Core-shell Fe3O4@SnO2 nanochains toward the application of radar-infrared-visible compatible stealth.

Multiband-compatible stealth materials play an increasingly crucial role in the field of modern military defence because they can enable the targeted objects to dodge advance detection technologies. In this study, chain-like Fe3O4@poly(ethyleneglycol dimethacrylate-co-methacrylic acid) nanocomposites were constructed as precursors through the magnetic field-induced distillation precipitation polymerisation. Then, the liquid-phase seed-mediated growth method, together with subsequent calcination, was applied to introduce SnO2 shells and remove poly(ethyleneglycol dimethacrylate-co-methacrylic acid) shells, which led to the successful preparation of innovative core-shell Fe3O4@SnO2 nanochains. The unique microstructure and appropriate components endowed nanochains with multiple functional applications. The minimum reflection loss value was approximately -39.4 dB (5.67 GHz), exhibiting excellent microwave absorption performance. The possible microwave absorption mechanisms involve interfacial polarisation, space charge polarisation, natural resonance, and multiple reflections and scatterings. The optimal infrared reflectivity reached 0.64, 0.51, and 0.37 in three atmospheric windows, indicating outstanding infrared stealth performance, which was attributed to the intense infrared reflection of SnO2 shells. Furthermore, three nanochains showed different colours (dark green, brick red, and bright orange), revealing selection absorption for visible light. This can be attributed to the combined effect of visible responses of SnO2 shells along with Bragg diffraction from the periodic arrangement of Fe3O4 particles in a single nanochain. Thus, core-shell Fe3O4@SnO2 nanochains can be considered as promising radar-infrared-visible compatible stealth materials. This discovery opens a new means to exploit multiband-compatible stealth materials.

Mechanically Strong, Thermally Stable Gas Barrier Polyimide Membranes Derived from Carbon Nanotube-Based Nanofluids.

Gas barrier membranes with impressive moisture permeability are highly demanded in air or nature gas dehumidification. We report a novel approach using polyetheramine oligomers covalently grafted on the carbon nanotubes (CNTs) to engineer liquid-like CNT nanofluids (CNT NFs), which are incorporated into a polyimide matrix to enhance the gas barrier and moisture permeation properties. Benefiting from the featured liquid-like characteristic of CNT NFs, a strong interfacial compatibility between CNTs and the polyimide matrix is achieved, and thus, the resulting membranes exhibit high heat resistance and desirable mechanical strength as well as remarkable fracture toughness, beneficially to withstanding creep, impact, and stress fatigue in separation applications. Positron annihilation lifetime spectroscopy measurements indicate a significant decrease in fractional free volume within the resulting membranes, leading to greatly enhanced gas barrier properties while almost showing full retention of moisture permeability compared to that of the pristine membrane. For membranes with 10 wt % CNT NFs, the gas transmission rates, respectively, decrease 99.9% for CH4, 94.4% for CO2, 99.2% for N2, and 97.9% for O2 compared with that of the pristine membrane. Most importantly, with the increasing amount of CNT NFs, the hybrid membranes demonstrate a simultaneous increase of barrier performance and permselectivity for H2O/CH4, H2O/N2, H2O/CO2, and H2O/O2. All these results make these membranes potential candidates for high-pressure natural gas or hyperthermal air dehydration.

One-dimensional Ag-CoNi nanocomposites modified with amorphous Sn(OH)2/SnO2 shells for broadband microwave absorption.

High-performance microwave absorption absorbers play important roles in the fields of radar stealth, electromagnetic protection, and antenna technology. In this work, high aspect-ratio Ag nanowires were decorated with magnetic CoNi nanoparticles via a PVP-induced solvothermal method, and then amorphous Sn(OH)2/SnO2 shells were introduced through an in-situ oxidative hydrolysis method, successfully preparing Ag-CoNi@Sn(OH)2/SnO2 composites. The morphology and ingredient of composites were ascertained by SEM, TEM, XRD, EDX, and XPS. As Ag-CoNi nanocomposites are coated by Sn(OH)2/SnO2 shells, the minimum reflection loss value is decreased from -31.7 dB (10.1 GHz) to -37.8 dB (6.4 GHz), and the maximum effective absorption bandwidth is extended from 3.9 GHz (10.3-14.2 GHz) to 5.8 GHz (10.7-16.5 GHz). Analyses of electromagnetic parameters reveal the possible mechanisms, involving surface plasma resonance, conductive loss, interfacial polarization, dipole polarization, exchange resonance, eddy current effect, multiple reflection and scattering. Thus, Ag nanowires modified with CoNi nanoparticles and amorphous Sn(OH)2/SnO2 shells can effectively balance the impedance matching and attenuation capability. It is a new strategy to achieve broadband microwave absorbers.

Electrochemical Delamination of Ultralarge Few-Layer Black Phosphorus with a Hydrogen-Free Intercalation Mechanism.

Due to strong interlayer interaction and ease of oxidation issues of black phosphorus (BP), the domain size of artificial synthesized few-layer black phosphorus (FL-BP) crystals is often below 10 µm, which extremely limits its further applications in large-area thin-film devices and integrated circuits. Herein, a hydrogen-free electrochemical delamination strategy through weak Lewis acid intercalation enabled exfoliation is developed to produce ultralarge FL-BP single-crystalline domains with high quality. The interaction between the weak Lewis acid tetra-n-butylammonium acetate (CH3 COOTBA) and P atoms promotes the average domain size of FL-BP crystal up to 77.6 ± 15.0 µm and the largest domain size is found to be as large as 119 µm. The presence of H+ and H2 O is found to sharply decrease the size of as-exfoliated FL-BP flakes. The electronic transport measurements show that the delaminated FL-BP crystals exhibit a high hole mobility of 76 cm2 V-1 s-1 and an on/off ratio of 103 at 298 K. A broadband photoresponse from 532 to 1850 nm with ultrahigh responsivity is achieved. This work provides a scalable, simple, and low-cost approach for large-area BP films that meet industrial requirements for nanodevices applications.

Hydrogen Bonding-Derived Healable Polyacrylate Elastomers via On-demand Copolymerization of n-Butyl Acrylate and tert-Butyl Acrylate.

Achieving a desirable combination of good mechanical properties and healing efficiency is a great challenge in the development of self-healing elastomers. Herein, a class of tough and strong self-healing polyacrylate elastomers (denoted as HPs) was developed simply by free-radical copolymerization of n-butyl acrylate (nBA) and tert-butyl acrylate (tBA) and a subsequent hydrolysis reaction rather than direct copolymerization of nBA and acrylic acid (AA). The tiny difference in reactivity between nBA and tBA makes the structural units of the copolymer easy to control. Precise regulation of molecular composition can be realized just by varying the relative monomer content, making its mechanical properties to vary from ductile to robust. Strikingly, when HP samples are cut off within the gauge length, they can heal into coherent and smooth samples and recover at least 79% of the original strength. Hydrogen bond interactions serve as physical cross-linking points, contributing to the high mechanical performance (fracture energy of up to 73.78 MJ·m-3 and tensile strength of up to 17.80 MPa) as well as shape memory function. Moreover, the HP samples emit strong fluorescence when exposed to a 365 nm UV lamp and exhibit an aggregation-enhanced emission effect in the state of dissolution.

Controlled growth of large-scale uniform 1T' MoTe2 crystals with tunable thickness and their photodetector applications.

The monoclinic-phase 1T' MoTe2 crystal exhibits inversion symmetry as an anisotropic semi-metal, dictating its interesting quantum transport phenomenon and other novel physical properties. However, large-scale controllable growth of uniform MoTe2 crystals still remains a great challenge, hindering its further fundamental research and applications for novel devices. Herein, we report a modified growth method for synthesizing few-layer 1T' MoTe2 crystals with large-scale uniformity with the assistance of molecular sieves. The theoretical simulations demonstrated that due to the temperature-dependent formation energies of different edges, the edge of (010) orientation shows a higher thermodynamic stability than that of (100) orientation, and results in the anisotropic growth behavior of 1T' MoTe2 crystals while the temperature changes. The photoresponse of tri-layer 1T' MoTe2-based devices shows a broad-spectrum response from 532 nm to 1550 nm. The photo-response time of 1T' MoTe2 crystals demonstrates that it supposes to be the synergistic mechanism of photo-conductive and photo-radiation effects. Our findings not only provide a method for the controllable growth of anisotropic two-dimensional materials at a wafer scale, but also explore a broad-spectrum photodetector with the MoTe2-based device.

Rehealable, fully recyclable, and malleable electronic skin enabled by dynamic covalent thermoset nanocomposite.

Electronic skin (e-skin) mimicking functionalities and mechanical properties of natural skin can find broad applications. We report the first dynamic covalent thermoset-based e-skin, which is connected through robust covalent bonds, rendering the resulting devices good chemical and thermal stability at service condition. By doping the dynamic covalent thermoset with conductive silver nanoparticles, we demonstrate a robust yet rehealable, fully recyclable, and malleable e-skin. Tactile, temperature, flow, and humidity sensing capabilities are realized. The e-skin can be rehealed when it is damaged and can be fully recycled at room temperature, which has rarely, if at all, been demonstrated for e-skin. After rehealing or recycling, the e-skin regains mechanical and electrical properties comparable to the original e-skin. In addition, malleability enables the e-skin to permanently conform to complex, curved surfaces without introducing excessive interfacial stresses. These properties of the e-skin yield an economical and eco-friendly technology that can find broad applications in robotics, prosthetics, health care, and human-computer interface.

Preparation and characterization of bovine serum albumin surface-imprinted thermosensitive magnetic polymer microsphere and its application for protein recognition.

A novel bovine serum albumin surface-imprinted thermosensitive magnetic composite microsphere was successfully prepared by the surface grafting copolymerization method in the presence of temperature-sensitive monomer N-isopropylacrylamide (NIPAM), functional monomer methacrylic acid (MAA) and cross-linking agent N,N'-methylenebisacrylamide (MBA). The structure and component of the thermosensitive magnetic molecularly imprinted microsphere were investigated by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA). The results of thermosensitivity, adsorption capacity, selectivity and reusability showed the formation of a thermosensitivity grafting polymer layer P(NIPAM-MAA-MBA) on the surface of Fe3O4@SiO2 and the good adsorption capacity and specific recognition for template protein. When the adsorption temperature was higher than the lower critical solution temperature (LCST) of poly(N-isopropylacrylamide) (PNIPAM), shape memory effect of imprinted cavities would be more effective. In other words, it was more conducive to capture template molecules under this condition and the imprinting factor would be higher. On the other hand, when the desorption temperature was lower than LCST of PNIPAM, the decrease of shape memory effect between imprinted cavities and template molecules would facilitate the release of template molecules from the imprinted cavities. Based on this property, the adsorption and desorption of template molecules could be regulated by system temperature indirectly which benefited from the existence of thermosensitivity imprinting layer.

Synthesis of BSA/Fe3O4 magnetic composite microspheres for adsorption of antibiotics.

BSA/Fe3O4 magnetic composite microspheres with high saturation magnetization and paramagnetic property were prepared via inverse emulsion technology at room temperature, bovine serum albumin (BSA, 60 KD), magnetic nanoparticles (Fe3O4) and glutaraldehyde as macromonomer, inorganic particles and cross-linking agent, respectively. Fourier transform infrared (FTIR), scanning electron microscope (SEM), metalloscope, and particle size analyzer were used to characterize morphology and structure of composite microspheres. Vibrating sample magnetometer (VSM) and thermogravimetric analysis (TGA) were used to test magnetic properties of the synthesized samples, adsorption capacity of microspheres was determined by ultraviolet spectrophotometer (UV). The results showed that BSA/Fe3O4 microspheres were 43 µm with relatively narrow particle size distribution, perfect sphere-shaped morphologies, superparamagnetism with a saturation magnetization of 11 emu/g, and high magnetic content with a value of 57.29%. The main factors influencing properties of microspheres including raw material ratio, the amount of emulsifier and cross-linking agent, agitation speed were investigated and optimized. Furthermore, these microspheres accompanying with high separable and reusable efficient may have great potential application in the field of separation, in particular, removal of antibiotics. Adsorption capacities of the microspheres of four different kinds of antibiotics (erythromycin, streptomycin, tetracycline and chloramphenicol) ranging from 69.35 mg/g to 147.83 mg/g were obtained, and Langmuir isotherm model coincided with equilibrium data than that of the Freundlich model.