Pomegranate plasma heterostructure regulated 1D biomass derived microtube networks for lightweight broadband microwave absorber.

The excessive aggregation of magnetic metal particles and the resulting skin effect tend to cause a serious imbalance in impedance matching, which hinders its application in aerospace and military wave absorption fields. Obviously, effective dispersion configuration and network construction are two practical measures to develop broadband lightweight absorbers. Based on the recycling theme, pomegranate plasma heterostructure regulated one-dimensional (1D) biomass derived microtube networks are achieved through the conversion and utilization of waste Platanus ball fibers. The metal-organic framework strategy successfully avoids the hard agglomeration of metal particles. The pomegranate seed-like heterostructure effectively modulated the impedance of carbon microtubes, resulting in coordinated dielectric and magnetic losses. Such composites exhibited an effective absorbing bandwidth of 6.08 GHz and a minimum reflection loss of -29.8 dB. This work provides a new approach for constructing sustainable ultralight electromagnetic wave absorbers using plasmon modification and a 1D built-up network structure.

Checkerboard-like nickel nanoislands/defect graphene aerogel with enhanced surface plasmon resonance for superior microwave absorption.

To solve the problem of dispersion of magnetic nanoparticles in ultralight electromagnetic absorption field, checkerboard-like nickel nanoislands/defect graphene aerogel (NIDG) with enhanced surface plasmon resonance was designed and prepared through electrostatic self-assembly method. This special structure successfully overcame the aggregation phenomenon of magnetic metals and built high-density gap regions to enhance surface plasmon resonance. And the NIDG has achieved excellent electromagnetic wave absorption performance in C band. Specially, NIDG is superior in ultra-lightness with only 6.2 wt%, compared to some recently reported magnetic electromagnetic wave absorbers. Such great performance can be attributed to the enhanced surface plasmon resonance and improved impedance matching. This work is significant for achieving effective dielectric loss and designing lightweight low-frequency EMW absorbing materials.

Quadrangular cone carbon-constructed effective 3D network for a lightweight and broadband microwave absorbent.

Three-dimensional carbon-based materials have attracted much attention for electromagnetic wave absorption because low-dimensional materials have failed to meet the needs of constructing effective networks with ultra-light properties due to their easy agglomeration and in-plane stacking. The 3D element of quadrangular cone carbon was innovatively applied in this work to construct interconnected networks (MFC). This material successfully overcomes the disadvantages of easy agglomeration and in-plane stacking in low-dimensional elements, allowing for more efficient construction of absorbing networks. The prepared MFC exhibits excellent EAB (6.70 GHz) and RL (-50.92 dB), especially at an ultra-low filling ratio (1.04 wt%). Such superior performance can be attributed to the MFC effective network constructed by quadrangular cone carbon facilitating the entrance and diffuse scattering of electromagnetic waves. This study may provide new inspiration for constructing an effective absorbing network of pure carbon with 3D elements (quadrangular cone carbon), realizing ultra-low filling and broadband microwave performance.

High aspect-ratio sycamore biomass microtube constructed permittivity adjustable ultralight microwave absorbent.

Excessive conductivity of carbon-based materials led to poor impedance matching, hindering their electromagnetic absorbing application in aerospace and military fields. While, one-dimensional carbon materials are more favorable to build networks, satisfying impedance matching. One-dimensional carbon materials, such as carbon fibers, carbon nanotubes, carbon microtubes, etc., are recently limited by strict preparation and hard to industrialize. Inspired by the traditional handicraft of candied haw, ZnO/porous carbon micron tubes (ZnO/PCMT), are achieved by conducting a dip-coating and thermal etching process on recycling the abandoned Sycamore microtube. The prepared ZnO/PCMT exhibits higher specific surface area (1076m2g-1) and excellent microwave absorption performance. With a filler loading of only 6.7wt.%, the ZnO/PCMT achieved a great electromagnetic wave absorbing performance. Such excellent ultralight absorption performance can be attributed to their distinct hollow tubular structure of Sycamore based carbon microtube, which can easily construct conductive networks, improving the impedance matching. This work expands a new direction for the development of one-dimensional natural Sycamore microtube as ultra-light and broadband high-performance microwave absorbing materials.

Fast Terahertz Imaging Model Based on Group Sparsity and Nonlocal Self-Similarity.

In order to solve the problems of long-term image acquisition time and massive data processing in a terahertz time domain spectroscopy imaging system, a novel fast terahertz imaging model, combined with group sparsity and nonlocal self-similarity (GSNS), is proposed in this paper. In GSNS, the structure similarity and sparsity of image patches in both two-dimensional and three-dimensional space are utilized to obtain high-quality terahertz images. It has the advantages of detail clarity and edge preservation. Furthermore, to overcome the high computational costs of matrix inversion in traditional split Bregman iteration, an acceleration scheme based on conjugate gradient method is proposed to solve the terahertz imaging model more efficiently. Experiments results demonstrate that the proposed approach can lead to better terahertz image reconstruction performance at low sampling rates.

Hybrid Sparsity Model for Fast Terahertz Imaging.

In order to shorten the long-term image acquisition time of the terahertz time domain spectroscopy imaging system while ensuring the imaging quality, a hybrid sparsity model (HSM) is proposed for fast terahertz imaging in this paper, which incorporates both intrinsic sparsity prior and nonlocal self-similarity constraints in a unified statistical model. In HSM, a weighted exponentiation shift-invariant wavelet transform is introduced to enhance the sparsity of the terahertz image. Simultaneously, the nonlocal self-similarity by means of the three-dimensional sparsity in the transform domain is exploited to ensure high-quality terahertz image reconstruction. Finally, a new split Bregman-based iteration algorithm is developed to solve the terahertz imaging model more efficiently. Experiments are presented to verify the effectiveness of the proposed approach.

Spatial Domain Terahertz Image Reconstruction Based on Dual Sparsity Constraints.

Terahertz time domain spectroscopy imaging systems suffer from the problems of long image acquisition time and massive data processing. Reducing the sampling rate will lead to the degradation of the imaging reconstruction quality. To solve this issue, a novel terahertz imaging model, named the dual sparsity constraints terahertz image reconstruction model (DSC-THz), is proposed in this paper. DSC-THz fuses the sparsity constraints of the terahertz image in wavelet and gradient domains into the terahertz image reconstruction model. Differing from the conventional wavelet transform, we introduce a non-linear exponentiation transform into the shift invariant wavelet coefficients, which can amplify the significant coefficients and suppress the small ones. Simultaneously, the sparsity of the terahertz image in gradient domain is used to enhance the sparsity of the image, which has the advantage of edge preserving property. The split Bregman iteration scheme is utilized to tackle the optimization problem. By using the idea of separation of variables, the optimization problem is decomposed into subproblems to solve. Compared with the conventional single sparsity constraint terahertz image reconstruction model, the experiments verified that the proposed approach can achieve higher terahertz image reconstruction quality at low sampling rates.

Bi and oxygen defects improved visible light photocatalysis with BiOBr nanosheets.

Bi metal attached BiOBr with oxygen defect (BiOBr(3)-Bi(x%, x = 10, 20, 30)) nanosheets was prepared via the hydrothermal process in this study. The different characterization techniques of x-ray diffraction, x-ray photoelectron spectrometer, electron spin resonance (ESR), field emission scanning electron microscope, and high resolution transmission electron microscope were used to distinguish the composition, crystal structure, and morphology of the samples. Under visible light irradiation, the BiOBr(3)-Bi(x%, x = 10, 20, 30) samples exhibited improved photocatalytic activity for the degradation of colored dyes (RhB) and colorless tetracycline hydrochloride. Such an improvement was ascribed to the widened visible light absorption and enhanced separation of the photogenerated electron-hole pairs because of the synergistic effect of oxygen vacancies and Bi metal with plasmon resonance effects. A possible photocatalytic mechanism of the quasi Z-scheme process was proposed on the basis of ESR measurements and radical-trapping experiments.

Band-Gap Tuning of Organic-Inorganic Hybrid Palladium Perovskite Materials for a Near-Infrared Optoelectronics Response.

Organic-inorganic hybrid material is a recent hot topic in the scientific community. The best band gap for the entire solar absorption spectrum is about 1.1 eV. However, the lead perovskite band gap is about 1.5 eV. Therefore, developing organic-inorganic hybrid material toward the broader light harvesting of the solar spectrum is extremely urgent. In this study, we prepare three kinds of organic-inorganic hybrid palladium perovskite materials, including (CH3NH3)2PdCl4, (CH3NH3)2PdCl4-x Br x , and CH3NH3PdI3, for an optoelectronic response. The absorption cut offs of (CH3NH3)2PdCl4, (CH3NH3)2PdCl4-x Br x , and CH3NH3PdI3 are approximately 600, 700, and 1000 nm, respectively. The band gaps of (CH3NH3)2PdCl4, (CH3NH3)2PdCl4-x Br x , and CH3NH3PdI3 are determined to be approximately 2.15, 1.87, and 1.25 eV, respectively. To the best of our knowledge, this is the first study that discusses adsorption properties and photoelectric behavior of organic-inorganic hybrid palladium perovskite materials. Interestingly, the photoelectric response of the devices based on CH3NH3PdI3 reaches 950 nm. The results will attract attention in the fields of optical recorders, optical memory, security, light capture, and light treatment.

Tuning Ni-Foam into NiOOH/FeOOH Heterostructures toward Superior Water Oxidation Catalyst via Three-Step Strategy.

Splitting of water into hydrogen and oxygen has become a strategic research topic. In the two semi-reactions of water splitting, water oxidation is preferred to the four-electron-transfer process with a higher overpotential (η) and is the decisive step in water splitting. Therefore, efficient water oxidation catalysts must be developed. IrO x and RuO x catalysts are currently the most efficient catalysts in water oxidation. However, the limited reserve and high prices of precious metals, such as Ir and Ru, limit future large-scale industrial production of water oxidation catalysts. In this study, we tune inert Ni-foam into highly active NiOOH/FeOOH heterostructures as water oxidation catalysts via three-step strategy (surface acid-treating, electroplating, and electrooxidation). NiOOH/FeOOH heterostructures as water oxidation catalysts only require η of 257 mV to reach a current density of 10 mA cm-2, which is superior to that of IrO2/Ni-foam (280 mV). The high electrochemically active surface area (72.50 cm2) and roughness factor demonstrate abundant interfaces in NiOOH/FeOOH heterostructures, thus accelerating water oxidation activity. The small value (4.8 Ω cm2) of charge transfer resistance (R ct) indicate that fast electronic exchange occurs between NiOOH/FeOOH heterostructures catalyst and reaction of water oxidation. Hydrogen-to-oxygen volume ratios (approximately 2:1) indicate an almost overall water splitting by the double-electrode system. Faraday efficiency of H2 or O2 is close to 90% at 2:1 hydrogen-to-oxygen volume ratio. NiOOH/FeOOH heterostructures exhibit good stability. The results provide significance in fundamental research and practical applications in solar water splitting, artificial photoelectrochemical cells, and electrocatalysts.

Earth-abundant and environment friendly organic-inorganic hybrid tetrachloroferrate salt CH3NH3FeCl4: structure, adsorption properties and photoelectric behavior.

Organic-inorganic hybrid-based lead perovskites show inherent and unavoidable problems such as structural instability and toxicity. Therefore, developing low-cost and environment-friendly organic-inorganic hybrid materials is extremely urgent. In this study, we prepared earth-abundant and environment-friendly organic-inorganic hybrid tetrachloroferrate salt CH3NH3FeCl4 (MAFeCl4) for optoelectronic applications. The single crystal diffraction data are assigned to the orthorhombic MAFeCl4 (Pnma space group), with parameters a = 11.453 (5) Å, b = 7.332 (3) Å, c = 10.107 (5) Å, α = 90.000, ß = 90.000, and γ = 90.000. The band gap of MAFeCl4 is approximately 2.15 eV. Moreover, three-emission luminescence (398, 432 and 664 nm) was observed. To the best of our knowledge, this is the first study involving the investigation of the structure, adsorption properties and photoelectric behavior of MAFeCl4. A low cost photodetector based on the MAFeCl4 thin film is efficient under different monochromatic light from 330 nm to 410 nm with different chopping frequencies (1.33 Hz to 40 Hz). The photoelectric conversion efficiency based on FTO/TiO2/MAFeCl4/carbon electrode device reaches 0.054% (V oc = 319 mV, J sc = 0.375 mA cm-2, and fill factor = 0.45) under AM1.5, 100 mW cm-2 simulated illumination. Our findings will attract attention from the magnetic, piezoelectric and photoelectronic research fields.

General model for phase shifting profilometry with an object in motion.

When implementing the phase shifting profilometry to reconstruct an object, the object is always required to be kept stable as multiple fringe patterns are required. Movement during the measurement will cause failed reconstruction. This paper proposes a general model describing the fringe patterns with any three-dimensional movement based on phase shifting profilometry. The object movement is classified as five types and their characteristics are analyzed respectively. Then, by introducing a virtual plane, the influence on the phase value caused by different types of movement is described mathematically and a new model including movement information is proposed. At last, with the help of the movement tracking and least-square algorithm, the moving object is reconstructed with high accuracy. The proposed method can remove the reference plane during the reconstruction of the moving object, which extends the application range of the phase shifting profilometry. The effectiveness of the proposed model is verified by the experiments.

Identification of Buried Objects in GPR Using Amplitude Modulated Signals Extracted from Multiresolution Monogenic Signal Analysis.

It is necessary to detect the target reflections in ground penetrating radar (GPR) images, so that surface metal targets can be identified successfully. In order to accurately locate buried metal objects, a novel method called the Multiresolution Monogenic Signal Analysis (MMSA) system is applied in ground penetrating radar (GPR) images. This process includes four steps. First the image is decomposed by the MMSA to extract the amplitude component of the B-scan image. The amplitude component enhances the target reflection and suppresses the direct wave and reflective wave to a large extent. Then we use the region of interest extraction method to locate the genuine target reflections from spurious reflections by calculating the normalized variance of the amplitude component. To find the apexes of the targets, a Hough transform is used in the restricted area. Finally, we estimate the horizontal and vertical position of the target. In terms of buried object detection, the proposed system exhibits promising performance, as shown in the experimental results.

Deposition of luminescent Y2O3:Eu3+ on ferromagnetic mesoporous CoFe2O4@mSiO2 nanocomposites.

Luminescent Y2O3:Eu(3+) particles have been deposited on the surface of ferromagnetic mesoporous CoFe2O4@mSiO2 nanoparticles by a co-precipitation method, obtaining multifunctional CoFe2O4@mSiO2@Y2O3:Eu(3+) nanocomposites. XRD, SEM, TEM, EDX, XPS, N2-adsorption-desorption, FT-IR, VSM and PL were used to characterized the samples. The results reveal that the nanocomposites display typical mesoporous characteristics with high surface areas (BET), large pore volumes and core-shell structures. The composites show ferromagnetic properties and red luminescence from the (5)D0-(7)F2 transition at 610 nm. The size and the magnetic and luminescence properties of the composites could be tuned by systematically varying the experimental parameters, such as the annealing temperature, the mass ratio of CoFe2O4@mSiO2 to Y2O3:Eu(3+), and the volume of TEOS. A possible quenching mechanism of the luminescent Y2O3:Eu(3+) by the ferromagnetic CoFe2O4 is proposed. The high BET and large pore volume may give the composite potential application in controlled drug release.

In situ assembly of monodisperse, multifunctional silica microspheres embedded with magnetic and fluorescent nanoparticles and their application in adsorption of methylene blue.

Many efforts have been devoted towards the fabrication of multifunctional (mesoporous, magnetic and fluorescent) nanocomposites due to their growing applications as adsorbents, catalysts, and biomedical application, etc. Novel, flower-structured multifunctional Fe3O4/YVO4:Eu(3+)@SiO2 microspheres were successfully synthesized through a simple self-assembled process. The as-obtained products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption, photoluminescence (PL) spectroscopy and using a vibrating sample magnetometer (VSM). The results reveal that the novel composites exhibit typical mesoporous structure, narrow size distribution, good monodispersity, excellent luminescent properties and superparamagnetic features. The effects of magnetic field on the luminescent intensity of multifunctional composites have been discussed in our manuscript. Furthermore, the adsorption experiments indicate that the resulting multifunctional composites are powerful adsorbents for the removal of methylene blue from water with a maximum adsorption efficiency of 98%. It is envisioned that multifunctional composites with high surface area are of particular interest for adsorption of pollutants, separation, and water purification.