Metal-Organic Framework-Manipulated Dielectric Genes Inside Silicon Carbonitride toward Tunable Electromagnetic Wave Absorption.

Heterointerface engineering for different identifiable length scales has emerged as a key research area for obtaining materials capable of high-performance electromagnetic wave absorption; however, achieving controllable architectural and compositional complexity in nanomaterials with environmental and thermal stabilities remains challenging. Herein, metal-containing silicon carbonitride (SiCN/M) nanocomposite ceramics with multiphase heterointerfaces were in situ synthesized via coordination crosslinking, catalytic graphitization, and phase separation processes using trace amounts of metal-organic frameworks (MOFs). The results reveal that the regulation of dielectric genes by MOFs can yield considerable lattice strain and abundant lattice defects, contributing to strong interfacial and dipole polarizations. The as-prepared SiCN/M ceramics demonstrate excellent microwave absorption performance: the minimum reflection loss (RLmin ) is -72.6 dB at a thickness of only 1.5 mm and -54.1 dB at an ultralow frequency of 3.56 GHz for the SiCN/Fe ceramics and the RLmin is -55.1 dB with a broad bandwidth of 3.4 GHz at an ultralow thickness of 1.2 mm for the SiCN/CoFe ceramic. The results are expected to provide guidance for the design of future dielectric microwave absorption materials based on heterointerface engineering while offering a paradigm for developing MOF-modified SiCN nanocomposite ceramics with desirable properties.

The NLRP3 Inflammasome: An Important Driver of Neuroinflammation in Hemorrhagic Stroke.

Hemorrhagic stroke is a devastating clinical event with no effective medical treatment. Neuroinflammation, which follows a hemorrhagic stroke, is an important element that involves both acute brain injury and subsequent brain rehabilitation. Therefore, delineating the key inflammatory mediators and deciphering their pathophysiological roles in hemorrhagic strokes is of great importance in the development of novel therapeutic targets for this disease. The NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome is a multi-protein complex that is localized within the cytoplasm. This NOD-like receptor orchestrates innate immune responses to pathogenic organisms and cell stress through the activation of caspase-1 and the maturation of the proinflammatory cytokines such as interleukin-1ß (IL-1ß) and IL-18. Mounting evidence has demonstrated that when the NLRP3 inflammasome is activated, it exerts harmful effects on brain tissue after a hemorrhagic stroke. This review article summarizes the current knowledge regarding the role and the underlying mechanisms of the NLRP3 inflammasome in the pathophysiological processes of hemorrhagic strokes. A better understanding of the function and regulation of the NLRP3 inflammasome in hemorrhagic strokes will provide clues for devising novel therapeutic strategies to fight this disease.

Elevated serum IL-11, TNF α, and VEGF expressions contribute to the pathophysiology of hypertensive intracerebral hemorrhage (HICH).

To study the changes in serum interleukin-11 (IL-11), tumor necrosis factor-α (TNF-α) and vascular endothelial growth factor (VEGF) expressions following hypertensive intracerebral hemorrhage (HICH), and explore their associations with disease severity and prognosis. Serum IL-11, TNF-α, and VEGF levels after 1, 3, 7, and 14 days after HICH were assayed using enzyme-linked immunosorbent assay (ELISA), and neurological deficit score (NDS) were recorded at admission and discharge for 99 HICH cases. Then 45 healthy controls were included and assayed for serum IL-11, TNF-α, and VEGF levels. Serum IL-11, TNF-α, and VEGF levels were higher in HICH patients than healthy controls (all P < 0.05). TNF-α was higher at the 3rd day following disease onset than other time points (all P < 0.05), while IL-11 and VEGF peaked at the 7th day and dropped below baseline values at the 14th day (all P < 0.05). Serum IL-11 was positively correlated with TNF-α (r = 0.70, P < 0.05) and VEGF (r = 0.72, P < 0.05). Serum TNF-α was positively correlated with VEGF (r = 0.46, P < 0.05). Serum IL-11, TNF-α, and VEGF were associated with disease severity in HICH patients. Patients with more severe disease tended to have higher NDS at admission, and higher IL-11, TNF-α, and VEGF during treatment were associated with higher NDS at discharge. Serum IL-11, TNF-α, and VEGF may involve in the pathophysiology of HICH, thus IL-11, TNF-α, and VEGF may be prognostic factors for post HICH neurologic damage.

Clinical effect of minimally invasive intracranial hematoma in treating hypertensive cerebral hemorrhage.

OBJECTIVE: To evaluate the clinical effect of minimally invasive intracranial hematoma in treating hypertensive cerebral hemorrhage. METHODS: One hundred and fifty-six patients with hypertensive cerebral hemorrhage were selected. They were randomly divided into the control group (78 cases) and observation group (78 cases). The control group was treated with conventional craniotomy evacuation of hematoma, while the observation group was treated with minimally invasive intracranial hematoma. Neurological impairment score, treatment efficacy and Barthel index were compared between two groups. Comparison results and clinical data of these patients were retrospectively analyzed. RESULTS: Neurological impairment score in observation group had a significantly obvious decrease compared to control group (p < 0.05). Curative effect of observation group was superior to control group and the difference was significant (p < 0.05). Average operation time in observation group (51.20±10.30 minutes) was much shorter than control group (108.60±12.80 minutes). Amount of hematoma cleared for the first time in control group (75.40±10.20 (%)) was more than observation group (45.10±8.70 (%)). Hematoma in observation group (3.90±0.80 days) disappeared faster than control group (5.80±0.90 days). Differences of the above indexes between two groups were all significant (p < 0.05). Moreover, Barthel index of observation group was much better than control group (p < 0.05). CONCLUSION: Treating hypertensive cerebral hemorrhage with minimally invasive intracranial hematoma is remarkably effective. It should be promoted and practiced extensively.

Freeze-Cast Ni-MOF Nanobelts/Chitosan-Derived Magnetic Carbon Aerogels for Broadband Electromagnetic Wave Absorption.

The exceptional benefits of carbon aerogels, including their low density and tunable electrical characteristics, infuse new life into the realm of creating ultralight electromagnetic wave absorbers. The clever conceptualization and straightforward production of carbon-based aerogels, which marry aligned microporous architecture with nanoscale heterointerfaces and atomic-scale defects, are vital for effective multiscale microwave response. We present an uncomplicated synthesis method for crafting aligned porous Ni@C nanobelts anchored on N, S-doped carbon aerogels (Ni@C/NSCAs), featuring multiscale structural intricacies─achieved through the pyrolysis of freeze-cast Ni-MOF nanobelts and chitosan aerogel composites. The well-ordered porous configuration, combined with multiple heterointerfaces adopting a "nanoparticles-nanobelts-nanosheets" contact schema, along with a wealth of defects, adeptly modulates conductive, polarization, and magnetic losses to realize an equilibrium in impedance matching. This magnetically doped carbon aerogel showcases an impressive effective absorption bandwidth of 8.96 GHz and a minimum reflection loss of -68.82 dB, while maintaining an exceptionally low filler content of 1.75 wt %. Additionally, the applied coating exhibits an astonishing radar cross-section reduction of 51.7 dB m2, signifying its superior radar wave scattering capabilities. These results offer key insights into the attainment of broad-spectrum microwave absorption features by enhancing the multiscale structure of current aerogels.

Ag-Incorporated Cr-Doped BaTiO3 Aerogel toward Enhanced Photocatalytic Degradation of Methyl Orange.

A novel Cr-doped BaTiO3 aerogel was successfully synthesized using a co-gelation technique that involves two metallic alkoxides and a supercritical drying method. This freshly prepared aerogel has a high specific surface area of over 100 m2/g and exhibits improved responsiveness to the simulated sunlight spectrum. Methyl orange (MO) was chosen as the simulated pollutant, and the results reveal that the Cr-doped BaTiO3 aerogel, when modified with the noble metal silver (Ag), achieves a pollutant removal rate approximately 3.2 times higher than that of the commercially available P25, reaching up to 92% within 60 min. The excellent photocatalytic performance of the Ag-modified Cr-doped BaTiO3 aerogel can be primarily attributed to its extensive specific surface area and three-dimensional porous architecture. Furthermore, the incorporation of Ag nanoparticles effectively suppresses the recombination of photo-generated electrons and holes. Stability and reusability tests have confirmed the reliability of the Ag-modified Cr-doped BaTiO3 aerogel. Therefore, this material emerges as a highly promising candidate for the treatment of textile wastewater.

Morphology engineering of defective graphene for microwave absorption.

Graphene with abundant defects has been considered as the most lightweight electromagnetic functional materials. Although important, the dominant electromagnetic response of defective graphene with diverse morphologies is rarely the focus of existing research. Herein, the defective graphene with two-dimensional planar structure (2D-ps) and three-dimensional continuous network (3D-cn) morphologies were dexterously designed with 2D mixing and 3D filled systems of polymeric matrix. A comparison between the topologies of defective graphene-based nanofillers and the microwave attenuation behaviors was examined. Defective graphene with 3D-cn morphology can achieve ultralow filling content and broadband absorption, which is attributed to the presence of numerous pore structures that promote impedance matching, induce continuous conduction loss and provide multiple reflection and scattering sites for electromagnetic wave attenuation. Comparatively, by virtue of the increased filling content of 2D-ps, the dielectric losses primarily originate from the dielectric genes, including aggregation-induced-charge transport, abundant defect and dipole polarization, resulting in good microwave absorption at low thickness and low frequency. Therefore, this work provides a pioneering insight into morphology engineering of defective graphene microwave absorbers, and it will guide future exploration of customizing high-performance microwave absorption materials based on graphene-based low-dimensional building blocks.

Nanolayered Ceramic-Confined Graphene Aerogel with Conformal Heterointerfaces for Low-Frequency Microwave Absorption.

Graphene-based aerogels have garnered considerable attention for their lightweight and efficient microwave absorption (MA) properties; however, optimizing the relationship between impedance matching and attenuation capability at low frequencies remains a challenge. In this study, a three-dimensional (3D) silicon carbonitride (SiCN) nanoceramic-coated graphene aerogel with conformal heterogeneous interfaces is constructed by precursor infiltration and pyrolysis to optimize MA performance at low frequencies. Thanks to the enhanced impedance matching and significant interfacial polarization of the two-dimensional sandwiched SiCN/graphene/SiCN cell walls and multiple scattering occurring within the 3D porous skeleton, the aerogel achieves a minimum reflection loss of -57.9 dB at an ultralow frequency of 4.92 GHz (C-band) and a broad bandwidth of 5.0 GHz at an ultralow thickness of 1.7 mm. The strategy developed here provides a method for enhancing dielectric polarization loss in graphene aerogels by the joint optimization of interfacial polarization and impedance matching, inspiring the design of high-performance graphene-based materials for low-frequency MA.

Highly effective and tunable microwave absorber integrating multiscale attenuation behaviours derived from prussian blue analogue/graphene oxide aerogel.

Tunable and efficient absorption of graphene-based microwave absorbers are essential on the realms of electromagnetic compatibility and protection in various application scenarios. However, challenges arise owing to their limited microwave attenuation behaviors. Herein, CoNiFe Prussian blue analogue (PBA)-derived magnetic alloy@carbon nanocubes anchored on N-doped reduced graphene oxide (rGO) aerogels were achieved via CoNiFe-PBA nanocubes assisting assembly of GO and subsequent thermal annealing approach. Such three-dimensional (3D) graphene-based macroscopic architecture integrates multiple attenuation behaviours occurred across multiple length scales. Attributed to the synergy of multiple scattering, conduction loss, multiple heterogeneous interface and dipolar polarizations, and magnetic loss, the optimized CoNiFe-PBA/GO aerogel derivative simultaneously exhibits strong reflection loss and wide effective bandwidth with an ultralow filling content (1.1 wt%) at both X band (-66.01 dB and 5.2 GHz at 3.2 mm) and Ku band (-66.23 dB and 6.6 GHz at 2.6 mm). Multiscale assembly strategy of graphene-based electromagnetic functional materials from molecular level to macroscale proposed and demonstrated by this work shows promise for exploring tunable and efficient microwave absorbers.

Harnessing Pseudo-Jahn-Teller Disordering of Monoclinic Birnessite for Excited Interfacial Polarization and Local Magnetic Domains.

The symmetry in a polymorph is one of the most important elements for determining the inherent lattice nature. The MnO2 host tends to high-symmetry MnO6 octahedra as a result of the electronic structure t2g 3 eg 0 of Mn4+ ions, displaying an ordered structure accompanying with poor polarization loss and limiting its application toward high-performance microwave absorbers. Here, a pseudo-Jahn-Teller (PJT) distortion and PJT disordering design with abundant self-forming interfaces and local magnetic domains in the monoclinic birnessite-MnO2 host is first reported. The PJT distortion can give rise to asymmetric MnO6 octahedra, inducing the formation of interfaces and increased electron spin magnetic moment in the lattice. The resultant birnessite with PJT distortions and PJT disordering delivers an outstanding reflection loss value of -42.5 dB at an ultralow thickness of 1.7 mm, mainly derived from the excited interfacial polarization and magnetic loss. This work demonstrates an effective approach in regulating the lattice structure of birnessite for boosting microwave absorption performance.

A covalent organic framework/graphene aerogel electrocatalyst for enhanced overall water splitting.

The rational design of covalent organic framework (COF) based hybrid materials is of paramount importance to address the fundamental challenges of COFs with respect to their poor electron mobilization and the limited number of accessible active sites. Herein, we propose a new strategy for the fabrication of covalently bonded COF grafted graphene aerogel hybrid materials for electrocatalytic application. An in situ step-growth polymerization approach was developed to achieve the hybridization of COFs along the surface of amino-functionalized graphene nanosheets. By taking advantage of the three-dimensional conductive networks and highly accessible active sites, the cobalt-incorporated COF/graphene hybrid aerogel shows high oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances with an overpotential of 300 and 275 mV at 10 mA cm-2, respectively, under alkaline conditions. When applied to an electrochemical water-splitting electrolyzer, it is able to produce hydrogen and oxygen at competitive rates of 1.14 and 0.58 µL s-1, respectively, under ambient conditions, demonstrating its potential for practical applications.

Revealing Nanodomain Structures of Bottom-Up-Fabricated Graphene-Embedded Silicon Oxycarbide Ceramics.

Dispersing graphene nanosheets in polymer-derived ceramics (PDCs) has become a promising route to produce exceptional mechanical and functional properties. To reveal the complex nanodomain structures of graphene-PDC composites, a novel reduced graphene oxide aerogel embedded silicon oxycarbide (RGOA-SiOC) nanocomposite was fabricated bottom-up using a 3D reduced graphene oxide aerogel as a skeleton followed by infiltration of a ceramic precursor and high-temperature pyrolysis. The reduced graphene oxide played a critical role in not only the form of the free carbon phase but also the distribution of SiOxC4-x structural units in SiOC. Long-ordered and continuous graphene layers were then embedded into the amorphous SiOC phase. The oxygen-rich SiOxC4-x units were more prone to forming than carbon-rich SiOxC4-x units in SiOC after the introduction of reduced graphene oxide, which we attributed to the bonding of Si atoms in SiOC with O atoms in reduced graphene oxide during the pyrolysis process.

Ultralight Magnetic and Dielectric Aerogels Achieved by Metal-Organic Framework Initiated Gelation of Graphene Oxide for Enhanced Microwave Absorption.

HIGHLIGHTS: Metal-organic frameworks (MOFs) are used to directly initiate the gelation of graphene oxide (GO), producing MOF/rGO aerogels. The ultralight magnetic and dielectric aerogels show remarkable microwave absorption performance with ultralow filling contents. The development of a convenient methodology for synthesizing the hierarchically porous aerogels comprising metal-organic frameworks (MOFs) and graphene oxide (GO) building blocks that exhibit an ultralow density and uniformly distributed MOFs on GO sheets is important for various applications. Herein, we report a facile route for synthesizing MOF/reduced GO (rGO) aerogels based on the gelation of GO, which is directly initiated using MOF crystals. Free metal ions exposed on the surface of MIL-88A nanorods act as linkers that bind GO nanosheets to a three-dimensional porous network via metal-oxygen covalent or electrostatic interactions. The MOF/rGO-derived magnetic and dielectric aerogels Fe3O4@C/rGO and Ni-doped Fe3O4@C/rGO show notable microwave absorption (MA) performance, simultaneously achieving strong absorption and broad bandwidth at low thickness of 2.5 (- 58.1 dB and 6.48 GHz) and 2.8 mm (- 46.2 dB and 7.92 GHz) with ultralow filling contents of 0.7 and 0.6 wt%, respectively. The microwave attenuation ability of the prepared aerogels is further confirmed via a radar cross-sectional simulation, which is attributed to the synergistic effects of their hierarchically porous structures and heterointerface engineering. This work provides an effective pathway for fabricating hierarchically porous MOF/rGO hybrid aerogels and offers magnetic and dielectric aerogels for ultralight MA.

Chemical Surface Adsorption and Trace Detection of Alcohol Gas in Graphene Oxide-Based Acid-Etched SnO2 Aerogels.

An acidified SnO2/rGO aerogel (ASGA) is an attractive contributor in ethanol gas sensing under ultralow concentration because of the sufficient active sites and adsorption pores in SnO2 and the rGA, respectively. Furthermore, a p-n heterojunction is successfully constructed by the high electron mobility between ASP and rGA to establish a brand-new bandgap of 2.72 eV, where more electrons are released and the surface energy is decreased, to improve the gas sensitivity. The ASGA owns a specific surface area of 256.1 m2/g, far higher than SnO2 powder (68.7 m2/g), indicating an excellent adsorption performance, so it can acquire more ethanol gas for a redox reaction. For gas-sensing ability, the ASGA exhibits an excellent response of Ra/Rg = 137.4 to 20 ppm of ethanol at the optimum temperature of 210 °C and can reach a response of 1.2 even at the limit detection concentration of 0.25 ppm. After the concentration gradient change test, a nonlinear increase between concentration and sensitivity (S-C curve) is observed, and it indirectly proves the chemical adsorption between ethanol and ASGA, which exhibits charge transfer and improves electron mobility. In addition, a detailed energy band diagram and sensor response diagram jointly depict the gas-sensitive mechanism. Finally, a conversed calculation explains the feasibility of the nonlinear S-C curve from the atomic level, which further verifies the chemical adsorption during the sensing process.

On-chip assembly of 3D graphene-based aerogels for chemiresistive gas sensing.

Integration of the material preparation step into the device fabrication process is of prime importance for the development of high performance devices. This study presents an innovative strategy for the in situ assembly of graphene-based aerogels on a chip by polymerization-reduction and annealing processes, which are applied as chemiresistive gas sensors for the detection of NO2.

Freeze Casting: From Low-Dimensional Building Blocks to Aligned Porous Structures-A Review of Novel Materials, Methods, and Applications.

Freeze casting, also known as ice templating, is a particularly versatile technique that has been applied extensively for the fabrication of well-controlled biomimetic porous materials based on ceramics, metals, polymers, biomacromolecules, and carbon nanomaterials, endowing them with novel properties and broadening their applicability. The principles of different directional freeze-casting processes are described and the relationships between processing and structure are examined. Recent progress in freeze-casting assisted assembly of low dimensional building blocks, including graphene and carbon nanotubes, into tailored micro- and macrostructures is then summarized. Emerging trends relating to novel materials as building blocks and novel freeze-cast geometries-beads, fibers, films, complex macrostructures, and nacre-mimetic composites-are presented. Thereafter, the means by which aligned porous structures and nacre mimetic materials obtainable through recently developed freeze-casting techniques and low-dimensional building blocks can facilitate material functionality across multiple fields of application, including energy storage and conversion, environmental remediation, thermal management, and smart materials, are discussed.

Polymer-Derived SiOC Integrated with a Graphene Aerogel As a Highly Stable Li-Ion Battery Anode.

Amorphous polymer-derived silicon oxycarbide (SiOC) is an attractive candidate for Li-ion battery anodes, as an alternative to graphite, which is limited to a theoretical capacity of 372 mAh/g. However, SiOC tends to exhibit poor transport properties and cycling performance as a result of sparsely distributed carbon clusters and inefficient active sites. To overcome these limitations, we designed and fabricated a layered graphene/SiOC heterostructure by solvent-assisted infiltration of a polymeric precursor into a modified three-dimensional (3D) graphene aerogel skeleton. The use of a high-melting-point solvent facilitated the precursor's freeze drying, which following pyrolysis yielded SiOC as a layer supported on the surface of nitrogen-doped reduced graphene oxide aerogels. The fabrication method employed here modifies the composition and microstructure of the SiOC phase. Among the studied materials, the highest levels of performance were obtained for a sample of moderate SiOC content, in which the graphene network constituted 19.8 wt % of the system. In these materials, a stable reversible charge capacity of 751 mAh/g was achieved at low charge rates. At high charge rates of 1480 mA/g, the capacity retention was ∼95% (352 mAh/g) after 1000 consecutive cycles. At all rates, Coulombic efficiencies >99% were maintained following the first cycle. Performance across all indicators was majorly improved in the graphene aerogel/SiOC nanocomposites, compared with unsupported SiOC. The performance was attributed to mechanisms across multiple length scales. The presence of oxygen-rich SiO4-xCx tetrahedral units and a continuous free-carbon network within the SiOC provides sites for reversible lithiation, while high ionic and electronic transport is provided by the layered graphene/SiOC heterostructure.

Robust monolithic polymer(resorcinol-formaldehyde) reinforced alumina aerogel composites with mutually interpenetrating networks.

Monolithic polymer(resorcinol-formaldehyde) reinforced alumina (RF/Al2O3) aerogel composites were prepared using a sol-gel method and supercritical fluid CO2 drying. The formation mechanism, chemical compositions, pore structures, morphologies, thermal and mechanical performances of RF/Al2O3 aerogel composites with different RF/Al molar ratios were investigated. The results show that the two networks of organic resorcinol-formaldehyde and inorganic alumina are completely independent of one another. The as-synthesized RF/Al2O3 aerogels consist of spherical organic carbon particles and fibrous alumina, which possess low bulk density (0.077-0.112 g cm-3), low shrinkage (1.55-2.76%), low thermal conductivity (0.024-0.028 W m-1 K-1), and high specific surface area (453.26-722.75 m2 g-1). Especially, the sample prepared with molar ratio RF/Al = 1 shows the best network structure with the higher compressive strength (1.83 MPa) and Young's modulus (122.57 MPa). The resulting robust RF/Al2O3 aerogel composites could be potentially used as thermal insulators, catalysts and adsorbents.

Serum netrin-1 serves as a prognostic biomarker of aneurysmal subarachnoid hemorrhage.

BACKGROUND: Netrin-1 exhibits anti-inflammatory properties. Netrin-1 could alleviate brain injury of subarachnoid hemorrhage (SAH) rat. This study was designed to discern the utility of serum netrin-1 as a biomarker for assessing the severity and prognosis of patients with aneurysmal SAH. METHODS: Netrin-1 concentrations were gauged in serum from 104 patients and 104 controls. Hemorrhagic clinical and radiological severity was assessed utilizing World Federation of Neurological Surgeons (WFNS) score, modified Fisher score, and Hunt Hess score. Glasgow Outcome Scale (GOS) score was recorded at 6 months after SAH. GOS score of 1-3 was considered as a poor outcome. RESULTS: Patients showed substantially lower serum netrin-1 concentrations than controls (median, 237.9 pg/ml; interquartile range, 189.6-271.2 pg/ml vs. median, 815.4 pg/ml; interquartile range, 581.8-990.4 pg/ml). Netrin-1 concentrations were independently correlated with WNFS score, modified Fisher score, Hunt Hess score and serum C-reactive protein concentrations (t = -4.667, -3.792, -4.304 and - 3.549 respectively). Area under ROC curve was 0.837 (95% CI, 0.752-0.902) for predicting 6-month poor prognosis. Serum netrin-1 concentrations <229.3 pg/ml emerged as an independent prognostic predictor (odds ratio, 14.316; 95% confidence interval, 5.032-40.726). CONCLUSIONS: Serum netrin-1 might represent a potential biomarker for reflecting severity, inflammation and prognosis of human aneurysmal SAH.