A multi-layer core-shell structure CoFe2O4@Fe3C@NiO composite with high broadband electromagnetic wave-absorption performance.

Enhancing the absorption strength of electromagnetic waves and broadening the absorption band are constant goals in designing and preparing absorbing materials. The use of composites has shown to be a very efficient method for acquiring broadband-absorbing materials, while the construction of a core-shell structure has demonstrated a significant enhancement in absorption capability. In this paper, the nanocomposite metal-organic framework (MOF) derivative CoFe2O3@C with a double core-shell structure and the nanocomposite MOF derivative CoFe2O4@Fe3C@NiO with a three-layered core-shell structure have been prepared using a chemical compound. The multi-layer structure provides more active sites for the multiple reflection and scattering of electromagnetic waves, effectively improving the attenuation capability. The effective absorption band (EAB) (reflection loss (RL) ≤ -5 dB) of both CoFe2O3@C and CoFe2O4@Fe3C@NiO are broadened compared to that of the ZIF-67 derivative. In particular, the minimum reflection loss (RLmin) of CoFe2O3@C was -52.7 dB at 13.3 GHz and 2.04 mm, and the EAB (RL ≤ -5 dB) is as wide as 9.35 GHz. Compared with the ZIF-67 derivative, the EAB exhibits a twofold rise, accompanied by a corresponding thickness increase of just 0.24 mm. At a matched thickness of 2.2 mm, the EAB of CoFe2O4@Fe3C@NiO can even reach 11.9 GHz.

In Situ Silver Nanonets for Flexible Stretchable Electrodes.

Shape-controlled synthesis is an effective method for controlling the physicochemical properties of nanomaterials, especially single-crystal nanomaterials, but it is difficult to control the morphology of single-crystal metallic nanomaterials. Silver nanowires (AgNWs) are regarded as key materials for the new generation of human-computer interaction, which can be applied in large-scale flexible and foldable devices, large-size touch screens, transparent LED films, photovoltaic cells, etc. When used on a large scale, the junction resistance will be generated at the overlap between AgNWs and the conductivity will decrease. When stretched, the overlap of AgNWs will be easily disconnected, which will lead to a decrease in electrical conductivity or even system failure. We propose that in situ silver nanonets (AgNNs) can solve the above two problems. The AgNNs exhibited excellent electrical conductivity (0.15 Ω∙sq-1, which was 0.2 Ω∙sq-1 lower than the 0.35 Ω∙sq-1 square resistance of AgNWs) and extensibility (the theoretical tensile rate was 53%). In addition to applications in flexible stretchable sensing and display industries, they also have the potential to be used as plasmonic materials in molecular recognition, catalysis, biomedicine and other fields.

Silver-Based Surface Plasmon Sensors: Fabrication and Applications.

A series of novel phenomena such as optical nonlinear enhancement effect, transmission enhancement, orientation effect, high sensitivity to refractive index, negative refraction and dynamic regulation of low threshold can be generated by the control of surface plasmon (SP) with metal micro-nano structure and metal/material composite structure. The application of SP in nano-photonics, super-resolution imaging, energy, sensor detection, life science, and other fields shows an important prospect. Silver nanoparticles are one of the commonly used metal materials for SP because of their high sensitivity to refractive index change, convenient synthesis, and high controllable degree of shape and size. In this review, the basic concept, fabrication, and applications of silver-based surface plasmon sensors are summarized.

In Situ Growth of Nanosilver on Fabric for Flexible Stretchable Electrodes.

Flexible sensing can disruptively change the physical form of traditional electronic devices to achieve flexibility in information acquisition, processing, transmission, display, and even energy, and it is a core technology for a new generation of the industrial internet. Fabric is naturally flexible and stretchable, and its knitted ability makes it flexibility and stretchability even more adjustable. However, fabric needs to be electrically conductive to be used for flexible sensing, which allows it to carry a variety of circuits. The dip-coating technique is a common method for preparing conductive fabrics, which are made conductive by attaching conductive fillers to the fabrics. However, the adhesion of the conductive fillers on the surface of such conductive fabrics is weak, and the conductive property will decay rapidly because the conductive filler falls off after repeated stretching, limiting the lifespan of flexible electronic devices based on conductive fabric. We chose multifunctional nanosilver as a conductive filler, and we increased the adhesion of nanosilver to fabric fiber by making nanosilver grow in situ and cover the fiber, so as to obtain conductive fabric with good conductivity. This conductive fabric has a minimum square resistance of 9 Ω/sq and has better electrical conductivity and more stable electrical properties than the conductive fabric prepared using the dip-coating process, and its square resistance did not increase significantlyafter 60 stretches.

Split-Ring Structured All-Inorganic Perovskite Photodetector Arrays for Masterly Internet of Things.

Photodetectors with long detection distances and fast response are important media in constructing a non-contact human-machine interface for the Masterly Internet of Things (MIT). All-inorganic perovskites have excellent optoelectronic performance with high moisture and oxygen resistance, making them one of the promising candidates for high-performance photodetectors, but a simple, low-cost and reliable fabrication technology is urgently needed. Here, a dual-function laser etching method is developed to complete both the lyophilic split-ring structure and electrode patterning. This novel split-ring structure can capture the perovskite precursor droplet efficiently and achieve the uniform and compact deposition of CsPbBr3 films. Furthermore, our devices based on laterally conducting split-ring structured photodetectors possess outstanding performance, including the maximum responsivity of 1.44 × 105 mA W-1, a response time of 150 µs in 1.5 kHz and one-unit area < 4 × 10-2 mm2. Based on these split-ring photodetector arrays, we realized three-dimensional gesture detection with up to 100 mm distance detection and up to 600 mm s-1 speed detection, for low-cost, integrative, and non-contact human-machine interfaces. Finally, we applied this MIT to wearable and flexible digital gesture recognition watch panel, safe and comfortable central controller integrated on the car screen, and remote control of the robot, demonstrating the broad potential applications.

Ultra-fast fabrication of Bi2Te3 based thermoelectric materials by flash-sintering at room temperature combining with spark plasma sintering.

Highly crystalline Bi2Te3 based compounds with small grain size were successfully synthesized by flash sintering (FS) method in 10 s at room temperature under suitable current density using Bi, Te and Se powders. The instantaneously generated local Joule heat at grain boundary is regarded as the main reason for the rapid completion of chemical reaction and crystallization. By combining FS synthesis method with spark plasma sintering (SPS), Bi2Te3 based bulk materials with high relative density were fabricated in 10 min. Suitably prolonging sintering temperature and holding time in SPS process can decrease carrier concentration and phonon thermal conductivity, while increasing carrier mobility. Hence, the sample prepared at 753 K for 3 min shows 20% higher ZT value than that of the sample prepared at 723 K for 3 min. Compared with common zone melting or powder metallurgy methods taking several hours by complex operation, this method is time-saving and low cost.

Phase Behaviors of ABA Star Polymer and Nanoparticles Confined in a Sphere with Soft Inner Surface.

The phase behaviors of an ABA star polymer and nanoparticles confined in a sphere with soft inner surface, which is grafted with homopolymer brushes have been studied by the self-consistent field theory (SCFT). The morphologies of mixture in the center slice of sphere were focused. Two cases are considered: one is that the nanoparticles interact with the B blocks and the other is that the nanoparticles preferentially wet the B blocks. Under the two conditions, through changing the block ratio of the ABA star polymer, the concentration and radius of the nanoparticles, the phase behaviors of the mixtures confined the soft sphere are studied systematically. With increasing the concentration of nanoparticles, the entropy and the steric repulsive interaction of nanoparticles, and the nanoparticle density distributions along the perpendicular line through the center of sphere are plotted. The phase diagram is also constructed to analyze the effects of the nanoparticle volume fraction and radius on morphologies of ABA star polymers, and to study the effect of confinement on the phase behaviors. The results in this work provide a useful reference for controlling the ordered structures in experiment, which is an effective way to fabricate the newly multifunctional materials.

Structural dependence of microwave dielectric properties of ixiolite structured ZnTiNb2O8 materials: crystal structure refinement and Raman spectra study.

Structural and property relationships of ixiolite structured ZnTiNb(2)O(8) microwave dielectric materials were studied by structure refinement and Raman spectra analysis. The vibration modes which have Raman activities of the ixiolite structure were assigned for the first time. The bands with wavenumbers greater than 450 cm(-1) can be associated with several modes (A(g(2)), B(3g(1)), B(3g(2)), A(g(1)), B(1g(2)), A(g(3)), B(2g(2))) involving the stretching of the cation-O bonds. For wavenumbers between 250 and 450 cm(-1), the bands are due, principally, to the bending of O-cation-O (B(1g(1)), B(2g(1)), B(1g(3))). The origin of the bands with wavenumbers below 250 cm(-1) would be lattice vibrations (B(1g(4)), A(g(4)), B(3g(4)), B(2g(4))), mainly associated with cation ions. The correlation between bond strength and packing fraction, Raman shift, full width at half maximum (FWHM) of Raman spectra were discussed. With increase of bond strength, the oxygen octahedron became rigid, the Raman shift increased, and the damping behavior became weaker. With increase of Raman shift, the dielectric constant decreased. With increase of packing fraction and decrease of FWHM, the Q(f) (quality factor × resonance frequency) value increased. The τ(f) (temperature coefficient of resonance frequency) decreased with increase of bond strength. And there was no direct relationship between oxygen octahedron distortion and τ(f). The excellent microwave dielectric properties of ZnTiNb(2)O(8) in this work were: dielectric constant (ε) = 34.4, Q(f) = 56,900 GHz, τ(f) = -47.94 × 10(-6)/°C.