Hollow Engineering to Co@N-Doped Carbon Nanocages via Synergistic Protecting-Etching Strategy for Ultrahigh Microwave Absorption

Rational manipulation of hollow structure with uniform heterojunctions is evolving as an effective approach to meet the lightweight and high-performance microwave absorption for metal-organic frameworks (MOFs) derived absorbers. Herein, a new and controlled synergistic protecting-etching strategy is proposed to construct shelled ZIF-67 rhombic dodecahedral cages using tannic acid under theoretical guidance, then hollow Co@N-doped carbon nanocages with uniform heterojunctions and hierarchical micro-meso-macropores are obtained via a pyrolysis process, which addresses the shortcomings of using sacrificing templates or corrosive agents. The outer Co@N-doped carbon shell, composed of highly dispersive core-shell heterojunctions, possesses micro-mesopores while the inner hollow macroporous cavity endows the absorbers with lightweight characteristics. Accordingly, the maximum reflection loss is −60.6 dB at 2.4 mm and the absorption bandwidth reaches 5.1 GHz at 1.9 mm with 10 wt% filler loading, exhibiting superior specific reflection loss compared with the vast majority of previous MOFs derived absorbers. Furthermore, this synergistic protecting-etching strategy provides inspiration for precisely creating a hollow void inside other MOFs crystals and broadens the desirable candidates for lightweight and high-efficient microwave absorbers.     

Neuro-Glia-Vascular-on-a-Chip System to Assess Aggravated Neurodegeneration via Brain Endothelial Cells upon Exposure to Diesel Exhaust Particles

Air pollution induces neurodegeneration, including cognitive deficits, neuroinflammation, and disruption of the blood–brain barrier. The mechanisms underlying air pollution-mediated neurodegeneration have not yet been fully elucidated given the limited knowledge on intercellular interactions. A brain-on-a-chip platform is presented comprising neurons, glia, and brain endothelial cells (bECs; neuro-glia-vascular, NGV) and diesel exhaust particle (DEP)-induced neurodegeneration is evaluated with a particular focus on the intercellular interactions. DEP exposure in the NGV model yields Alzheimer's disease-like signatures, including amyloid beta accumulation, tau phosphorylation, hydrogen peroxide (H₂O₂)/reactive oxygen species (ROS) production, and neuronal cell death. bEC-secreted granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulates microglial activation and the overproduction of H₂O₂/ROS in microglia, suggesting that the bEC-microglia-neuron is a neurodegeneration cascade. Pharmacological inhibition at each step of the cascade, including GM-CSF neutralization, microglial activation suppression, and ROS scavenging, prohibits neurodegeneration in the NGV model. Therefore, intercellular interactions should be further studied of air pollution-induced neurodegeneration.     

Water‐Stable,Magnetic Silica–Cobalt/Cobalt Oxide–Silica Multishell Submicrometer Spheres

A method to produce monodisperse magnetic composite spheres with diameters from less than 100 nm to more than 1 μm in water solution is reported. The spheres consist of a dielectric silica core and a cobalt/cobalt oxide shell which can be protected from further oxidation with an outer shell of silica or, alternatively, they can be covered with the polymer polyvinylpyrrolidone as a stabilizer. The formation of a uniform magnetic shell proceeds with the adsorption of metallic cobalt seeds, produced by the reduction of cobalt chloride with sodium borohydride, on a self‐assembled layer of polyelectrolytes on the silica core. In the second step, an outer silica shell can be formed by the hydrolysis and condensation of (3‐aminopropyl)trimethoxysilane and tetraethoxysilane. The double‐shell composite spheres show excellent sphericity, monodispersity, and a magnetic hysteresis loop at room temperature.     

一种用于碳纳米管FED的荧光粉SiO2包膜处理

针对用于 FED 的荧光粉应该是适合 FED 特殊工作机理的专用阴极射线激发发光材料,提出一种以绿色荧光粉ZnS:Cu,Al 为基质,采用溶胶一凝胶法在其表面包覆一层 SiO＜2 薄膜作为 FED 用荧光粉.通过对包膜过程中的工艺条件,主要是 TEOS 浓度、溶液的 pH 值和回流温度的改变,在可拆卸式 FED 中研究生成 SiO2 薄膜包复的荧光粉对FED发光性能的影响,从而得到可获得高发光性能 FED 的包复 SiO2薄膜的最佳工艺条件.     

Two‐Dimensional Assembly of Symmetric Colloidal Dimers under Electric Fields

Like atoms and molecules with directional interactions, anisotropic particles could potentially assemble into a much wider range of crystalline arrays and meso‐structures than spherical particles with isotropic interactions. In this paper, the electric‐field directed assembly of geometrically anisotropic particles–colloidal dimers is studied. Rich phase behavior and different assembly regimes are found, primarily arising from the broken radial symmetry in particles. The orientations of individual dimers depend on the frequency of the electric field, the ramping direction of frequency, and the salt concentration. The competition and balance between the hydrodynamic, electric, and Brownian torques determine the orientation of individual particles, while the competition between the electrohydrodynamic force and dipolar interaction determines the aggregation of aligned particles at a given experimental condition. The field distribution near the electrode is critical to understand the orientation and assembly behavior of colloidal dimers on a conducting substrate. This study also demonstrates the effectiveness, the reversibility, and potential opportunity of applying electric field to control the orientation and direct the assembly of non‐spherical particles. In particular, two dimensional close‐packed crystals of perpendicularly aligned dimers are obtained, which shows promise in fabricating 3D photonic crystals based on dimer‐like colloids and field‐directed display.     

Janus‐Structured Co‐Ti3C2 MXene Quantum Dots as a Schottky Catalyst for High‐Performance Photoelectrochemical Water Oxidation

MXene materials have attracted increasing attention in electrochemical energy‐storage applications while MXene also becomes photo‐active at the quantum dot scale, making it an alternative for solar‐energy‐conversion devices. A Janus‐structured cobalt‐nanoparticle‐coupled Ti₃C₂ MXene quantum dot (Co‐MQD) Schottky catalyst with tunable cobalt‐loading content serving as a photoelectrochemical water oxidation photoanode is demonstrated. The introduction of cobalt triggers concomitant surface‐plasmon effects and acts as a water oxidation center, enabling visible‐light harvesting capability and improving surface reaction kinetics. Most importantly, due to the rectifying effects of Co‐MQD Schottky junctions, photogenerated carrier separation/injection efficiency can be fundamentally facilitated. Specifically, Co‐MQD‐48 exhibits both superior photoelectrocatalysis (2.99 mA cm^?2 at 1.23 V vs RHE) and charge migration performance (87.56%), which corresponds to 194% and 236% improvement compared with MQD. Furthermore, excellent photostability can be achieved with less than 6.6% loss for 10 h cycling reaction. This fills in gaps in MXene material research in photoelectrocatalysis and allows for the extension of MXene into optical‐related fields.     

激光熔覆NbC/Ni60合金复合涂层的组织与性能

利用激光熔覆在45钢基体上制备了NbC颗粒增强的Ni60合金复合涂层。结果表明,复合涂层的组织由γ-Ni奥氏体枝晶、枝晶间的共晶、M₂₃C₆、NbC、和少量的CrB相等组成。NbC颗粒是在激光熔覆过程中原位合成的,其形貌为不规则的块状或花瓣状。原位合成NbC颗粒增强的Ni60合金激光熔覆涂层的显微硬度可达HV0.2 1 000左右,相比于纯Ni60合金涂层,复合涂层的显微硬度提高了约38%。并且,通过激光熔覆（Nb+C）/Ni60混合粉末成功修复了2Cr13材质汽蚀的汽轮机叶片。     

Reconfigurable Anisotropic Coatings via Magnetic Field‐Directed Assembly and Translocation of Locking Magnetic Chains

A method for the generation of remotely reconfigurable anisotropic coatings is developed. To form these coatings, locking magnetic nanoparticles (LMNPs) made of a superparamagnetic core and a two‐component polymer shell are employed. Two different polymers form phase‐separated coaxial shells. The outer shell provides repulsive interactions between the LMNPs while the inner shell exerts attractive forces between the particles. Applying a non‐uniform magnetic field, one gathers the particles together, pushing them to come in contact when the internal shells could effectively hold the particles together. When the magnetic field is turned off, the particles remain locked due to these strong interactions between internal shells. The shells are thus made stimuli‐responsive, so this locking can be made reversible and the chains can be disintegrated on demand. In a non‐uniform magnetic field, the assembled chains translocate, bind to the solid substrate and form anisotropic coatings with a “locked” anisotropic structure. The coatings can be constructed, aligned, realigned, degraded, and generated again on demand by changing the magnetic field and particle environment. The mechanism of the coating formation is explained using experimental observations and a theoretical model.     

A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands

Controlled Suzuki–Miyaura coupling polymerization of 7′‐bromo‐9′,9′‐dioctyl‐fluoren‐2′‐yl‐4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolane initiated by bromo(4‐tert‐butoxycarbonylamino‐phenyl)(tri‐tert‐butylphosphine)palladium ( 1 ) or bromo(4‐diethoxyphosphoryl‐phenyl)(tri‐tert‐butylphosphine)palladium ( 2 ) yields functionalized polyfluorenes (M_n = 4 × 10³ g mol^?1, M_w/M_n < 1.2) with a single amine or phosphonic acid, respectively, end‐group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution σ < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino‐functionalized polyfluorene ligands. Single particle micro‐photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot.