Search

[Display omitted] • A series of rare earth MOF derivatives with various structures were obtained. • The EMW absorption performance was regulated by tunable structural anisotropy. • A basis from structure for designing MOF-based EMW absorption materials was laid. Structural engineering and component design are crucial for conceiving outstanding metal-organic frameworks (MOFs)-based electromagnetic wave (EMW) absorption materials. However, an efficient and direct clarification of the structural influences on the EMW absorption performance of MOF-based absorption materials remains highly challenging and still awaits exploration. To this end, we synthesized a new type of rare earth (RE) MOFs with hexagonal-bipyramidal, snowflake-like, and dendritic structures through facilely controlling the solvent ratios in a scalable coprecipitation approach. The MOF-derived CeO 2 /Co/C hybrids with the same component content inheriting the morphological structures showcased tunable dielectric property and EMW absorption performance. The dendritic MOF derivatives with the highest anisotropy achieved a superior EMW absorption performance, manifesting a minimum reflection loss value of −71.5 dB at 1.7 mm and an effective absorption bandwidth of 5.2 GHz at 1.6 mm thickness, comparable to those of the best EMW absorbers. This work not only confirmed the high potential of RE MOF derivatives for EMW absorption, but also directly and efficiently unveiled the mechanism of morphological structure on the dielectric property and EMW absorption performance for the MOF-based EMW absorption material. [ABSTRACT FROM AUTHOR]

The carbon-coated TiO 2 (TiO 2 @C) and FeTiO 3 (TiO 2 /FeTiO 3 @C) hybrid porous microspheres with a specific surface area of 35.1 m 2 g −1 have been successfully synthesized by carbonizing the mixture of pyrrole with lab-made TiO 2 /Fe 2 O 3 porous microspheres. The as-prepared TiO 2 /FeTiO 3 @C porous electrode material possessed a reversible capacity of 441.5 mAh g −1 after 300 cycles at a current density of 100 mA g −1 and a coulombic efficiency of 99%. Comparing with TiO 2 , TiO 2 @C, and TiO 2 /Fe 2 O 3 porous microspheres, the TiO 2 /FeTiO 3 @C porous composites exhibited superior cycling and rate performances, which are rooted in the synergistic effect that generated by little volume variation of TiO 2 matrix, high capacity of FeTiO 3 and good electrical conductivity of carbon coating (with a thickness of 2–5 nm deposited on the surface and inner wall of pores) during the charge/discharge processes. [ABSTRACT FROM AUTHOR]

Abstract: Hollow Fe3O4 at ZnO at anatase TiO2 core–shell structured spheres have been successfully synthesized through a simple two-step sol–gel method and the synthesis process is illustrated as an explicit schematic diagram. Surfactant cetyltrimethylammonium bromide was employed to realize the mesoporous anatase TiO2 shell on the surface of Fe3O4 at ZnO composite spheres. Electron microscopy examinations indicate that the composite core–shell structured hollow spheres have a homogeneous ZnO interlayer and an anatase TiO2 shell outside the ZnO layer, both of which have a thickness of about 20nm. The magnetization hysteresis curves of the samples show that the core–shell structured composites have a magnetic saturation value of 41.5emu/g, suggesting that the obtained product can be separated easily from reaction system and put into recyclable applications. [Copyright &y& Elsevier]

Large-scale octahedral FeO nanocrystallines with crystalline size of 100−500 nm were synthesized by a facile solvent-thermal method for electromagnetic wave application. The FeO nanocrystallines showed a higher saturation magnetization ( M) value of 86.8 emu/g and larger coercivity ( H) value of 255 Oe than that of magnetite polycrystallines because of their good crystallization and dispersion. The epoxy resin composites with 40 vol% FeO powders provided good electromagnetic wave absorption performance (RL < −20 dB) in the range of 2.0-4.3 GHz over the absorber thicknesses of 3.5-6.8 mm. A minimum RL value of −47 dB was observed at 3.1 GHz with a thickness of 4.8 mm. [ABSTRACT FROM AUTHOR]

Abstract: Macroporous yttria-stablized tetragonal zirconia has been synthesized combining the sol–gel with Pechini method. Polyacetylacetonatozirconium (PAZ) served as the zirconium precursor while polyvinyl alcohol (PVA) was used as pore template. The thermal behaviors of xerogel and porous zirconia were determined by thermogravimetric/differential thermal analysis (TG/DTA). FT-IR, FE-SEM, and XRD analysis indicated that the organic components of xerogel have been completely removed and porous zirconia was formed after annealing at 600°C for 2h in air. The skeleton is composed of zirconia particles with diameter of about 60nm and the pore diameter is about 68nm. The surface area and pore volume of the bulk macroporous yttria-stablized tetragonal zirconia are 9.4m2/g and 0.016cm3/g, respectively, evaluated from nitrogen adsorption/desorption measurements. [Copyright &y& Elsevier]

Ceramic aerogels are gaining increasing attention due to their low density, high‐temperature resistance, and excellent chemical stability. However, conventional ceramic aerogels are hindered by their intrinsic brittleness and limited dielectric properties, which restrict their scalable manufacturing and multifunctional applications. Here, ultralight, biomimetic porous, electrically and magnetically conductive ceramic nanofibrous aerogels composed of silicon dioxide (SiO2) nanofibers, graphene, and metal–organic framework (MOF) derivatives are prepared through an ice‐templating freeze‐casting followed by annealing approach. The renewable SiO2 nanofibers form robust bonding points with graphene, constructing interconnected high‐porosity aerogels with good mechanical resilience. This allows for efficient integration of MOF‐derived magnetic nanoparticles associated with a synergistic mechanical enhancement. The synergies of the dielectric and magnetic components, combined with the uniformly arranged sheet‐like cell walls which facilitate the outstanding electromagnetic wave absorption performance. Moreover, the hydrophobic ceramic aerogels showcase excellent magnetothermal conversion, contributing to the application in wireless therapy, antibacterial, and magnetothermal deicing. Furthermore, the nanofibrous aerogels exhibit good thermal stability and insulation properties, rendering them highly suitable for thermal management devices in extreme conditions. With the renewable, convenient, and scalable manufacturing method, these multifunctional ceramic nanofibrous aerogels thus hold great promise in electromagnetic protection, wireless heating, and next‐generation thermal management devices. [ABSTRACT FROM AUTHOR]

Improving interface connectivity of magnetic nanoparticles in carbon aerogels is crucial, yet challenging for assembling lightweight, elastic, high‐performance, and multifunctional carbon architectures. Here, an in situ growth strategy to achieve high dispersion of metal–organic frameworks (MOFs)‐anchored cellulose nanofibrils to enhance the interface connection quality is proposed. Followed by a facile freeze‐casting and carbonization treatment, sustainable biomimetic porous carbon aerogels with highly dispersed and closely connected MOF‐derived magnetic nano‐capsules are fabricated. Thanks to the tight interface bonding of nano‐capsule microstructure, these aerogels showcase remarkable mechanical robustness and flexibility, tunable electrical conductivity and magnetization intensity, and excellent electromagnetic wave absorption performance. Achieving a reflection loss of −70.8 dB and a broadened effective absorption bandwidth of 6.0 GHz at a filling fraction of merely 2.2 wt.%, leading to a specific reflection loss of −1450 dB mm−1, surpassing all carbon‐based aerogel absorbers so far reported. Meanwhile, the aerogel manifests high magnetic sensing sensibility and excellent thermal insulation. This work provides an extendable in situ growth strategy for synthesizing MOF‐modified cellulose nanofibril structures, thereby promoting the development of high‐value‐added multifunctional magnetic carbon aerogels for applications in electromagnetic compatibility and protection, thermal management, diversified sensing, Internet of Things devices, and aerospace. [ABSTRACT FROM AUTHOR]

The construction of lightweight yet robust, durable magnetic transition metal carbides and/or nitride (MXene) aerogels is highly desired for assembling high‐performance, multifunctional architectures. However, the fabrication and application of magnetic MXene aerogels is severely restricted by their inferior mechanical strength and poor water/oxygen resistance. Here, sustainable cellulose nanofibrils (CNFs) are employed for assisting in the physical and chemical dual cross‐linking to strongly bind the MXenes and MOF‐derived magnetic nanoparticles. The dual‐crosslinked magnetic MXene aerogels (D‐MMAs) achieve a density as low as 12 mg cm−3, and acquire a significantly improved mechanical strength of up to 1311% over physically crosslinked ones, as well as remarkably improved hydrophobicity, and oxidation stability. Furthermore, the multifunctional integration of efficient and tunable electromagnetic wave (EMW) absorption, remarkable photothermal conversion, thermal insulation, prominent oil‐water separation, thin/thick oil and dye absorption capability, and the remote magnetic controllability is accomplished. Notably, the D‐MMA performs a maximum absorption intensity of −63.9 dB, and accomplishes a specific reflection loss of −1105 dB mm−1, comparable to the best MXene‐based EMW absorbers ever reported. Given its facile, scalable, and sustainable manufacturing approach, the multifunctional D‐MMAs hold great application prospects in various fields of next‐generation electronics, special equipment protection, defense, and aerospace. [ABSTRACT FROM AUTHOR]

Abstract: Alpha-Fe2O3 nanotubes and alpha-Fe2O3@ZnO heterostructured nanotubes have been synthesized through a hydrothermal method and a sol–gel route, respectively. Electronic microscopy examinations demonstrate that the alpha-Fe2O3 nanotubes with lengths ranging from 200 to 300nm and width around 150nm have a hollow feature and the thickness of the wall is about 30nm. After a sol–gel process, a layer of ZnO with a thickness of 20nm formed on the surface. X-ray diffraction patterns show that the obtained products are well crystallized and have high purity. The synthesized alpha-Fe2O3 nanotubes and alpha-Fe2O3@ZnO heterostructured nanotubes have specific surface area of 26.5m2g−1 and 35m2g−1, respectively. The gas sensing test reveals that the heterostructured nanotubes can get a high sensitivity (32) to acetone at the temperature of 642K. [Copyright &y& Elsevier]

The poor electronic conductivity restricts the wide applications of Li4Ti5O12 as anode materials in Li‐ion batteries. We report a facile approach to fabricate nitrogen‐doped carbon‐coated Li4Ti5O12 through carbonizing pyrrole and pyridine at different temperatures. Comparative experiments demonstrated that the carbon content plays a key role in governing the cycling performance and rate capability of Li4Ti5O12. The composites with higher carbon content exhibited superior cycling performance, and the composite prepared at 600 °C using pyridine as the carbon source gave the best cycling and rate performance. [ABSTRACT FROM AUTHOR]

Highlights: An ingenious design achieved magnetic-dielectric-carbon coupling. Nickel and manganese oxide particles were in situ reduced and grew on the carbon aerogels. The aerogels demonstrated radar stealth, infrared stealth and thermal management capability. Carbon-based aerogels derived from biomass chitosan are encountering a flourishing moment in electromagnetic protection on account of lightweight, controllable fabrication and versatility. Nevertheless, developing a facile construction method of component design with carbon-based aerogels for high-efficiency electromagnetic wave absorption (EWA) materials with a broad effective absorption bandwidth (EAB) and strong absorption yet hits some snags. Herein, the nitrogen-doped magnetic-dielectric-carbon aerogel was obtained via ice template method followed by carbonization treatment, homogeneous and abundant nickel (Ni) and manganese oxide (MnO) particles in situ grew on the carbon aerogels. Thanks to the optimization of impedance matching of dielectric/magnetic components to carbon aerogels, the nitrogen-doped magnetic-dielectric-carbon aerogel (Ni/MnO-CA) suggests a praiseworthy EWA performance, with an ultra-wide EAB of 7.36 GHz and a minimum reflection loss (RLmin) of − 64.09 dB, while achieving a specific reflection loss of − 253.32 dB mm−1. Furthermore, the aerogel reveals excellent radar stealth, infrared stealth, and thermal management capabilities. Hence, the high-performance, easy fabricated and multifunctional nickel/manganese oxide/carbon aerogels have broad application aspects for electromagnetic protection, electronic devices and aerospace. [ABSTRACT FROM AUTHOR]

Highlights: MXene-based macrostructure development and EMI shielding mechanisms are reviewed. Various structural design strategies for MXene-based EMI shielding materials are highlighted and discussed. Current challenges and future directions for MXenes in electromagnetic interference shielding are outlined. There is an urgent demand for flexible, lightweight, mechanically robust, excellent electromagnetic interference (EMI) shielding materials. Two-dimensional (2D) transition metal carbides/nitrides (MXenes) have been potential candidates for the construction of excellent EMI shielding materials due to their great electrical electroconductibility, favorable mechanical nature such as flexibility, large aspect ratios, and simple processability in aqueous media. The applicability of MXenes for EMI shielding has been intensively explored; thus, reviewing the relevant research is beneficial for advancing the design of high-performance MXene-based EMI shields. Herein, recent progress in MXene-based macrostructure development is reviewed, including the associated EMI shielding mechanisms. In particular, various structural design strategies for MXene-based EMI shielding materials are highlighted and explored. In the end, the difficulties and views for the future growth of MXene-based EMI shields are proposed. This review aims to drive the growth of high-performance MXene-based EMI shielding macrostructures on basis of rational structural design and the future high-efficiency utilization of MXene. [ABSTRACT FROM AUTHOR]

Transition metal carbides/nitrides (MXenes) show great potential for preparing wearable, flexible multifunctional e‐textiles due to the exceptional electrical and mechanical properties and easy processing in aqueous medium. At present, MXene‐based e‐textiles face challenges including high production costs, low utilization of precursor titanium aluminum carbide (MAX), poor durability in extreme environments, and the inability to achieve a balance between large‐scale fabrication and high performance. Here, this work proposes a "100%" utilization of MAX/MXene strategy to produce additive‐free conductive inks with controllable viscosity, subsequently enabling an accessible, scalable direct‐blade‐coating followed by chemical cross‐linking approach for creating wearable, high‐performance, multifunctional MXene‐based e‐textiles that perform in extreme conditions. The structural design provides integrated multifunctionality involving controllable and exceptional electromagnetic interference (EMI) shielding within an ultrabroadband frequency range, visual electrothermal conversion, electrothermal deicing, remarkable visual photothermal, and antibacterial performance. This work employs a fabrication process that is simple, cost‐effective, and scalable, presenting a novel "100% efficiency" and "waste‐to‐wealth" strategy to manufacture robust, durable, multifunctional e‐textiles. This approach provides exciting potential for the next generation of wearable electronics, EMI compatibility, visual heating, thermotherapy, antibacterial treatments, deicing, defense, and aerospace applications. [ABSTRACT FROM AUTHOR]

Achieving scalable synthesis of nanoscale transition‐metal carbides (TMCs), regarded as substitutes for platinum‐group noble metals, remains an ongoing challenge. Herein, a 100‐g scale synthesis of single‐phased cobalt carbide (Co2C) through carburization of Co‐based Prussian Blue Analog (Co‐PBA) is reported in CO2/H2 atmosphere under mild conditions (230 °C, ambient pressure). Textural property investigations indicate a successful preparation of orthorhombic‐phased Co2C nanomaterials with Pt‐group–like electronic properties. As a demonstration, Co2C achieves landmark photo‐assisted thermal catalytic CO2 conversion rates with photo‐switched product selectivity, which far exceeds the representative Pt‐group‐metal–based catalysts. This impressive result is attributed to the excellent activation of reactants, colorific light absorption, and photo‐to‐thermal conversion capacities. In addition to CO2 hydrogenation, the versatile Co2C materials show huge prospects in antibacterial therapy, interfacial water evaporation, electrochemical hydrogen evolution reaction, and battery technologies. This study paves the way toward unlocking the potential of multi‐functional Co2C nanomaterials. [ABSTRACT FROM AUTHOR]

Photo‐thermal catalytic CO2 hydrogenation is currently extensively studied as one of the most promising approaches for the conversion of CO2 into value‐added chemicals under mild conditions; however, achieving desirable conversion efficiency and target product selectivity remains challenging. Herein, the fabrication of Ir‐CoO/Al2O3 catalysts derived from Ir/CoAl LDH composites is reported for photo‐thermal CO2 methanation, which consist of Ir‐CoO ensembles as active centers that are evenly anchored on amorphous Al2O3 nanosheets. A CH4 production rate of 128.9 mmol gcat⁻1 h⁻1 is achieved at 250 °C under ambient pressure and visible light irradiation, outperforming most reported metal‐based catalysts. Mechanism studies based on density functional theory (DFT) calculations and numerical simulations reveal that the CoO nanoparticles function as photocatalysts to donate electrons for Ir nanoparticles and meanwhile act as "nanoheaters" to effectively elevate the local temperature around Ir active sites, thus promoting the adsorption, activation, and conversion of reactant molecules. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) demonstrates that illumination also efficiently boosts the conversion of formate intermediates. The mechanism of dual functions of photothermal semiconductors as photocatalysts for electron donation and as nano‐heaters for local temperature enhancement provides new insight in the exploration for efficient photo‐thermal catalysts. [ABSTRACT FROM AUTHOR]

Zinc hydroxyfluoride (ZnOHF) is a newly found resistive semiconductor used as a gas-sensing material with excellent selectivity to NO2 because of its unique energy band structure. In this paper, Al3+ doping and UV radiation were used to further improve the gas-sensing performance of ZnOHF. The optimized 0.5 at.% Al-ZnOHF sample exhibits improved sensitivity to 10 ppm NO2 at a lower temperature (100 °C) under UV assistance, as well as a short response/recovery time (35 s/96 s). The gas-sensing mechanism demonstrates that Al3+ doping increases electron concentration and promotes electron transfer of the nanorods by reducing the bandgap of ZnOHF, and the photogenerated electrons and holes with high activity under UV irradiation provide new reaction routes in the gas adsorption and desorption process, effectively promoting the gas-sensing process. The synergistic effect of Al3+ and UV radiation contribute to the enhanced performance of Al-ZnOHF. [ABSTRACT FROM AUTHOR]

With the speedy advancement of wireless communications, electromagnetic wave (EMW) pollution and electromagnetic interference (EMI) are gradually austere, which makes it an urgent need to develop high-performance EMW absorbers and shields. Carbon-based materials are important members of the family of EMW absorbing and shielding materials, due to their satisfactory electrical conductivity, low density, and good corrosion resistance. Especially, wood biomass-derived carbon materials, including carbonized cellulose, lignin and wood monolith, are acclaimed for their rich conductive network, unique porous structure, and effective loading of functional fillers, which promotes high-efficiency EMW absorption and shielding, and provides a new idea for using wood biomass resources in a high-value way. Additionally, due to the high yield of wood biomass, the mass production of carbonized wood biomass-derived EMW absorbers and EMI shields becomes more promising compared with other carbon materials. Hence, relevant studies should be summarized. Meanwhile, the functions of carbon materials need to be clarified and the importance of carbon materials needs to be highlighted. In this review, the roles of wood biomass-derived carbon in various EMW absorbing and shielding materials were emphasized, along with an analysis of related studies. Meanwhile, the main obstacles and the prospects of wood biomass-derived carbon were proposed. [Display omitted] • Clarifying the electromagnetic wave (EMW) absorption/shielding mechanism. • Reviewing the main functions of wood biomass-derived carbon in EMW absorbing/shielding. • Discussing future research directions and challenges of wood biomass-derived carbon. [ABSTRACT FROM AUTHOR]

In this work, we collected 101 geothermal water samples to investigate comprehensively the radioactivity of geothermal water in Beijing. The concentrations of gross beta, Ra and Rn were measured and the obtained values were in the range of 0.032-7.060, 0.023-0.363 and 0.470-29.700 Bq/L, respectively. The samples with higher concentration of Rn were found to be located near large faults. The effective dose of Rn in the air for three cases were calculated to be greater than radiation dose limit of 1 mSv/a. [ABSTRACT FROM AUTHOR]

Transition metal carbides/nitrides (MXenes) with metallic electrical conductivity and excellent processability attract increasing attention for assembling multifunctional macrostructures. However, the challenges, involving poor mechanical strength, inferior oxidation stability, and limited scalable manufacturing, impede their wide applications. Herein, the large‐area, high‐strength, ultra‐flexible hybrid films are developed through the multiple physical and chemical cross‐linking of MXene/cellulose films facilitated by graphene oxide. The MXene‐based films manifest significantly improved hydrophobicity, water/solvent resistance, and oxidation stability, and meanwhile, maintain excellent conductivity and electromagnetic interference shielding performance. The X‐band surface‐specific shielding effectiveness (SE) of 18,837.5 dB cm2 g−1 and an SE over 60 dB in an ultra‐broadband frequency range are achieved, comparable to the best shields ever reported. Furthermore, the wearable films demonstrate excellent photothermal antibacterial and electrothermal deicing applications. Thus, such high‐performance MXene‐based films developed through a facile and scalable manufacturing method have substantial application prospects in flexible electronics, thermotherapy, electromagnetic compatibility, and aerospace. [ABSTRACT FROM AUTHOR]

Methane (CH4), as the main component of natural gas and coal mine gas, is widely used in daily life and industrial processes and its leakage always causes undesirable misadventures. Thus, the rapid detection of low concentration methane is quite necessary. However, due to its robust chemical stability resulting from the strong tetrahedral-symmetry structure, the methane molecules are usually chemically inert to the sensing layers in detectors, making the rapid and efficient alert a big challenge. In this work, palladium nanoparticles (Pd NPs) embedded indium oxide porous hollow tubes (In2O3 PHTs) were successfully synthesized using Pd@MIL-68 (In) MOFs as precursors. All In2O3-based samples derived from Pd@MIL-68 (In) MOFs inherited the morphology of the precursors and exhibited the feature of hexagonal hollow tubes with porous architecture. The gas-sensing performances to 5000 ppm CH4 were evaluated and it was found that Pd@In2O3-2 gave the best response (Ra/Rg = 23.2) at 370 °C, which was 15.5 times higher than that of pristine-In2O3 sensors. In addition, the sensing materials also showed superior selectivity against interfering gases and a rather short response/recovery time of 7 s/5 s. The enhancement in sensing performances of Pd@In2O3-2 could be attributed to the large surface area, rich porosity, abundant oxygen vacancies and the catalytic function of Pd NPs. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: The rapid development of communication technology and electronic industry has brought unprecedented serious electromagnetic interference (EMI) and electromagnetic wave (EMW) pollution. Although EMI shields and EMW absorbers based on metal or magnetic materials were used to solve these problems, they have long been criticized for their high price, high density and easy corrosion. In order to achieve low density and efficient dissipation of electromagnetic energy, aerogels stand out among manifold materials. However, constructing aerogels with good EMI shielding or EMW absorption performance and acceptable mechanical properties is not an easy task. Burgeoning biopolymers, such as cellulose, lignin, chitin/chitosan and alginate, breathe new life into aerogels for high‐efficiency EMW shielding and absorbing. Here, we reviewed the contributions of biopolymers in the fields of aerogels for EMW shielding and absorbing. At the same time, some challenges and outlook were also pointed out, aiming to promote the advance of aerogel‐based EMI shields and EMW absorbers as well as the rational utilization of biopolymers. [ABSTRACT FROM AUTHOR]

Thanks to the high strength-to-weight ratio and aspect ratio, large specific surface area, and sustainability, cellulose nanofibers (CNFs) have incomparable advantages in constructing multifunctional aerogels. However, efficient utilization of the nanofibrous microstructure for developing aerogels of high-performance is extremely challenging due to the severe agglomeration of CNF. Here, a novel type of ultralight aerogel spheres composed of fibrous or sheet-like CNF-derived nanocarbon are manufactured via a facile, scalable drop-freezing followed by a pyrolysis approach. The nanostructured carbons of tunable morphologies are accomplished, endowing the aerogel spheres with abundant hierarchical pores, large specific surface area, and three-dimensional conductive skeletons with ultralight nature. In addition to the high-efficiency adsorption of the organic dye, the aerogel spheres enable a controllable and excellent electromagnetic wave absorption. The aerogels composed of coexisting fibrous and layered nanocarbons display an effective absorption bandwidth of 6.16 GHz, and a minimum reflection loss of −66.3 dB at the thickness of 2.14 mm, and a merely 1 wt% filler loading, which significantly outperforms that of other carbon-based absorbers. This work thus suggests a new avenue for designing high-performance, sustainable multifunctional biomass-based aerogels, demonstrating extensive application potentials in adsorption, electromagnetic absorption, and aerospace. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] One-dimensional carbon-based materials have emerged as promising electromagnetic wave absorption agents due to their outstanding conductivity, high stability, low weight, and easy availability. Properly optimizing their electromagnetic parameters is expected to further enhance the electromagnetic wave attenuation capacity. In this work, efficient Cu 9 S 5 /C nanocomposite fibers are prepared by a combined approach of electrospinning and subsequent carbonization-sulfurization processes. The Cu 9 S 5 nanoparticles with size of ca. 100–200 nm were homogeneously embedded in fibrous carbon matrix with diameter of 300 nm. For electromagnetic wave absorption, the optimized composited nanofibers (Cu 9 S 5 /C-3) exhibited an extremely superb reflection loss of −65.4 dB (9.5 GHz, 2.7 mm) at a lower mass fraction (20 wt%). And the effective absorption bandwidth could be up to 4.1 GHz (8.0–12.1 GHz) with a matching thickness of 2.9 mm, covering the whole X-band. Electromagnetic wave attenuation mechanism investigation revealed that the performance enhancement originated from the synergy of various loss pathways, including interfacial polarization, dipole polarization, and conductive loss. The unique hierarchical structure from particle embedding, one-dimensional fiber, to three-dimensional network further amplified the performance advantages of each component. This work is anticipated to provide a feasible strategy to synthesize sulfide/carbon binary composite fibers for efficient electromagnetic wave absorption. [ABSTRACT FROM AUTHOR]

[Display omitted] Regulating electromagnetic parameters and thus improving impedance matching characteristics by multi-component design is regarded as a prospective approach to obtain highly efficient electromagnetic wave absorption materials. Whereas, it is still challenging to fabricate microwave absorbers with strong absorption capacity and durability in harsh conditions. Based on the above considerations, three-dimensional porous multi-functional manganese oxide/nickel/carbon microspheres had been designed and prepared through a combined approach of facile solvothermal reactions and subsequent carbonization processes. The textural characteristic examinations demonstrated that, numerous manganese oxide and Ni nanoparticles of 15–20 nm in diameter were well dispersed in the carbon-based microspheres of approximately 0.8–1 μm in size. Microwave absorption property evaluation indicated that the minimum reflection loss reached up to −53.6 dB at 9.5 GHz, and effective absorption bandwidth of 3.7 GHz was achieved at matching thickness of merely 2.0 mm. The electromagnetic wave attenuation mechanisms analysis displayed that excellent impedance matching and various dissipation pathways, including magnetic loss, interfacial and dipole polarization relaxation synergistically contributed to the high microwave absorption performances of the porous composites. Radar cross-sectional simulation and photothermal measurements verified that the materials were supposed to have promising foregrounds in complicated circumstances. [ABSTRACT FROM AUTHOR]

Highlights: Fabrication, characterizations and photothermal properties of MXenes are systematically described. Photothermal-derived antibacterial performances and mechanisms of MXenes-based materials are summarized and reviewed. Recent advances in the derivative applications relying on antibacterial properties of MXenes-based materials, including in vitro and in vivo sterilization, solar water evaporation and purification, and flexible antibacterial fabrics, are investigated. The pernicious bacterial proliferation and emergence of super-resistant bacteria have already posed a great threat to public health, which drives researchers to develop antibiotic-free strategies to eradicate these fierce microbes. Although enormous achievements have already been achieved, it remains an arduous challenge to realize efficient sterilization to cut off the drug resistance generation. Recently, photothermal therapy (PTT) has emerged as a promising solution to efficiently damage the integrity of pathogenic bacteria based on hyperthermia beyond their tolerance. Until now, numerous photothermal agents have been studied for antimicrobial PTT. Among them, MXenes (a type of two-dimensional transition metal carbides or nitrides) are extensively investigated as one of the most promising candidates due to their high aspect ratio, atomic-thin thickness, excellent photothermal performance, low cytotoxicity, and ultrahigh dispersibility in aqueous systems. Besides, the enormous application scenarios using their antibacterial properties can be tailored via elaborated designs of MXenes-based materials. In this review, the synthetic approaches and textural properties of MXenes have been systematically presented first, and then the photothermal properties and sterilization mechanisms using MXenes-based materials are documented. Subsequently, recent progress in diverse fields making use of the photothermal and antibacterial performances of MXenes-based materials are well summarized to reveal the potential applications of these materials for various purposes, including in vitro and in vivo sterilization, solar water evaporation and purification, and flexible antibacterial fabrics. Last but not least, the current challenges and future perspectives are discussed to provide theoretical guidance for the fabrication of efficient antimicrobial systems using MXenes. [ABSTRACT FROM AUTHOR]

Highlights: Ultrathin, lightweight, and ultraflexible aligned single-walled carbon nanotube (SWCNT) films were fabricated via a facile, environmentally friendly, and scalable printing methodology. The aligned pattern and outstanding intrinsic properties of SWCNTs rendered "metal-like" thermal conductivity, excellent mechanical strength, hydrophobicity, and remarkable electromagnetic interference (EMI) shielding performance of the films. The excellent EMI shielding stability and reliability when subjected to mechanical deformation, chemical corrosion, and extreme environments demonstrated the significant potential of the films in aerospace, defense, and smart wearable electronics. Ultrathin, lightweight, and flexible aligned single-walled carbon nanotube (SWCNT) films are fabricated by a facile, environmentally friendly, and scalable printing methodology. The aligned pattern and outstanding intrinsic properties render "metal-like" thermal conductivity of the SWCNT films, as well as excellent mechanical strength, flexibility, and hydrophobicity. Further, the aligned cellular microstructure promotes the electromagnetic interference (EMI) shielding ability of the SWCNTs, leading to excellent shielding effectiveness (SE) of ~ 39 to 90 dB despite a density of only ~ 0.6 g cm−3 at thicknesses of merely 1.5–24 µm, respectively. An ultrahigh thickness-specific SE of 25 693 dB mm−1 and an unprecedented normalized specific SE of 428 222 dB cm2 g−1 are accomplished by the freestanding SWCNT films, significantly surpassing previously reported shielding materials. In addition to an EMI SE greater than 54 dB in an ultra-broadband frequency range of around 400 GHz, the films demonstrate excellent EMI shielding stability and reliability when subjected to mechanical deformation, chemical (acid/alkali/organic solvent) corrosion, and high-/low-temperature environments. The novel printed SWCNT films offer significant potential for practical applications in the aerospace, defense, precision components, and smart wearable electronics industries. [ABSTRACT FROM AUTHOR]

Highlights: Fabrication, characterizations and photothermal properties of MXenes are systematically described. Photothermal-derived antibacterial performances and mechanisms of MXenes-based materials are summarized and reviewed. Recent advances in the derivative applications relying on antibacterial properties of MXenes-based materials, including in vitro and in vivo sterilization, solar water evaporation and purification, and flexible antibacterial fabrics, are investigated. The pernicious bacterial proliferation and emergence of super-resistant bacteria have already posed a great threat to public health, which drives researchers to develop antibiotic-free strategies to eradicate these fierce microbes. Although enormous achievements have already been achieved, it remains an arduous challenge to realize efficient sterilization to cut off the drug resistance generation. Recently, photothermal therapy (PTT) has emerged as a promising solution to efficiently damage the integrity of pathogenic bacteria based on hyperthermia beyond their tolerance. Until now, numerous photothermal agents have been studied for antimicrobial PTT. Among them, MXenes (a type of two-dimensional transition metal carbides or nitrides) are extensively investigated as one of the most promising candidates due to their high aspect ratio, atomic-thin thickness, excellent photothermal performance, low cytotoxicity, and ultrahigh dispersibility in aqueous systems. Besides, the enormous application scenarios using their antibacterial properties can be tailored via elaborated designs of MXenes-based materials. In this review, the synthetic approaches and textural properties of MXenes have been systematically presented first, and then the photothermal properties and sterilization mechanisms using MXenes-based materials are documented. Subsequently, recent progress in diverse fields making use of the photothermal and antibacterial performances of MXenes-based materials are well summarized to reveal the potential applications of these materials for various purposes, including in vitro and in vivo sterilization, solar water evaporation and purification, and flexible antibacterial fabrics. Last but not least, the current challenges and future perspectives are discussed to provide theoretical guidance for the fabrication of efficient antimicrobial systems using MXenes. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) have attracted more and more attentions for preparing electromagnetic wave (EMW) absorption materials because of the porous structure, high specific surface area, and designable configuration. Herein, a series of MOF-74 derived nanocomposites were synthesized by hydrothermal process and subsequent carbonization. The EMW absorption performance and the functions of each component were investigated in depth. Moreover, the inherent EMW absorption mechanisms were comprehensively revealed. Benefiting from the synergistic effect of constituents and microstructure, the MnCo-MOF-74 derived MnO/Co/C nanocomposites delivered a minimum reflection loss value of −68.89 dB at the thickness of 2.64 mm and an effective absorption band of 5.3 GHz at the thickness of 2.3 mm. The high EMW absorption performance was ascribed to the optimized impedance matching and multiple attenuation mechanisms including interfacial and dipole polarization loss, magnetic loss, conductive loss, and multiple scatterings capability. This study shed light on exploring high-efficiency MOF-based EMW absorption materials with rational design of components and structure. [Display omitted] • A series of MOF-74 derived nanocomposites including MnO/Co/C, MnO/C, Co/C, and MnO/Co were successfully fabricated by hydrothermal and subsequent carbonization processes. • The EMW absorption performance of the MOF-74 derivatives was systematically studied, and the absorption mechanism was clarified in depth. • The multiple attenuation mechanisms and impedance matching derived from the rational design of constituents and microstructure led to the excellent EMW absorption performance of the MOF-derived porous MnO/Co/C nanocomposites. [ABSTRACT FROM AUTHOR]

Realizing nitrogen dioxide (NO 2) detections based on semiconductor-based gas sensors with high tolerance to humidity conditions is deemed to be a long-term challenge. To independently acknowledge the physiosorbed-water influence mechanism on semiconductor-based sensors, hydrophobic zeolitic imidazolate framework-8 (ZIF-8) covered chemisorbed-oxygen-nonexistence zinc hydroxyfluoride (ZnOHF) snowflake-like nanorod bundles are synthesized for NO 2 detections with non-hindrance of interfering gases and high humidity in our work. Gas-sensing testing results display that the 0.6ZIF-8/ZnOHF-based gas sensor provides an optimum NO 2 response of 12.1–10 ppm NO 2 at the operating temperature of 200 ℃ with excellent NO 2 selectivity. As the relative humidity (RH) increases from 20% RH to 80% RH, the response of the 0.6ZIF-8/ZnOHF sensor shows a marginal fluctuation of only 13%, exhibiting outstanding anti-humidity characteristics towards NO 2 detections, the outperformed NO 2 selectivity and humidity tolerance of which are greatly attributed to the unique band structures of ZnOHF and the surficial hydrophobic treatment by ZIF-8, which is further validated via In-situ diffuse reflection infrared Fourier transform spectroscopy (In-situ DRIFTS) and electronic structure analyses. Humidity impact on ZnOHF poses a persuasive evidence for establishing the separate physiosorbed water interfering mechanism on semiconductors. This work endows a perspective on optimizing humidity tolerance for semiconductor-based sensors at low operating temperature. • Snowflake-like ZIF-8/ZnOHF was synthesized via an in-situ chemical process. • Hydroxyl-independent humidity-interfered behaviors were identified of ZnOHF. • Optimized ZIF-8/ZnOHF sensor exhibits excellent anti-humidity NO 2 sensitivity. • In-situ Fourier Transform infrared spectra verify the anti-humidity mechanism. [ABSTRACT FROM AUTHOR]

We report for the first time using pure cobaltous tungstate (CoWO 4) as an efficient ethanol sensor by controlling the Co3+-Co2+ redox couple in CoWO 4. The prepared Co x WO 4 has a flower-like structure self-assembled by a mesoporous microbelt. Moreover, the Co x WO 4 sensor with a Co3+/Co2+ ratio of 38.9% exhibits a high response (42.9–100 ppm ethanol), fast response/recovery time (11/13 s), low detection limit (0.42 ppm), as well as remarkable short-term and long-term repeatability. Notably, the Co x WO 4 sample maintains a constant response value over a wide range of humidity (30–90 RH%), manifesting its good anti-humidity properties. The outstanding sensing performance is owing to the Co3+-Co2+ redox couple, high surface area and moderate porosity of the obtained samples. The self-transforming of the Co3+-Co2+ redox couple contributes to the formation of absorbed oxygen (O 2 -), oxygen vacancies and the reduction of the band gap, which is a crucial factor in improving the sensing properties of Co x WO 4. • Pure cobalt tungstate was used for the first time as an efficient ethanol sensor. • The sensor shows a fast response/recovery time and low detection limit. • The self-transforming of Co3+-Co2+ redox on the surface is also a crucial factor. [ABSTRACT FROM AUTHOR]

[Display omitted] • The well-designed structures bring about optimized impedance matching, multiple polarization and loss pathways. • The NTMRG-2 aerogel exhibits a RL min of −71.4 dB and a maximum EAB of 6.48 GHz. • The ultralow thermal conductivity (27 mW m−1K−1) and hydrophobicity endow the aerogel with multifunction characteristic. The demand for high-performance electromagnetic wave absorbing (EMA) materials featured with strong attenuation ability, extended absorption bandwidth and ultralight property is imperative yet remains challenging. Herein, a three-dimensional hierarchically porous reduced graphene oxide (rGO)/Ti 3 C 2 T x MXene aerogel embedded with Ni@TiO 2 core–shell microspheres was prepared via directional freeze-drying followed by a mild annealing process. The divergence in structure and multicomponent dielectric/magnetic features bring about optimized impedance matching characteristic, multiple polarization and loss pathways, collectively contributing to the excellent absorption performance. As a result, the Ni@TiO 2 /MXene/rGO (NTMRG-2) aerogel exhibits optimized EMA capability with a maximal effective absorption bandwidth (EAB max) of 6.48 GHz at a lower loading level of 5 wt% in the supporting matrix, covering the whole Ku band. Additionally, it achieves a minimum reflection loss (RL min) of −71.4 dB with a matching thickness of 2.04 mm. Moreover, the aerogel also exhibits an ultra-light density of 5.58 mg cm−3, superior thermal insulation capacity (close to air) and hydrophobicity, underscoring its potential for multiple applications in various scenarios. [ABSTRACT FROM AUTHOR]

Graphene-based electromagnetic wave (EMW) absorbing materials have become a focus of scientific research as the demand for addressing the adverse electromagnetic radiation or pollution. Furthermore, graphene-based EMW absorbers promise richer application scenarios than other carbon materials due to graphene's low density, high electrical conductivity, and thermal stability. Consequently, a summary of relevant studies is required. Simultaneously, the functionalities of graphene materials need to be clarified and the importance of graphene materials needs to be emphasized. This work summarizes the research progress of structural optimization strategies of graphene-based EMW absorbing materials from the micro and macro perspectives. The general EMW absorption mechanism is first briefly explained, and the effects of microstructure, components, and varies of loss mechanisms on the EMW absorbing performance of graphene-based EMW absorbing materials are discussed, in particular, the differences in electromagnetic parameters and absorbing properties caused by anisotropic structures are summarized. Finally, the outlook regarding the research focus and development direction of graphene-based EMW absorbing materials is proposed. [Display omitted] • Clarifying the electromagnetic wave (EMW) absorption development requirements. • The structural design of graphene was reviewed from both micro and macro aspects. • Discussing future research directions and challenges of graphene in EMW absorbing. [ABSTRACT FROM AUTHOR]

• Pt-WO 3 nanorods are synthesized via hydrothermal and chemical reduction method. • The sensor based on Pt-WO 3 shows excellent comprehensive performance with high sensitivity and fast response/recovery speed. • The minimum detection limit of Pt-WO 3 based sensors to H 2 S was as low as 5 ppb. • The electron sensitization and chemical catalysis of Pt nanoparticles greatly enhanced the gas sensing properties of WO 3. [Display omitted] The Pt-loaded WO 3 materials have been synthesized via simple hydrothermal and chemical reduction methods. The microstructure of prepared Pt-WO 3 exhibits as nanorods consisting of bundles of finer nanorods and the Pt nanoparticles with a size of ca. 5 nm loaded on the surface of WO 3. The gas sensing measurements of Pt-WO 3 material show excellent gas sensing selectivity to H 2 S compared with many other pollution gases (e.g. NO 2 , SO 2 , NH 3 , CO and CO 2). In particular, 0.2 at% Pt-WO 3 exhibits extremely high response (1638–10 ppm H 2 S), short response/recovery time (42 s/37 s) and low detection limit (1.27–5 ppb H 2 S) at 200 °C. The superior performance of 0.2 at% Pt-WO 3 compared with pure WO 3 mainly originate from its modulating action to conductive band electrons of WO 3 and its catalysis to the chemisorption reaction on the surface. [ABSTRACT FROM AUTHOR]

[Display omitted] Globally, drug-resistant bacteria are a potential threat to human society owing to the overuse of antibiotics and thus, non-antibiotic bactericides are urgently needed. Herein, an innovative antibacterial nanoplatform based on quaternized chitosan (QCS)/ silver (Ag)/ cobalt phosphide (CoP) nanocomposites is envisaged for achieving near-infrared (NIR) laser-inducible rapid sterilisation. In the core-shell hybrids, Ag nanoparticles (NPs) with a size of ∼ 25 nm were uniformly deposited on CoP nanoneedles, upon which a layer of QCS (approximately 10 wt%), is coated. Numerical calculations revealed that under NIR irradiation, high-energy hot electrons arising from the surface plasmon resonance effect of Ag migrate into the interface between Ag and CoP, and amplify the photothermal effect of CoP. Meanwhile, photo-excited electrons from CoP are transported onto Ag NPs because the Schottky heterostructure facilitates the production of reactive oxygen species. Ag loading simultaneously enhances the photocatalytic and photothermal effects of CoP, achieving rapid antibacterial activity synergistically. The QCS coating improves the dispersibility of power in an aqueous system and provides contact between the antiseptics and bacteria. The ternary QCS/Ag/CoP nanocomposites achieved greater than 99.6% inactivation against S. aureus and E. coli within 10 min. In addition, the nanocomposites were confirmed to be noncytotoxic to mammals. Consequently, the QCS/Ag/CoP nanoplatforms possess great potential for rapid and effective antibacterial applications. [ABSTRACT FROM AUTHOR]

Broadening absorption bandwidth is of great significance to extend application scenarios for electromagnetic wave (EMW) absorption materials. Since the electromagnetic character changes caused by high shape anisotropy, one-dimensional fibrous materials have been widely concerned. In this work, manganese sulfide (MnS)/carbon nanocomposite fibers are facilely synthesized by a facile combination of electrospinning and high-temperature processing. The fibrous carbon supports with a 350-nm average diameter are embedded with dense MnS nanoparticles on the surface. Under the premise of ensuring a strong EMW absorption intensity (−68.9 dB, 11.1 GHz, 3.6 mm), the MnS/carbon nanocomposite fibers can achieve a wide effective absorption bandwidth of 7.2 GHz (9.5–16.7 GHz, 3.3 mm). In-depth study verifies that MnS can help to achieve superior synergy between conductive and polarized attenuation capacity, enhance the attenuation ability and optimize impedance matching characteristic. Besides, considering the few studies about MnS in this field, this work confirmed the huge potentials of MnS for EMW absorption applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Polypyrrole (PPy)/cobalt oxide (Co 3 O 4 )/carbon paper (CP) ternary composites prepared by potentiodynamic electropolymerization of pyrrole monomers onto flower-like Co 3 O 4 (f-Co 3 O 4 ) nanoparticles coated on CP (PPy/f-Co 3 O 4 /CP) were studied serving as electrode materials for supercapacitor applications. The f-Co 3 O 4 with unique porous morphology on CP was first obtained by drop casting Co 3 O 4 ethanol suspensions onto CP. Ball-like Co 3 O 4 (b-Co 3 O 4 ) with dense structure was also prepared for comparison. The electrochemical results including cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) in 2.0 M KOH aqueous solution revealed that the PPy/Co 3 O 4 /CP ternary composites exhibited superior supercapacitive performances than both f-Co 3 O 4 /CP and b-Co 3 O 4 /CP. Specifically, a specific capacitance of 398.4 F/g was obtained for the PPy/f-Co 3 O 4 /CP, much higher than that of 40.9 and 22.0 F/g for f-Co 3 O 4 /CP and b-Co 3 O 4 /CP, respectively. The electrochemical impedance spectroscopy studies suggested that better capacitive properties in PPy/f-Co 3 O 4 /CP were attributed to the pseudocapacitive contributions from the PPy nanocoating and greatly reduced charge transfer resistance in the composites. PPy/f-Co 3 O 4 /CP also displayed an excellent cycling stability with negligible capacitance loss after 1000 cycles. [ABSTRACT FROM AUTHOR]

The optimal impedance matching and strong dissipation ability could be obtained by tuning the content of NiS and ZnS in the ZnS/NiS/C hollow spheres. The synergistic effects between ZnS and NiS on absorbing performances were thoroughly investigated. [Display omitted] Utilizing the synergistic effect of multiple components in heterostructured composites has been regarded as a promising strategy for achieving high-performance electromagnetic wave absorption. Nonetheless, rationally collocate the components of absorbers in order to legitimately achieve synergy remains an intractable problem. By adjusting the NiS and ZnS composition ratios in the ZnS/NiS/C composites, the optimal impedance matching and dissipation capability can be obtained. The formation of a ZnS/NiS heterostructure is found to significantly enhance polarization relaxation, and the relative ratios of ZnS and NiS have a significant effect on the electromagnetic properties. The optimal performance was obtained on Z1N2, with a minimum reflection loss of –51.45 dB at 4.72 GHz and –56.69 dB at 11.12 GHz, respectively, and an effective absorption bandwidth of up to 3.68 GHz at 1.16 mm. The potential of heterogeneous bimetal sulfides as high-performance absorbers is demonstrated in this study. [ABSTRACT FROM AUTHOR]

Mesoporous tin oxide (SnO2) spheres with a size of 500-700 nm have been successfully synthesized through annealing a tin hydroxide precursor was obtained by a one-pot solvothermal process from a methanol system containing the surfactant polyvinyl pyrrolidone (PVP). Experimental studies revealed that polyvinyl pyrrolidone plays a pivotal role in controlling the size and agglomeration of mesoporous spheres. The mesoporous SnO2 spheres with a surface area of 78.2 m2 g-1 and an average pore size of ca. 10 nm are monodispersed and the mesoporous structure can be maintained even after annealing at 500 °C for 2 h in air. Gas sensing tests showed that the SnO2 mesoporous spheres exhibit high sensitivity to H2, enhanced response to CO and also fast response and recovery rates, suggesting potential application as an advanced gas sensing material. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zn-doped Fe3O4 with carbon coating achieves a reversible capacity of 713.6 mAh g−1. [•] Zn-doped Fe3O4 exhibits superior rate performances. [•] Appropriate Zn-doping improves the electronic and ionic conductivity. [•] Nitrogen-doped carbon coating is beneficial to electrochemical performance. [ABSTRACT FROM AUTHOR]

Constructing heterojunctions in semiconductor-based sensors is a vital method of modulating electronic structures and designing high-performance sensors for toxic gas detection. In this study, F-doped SnS x (F-SnS x) decorated ZnOHF composites were acquired via a two-step solvothermal method. The experimental results confirmed the establishment of heterojunctions between ZnOHF and F-SnS x. The optimized F-SnS x decorated ZnOHF snowflake-like nanoflowers-based NO 2 sensors exhibited incomparable selectivity along with supreme sensitivity (S = 137–10 ppm NO 2 at 200 ℃), rapid responding/recovering speed (34 s/6 s) and low detection limit (50 ppb). NO 2 sensing mechanism and the influence of humidity interference on NO 2 sensing performances were fully discussed. This work not only evidences the great potential of F-SnS x /ZnOHF snowflake-like nanoflowers for NO 2 recognitions but also paves a feasible routine for advancing NO 2 sensing performances by electronic structure regulations. [Display omitted] • Snowflake-like F-SnS x /ZnOHF was obtained via facile solvothermal syntheses. • The optimized F-SnS x /ZnOHF sensor performs exceptional NO 2 sensing performance. • Chemisorbed nonexistence validate the potential NO 2 sensing mechanism. • Anti-humidity stability enhancement induced by F- has been proposed. [ABSTRACT FROM AUTHOR]

Statistical study of analyses of water from 43 samples from geothermal wells, three groundwater wells, and one sample of local rainwater along with rainwater data from the Global Network of Isotopes in Precipitation has been used to identify the origin and evolution of geothermal water in the Niutuozhen (牛驼镇) geothermal field and estimate the renewability rate of its geothermal resource. The results show that the geothermal waters of the Jixianian Wumishanian dolomite reservoir and the Ordovician limestone reservoir are of Cl-Na type, the geothermal water of the Pliocene Minghuazhen (明化镇) Formation sandstone reservoir are Cl-Na type and HCO 3-Na type and the groundwater of the Quaternary aquifer is HCO 3-Na and HCO 3-Na·Mg·Ca type. A linear relationship between silica concentration and temperature indicates that higher temperature probably enhances concentration of silica in Jixianian geothermal water. δ 18O shift in Wumishanian geothermal water averaged 1.57‰, and was less than 1‰ in the other geothermal waters. The minimum and maximum 14C ages of Wumishanian geothermal water are 17 000 and 33 000 years from north to the south of the Niutuozhen geothermal field. Geothermal water and Quaternary groundwater belong to different groundwater systems with no hydraulic connections. Although the geothermal field receives some recharge from the Yanshan and Taihang mountains outside the northern and western boundaries of the geothermal field respectively, the renewability rate of geothermal water is on the scale of 10 000 years. [ABSTRACT FROM AUTHOR]

Abstract: Strawberry-like ZnO mesoporous architectures with size of about 1μm have been synthesized by a one-pot solvothermal approach in the presence of methanol, zinc nitrate hexahydrate, and polyvinyl pyrrolidone (PVP), which was utilized to control the size, morphology, and agglomeration of ZnO particles. The measured surface area is 57.7m2/g and the pore size is ca. 2–10nm. Gas sensing tests showed that the strawberry-like ZnO mesoporous material exhibited superior gas sensing performances to ethanol and acetone due to high reaction surface area and abundant mesochannels. This synthesis approach featured low cost and easy operation will provide a possible strategy to synthesize other oxides with mesoporous structure for gas sensing application. [Copyright &y& Elsevier]

Water vapor greatly interferes with gas sensing characteristics of metal oxide semiconductors (MOS). Consequently, for the first time, Nd 2 O 3 -loaded In 2 O 3 porous nanorods were synthesized which exhibited excellent H 2 S sensitivity along with prominent humidity-independent characteristics, whereas pristine In 2 O 3 without Nd 2 O 3 showed deteriorated H 2 S sensing features under increasing ambient humid conditions in a wide operating temperature range. The mechanism of humidity-independent H 2 S sensing properties was researched via X-ray photoelectrons spectroscopy (XPS), in-situ Fourier Transform infrared spectroscopy (in-situ DRIFTS) and the corresponding gas sensing measurements, which is in close relations with the inhibition of chemisorbed oxygen and scavenging hydroxyl groups on In 2 O 3 surface induced by surficial Nd 2 O 3 component. This strategy poses a cutting-edge comprehending of temperature-dependent humidity-interference on MOS, paves a novel route for fabricating H 2 S sensors with exceptional sensitivity, selectivity and anti-humidity properties, which will be quite conducive for real-time exhaled breath analyses in disease diagnosis. [Display omitted] • Nd 2 O 3 -loaded In 2 O 3 porous nanorods were prepared for anti-humidity H 2 S detections. • Temperature-dependent anti-humidity behaviors of Nd 2 O 3 -loaded In 2 O 3 are identified. • The optimized H 2 S sensor exhibits well selectivity, sensitivity and low detection limit. • In-situ Fourier Transform infrared spectra verifies the anti-humidity mechanism. [ABSTRACT FROM AUTHOR]

Regulation based on the crystalline structure modulations is capable of optimizing the band gap and chemisorbed oxygen components thus adjusting the gas sensing characteristics of sensing materials. Herein, In 2 O 3 hierarchical-assembled microspheres with diverse crystalline structures were synthesized via a simple hydrothermal method combined with calcinating procedure under different temperatures. The gas sensor based on rhombohedral In 2 O 3 (rh-In 2 O 3) microspheres assembled by pine needle shaped nanorods annealed at 350 ℃ (350-In 2 O 3) exhibited superior H 2 S sensing performances at relative low operating temperature of 100 ℃ with low detection limit (50 ppb) and optimized stability compared with cubic In 2 O 3 (c-In 2 O 3). Notably, H 2 S sensing characteristics of In 2 O 3 samples with different crystalline structures certificated that crystal structures can dominate the H 2 S sensing reactions with different mechanisms. This work enlightened a novel prospect for designing rh-In 2 O 3 based sensors and provides an innovative pathway for analyzing the feasible H 2 S sensing mechanisms. [Display omitted] • In 2 O 3 materials with diverse crystalline structures were prepared for H 2 S detections. • Rhombohedral In 2 O 3 microspheres is composed of nanorods (diameter of 8 nm). • Rhombohedral In 2 O 3 based sensor displayed the optimized H 2 S sensitivity. • Crystalline structure controls H 2 S sensing mechanism. [ABSTRACT FROM AUTHOR]

Exploring the relationship between tungsten oxides with a controlled amount of oxygen vacancies and their gas-sensing properties with respect to hydrogen sulfide is interesting for developing excellent comprehensive gas-sensing performance materials with fast and accurate response. In this work, the WO 3 nanoparticles with oxygen defective structure were synthesized by a straightforward one-step muffle calcining method. The WO 3 nanoparticles prepared at the calcination temperature of 600 ℃ (Ov-WO 3 -600) display the high response value (2777) and ultra-fast response time (2 s) to 5 ppm hydrogen sulfide (H 2 S) at 100 ℃. Moreover, it also exhibits low practical detection limit (100 ppb), long-term stability, as well as remarkable admirable selectivity. The gas sensing mechanism can be explained by the fact that oxygen vacancies, as donor energy levels provide more electrons, increase the carrier mobility and narrow the band gap. This makes it easier for oxygen to capture electrons to form more adsorbed oxygen, which improves the gas sensing performance of WO 3 -based sensors. Hence, our study can offer guidance for the construction of fast and accurate sensing materials based on WO 3. [Display omitted] • The WO 3 nanoparticle was prepared by a simple one-step muffle calcining method. • The relationship between electronic structure and gas-sensing property was studied. • Sensor shows an ultra-fast response speed (15 s) to low concentration H 2 S(0.1 ppm). • Benefiting from the oxygen vacancy, the carrier mobility and band gap are enhanced. [ABSTRACT FROM AUTHOR]

Biomass chitosan-derived porous carbon-based materials take the advantage of light weight, adjustable intrinsic conductivity, and environmental friendliness, attracting more attention in the field of electromagnetic compatibility. However, exploring a facile fabrication method to achieve rational structure design and electrical-magnetic coupling for electromagnetic absorption performance enhancement still remains challenging. Here, a unique honeycomb-like porous cobalt/carbon aerogel is fabricated through the directional freezing-drying and carbonization process, and abundant and even-distributed cobalt particles in-situ grow on the carbon skeletons. The aerogel exhibits an impressive electromagnetic wave absorption performance of a −75.8-dB absorption intensity and a −256.9-dB mm−1 specific reflection loss at a low filling content (10%), as well as an 8.53-GHz effective absorption bandwidth. Besides, the aerogel also demonstrates classy radar stealth and thermal insulation performance. The eco-friendly, easily fabricated, and high-performance cobalt/carbon aerogel suggests broad application prospects for electromagnetic compatibility and protection, thermal management, and multifarious electron devices. [Display omitted] • A unique electrical-magnetic coupling honeycomb-like porous cobalt/carbon aerogel is fabricated. • Abundant and even-distributed cobalt particles in-situ grow on the carbon skeletons. • The aerogels have broad prospects in electromagnetic compatibility and thermal management application. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series straw-bundle-like rare earth metal-organic frameworks derivatives were fabricated. • The EMW absorption property was effectively regulated by tunable bandgap of rare earth oxides and different carbonization temperature. • The high potential of rare earth metal-organic frameworks derivatives for EMW absorption was confirmed. Metal-organic frameworks (MOFs) derivatives have been widely developed as electromagnetic wave (EMW) absorption materials. Nevertheless, owing to the diverse metal ions, organic ligands, and crystal morphologies of MOFs precursors, challenges still remain to overcome towards directly ascertaining the contribution of metal components on EMW absorption for precisely designing high EMW absorption performance of MOF derivatives. Here, we synthesize a series of rare earth (RE) MOF derivatives via a facile, scalable coprecipitation followed by carbonization approach. Thanks to the similar chemical property derived from lanthanide shrinkage of RE elements, the MOF-derived RE oxides (REO)/carbon (REO = CeO 2 , La 2 O 3 , Nd 2 O 3) hybrids exhibit the identical straw-bundle-like microstructure, efficiently assisting the elucidation of the roles of metal components in promoting EMW absorption. Benefiting from the tunable bandgap of various REO as well as carbonization temperature, the 800 °C-carbonized CeO 2 /carbon shows a minimum reflection loss of − 58.7 dB at a thickness of 1.7 mm and an effective absorption bandwidth of 5.0 GHz, comparable to the best EMW absorbers. This work not only demonstrates novel, high-performance RE-MOF derivatives, but also offers a general yet efficient strategy for designing metal components to achieve high-efficiency MOF-based EMW absorbers. [ABSTRACT FROM AUTHOR]

Grafting one-dimensional (1D) structure onto three-dimensional (3D) carbon foam is a practical and novel protocol to improve its microwave attenuation capability. Herein, a unique microwave absorber with NiCo 2 O 4 nanoneedle grew on carbon foam (NCOCF) has been built via a combined approach of carbonization and hydrothermal treatment. The obtained NCOCF exhibit good impedance matching and excellent attenuation capability, which means that the microwave energy can be dissipated through conductive loss, interfacial polarization and multiple-scattering. These advantages result in the effective transformation of microwave energy to heat, thus yielding a remarkable microwave adsorption (with a thickness of 2.8 mm, the maximum reflection loss (RL max) is −63.6 dB, and the effective absorption bandwidth (E AB) is as wide as 4.72 GHz with a thickness of 1.3 mm). The study would offer a strategy for development of the high-performance microwave absorber. [ABSTRACT FROM AUTHOR]

Highlights: In terms of components and structures, this review summarizes progresses and highlights strategies of MOF derivatives for efficient electromagnetic wave absorption. We also systematically delineate relevant theories and points out the prospects and current challenges. To tackle the aggravating electromagnetic wave (EMW) pollution issues, high-efficiency EMW absorption materials are urgently explored. Metal–organic framework (MOF) derivatives have been intensively investigated for EMW absorption due to the distinctive components and structures, which is expected to satisfy diverse application requirements. The extensive developments on MOF derivatives demonstrate its significantly important role in this research area. Particularly, MOF derivatives deliver huge performance superiorities in light weight, broad bandwidth, and robust loss capacity, which are attributed to the outstanding impedance matching, multiple attenuation mechanisms, and destructive interference effect. Herein, we summarized the relevant theories and evaluation methods, and categorized the state-of-the-art research progresses on MOF derivatives in EMW absorption field. In spite of lots of challenges to face, MOF derivatives have illuminated infinite potentials for further development as EMW absorption materials. [ABSTRACT FROM AUTHOR]

[Display omitted] Absorbing materials can convert electromagnetic wave (EMW) energy into heat and other energy and dissipate it. Carbon materials can attenuate EMW by generating large conduction losses due to their high conductivity. The introduction of low dielectric materials can improve impedance matching caused by high conductivity. However, the density of materials compounded with carbon materials is too large, which affects the overall density of composite materials. Therefore, this problem is solved by matching melamine foam with ZIF-67. As an ultra-light material, the melamine foam-based carbon material can significantly reduce the density of composite materials, and its developed three-dimensional structure can cause multiple scattering of EMW. The large specific surface area and evenly distributed metal oxides obtained after annealing of ZIF-67 can provide ultra-low-density carbon materials and abundant interfacial polarization to further attenuate EMW. So far, the methods of self-growing materials on the surface of melamine foam have not been reported. We prepared a 500 nm Co 3 O 4 nanosheet/carbon foam (CF) composite material coated on the surface by a two-step method. The sample had a maximum reflection loss of −46.58 dB at 10.72 GHz, and an effective absorption bandwidth (EAB) of 5.4 GHz. This research provides a new idea for the growth of porous materials on the surface of melamine foam-based carbon materials. [ABSTRACT FROM AUTHOR]