, improving the dielectric loss. Furthermore, the electromagnetic wave absorption performance was proved via radar reflectance cross section simulation. This work illustrates 1T/2H MoS2/CNFs is a promising material for electromagnetic absorption with wide bandwidth, strong absorption, low density, and high thermal stability.

Stable 1T-MoS2 by Facile Phase Transition Synthesis for Efficient Electrocatalytic Oxygen Evolution Reaction

The 1T phase of MoS2 exhibits much higher electrocatalytic activity and better stability than the 2H phase. However, the harsh conditions of 1T phase synthesis remain a significant challenge for various extensions and applications of MoS2. In this work, a simple hydrothermal-based synthesis method for the phase transition of MoS2 is being developed. For this, the NH2-MIL-125(Ti) (Ti MOF) is successfully utilized to induce the phase transition of MoS2 from 2H to 1T, achieving a high conversion ratio of ≈78.3%. The optimum phase-induced MoS2/Ti MOF heterostructure demonstrates enhanced oxygen evolution reaction (OER) performance, showing an overpotential of 290 mV at a current density of 10 mA cm-2. The density functional theory (DFT) calculations are demonstrating the benefits of this phase transition, determining the electronic properties and OER performance of MoS2.

Constructing Built-In Electric Fields with Semiconductor Junctions and Schottky Junctions Based on Mo-MXene/Mo-Metal Sulfides for Electromagnetic Response

The exploration of novel multivariate heterostructures has emerged as a pivotal strategy for developing high-performance electromagnetic wave (EMW) absorption materials. However, the loss mechanism in traditional heterostructures is relatively simple, guided by empirical observations, and is not monotonous. In this work, we presented a novel semiconductor-semiconductor-metal heterostructure system, Mo-MXene/Mo-metal sulfides (metal = Sn, Fe, Mn, Co, Ni, Zn, and Cu), including semiconductor junctions and Mott-Schottky junctions. By skillfully combining these distinct functional components (Mo-MXene, MoS2, metal sulfides), we can engineer a multiple heterogeneous interface with superior absorption capabilities, broad effective absorption bandwidths, and ultrathin matching thickness. The successful establishment of semiconductor-semiconductor-metal heterostructures gives rise to a built-in electric field that intensifies electron transfer, as confirmed by density functional theory, which collaborates with multiple dielectric polarization mechanisms to substantially amplify EMW absorption. We detailed a successful synthesis of a series of Mo-MXene/Mo-metal sulfides featuring both semiconductor-semiconductor and semiconductor-metal interfaces. The achievements were most pronounced in Mo-MXene/Mo-Sn sulfide, which achieved remarkable reflection loss values of - 70.6 dB at a matching thickness of only 1.885 mm. Radar cross-section calculations indicate that these MXene/Mo-metal sulfides have tremendous potential in practical military stealth technology. This work marks a departure from conventional component design limitations and presents a novel pathway for the creation of advanced MXene-based composites with potent EMW absorption capabilities.

Diatomite@MoS2 Nanocomposite Layers as Composite Coating Targeting for Mg Alloys Endowed with Properties of Anticorrosion and Antiwear

Molybdenum disulfide (MoS2) demonstrates promising applications in enhancing the corrosion and wear resistance of metals, but the susceptibility of this nanomaterial to agglomeration hinders its overall performance. In this study, the externally assisted corrosion inhibitor sodium molybdate (SM) was successfully constructed in diatomaceous earth (DE) and molybdenum disulfide (MoS2). This not only served as a molybdenum source for MoS2 but also enabled the preparation of DE@MoS2-SM microcapsules, achieving a corrosion inhibitor loading of up to 23.23%. The corrosion testing reveals that the composite coating, when compared to the pure epoxy coating, exhibits an impedance modulus 2 orders of magnitude higher (1.80 × 109 Ω·cm2), offering prolonged protection for magnesium alloys over a 40 day period. Furthermore, a filler content of 3% sustains a coefficient of friction (COF) at 0.55 for an extended duration, indicating commendable stability and wear resistance. The protective performance is ascribed to the synergistic enhancement of corrosion and wear resistance in the coatings, facilitated by the pore structure of DE, the high hardness of MoS2, and the obstructive influence of Na2MoO4. This approach offers a straightforward and efficient means of designing microcapsules for use in corrosive environments, whose application can be extended in industrial fields. In particular, we promote the application of nautical instruments, underwater weapons, and seawater batteries in the shipbuilding industry and marine engineering.

Optimization of CoFe2O4 nanoparticles and graphite fillers to endow thermoplastic polyurethane nanocomposites with superior electromagnetic interference shielding performance

The rapid growth, integration, and miniaturization of electronics have raised significant concerns about how to handle issues with electromagnetic interference (EMI), which has increased demand for the creation of EMI shielding materials. In order to effectively shield against electromagnetic interference (EMI), this study developed a variety of thermoplastic polyurethane (TPU)-based nanocomposites in conjunction with CoFe2O4 nanoparticles and graphite. The filler percentage and nanocomposite thickness were tuned and optimized. The designed GF15-TPU nanocomposite, which has a 5 mm thickness, 15 weight percent cobalt ferrite nanoparticles, and 35 weight percent graphite, showed the highest total EMI shielding effectiveness value of 41.5 dB in the 8.2-12.4 GHz frequency range, or 99.993% shielding efficiency, out of all the prepared polymer nanocomposites. According to experimental findings, the nanocomposite's dipole polarization, interfacial polarization, conduction loss, eddy current loss, natural resonance, exchange resonance, multiple scattering, and high attenuation significantly contribute to improving its electromagnetic interference shielding properties. The created TPU-based nanocomposites containing graphite and CoFe2O4 nanoparticles have the potential to be used in communication systems, defense, spacecraft, and aircraft as EMI shielding materials.

Preparation of MoS2@PDA-Modified Polyimide Films with High Mechanical Performance and Improved Electrical Insulation

Polyimide (PI) has been widely used in cable insulation, thermal insulation, wind power protection, and other fields due to its high chemical stability and excellent electrical insulation and mechanical properties. In this research, a modified PI composite film (MoS2@PDA/PI) was obtained by using polydopamine (PDA)-coated molybdenum disulfide (MoS2) as a filler. The low interlayer friction characteristics and high elastic modulus of MoS2 provide a theoretical basis for enhancing the flexible mechanical properties of the PI matrix. The formation of a cross-linking structure between a large number of active sites on the surface of the PDA and the PI molecular chain can effectively enhance the breakdown field strength of the film. Consequently, the tensile strength of the final sample MoS2@PDA/PI film increased by 44.7% in comparison with pure PI film, and the breakdown voltage strength reached 1.23 times that of the original film. It can be seen that the strategy of utilizing two-dimensional (2D) MoS2@PDA nanosheets filled with PI provides a new modification idea to enhance the mechanical and electrical insulation properties of PI films.

Construction of Hierarchical Yolk-Shell Co/N-Dope C@void@C@MoS2 Composites with Multiple Heterogeneous Interfaces toward Broadband Electromagnetic Wave Absorption

The synthesis of materials with a multicomponent hierarchical structure is an essential strategy for achieving high-performance electromagnetic wave (EMW) absorption. However, conventional design strategies face challenges in terms of the rational construction of specific architecture. In this study, we employ a combined space-restricted and hierarchical construction strategy to surface-plant MoS2 nanosheets on yolk-shell structural carbon-modified Co-based composites, leading to the development of high-performance Co/NC@void@C@MoS2 absorbers with advanced architecture. The surface-planted MoS2 nanosheets, the Co/NC magnetic yolk, and the dielectric carbon shell work together to enhance the impedance matching characteristics and synergistic loss capabilities in the composites. Experimental results indicate that Co/NC@void@C-700@MoS2 exhibited the best absorption performance with an effective absorption bandwidth of 7.54 GHz (at 2.05 mm) and a minimum reflection loss of -60.88 dB (at 1.85 mm). Furthermore, radar cross-section simulation results demonstrate that Co/NC@void@C-700@MoS2 effectively suppresses the scattering and transmission of EMWs on perfect electric conductor substrates, implying its superior practical application value. This study provides inspiration and experimental basis for designing and optimizing EMW absorption materials with hierarchical yolk-shell architecture.

Augmented photocatalysis induced by 1T-MoS2 bridged 2D/2D MgIn2S4@1T/2H-MoS2 Z-scheme heterojunction: mechanistic insights into H2O2 and H2 evolution

In the realm of composite photocatalysts, the fusion of the co-catalyst effect with interfacial engineering is recognized as a potent strategy for facilitating the segregation and migration of photo-induced charge carriers. Herein, an innovative mediator-based Z-scheme hybrid, i.e. MIS@1T/2H-MoS2, has been well designed by pairing MIS with 1T/2H-MoS2via a facile hydrothermal strategy as a competent photocatalyst for H2O2 and H2 generation. The co-catalyst, i.e. metallic 1T-phase bridging between semiconducting 2H-MoS2 and MIS, serves as a solid state electron mediator in the heterostructure. Morphological findings revealed the growth of 1T/2H-MoS2 nanoflowers over MIS microflowers, verifying the close interaction between MIS and 1T/2H-MoS2. By virtue of accelerated e-/h+ pair separation and migration efficiency along with a proliferated density of active sites, the MMoS2-30 photocatalyst yields an optimum H2O2 of 35 μmol h-1 and H2 of 370 μmol h-1 (ACE of 5.9%), which is 3 and 2.7 fold higher than pristine MIS. This obvious enhancement can be attributed to photoluminescence and electrochemical aspects that substantiate the diminished charge transfer resistance along with improved charge carrier separation, representing a good example of a noble metal-free photocatalyst. The proposed Z-scheme charge transfer mechanism is aided by time-resolved photoluminescence (TRPL), XPS, radical trapping experiments, and EPR analysis. Overall, this endeavour provides advanced insights into the architecture of noble metal-free Z-scheme heterostructures, offering promising prospects in photocatalytic applications.

From VIB- to VB-Group Transition Metal Disulfides: Structure Engineering Modulation for Superior Electromagnetic Wave Absorption

The laminated transition metal disulfides (TMDs), which are well known as typical two-dimensional (2D) semiconductive materials, possess a unique layered structure, leading to their wide-spread applications in various fields, such as catalysis, energy storage, sensing, etc. In recent years, a lot of research work on TMDs based functional materials in the fields of electromagnetic wave absorption (EMA) has been carried out. Therefore, it is of great significance to elaborate the influence of TMDs on EMA in time to speed up the application. In this review, recent advances in the development of electromagnetic wave (EMW) absorbers based on TMDs, ranging from the VIB group to the VB group are summarized. Their compositions, microstructures, electronic properties, and synthesis methods are presented in detail. Particularly, the modulation of structure engineering from the aspects of heterostructures, defects, morphologies and phases are systematically summarized, focusing on optimizing impedance matching and increasing dielectric and magnetic losses in the EMA materials with tunable EMW absorption performance. Milestones as well as the challenges are also identified to guide the design of new TMDs based dielectric EMA materials with high performance.

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.

Core-shell FeCo@carbon nanocages encapsulated in biomass-derived carbon aerogel: Architecture design and interface engineering of lightweight, anti-corrosion and superior microwave absorption

The development of multifunctional microwave absorbing materials for practical applications in complex environments is a challenging research hotspot. Herein, the core-shell structure FeCo@C nanocages were successfully anchored on the surface of biomass-derived carbon (BDC) from pleurotus eryngii (PE) via freeze-drying and electrostatic self-assembly process, achieving lightweight, anti-corrosive, and excellent absorption properties. The superior versatility benefits from the large specific surface area, high conductivity, three-dimensional cross-linked networks, and appropriate impedance matching characteristics. The as-prepared aerogel realizes a minimum reflection loss (RL_min) of -69.5 dB with a corresponding effective absorption bandwidth (EAB) of 8.6 GHz at 2.9 mm. Simultaneously, the computer simulation technique (CST) further proves that the multifunctional material can dissipate microwave energy in actual applications. More importantly, the special heterostructure of aerogel endows excellent resistance to acid, alkali, salt medium, allowing potential applications of the microwave absorbing materials under complex environmental conditions.

Phase Transition Induced via the Template Enabling Cocoon-like MoS2 an Exceptionally Electromagnetic Absorber

Structural engineering via the template method is efficient for micro-nano assembling. However, only structural design and lack of composition control restrict their advanced application. To overcome this issue, applying a template to simultaneously realize the structural design and fine component control is highly desired, which has been ignored. In this study, a spinel-shaped MoS₂ heterostructure with controlled phase ratios of 1H and 2H phase is developed using the AlOOH template method. This work demonstrates that the MoS₂ phase transition mechanism from 2H to 1T is substantially attributed to the close exposed crystal's surface and approximately accordant surface energy. The superiority and additional proof are provided based on density-functional theory simulation, transmission electron microscope holography, etc. With an effective absorptance region of 6.3 GHz under a thickness of 1.4 mm, the reported samples present outstanding microwave absorption capacity. This is attributed to the beneficial coupled effect between the well-designed structure and phase regulation. This work offers valuable insights into structural engineering and component regulation template methods.

Optimized electromagnetic wave absorption ofα-Fe2O3@MoS2nanocomposites with core-shell structure

Core-shell structures and interfacial polarization are of great significance to meet the diversified requirements of microwave attenuation. Herein,α-Fe₂O₃@MoS₂nanocomposites are fabricated via a simple two-step hydrothermal process, in which MoS₂nanosheets as the shell are self-assembled andα-Fe₂O₃microdrums are used as the core to constitute a special flower-like morphology with core-shell structure. This structure can provide more interface contact to achieve strong interfacial polarization and possibly offer more multiple reflection and scattering of electromagnetic waves. Furthermore, the microwave dissipation performances ofα-Fe₂O₃@MoS₂nanocomposites can be significantly improved through construction of core-shell structure and flower-like morphology, controlling the content ofα-Fe₂O₃microdrums and adjusting the filler loading ratios. This work proves that the as-synthesized nanocomposites achieve excellent effective absorption bandwidth and outstanding electromagnetic wave absorption capabilities due to their special interfaces, core-shell structures and good impedance matching conditions. Therefore,α-Fe₂O₃@MoS₂nanocomposites are expected to be a novel and desirable candidate for high-performance electromagnetic wave absorbers.

High-performance electromagnetic wave absorption in cobalt sulfide flower-like nanospheres

A heterophase cobalt sulfide absorbing material with petal-like surface structure was prepared by a simple hydrothermal method. The cobalt sulfide sample with the optimal microwave absorption capacity was achieved through regulating the reaction temperature. By regulating the reaction temperature to 200 °C, the optimal reflection loss was -48.4 dB at 16.8 GHz with filler loading of 50%, and the effective absorption bandwidth was 4.3 GHz at Ku band corresponding to a thickness of only 1.5 mm. The petal-like surface structure of cobalt sulfide gradually disappears as the reaction temperature rises, and the reduction of specific surface area has a negative effect on the microwave absorption capacity of the sample. Meanwhile, by adjusting the sample thickness from 1.5 to 5.0 mm, the effective absorption bandwidth could cover almost the whole test frequency range. The results show that the cobalt sulfide absorbing material with regulated reaction temperature has a strong electromagnetic wave absorption ability, light weight, thin thickness and simple synthesis, which is a promising microwave absorbing material for actual application.

Metamaterial Absorbers: From Tunable Surface to Structural Transformation

Since the first demonstration, remarkable progress has been made in the theoretical analysis, structural design, numerical simulation, and potential applications of metamaterial absorbers (MAs). With the continuous advancement of novel materials and creative designs, the absorption of MAs is significantly improved over a wide frequency spectrum from microwaves to the optical regime. Further, the integration of active elements into the MA design allows the dynamical manipulation of electromagnetic waves, opening a new platform to push breakthroughs in metadevices. In the last several years, numerous efforts have been devoted to exploring innovative approaches for incorporating tunability to MAs, which is highly desirable because of the progressively increasing demand on designing versatile metadevices. Here, a comprehensive and systematical overview of active MAs with adaptive and on-demand manner is presented, highlighting innovative materials and unique strategies to precisely control the electromagnetic response. In addition to the mainstream method by manipulating periodic patterns, two additional approaches, including tailoring dielectric spacer and transforming overall structure are called back. Following this, key parameters, such as operating frequency, relative tuning range, and switching speed are summarized and compared to guide for optimum design. Finally, potential opportunities in the development of active MAs are discussed.

Constructing MoSe2/MoS2 and MoS2/MoSe2 inner and outer-interchangeable flower-like heterojunctions: A combined strategy of interface polarization and morphology configuration to optimize microwave absorption performance

Interfacial polarization and geometrical morphology play a significant role in the attenuation of electromagnetic (EM) wave. Herein, the two-dimensional (2D)/2D heterojunction with flower-like geometrical morphology is proposed and produced, which may simultaneously provide a large contact area for achieving strong interfacial polarization and activates more sites for the possible multiple EM wave reflection and scattering. By adopting a simple two-step hydrothermal method, MoSe₂/MoS₂and MoS₂/MoSe₂ inner and outer-interchangeable heterojunctions consisting of 2D MoSe₂ and MoS₂ nanosheets with flower-like geometrical morphology were successfully synthesized. The results revealed that the hydrothermal temperatures significantly impacted the flower-like geometrical morphology and MoS₂ content. By optimizing the microstructures, the designed MoSe₂/MoS₂ and MoS₂/MoSe₂ heterojunctions presented enhanced comprehensive EM wave absorption properties (EMWAPs), possessing strong absorption capability, wide absorption bandwidth and thin matching thicknesses. Generally, this work demonstrates that the optimized EMWAPs of designed heterojunctions mainly originate from the special interfaces and morphology configuration, which also paves a new way for the designing and synthesis of transition metal dichalcogenides-based heterojunction as a novel and desirable candidate for high-performance microwave absorbers.

A General Way to Fabricate Chain-like Ferrite with Ultralow Conductive Percolation Threshold and Wideband Absorbing Ability

The magnetic nanochain-like material has been regards as one of the most promising electromagnetic (EM) absorbing material but remains a challenging. Herein, magnetic chain-like ferrite (included Fe3O4, CoFe2O4 and NiFe2O4) are successfully produced through a general solvothermal method, using PVP as the structural-liking agent. Experimental results confirm the ultimate sample possess a 3-dimensional chain-like structure which are constructed by numerous ferrite's nanoparticles with ~60 nm in diameter. Their electromagnetic parameters can be also manipulated by such a chain structure, especially the dielectric loss, where a sharply increases can be observed on within a lower filling ratio. It greatly benefits to the EM absorbing property. In this article, the electromagnetic absorption layer made with a lower content of ferrite possess the excellent electromagnetic absorption ability, where the optimized effective absorption band was nearly 6.4 GHz under a thickness of 1.8 mm. Moreover, the filling ratio is only 30 wt%. Our method for designing of chain-like magnetic material can be helpful for producing wideband electromagnetic absorption in a low filling ratio.

2D Molybdenum Sulfide-Based Materials for Photo-Excited Antibacterial Application

Bacterial infections have seriously threatened human health and the abuse of natural or artificial antibiotics leads to bacterial resistance, so development of a new generation of antibacterial agents and treatment methods is urgent. 2D molybdenum sulfide (MoS₂ ) has good biocompatibility, high specific surface area to facilitate surface modification and drug loading, adjustable energy bandgap, and high near-infrared photothermal conversion efficiency (PCE), so it is often used for antibacterial application through its photothermal or photodynamic effects. This review comprehensively summarizes and discusses the fabrication processes, structural characteristics, antibacterial performance, and the corresponding mechanisms of MoS₂ -based materials as well as their representative antibacterial applications. In addition, the outlooks on the remaining challenges that should be addressed in the field of MoS₂ are also proposed.

Magnetic CoNi alloy particles embedded N-doped carbon fibers with polypyrrole for excellent electromagnetic wave absorption

Increasing electromagnetic (EM) radiation has driven the rapid development of carbon-based EM wave absorption materials, but the design of light-weight and efficient carbon-based materials remains a huge challenge. Herein, N-doped carbon fibers embedded with CoNi alloy particles (CoNi/C fibers) were synthesized via electrospinning technology and carbonization. Then, conductive polypyrrole-coated CoNi/C fibers (CoNi/C@PPy composites) were synthesized by chemical polymerization. As-synthesized CoNi/C@PPy composites showed outstanding EM wave absorption property due to the synergistic effect between CoNi, N-doped carbon fibers and PPy. The optimal reflection loss (RL) is -68.78 dB (12.90 GHz) with the thickness of 2.43 mm and the low filler loading of 15 wt%. The widest effective absorption bandwidth (EAB) is 5.62 GHz with the thickness of 2.10 mm and the low filler loading of 20 wt%. The outstanding EM wave absorption property is mainly attributed to 3D network structure, great impedance matching and strong dielectric loss. The results showed that embedding magnetic alloy particles in carbon fibers coated with conductive polymers is an effective strategy for constructing efficient lightweight EM wave absorption materials.

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.

Micro-flower like Core-shell structured ZnCo@C@1T-2H-MoS2 composites for broadband electromagnetic wave absorption and photothermal performance

Core-shell structure has been receiving extensive attention to enhance the electromagnetic wave (EMW) absorption performance due to its unique interface effect. In this paper, a micro-flower like ZnCo@C@1T-2H-MoS₂ was prepared through MOF self-template method. The introduction 1T-2H-MoS₂ shell helps optimize impedance matching of the CoZn@C particles to improve the EMW absorption ability. The minimal reflection loss (RL_min) value of ZnCo@C@1T-2H-MoS₂ is -35.83 dB with a thickness of 5.0 mm at 5.83 GHz and the effective absorption (RL < -10 dB) bandwidth up to 4.56 GHz at 2.0 mm thickness. Meanwhile, the overall effective absorption bandwidth (OEAB) can reach up to 13.44 GHz from 4.56 to 18.0 GHz. Moreover, ultrafast photothermal performances are also achieved, which can guarantee the normal functioning of ZnCo@C@1T-2H-MoS₂ materials in cold conditions. The excellent EMW absorption and photothermal performance are attributed to the unique structure designed with the core of magnetic ZnCo@C rhombic dodecahedral and the shell of dielectric micro-flower like 1T-2H-MoS₂ optimize impedance matching.

MoS2 decorated on one-dimensional MgFe2O4/MgO/C composites for high-performance microwave absorption

Advanced microwave absorption (MA) materials have attracted widespread attention to meet the challenges of electromagnetic (EM) pollution. Herein, MgFe₂O₄/MgO/C fibers were successfully prepared via electrospinning technology and carbonization, and their surfaces were coated by MoS₂ via hydrothermal method. The EM wave absorption performance of composites was enhanced due to the introduction of MoS₂. The results showed that the EM wave absorption performance of MgFe₂O₄/MgO/C could not meet the requirements due to low dielectric loss and poor impedance matching. The performance of the composites was improved after coating of MoS₂, which showed the strong wave absorption capability and the broad absorption bandwidth. The optimal reflection loss (RL) is -56.94 dB at 9.5 GHz and the effective absorption bandwidth is 3.9 GHz (8.08-11.98 GHz) with a thickness of 2.7 mm. The excellent MA performance can be mainly attributed to excellent synergistic effect between MgFe₂O₄/MgO/C and MoS₂. Furthermore, MoS₂ also contributes to dielectric loss and ideal impedance matching. MgFe₂O₄/MgO/C@MoS₂ composites may be utilized for lightweight and high-efficient MA materials.

Morphology optimization strategy of flower-like CoNi2S4/Co9S8@MoS2 core@shell nanocomposites to achieve extraordinary microwave absorption performances

Morphology optimization is an effective strategy to take full advantage of interface polarization for the improvement of electromagnetic wave attenuation capability. Herein, a general route was proposed to produce the flower-like core@shell structured MoS₂-based nanocomposites through a simple hydrothermal process. Through the in-situ hydrothermal reaction between the Mo and S sources on the surface of CoNi nanoparticles, flower-like core@shell structured CoNi₂S₄/Co₉S₈@MoS₂ nanocomposites could be successfully synthesized. By regulating the hydrothermal temperature, the flower-like geometrical morphology of samples could be effectively optimized, and the as-prepared sample (S2) synthesized at 200 °C displayed very excellent flower-like morphology compared to the samples (S1 and S3) obtained at 180 and 220 °C. Owing to the excellent interface polarization effect, the as-prepared S2 presented the evidently superior comprehensive microwave absorption properties in terms of strong aborption capability, wide absorption bandwidth and thin matching thicknesses compared to those of S1 and S3. The as-prepared core@shell structured CoNi₂S₄/Co₉S₈@MoS₂ sample with very excellent flower-like morphology simultaneously displayed the minimal reflection loss of -50.61 dB with the matching thickness of 2.98 mm, and the effective absorption bandwidth of 8.40 GHz with the matching thickness of 2.36 mm. Therefore, we provided a general route for the production of flower-like core@shell structured MoS₂-based nanocomposites, which could make the best of interface polarization to develop high-efficiency microwave absorbers.

Tailoring the fusion effect of phase-engineered 1T/2H-MoS2 towards photocatalytic hydrogen evolution

Enhanced photocatalytic hydrogen evolution on 30-1T/2H-MoS2 with a higher concentration of the 1T phase was achieved due to the higher availability of electrons and dense active sites after the incorporation of the 1T phase in 2H-MoS2.

Heterointerface Engineering in Electromagnetic Absorbers: New Insights and Opportunities

Electromagnetic (EM) absorbers play an increasingly essential role in the electronic information age, even toward the coming "intelligent era". The remarkable merits of heterointerface engineering and its peculiar EM characteristics inject a fresh and infinite vitality for designing high-efficiency and stimuli-responsive EM absorbers. However, there still exist huge challenges in understanding and reinforcing these interface effects from the micro and macro perspectives. Herein, EM response mechanisms of interfacial effects are dissected in depth, and with a focus on advanced characterization as well as theoretical techniques. Then, the representative optimization strategies are systematically discussed with emphasis on component selection and structural design. More importantly, the most cutting-edge smart EM functional devices based on heterointerface engineering are reported. Finally, current challenges and concrete suggestions are proposed, and future perspectives on this promising field are also predicted.

Metal–organic framework-derived porous CoFe2O4/carbon composite nanofibers for high-rate lithium storage

Upon assembled into full cells, metal–organic frameworks derived porous CoFe2O4/carbon composite nanofibers achieved long-cycling and high-rate performance, and a series of LED bulbs can be lit to demonstrate its potential in real applications.

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.

High-Performance, Lightweight, and Flexible Thermoplastic Polyurethane Nanocomposites with Zn2+-Substituted CoFe2O4 Nanoparticles and Reduced Graphene Oxide as Shielding Materials against Electromagnetic Pollution

The development of flexible, lightweight, and thin high-performance electromagnetic interference shielding materials is urgently needed for the protection of humans, the environment, and electronic devices against electromagnetic radiation. To achieve this, the spinel ferrite nanoparticles CoFe2O4 (CZ1), Co0.67Zn0.33Fe2O4 (CZ2), and Co0.33Zn0.67Fe2O4 (CZ3) were prepared by the sonochemical synthesis method. Further, these prepared spinel ferrite nanoparticles and reduced graphene oxide (rGO) were embedded in a thermoplastic polyurethane (TPU) matrix. The maximum electromagnetic interference (EMI) total shielding effectiveness (SET) values in the frequency range 8.2-12.4 GHz of these nanocomposites with a thickness of only 0.8 mm were 48.3, 61.8, and 67.8 dB for CZ1-rGO-TPU, CZ2-rGO-TPU, and CZ3-rGO-TPU, respectively. The high-performance electromagnetic interference shielding characteristics of the CZ3-rGO-TPU nanocomposite stem from dipole and interfacial polarization, conduction loss, multiple scattering, eddy current effect, natural resonance, high attenuation constant, and impedance matching. The optimized CZ3-rGO-TPU nanocomposite can be a potential candidate as a lightweight, flexible, thin, and high-performance electromagnetic interference shielding material.

Core-shell CoFe2O4@C nanoparticles coupled with rGO for strong wideband microwave absorption

Strong absorption and large bandwidth are two contributors to materials' absorbing performance. In this work, a series of multi-element core-shell magnetic nano-particle composite layered graphene absorbing materials CoFe₂O₄@C/rGO (CCr) were prepared by adjusting carbon shell thickness. The CCr at a low thickness achieved strong microwave absorption and a wide effective absorption bandwidth. Not only the core-shell structure of the magnetic nanoparticle CoFe₂O₄@C (CFO@C) increases the interface loss, but both the coating carbon shell and the core CoFe₂O₄ (CFO) are beneficial to improve impedance matching. Due to the synergistic effect of the dielectric and magnetic properties of graphene and ferrite, CCr possessed high absorption performance, and its minimum reflection loss reached (R_Lmin) -52.5 dB when the thickness was only 2 mm. At the same time, the effective absorption bandwidth (EAB) was 5.68 GHz when the thickness was only 1.7 mm. The chemically stable core-shell dielectric nanocomposite provided a new solution for preparing materials with excellent chemical structure and high absorbing properties.

Fabrication of one-dimensional CoFe2/C@MoS2 composites as efficient electromagnetic wave absorption materials

New types of electromagnetic (EM) wave absorption materials with a light weight, strong absorption ability and wide absorption frequency have been widely explored. Nevertheless, it is still an intractable challenge to design the structure of the materials and rationalize multiple components. In this work, one-dimensional (1D) CoFe₂/C@MoS₂ composites were prepared via electrospinning technology, high-temperature carbonization and hydrothermal method. SEM and TEM images reveal that the as-prepared CoFe₂/C fibers with a 1D structure are well coated with MoS₂. The excellent absorption performance of the composites is mainly attributed to the 1D structure and the ideal impedance matching. CoFe₂/C@MoS₂ composites show strong absorption ability with an optimal reflection loss (RL) of -66.8 dB (13.28 GHz) at a matching thickness of 2.12 mm. Meanwhile, the composite possesses an effective absorption frequency range between 10.70 and 16.02 GHz with a bandwidth of 5.32 GHz. These results indicate that CoFe₂/C@MoS₂ composites will become promising lightweight and highly efficient MA materials.

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

In this work, a 3D ternary core-shell Fe₃O₄@SiO₂@MoS₂ composite is synthesized by a hydrothermal technique and a modified Stöber method, where magnetic Fe₃O₄@SiO₂ microsphere with the core of raspberry-like Fe₃O₄ nanoparticles is completely coated by the flower-like MoS₂. Herein, the electromagnetic parameters of the composites are effectively tuned by the combination of magnetic Fe₃O₄ with dielectric SiO₂ and MoS₂. The obtained ternary composites exhibit remarkable enhancement of microwave absorption. The measurement results indicate that the minimum reflection loss (RL) of Fe₃O₄@SiO₂@MoS₂ composites reaches -62.98 dB at 1.83 mm with the effective absorption bandwidth (RL < -10 dB) of 5.76 GHz (from 11.28 to 17.04 GHz) at 1.92 mm, much higher than those of pure Fe₃O₄ particles and Fe₃O₄@SiO₂ microsphere. It is believed that the improved performances come from the specific structural design and the plentiful interfacial construction. Further, the synergistic effect of the dielectric and magnetic loss as well as the promoted impedance matching also help to enhance the microwave absorption of the composites. The microwave absorption behavior of the composites conforms to the quarter-wavelength cancellation theory. Our study offers an effective and promising strategy in the structural design and interfacial construction of the novel magnetic/dielectric composites with high-efficiency microwave absorption.

Structural Engineering of Hierarchical Aerogels Comprised of Multi-dimensional Gradient Carbon Nanoarchitectures for Highly Efficient Microwave Absorption

Recently, multilevel structural carbon aerogels are deemed as attractive candidates for microwave absorbing materials. Nevertheless, excessive stack and agglomeration for low-dimension carbon nanomaterials inducing impedance mismatch are significant challenges. Herein, the delicate "3D helix-2D sheet-1D fiber-0D dot" hierarchical aerogels have been successfully synthesized, for the first time, by sequential processes of hydrothermal self-assembly and in-situ chemical vapor deposition method. Particularly, the graphene sheets are uniformly intercalated by 3D helical carbon nanocoils, which give a feasible solution to the mentioned problem and endows the as-obtained aerogel with abundant porous structures and better dielectric properties. Moreover, by adjusting the content of 0D core-shell structured particles and the parameters for growth of the 1D carbon nanofibers, tunable electromagnetic properties and excellent impedance matching are achieved, which plays a vital role in the microwave absorption performance. As expected, the optimized aerogels harvest excellent performance, including broad effective bandwidth and strong reflection loss at low filling ratio and thin thickness. This work gives valuable guidance and inspiration for the design of hierarchical materials comprised of dimensional gradient structures, which holds great application potential for electromagnetic wave attenuation.

Constructing a nitrogen-doped carbon and nickel composite derived from a mixed ligand nickel-based a metal-organic framework toward adjustable microwave absorption

The rational design of nanostructures for absorbers has great potential in the microwave absorption field. In this work, a mixed ligand nickel metal-organic framework (ML-Ni MOF) was first prepared by the self-assembly of pyrazine and 1,3,5-benzenetricarboxylic acid with nickel ions. Then, the as-prepared ML-Ni MOF was used as a precursor to fabricate a nitrogen-doped carbon and nickel composite (ML-Ni/C). With the molar ratio of pyrazine and 1,3,5-benzenetricarboxylic acid of 1 : 1, the flower-like ML-Ni MOF was obtained. After pyrolysis, the ML-Ni MOF-derived ML-Ni/C composite showed an optimal reflection loss value of -65.33 dB with a thickness of 2.4 mm and a corresponding effective absorbing bandwidth (EAB, RL ≤ -10 dB) of 5.1 GHz. Besides, the broadest EAB of 7.6 GHz was achieved when the thickness was about 2.8 mm. This strategy paves a new way to design novel MOFs as precursors for fabricating absorbers.

Facile synthesis of nickel/carbon nanotubes hybrid derived from metal organic framework as a lightweight, strong and efficient microwave absorber

Transition metal carbon composites derived from metal organic frameworks (MOFs) attract increasing attention in microwave absorption field. However, finding a relatively facile and green method to prepare MOFs precursor is still a challenge. Besides, it is also difficult to obtain carbon nanotubes based compounds by only using MOF as sacrificed template. Herein, nickel (Ni) MOF is fabricated at room temperature with water as solvent. Afterwards, nickel/carbon nanotubes composite (Ni/CN) is prepared via only in-situ pyrolysis of Ni MOF. The pyrolysis temperature greatly affects nitrogen (N) dopant state for Ni/CN composites. The Ni/CN composite prepared at 700 °C (Ni/CN-700) exhibits the maximum reflection loss (RL) of -65 dB with the effective absorbing bandwidth (EAB) about 4.6 GHz at 1.9 mm, when the filling loading is only 10 wt% in the matrix. Remarkably, the Ni/CN composite is excellent microwave absorber with lightweight and strong absorption. The magnetic metal/carbon nanotubes derived from MOF prepared in green solvent offers a facile, environmentally friendly and designable strategy for exploring excellent microwave absorber.

Electrochemical Fixation of Nitrogen by Promoting N2 Adsorption and N-N Triple Bond Cleavage on the CoS2/MoS2 Nanocomposite

An electrochemical N₂ reduction reaction (NRR), as an environmentally benign method to produce NH₃, is a suitable alternative to substitute the energy-intensive Haber-Bosch technology. Unfortunately, to date, it is obstructed by the lack of efficient electrocatalysts. Here, a CoS₂/MoS₂ nanocomposite with CoS₂ nanoparticles decorated on MoS₂ nanosheets is fabricated and adapted as a catalyst for the NRR. As unveiled by experimental and theoretical results, the strong interaction between CoS₂ and MoS₂ modulates interfacial charge distribution with electrons transferring from CoS₂ to MoS₂. Consequently, a local electrophilic region is formed near the CoS₂ side, which enables effective N₂ absorption. On the other hand, the nucleophilic area formed near the MoS₂ side is in favor of breaking stable N≡N, the potential-determining step (*N₂ → *N₂H) which brings about a much decreased energy barrier than that on pure MoS₂. As a result, this catalyst exhibits an excellent NRR performance, NH₃ yield and Faradaic efficiency of 54.7 μg·h^-1·mg^-1 and 20.8%, respectively, far better than most MoS₂-based catalysts.

MoS2-Decorated/Integrated Carbon Fiber: Phase Engineering Well-Regulated Microwave Absorber

Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide (MoS2). MoS2-based composites are usually used for the electromagnetic wave (EMW) absorber, but the effect of different phases on the EMW absorbing performance, such as 1T and 2H phase, is still not studied. In this work, micro-1T/2H MoS2 is achieved via a facile one-step hydrothermal route, in which the 1T phase is induced by the intercalation of guest molecules and ions. The EMW absorption mechanism of single MoS2 is revealed by presenting a comparative study between 1T/2H MoS2 and 2H MoS2. As a result, 1T/2H MoS2 with the matrix loading of 15% exhibits excellent microwave absorption property than 2H MoS2. Furthermore, taking the advantage of 1T/2H MoS2, a flexible EMW absorbers that ultrathin 1T/2H MoS2 grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%. This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.

Defect Induced Polarization Loss in Multi-Shelled Spinel Hollow Spheres for Electromagnetic Wave Absorption Application

Defect engineering is an effective approach to manipulate electromagnetic (EM) parameters and enhance absorption ability, but defect induced dielectric loss dominant mechanism has not been completely clarified. Here the defect induced dielectric loss dominant mechanism in virtue of multi-shelled spinel hollow sphere for the first time is demonstrated. The unique but identical morphology design as well as suitable composition modulation for serial spinels can exclude the disturbance of EM wave dissipation from dipolar/interfacial polarization and conduction loss. In temperature-regulated defect in NiCo2O4 serial materials, two kinds of defects, defect in spinel structure and oxygen vacancy are detected. Defect in spinel structure played more profound role on determining materials' EM wave dissipation than that of oxygen vacancy. When evaluated serial Co-based materials as absorbers, defect induced polarization loss is responsible for the superior absorption performance of NiCo2O4-based material due to its more defect sites in spinel structure. It is discovered that electron spin resonance test may be adopted as a novel approach to directly probe EM wave absorption capacities of materials. This work not only provides a strategy to prepare lightweight, efficient EM wave absorber but also illustrates the importance of defect engineering on regulation of materials' dielectric loss capacity.