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Electromagnetic metasurfaces are structured surfaces consisting of a thin array of subwavelength elements with engineered scattering properties, thus providing a promising means of holographic display by controlling the field distributions. However, the existing metasurface holography has limited capabilities in achieving 3-D fields with simultaneous features of high spatial resolution and energy efficiency due to the design methods. In this work, we present a transmissive metasurface to achieve polarization-dependent field distributions in 3-D space with both high resolution and efficiency. In the design, a new method that utilizes dyadic Green’s function (DGF) as the rigorous propagator is used. Using the method, the sources and fields are linked directly and can be located on arbitrary 3-D points with the intermediate spaces being equal or unequal. The design is successfully validated by full-wave simulations and experimental measurements. The broadband simulation results indicate that the design has a bandwidth of 0.8 GHz. This work demonstrates a feasible and simple route of field synthesis for real-world applications that require high resolution, high efficiency, and 3-D scenarios.

A dual-polarization frequency-selective rasorber (FSR) with two absorptive bands at both sides of a passband is presented. Based on the characteristic mode analysis, a circuit analog absorber is designed using a lossy frequency-selective surface (FSS) that consists of miniaturized meander lines and lumped resistors. The positions and values of resistors are determined according to the analysis of modal significances and modal current. After that, the presented rasorber is designed by cascading of the lossy FSS and a lossless bandpass FSS. Equivalent circuits of the FSR are modeled, and surface current distributions of both FSSs are illustrated to explain the operation mechanism. Measurement results show that, under the normal incidence, a minimum insertion loss of 0.27 dB is achieved at a passband around 6 GHz, and the absorption bands with an absorption rate higher than 80% are 2.5–4.6 GHz in the lower band and 7.7–12 GHz in the higher band, respectively. Our results exhibit good agreements between measurements and simulations.

A prismatic conformal metasurface, based on optimized multielement phase cancellation, is proposed for wideband radar cross-sectional (RCS) reduction. The metasurface is composed of 35 lattices located in seven zones of a prismatic structure. The lattices in different zones are simulated under corresponding incident angles and taken into account the difference of wave path caused by the bending of the conformal structure. The interactions between multiple backscattered waves produced by the lattices are manipulated and optimized simultaneously by the hybrid array pattern synthesis and particle swarm optimization to achieve wideband destructive interference. The proposed metasurface can realize a 10 dB reduction in backscattered RCS under normal incidence for HH polarization from 9.6 to 10.6 GHz and 11.7 to 17.7 GHz with the fractional bandwidths of 9.9% and 40.8%, respectively. The theoretical analysis, simulated, and measured results are in a good agreement. The proposed approach verifies the innovation and effectiveness in achieving wideband RCS reduction for conformal metasurface.

The boundary element method (BEM) is an efficient way to compute solutions of eddy current nondestructive evaluation (NDE) problems. However, in boundary element analysis of eddy currents, the computational accuracy and efficiency depend on the element discretization employed and are very sensitive to the liftoff distance and the relative geometry size between the detecting coil and object under evaluation or test. In this paper, the skin depth parameter is applied to study the element discretization effects on boundary element analysis for 3D eddy current NDE problems. The element discretization rules are concluded by conducting numerical experiments for different liftoff distances and relative probe sizes so that they can be adjusted to account for variations in these parameters, and validated against the analytical method, semi-analytical method, and experiments of some benchmark problems. With the help of the rules, the overall computational accuracy is improved while the cost is reduced for the BEM modeling of eddy current NDE problems.

In this article, the multilevel adaptive cross approximation (MLACA) algorithm is presented to accelerate the boundary element method (BEM) for eddy current nondestructive evaluation (NDE) 3D problems involving arbitrary shapes. The Stratton-Chu formula, which does not have the low frequency breakdown issue, has been selected for modeling. The equivalent electric and magnetic surface currents are expanded with Rao-Wilton-Glisson (RWG) vector basis functions while the normal component of the magnetic field is expanded with pulse basis functions. The MLACA compresses the rank deficient matrices with the ACA and the butterfly algorithm. We improve the efficiency of MLACA by truncating the integral kernels after a certain distance and applying the multi-stage (level) algorithm adaptively based on the criteria for different operators to further decrease the memory and CPU time requirements while keeping almost the same accuracy comparing with the traditional MLACA. The proposed method is especially helpful to deal with the large solution domain issue of the BEM for eddy current problems. Numerical predictions are compared with the analytical, the semi-analytical predictions and the experimental results for 3D eddy current NDE problems of practical interest to demonstrate the robustness and efficiency of the proposed method.

This letter presents an absorptive/transmissive frequency selective surface (ATFSS) with wide absorption bands at both sides of a passband. A double-layer structure consisting of a lossy FSS and a lossless FSS was employed. The lossy and lossless FSSs were designed based on tripole loops and tripole slots, respectively. The tripole loops and slots were constructed as a hexagonal periodic structure. The tripole loops equated to a series-parallel circuit and exhibited lossy feature after they were loaded with lumped resistors, which were used to absorb the incident wave at lower and upper absorption bands. Surface current distributions were illustrated to explain the operation mechanism. A prototype of the proposed ATFSS was fabricated and measured. Our results showed good agreement between measurements and simulations. Measurement results showed that a passband with a center frequency of 5 GHz and a minimum insertion loss of 0.35 dB was obtained. Out of the passband, absorption rates higher than 80% were obtained at a lower absorption band, from 2.66 to 4.5 GHz, and at a higher absorption band, from 5.66 to 8.56 GHz.

MnO2 possesses multiple crystal phases and various geometrical morphologies, so there remains a big challenge to simultaneously control the crystal phases and geometrical morphologies of MnO2 by a facile process. Indeed, these controllable syntheses will provide material bases to investigate their effects on the specific capacitance. Herein, benefiting from the first attempt of using Co2+ as a phase transformation-inducing agent and a doping ion, we present an interesting report on controllable phase transformation from δ- to α-MnO2 and their morphology evolution from nanosheets to nanowires. These transformations need the synergistic effect between MnCO3 and Co2+. Furthermore, three dimensional hierarchical α-MnO2@δ-MnO2 core–shell heterophase nanostructures were fabricated to improve capacitance performance. Impressively, the specific capacitance of α-MnO2@δ-MnO2 reaches up to 206 F g−1, which is higher than those of the corresponding single components. An asymmetric supercapacitor device based on the α-MnO2@δ-MnO2 cathode exhibits a good energy density of 12.9 W h kg−1 at a power density of 230 W kg−1 and excellent cycle lives with a decrease of 26% capacitance after 10 000 charge/discharge cycles.

The eddy current non-destructive evaluation (NDE) modelling using Stratton-Chu formulation-based fast algorithm is analysed. Stratton-Chu formulations, which have no low frequency breakdown issue, are selected for modelling electromagnetic NDE problems with low frequency and high conductivity approximations. As the main contribution of this article, the robustness and efficiency of the approximations, which result in big savings in both memory and CPU time, are validated and analysed using examples from practical EC testing. The boundary element method (BEM) is used to discretize the integral equations into a linear system of equations: the first order Rao-Wilton-Glisson (RWG) vector basis functions with the flat triangle meshes of the object and pulse basis functions are selected to expand the equivalent surface currents and the normal component of magnetic fields, respectively. Then the multilevel adaptive cross approximation (MLACA) algorithm is applied to accelerate the iterative solution process. The performance and efficiency of adaptively applying a multi-stage (level) algorithm based on the criteria concluded for the operators are shown.This article is part of the theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’.

In this paper, a frequency selective surface (FSS) with tunable bandstop performance by integrating graphene is discussed. The graphene implanted in the circular FSS unit makes the transmission and reflection bands of the proposed FSS tunable owing to its alterable complex conductivity controlled by the chemical potential. The transmission zero of the proposed FSS performing as a reflection plane happens at the frequency from 1.65 THz to 2.19 THz when the chemical potentials of graphene change from 0 eV to 1 eV. Moreover, reconfigurable radiation pattern of a traditional dipole antenna is accomplished loaded with the proposed FSS by altering the complex conductivity of graphene. The dipole has a directional radiation pattern with enhanced directivity at 2.1 THz by adding the proposed FSS with μc = 0.8 eV. However, the omnidirectional radiation pattern is maintained by changing the value of chemical potential to 0 eV while the FSS is nearly transparent. Therefore, a radiation diversity property could be achieved by controlling the chemical potential of graphene loaded in FSS.

Air bearing has been widely applied in ultra-precision machine tools, aerospace and other fields. The restrictor of the porous material is the key component in air bearings, but its performance is limited by the machining accuracy. A combination of optimization design and material modification of the porous alumina ceramic membrane is proposed to improve performance within an air bearing. Porous alumina ceramics were prepared by adding a pore-forming agent and performing solid-phase sintering at 1600 °C for 3 h, using 95-Al2O3 as raw material and polystyrene microspheres with different particle sizes as the pore-forming agent. With 20 wt.% of PS50, the optimum porous alumina ceramic membranes achieved a density of 3.2 g/cm3, a porosity of 11.8% and a bending strength of 150.4 MPa. Then, the sintered samples were processed into restrictors with a diameter of 40 mm and a thickness of 5 mm. After the restrictors were bonded to aluminum shells for the air bearing, both experimental and simulation work was carried out to verify the designed air bearing. Simulation results showed that the load capacity increased from 94 N to 523 N when the porosity increased from 5% to 25% at a fixed gas supply pressure of 0.5 MPa and a fixed gas film thickness of 25 μm. When the gas film thickness and porosity were fixed at 100 μm and 11.8%, respectively, the load capacity increased from 8.6 N to 40.8 N with the gas supply pressure having been increased from 0.1 MPa to 0.5 MPa. Both experimental and simulation results successfully demonstrated the stability and effectiveness of the proposed method. The porosity is an important factor for improving the performance of an air bearing, and it can be optimized to enhance the bearing’s stability and load capacity.

Uniform Bi2WO6 pancakes were prepared via a solvothermal route in a solvent mixture of glycerol (Gly) and water (V/V = 1). A variety of techniques including scanning electron microscopy, transmission electron micrographs, X-ray powder diffraction, Brunauer–Emmett–Teller, FT-IR spectra, and UV–Vis diffuse reflectance spectra, were employed to characterize the structure and properties of the as-obtained Bi2WO6. It was found that Bi2WO6 pancakes showed prominent photocatalytic performance for the degradation of rhodamine B (RhB) under visible light (λ ≥ 420 nm) irradiation, which can be attributed to its good crystallization, large surface area, unique morphology and structural features.

In recent years, carbon particles have gained numerous attentions because of their simple synthetic process, low toxicity and water solubility. The present work involves synthesis of two types of graphene quantum dots (GQDs) by treating sulfydryl group (−SH) amino acid glutathione (GSH) in the presence and absence of AgNO 3 via one pot route, respectively. The Ag + ions from AgNO 3 can combine the −SH from GSH to form Ag 2 S, thus surfaces of the obtained graphene quantum dots (N-GQDs) are mainly modified by some free hydroxyl groups ( OH), amino groups ( NH 2 ) and carboxyl groups ( COOH). In the absence of Ag + ions, the surfaces of as-prepared graphene quantum dots (SN-GQDs) not only include OH, NH 2 and COOH, but also −SH. Interestingly, as-prepared two kinds of GQDs both have strong fluorescence with different emission wavelength. More importantly, these GQDs have special recognition ability for metal ions. The N-GQDs respond rapidly towards the presence of Fe 3+ ions, and can be used as a probe to detect Fe 3+ ions in waste water, while the SN-GQDs have a special recognition to Hg 2+ ions.

The present study is focused on employing Camellia japonica leaf extract as inductive and stabilizing agent to synthesis CuO and ZnO nanoparticles (NPs). The chemicals, such as (Cu(NO3)2·3H2O) and (Zn(NO3)2·6H2O) were converted into copper and zinc ions, respectively because of the different natural products present in the C. japonica leaf extract. The UV–vis spectra of CuO and ZnO NPs showed absorption peak at 290 nm and 301 nm, respectively. The XRD result revealed crystalline nature of the metal oxide NPs and the TEM images indicated that average sizes of the synthesized CuO and ZnO NPs were ∼17 nm and ∼20 nm, respectively. The FTIR spectra of C. japonica leaf extract showed the presence of organic groups, such as, OH, C N, and N−H, which would be responsible for forming CuO and ZnO NPs. The synthesized CuO and ZnO NPs were tested for the optical sensing of metal ions, viz. Li+ and Ag+ that illustrated excellent outcome and hence this method offers a novel lane for the synthesis of metal oxide NPs, which can be used as optical sensor for the detection of metal ions.

The cobalt sulfide/graphene oxide (CoS/GO) nanocomposite was synthesized by a simple hydrothermal reaction. The products as-synthesized were characterized by XRD, SEM, TEM, BET-BJH and TG. The electrochemical property and impedance of the CoS/GO nanocomposite were studied by cyclic voltammetry and EIS analysis, respectively. The results show that the presence of the GO enhances the electrode conductivity, and then improves the capacitance property of the CoS/GO nanocomposite. The galvanostatic charge/discharge measurement results show that the CoS/GO nanocomposite has a high specific capacitance (550 Fg-1) and long cycle life (over 1 000 cycles).

Developing efficient and economical catalysts for the oxygen reduction reaction (ORR) is important to promote the commercialization of fuel cells. Here, we report a simple and environmentally friendly method to prepare nitrogen (N) –doped hierarchical porous carbon (HPC)/reduced graphene oxide (RGO) composites by reusing waste biomass (pomelo peel) coupled with graphene oxide (GO). This method is green, low-cost and without using any acid or alkali activator. The typical sample (N-HPC/RGO-1) contains 5.96 at.% nitrogen and larger BET surface area (1194 m 2 /g). Electrochemical measurements show that N-HPC/RGO-1 exhibits not only a relatively positive onset potential and high current density, but also considerable methanol tolerance and long-term durability in alkaline media as well as in acidic media. The electron transfer number is close to 4, which means that it is mostly via a four-electron pathway toward ORR. The excellent catalytic performance of N-HPC/RGO-1 is due to the synergistic effect of the inherent interwoven network structure of HPC, the good electrical conductivity of RGO, and the heteroatom doping for the composite. More importantly, this work demonstrates a good example for turning discarded rubbish into valuable functional products and addresses the disposal issue of waste biomass simultaneously for environment clean.

This letter reports a novel directivity-reconfigurable wideband antenna in microwave regime. The antenna is formed by encasing liquid metal alloys into a highly stretchable elastomer. A two-arm Archimedean spiral antenna is adopted to implement the concept of optimizing directivity by inflating the elastomer to form a dome-shaped antenna. Microelectromechanical system-based microblowers are employed to pneumatically control the shape of the antenna. The antenna can operate in a wide frequency band from 6.9 to 13.8 GHz. The ability to change the shape of the antenna allows optimizing its radiation pattern by making it more directive in the inflation direction, while its passing band remains wide. The antenna also provides good circular polarization of an electromagnetic wave.

This letter reports on a fully conformal square-patch frequency-selective surface (FSS) consisting of liquid metal alloy embedded within a flexible silicone elastomer. The flexible and elastic nature of the FSS provides high conformity to doubly curved surfaces. The transmission properties of the FSS on both singly and doubly curved surfaces are studied. This FSS can facilitate electromagnetic interference reduction in the X-band frequency range when wrapped on cylindrical or spherical radomes over dipole-like antennas, thus surpassing many existing flexible FSS technologies that usually allow conformable contact only with singly curved surfaces.

In this paper, a method of moments (MoM) based multilevel adaptive cross approximation (MLACA) algorithm is proposed to accelerate the calculation of impedance changes for eddy current problems. The MLACA uses the butterfly algorithm and ACA algorithm to approximate the well-separated blocks in the impedance matrix. Numerical results show both the efficiency and robustness of the proposed method.

Efficient and novel cobalt doped MnO2 nanowires decorated with Graphene oxide was successfully synthesized with hydrothermal method and ultrasonic process. The nanocomposite phase was confirmed by XRD and XPS data. TEM and HRTEM analysis showed the good dispersion of MnO2 nanowires on graphene oxide sheets. Benefiting from the synergistic effect between cobalt-doped MnO2 nanowires and graphene oxide, the electrode material showed a satisfactory electrochemical performance with high specific capacitance of 397 F g−1 at 0.5 A g−1, high rate capability (328 F g−1 at 20 A g−1), and excellent capacitance retention only 2.5% decay after 4000 cycles at 10 A g−1 current density. As application for asymmetric supercapacitor device, the Cobalt doped MnO2 decorated with graphene oxide (MCo(0.25)/GO) electrode achieved a wide potential window up to 2.3 V with a high energy density of 35.3 Wh·kg−1 at power density of 590 W kg−1. Moreover, an energy density value of 25.8 Wh·kg−1 is maintained at high power density (5.6 kW kg−1). Therefore, the prepared MCo(0.25)/GO nanocomposite, with outstanding electrochemical performance, is considered as suitable and great potential application for supercapacitor device in the next generation.

Highly pure zinc oxide nanoparticles (ZnO NPs) and graphene-zinc oxide nanocomposites (G-ZnO NCs) were synthesized via chemical precipitation method. The structure, morphology, and composition of the synthesized ZnO NPs and G-ZnO NCs were characterized by using fourier transfer infrared spectroscopy, X-ray diffraction spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy (TEM). The TEM images revealed that the diameter of ZnO NPs is 8–12 nm and homogeneously dispersed onto the surface of graphene sheets. The photocatalytic degradation efficiency of the synthesized G-ZnO NCs against rhodamine-B (Rh-B), methylene blue (MB) and methyl orange (MO) was quantified under visible light irradiation. The irradiation time required for complete removal of the dyes are dependent on dye molecules (MB, MO and Rh-B) and their interaction with the prepared ZnO NPs and G-ZnO NCs. The synthesized NCs were highly efficient for the removal of Rh-B compared to other tested dyes. Hence, the synthesized G-ZnO NCs could be used for environmental dye remediation.

This paper presents the adaptive cross approximation (ACA) algorithm to accelerate boundary element method (BEM) for eddy current nondestructive evaluation (NDE) problem. The eddy current problem is formulated by boundary integral equation and discretized into matrix equations by BEM. Stratton–Chu formulation is selected and implemented for the conductive medium which does not has low frequency breakdown issue. The ACA algorithm has the advantage of purely algebraic and kernel independent. It starts with hierarchically partitioning the object to get diagonal blocks, near blocks and far blocks. The far-block interactions which are rank deficient can be compressed by ACA algorithm meanwhile the elements for diagonal-block interactions and near-block interactions are stored and computed by BEM. We apply modified ACA (MACA) for more memory saving while keeping almost same accuracy compared with original ACA. For numerical testing, several practical NDE examples such as coil above a half space conductor, tube in a fast reactor and Testing Electromagnetic Analysis Methods (TEAM) workshop benchmark problem are presented to show the robust and efficiency of our method. With the aid of ACA, for electrically small problems, the complexity of both the memory requirement and CPU time for BEM are reduced to $$ O\left( {N\log N} \right). $$

This paper shows an accelerated solution for low frequency eddy current nondestructive evaluation (NDE) problems with the boundary element method (BEM) by using adaptive cross approximation (ACA) algorithm. ACA algorithm is used to deal with the far-block interactions. Numerical results show the robust and efficiency of our method for low frequency NDE problems.

Visible light photocatalysts have stimulated great research efforts. In this contribution, graphene-like Co 3 S 4 nanosheet/Ag 2 S nanocomposite was prepared using a simple method, and characterized by transmission electron microscopy, X-ray diffraction, and UV–Vis DRS, etc. The photocatalytic properties of the nanocomposite was evaluated by the photocatalytic degradation of Methylene blue (MB) and Methyl orange (MO) under visible light irradiation. The nanocomposite photocatalyst displays excellent stability and photocatalytic activity compared with pure Co 3 S 4 nanosheet or Ag 2 S nanoparticles. The superior photocatalytic properties were attributed to its unique structures, which could promote efficiently electron/hole separation and transportation.

Using graphene quantum dots (GQDs) and H 2 SeO 3 as precursors, the reduced graphene quantum dots/Se nanowires (rGQDs/SeNWs) composite was electro-synthesized in the presence of cetyltrimethylammonium bromide (CTAB). The morphology and crystallization of the products as-synthesized was studied by a series of characterization techniques. The conductivity and photoresponse of rGQDs, Se NWs and rGQDs/SeNWs composite were determined respectively. Benefiting from the synergistic action of electron-deficient rGQDs and electron-rich Se NWs, significantly, the rGQDs/SeNWs composite showed excellent photoelectric conversion.

The Graphene Oxide/Polypyrrole/CdSe (GO/PPy/CdSe) nanocomposite with electrochemiluminescence (ECL) property was prepared by a novel and simple method. The composition and morphology of the nanocomposite as-prepared was characterized by a series of tests. Significantly, the electrode modified with GO/PPy/CdSe nanocomposite has strong and stable ECL emission, and can be used as ECL sensor. By studying the effect factors on ECL behavior and the ECL mechanism, it was found that the excellent ECL property of the modified electrode resulted from the synergistic effect of GO and PPy. The ECL sensor as assembled with the GO/PPy/CdSe nanocomposite was used to detect dopamine (DA), and the results show that the detection linear range for DA is from 0.01 to 16 nM with the detection limit of 0.004 nM.

A novel composite of Ag nanodendrites (AgNDs) wrapped with reduced graphene oxide (RGO) was prepared via a one-step electrodeposition approach. The characterization results show that three dimensional (3D) AgNDs with cubic phase are enwrapped by RGO sheets in the as-prepared RGO/AgNDs composite. Due to the synergistic effect of AgNDs and RGO, the RGO/AgNDs composite exhibited excellent photoelectrical conversion. Furthermore, due to its good electrochemical response to H2O2, an electrode modified with the RGO/AgNDs composite was used as a sensor for H2O2 detection, and the results show that the linear detection range is from 0.08 mM to 2.65 mM.

This letter reports on the acceleration of the infinite series summation in the multilayered shielded microstrip with multiple strips by using the spectral domain immitance approach (SDIA) and the Levin’s transformation. This technique does not need the asymptotic expansion for the Green’s functions and the basis functions by recasting the matrix elements into the form that is evaluated by the Levin’s transformation. It greatly saves the work for finding the asymptotic expansion coefficients. Using only the first leading term extraction, the overall acceleration performance is further improved. Convergence properties of SDIA by using this method match with or are even better than other acceleration techniques with high order leading term extraction.

A film of perovskite-type LaFeO3 nanoparticles (NPs) was deposited on fluorine-doped tin oxide (FTO) conducting glass via dipping-lifting and calcination. Scanning electron microscopy shows that the NPs are evenly distributed on the surface of the glass. The modified glass was further coated with antibody against human interleukin 6 (IL-6) to result in a photoelectrochemical immunosensor for IL-6. The well-established photoelectrochemical immunoassay has a linear current response in the range of 0.1 pg·mL−1 to 0.1 μg·mL−1 and a detection limit as low as 33 fg·mL−1.

The hierarchical flower-like β-In2S3 catalyst assembled from 2D nanosheets was prepared using an organic-component depletion method utilizing inorganic-organic hybrids indium diethyldithiocarbamate (In-DDTC) as a single-source precursor. The crystallization, morphology and composition of the as-synthesized β-In2S3 were characterized by XRD, SEM, TEM, EDS and XPS, respectively. The β-In2S3 possessed high specific surface area of 134.1 m2 g-1, adsorption capacity of 195.5 mg g-1 for methylene blue, and extreme photodecolorization speed under visible light irradiation for the complete removal of methyl orange (MO) dye within 15 min and tetracycline within 60 min. Although methyl orange concentration decreased quickly, the total organic carbon (TOC) decreased slowly. UV-vis and mass spectrometry (MS) were applied to analyze the intermediates coming from the photodecolorization of MO. In order to estimate the roles of active species during the decolorization of MO, trapping experiments were conducted to determine the main active species during the decolorization process. The results indicated that . O2 − radicals and e-1 were the key intermediates. This enhanced activity was attributed to its unique structures assembled from 2D nanosheets with thickness of ca. 5-7 nm, leading to high specific surface area, wide range of pore size distribution and great efficiency in absorbing light and electron/hole separation. The hierarchical flower-like β-In2S3 demonstrated great advantages in the treatment of various wastewater pollutants including textile dyes and antibiotics.

A novel sensor was assembled by combining CdTe quantum dots (QDs) with nitrogen-doped graphene (NG) on the surface of glassy carbon electrode. The sensor as-assembled with the NG/CdTe QDs composite exhibited high electrochemiluminescence (ECL) intensity and long-time ECL stability. The ECL mechanism and effect factors on ECL emission of the sensor are discussed. Significantly, the sensor was used in ascorbic acid (AA) detection based on the ECL quenching of AA. The results show that the sensor has a linear response range from 0.04 to 200 μM and the detection limit of 0.015 μM for AA.

Recyclable visible-light photocatalyst Fe3O4@TiO2 with core-shell structure was prepared by a simple synthetic strategy using solvothermal crystallization of titanium precursor on preformed Fe3O4 nanopartiles. The photo-degradation reaction of neutral red aqueous solution was tested to evaluate the visible-light photocatalytic activity of the as prepared Fe3O4@TiO2 nanoparticles, which show excellent photocatalytic activity compared with commercial P25 catalyst. Moreover, the Fe3O4@TiO2 nanocomposites can be easily separated from the reaction mixture, and maintain favorable photocatalytic activity after five cycles. The high visible light absorption of the Fe3O4@TiO2 nanocomposites may originate from the absence of electronic heterojunction, excellently dispersity and the high specific surface area of the as-synthesized Fe3O4@TiO2 samples.

8-Hydroxyquinoline manganese (Mnq2) nanobelts with width of 500 nm and length of 2–4 μm have been synthesized by a facile sonochemical route. The composition, morphology and size of the as-prepared sample were confirmed by elemental analysis (EA), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and field-emission scanning electron microscopy (FE-SEM). The reaction parameters, such as the mole ratio of reactants and the concentration of ethylene glycol, play an important part in the morphology of the final product. The electrogenerated chemiluminescence (ECL) properties of the Mnq2 sample with different morphologies have also been investigated. The ECL spectra show that the Mnq2 nanobelts exhibited excellent electrogenerated chemiluminescence (ECL) behavior.

A novel graphene oxide nanosheets/polyaniline nanowires/CdSe quantum dots (GO/PANi/CdSe) nanocomposites are successfully synthesized and use as ECL immunosensor for detection of human interleukin-6 (IL-6). The as-prepared GO/PANi/CdSe nanocomposites show excellent biocompatibility, dispersity and solubility. Electrochemiluminescence (ECL) of CdSe quantudm dots (QDs) was greatly enhanced by combining with GO/PANi nanocomposites. Herein, this GO/PANi/CdSe nanocomposite was applied to develop an ultrasensitive ECL immunosensor for detection of IL-6. The ECL immunosensor has a sensitive response to IL-6 in a linear range of 0.0005–10 ng mL −1 . The prepared ECL immunosensor exhibits high specificity, long-term stability and excellent reproducibility with a detection limit of 0.17 pg mL −1 .

Hollow perovskite-type LaCoO3 was successfully fabricated by surface-ion adsorption method utilizing the carbonaceous colloids as template under relatively low calcination temperature. Carbonaceous colloids not only acted as templates but also offered internal heat source during calcination process. The impact of calcined temperature and time on the structure and morphology of the product were studied and the possible formation process of perovskite-type LaCoO3 hollow spheres was illustrated. The obtained product was characterized by SEM, TEM, XRD, TG-DSC, ICP-OES, BET and UV–visible absorption spectra. The photocatalytic activities for degradation of methylene blue, methyl orange and neutral red were tested. The good photocatalytic degradation activity of the three different dyes and the band gap of 2.07 eV make it a promising candidate material for photocatalytic applications.

As a novel supercapacitor material, nickel sulfide/graphene oxide (NiS/GO) nanocomposite was synthesized by a hydrothermal process in the presence of graphene oxide. For the NiS/GO nanocomposite as-obtained, the characterization results show that the NiS particles (50 nm) distribute evenly on the GO sheets. The electrochemical property and impedance of the NiS/GO nanocomposite were studied by cyclic voltammetry and electron impedance spectroscopy analysis, respectively. The results show that the introduction of the GO enhanced the electrode conductivity, and then improved the supercapacitive behavior of the NiS/GO nanocomposite. The galvanostatic charge/discharge measurement results indicate that the NiS/GO nanocomposite has a high specific capacitance (800 F g −1 at 1 A g −1 ) and long cycle life (over 1000 cycles).

A novel amplification system for electrochemiluminescence (ECL) was developed by combining graphene oxide (GO) and Se nanoparticles, in which the chitosan (CHIT) was used as improver. Based on a series of experiments, the influencing factors and mechanism for ECL emission were determined. Under optimal conditions, the GO/Se nanocomposite produced an intense ECL emission and maintained long-term ECL stability. Significantly, the electrode modified with GO/Se nanocomposite was used to detect the biomolecule dopamine (DA), and showed a linear range from 0.1 to 100 µM, with a detection limit of 0.025 µM.

Well-defined octahedral Znq 2 has been synthesized via a facile solvothermal route. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images show that the as-prepared product has an octahedral structure with an edge length of 2 μm. The reaction parameters, such as solvent, reaction time and temperature, play an important part in the morphology of the final product. A possible formation mechanism for octahedral Znq 2 is proposed. The as-prepared octahedral Znq 2 exhibits excellent electrogenerated chemiluminescence (ECL) behaviour.

A novel graphene oxide sheets/polyaniline/CdSe quantum dots (GO/PANi/CdSe) nanocomposites were successfully synthesized and used for the sensitive electrochemiluminescence (ECL) biosensing. The GO/PANi/CdSe nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), ultraviolet–visible (UV–vis) absorption spectroscopy, photoluminescence (PL) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Finally, the nanocomposites were employed to construct the biosensor via layer-by-layer assembly for the ECL detection of Cytochrome C (Cyt C). The whole process was characterized by cyclic voltammogram (CV) and electrochemical impedance spectroscopy (EIS). Experimental parameters such as the ratio of GO/PANi, the K 2 S 4 O 8 concentration and the pH value of electrolyte solution were studied to investigate the effect on the ECL intensity. Under the optimized conditions, the ECL intensity decreased linearly with the Cyt C concentrations in the range from 5.0×10 −8 to 1.0×10 −4 M with detection limit of 2.0×10 −8 M. Besides, the as-proposed biosensor exhibits high specificity, good reproducibility, and stability, and may be applied in more bioanalytical systems.

Lanthanum oxycarbonate (La 2 O 2 CO 3 ) hollow microspheres with novel porous architectures were successfully fabricated by a simple one-pot hydrothermal treatment of an aqueous solution containing glucose, La(NO 3 ) 3 ·6H 2 O, and subsequent calcination. The as-prepared La 2 O 2 CO 3 porous hollow spheres are composed of nanoparticles with a mean particle size of 15 nm. Carbon microspheres act as not only templates but also carbon sources for the formation of La 2 O 2 CO 3 hollow spheres. Interestingly, the as-prepared La 2 O 2 CO 3 hollow spheres show a green emission band under UV excitation, which may be used as fluorescent biological labels.

8-Hydroxyquinoline cadmium (Cdq 2 ) nanobelts with width of 100–200 nm and lengths of 0.5–2 μm have been successfully synthesized through a facile solvothermal method at 120 °C for 24 h. The composition, morphology and structure of the as-prepared products were confirmed by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Experiment results indicated that the concentration of ethanol played an important effect in the morphology of the final products. Moreover, the electrogenerated chemiluminescence (ECL) properties of the Cdq 2 sample with different morphologies were investigated. The ECL spectra show that the Cdq 2 nanobelts exhibited excellent electrogenerated chemiluminescence (ECL) behavior.

Rational assembly of carbon nanostructures into large-area films is a key step to realize their applications in ubiquitous electronics and energy devices. Here, a self-assembly methodology is devised to organize diverse carbon nanostructures (nanotubes, dots, microspheres, etc.) into homogeneous films with potentially infinite lateral dimensions. On the basis of studies of the redox reactions in the systems and the structures of films, the spontaneous deposition of carbon nanostructures onto the surface of the copper substrate is found to be driven by the electrical double layer between copper and solution. As a notable example, the as-assembled multiwalled carbon nanotube (MWCNT) films display exceptional properties. They are a promising material for flexible electronics with superior electrical and mechanical compliance characteristics. Finally, two kinds of all-solid-state supercapacitors based on the self-assembled MWCNT films are fabricated. The supercapacitor using carbon cloth as the current collector delivers an energy density of 3.5 Wh kg−1 and a power density of 28.1 kW kg−1, which are comparable with the state-of-the-art supercapacitors fabricated by the costly single-walled carbon nanotubes and arrays. The supercapacitor free of foreign current collector is ultrathin and shows impressive volumetric energy density (0.58 mWh cm−3) and power density (0.39 W cm−3) too.

Graphene-like cobalt–nickel double hydroxide nanocomposites have been successfully prepared by a mild hydrolysis process at the room temperature. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analysis. The results reveal that the as-prepared samples are composed of α-Co(OH)2 and α-Ni(OH)2, and contain numerous thin flakes with wrinkle structure, and the thickness of the flakes is ca. 1 nm. Magnetic measurements indicate that the as-prepared nanocomposites have a weak ferromagnetic behavior at the room temperature, which is due to a small content of metallic Co. The as-synthesized products emerge large specific surface area (260.1 m2 g−1) from the measurement of Brunauer–Emmett–Teller. Interestingly, compared to single components, the obtained nanocomposites have exhibited superiorly and enhanced catalytic activity to the hydrogenation of p-nitrophenol in the presence of excess sodium borohydride at room temperature. In addition, the adsorption property of the nanocomposites for methyl blue has also been examined.

The boundary integral equations (BIE) method is a numerical computational method of solving linear partial differential equations which have been formulated as integral equations. It can be applied in many areas of engineering and science including fluid mechanics, acoustics, electromagnetics, and fracture mechanics. The eddy current problem is formulated by the BIE and discretized into matrix equations by the method of moments (MoM) or the boundary element method (BEM). The three dimensional arbitrarily shaped objects are described by a number of triangular patches. The Stratton-Chu formulation is specialized for the conductive medium. The equivalent electric and magnetic surface currents are expanded in terms of Rao-Wilton-Glisson (RWG) vector basis function while the normal component of magnetic field is expanded in terms of the pulse basis function. Also, a low frequency approximation is applied in the external medium. Additionally, we introduce Auld’s impedance formulas to calculate impedance variati...

A method is presented for solving the surface integral equation using the method of moments (MoM) at very low frequencies, which finds applications in geoscience. The nature of the Helmholtz decomposition leads the authors to choose loop-tree basis functions to represent the surface current. Careful analysis of the frequency scaling property of each operator allows them to introduce a frequency normalization scheme to reduce the condition number of the MoM matrix. After frequency normalization, the MoM matrix can be solved using LU decomposition. The poor spectral properties of the matrix, however, makes it ill-suited for an iterative solver. A basis rearrangement is used to improve this property of the MoM matrix. The basis function rearrangement (BFR), which involves inverting the connection matrix, can be viewed as a pre-conditioner. The complexity of BFR is reduced to O(N), allowing this method to be combined with iterative solvers. Both rectilinear and curvilinear patches have been used in the simulations. The use of curvilinear patches reduces the number of unknowns significantly, thereby making the algorithm more efficient. This method is capable of solving Maxwell's equations from quasistatic to electrodynamic frequency range. This capability is of great importance in geophysical applications because the sizes of the simulated objects can range from a small fraction of a wavelength to several wavelengths.

This letter studies the influence of embedded thin-film metallization layers, normally designed as ground planes, upon the dispersive characteristics of multilayer microstrip lines. The spectral domain approach is used to analyze the effects of the metallization thickness as a design parameter in two structures: the thin-film microstrip line and metal-insulator-metal-insulator line. Numerical results indicate that the thin metallization layer can excite the slow-wave mode and change significantly the dispersive characteristics. Moreover, at low frequencies a local minimal attenuation can be achieved with certain metallization thickness. Thus, it is necessary to take into account this thin-film metal ground to achieve reliable numerical simulation from dc to millimeter-wave frequencies

Neisseria meningitidis PorB class 3 porins obtained either from native membranes (wild-type) or recovered from inclusion bodies following expression in Escherichia coli (recombinant), have been reconstituted into solvent-free planar phospholipid membranes. The wild-type and recombinant porins exhibited the same single-trimer conductance (1–1.3 nS in 200 mM NaCl), tri-level closure pattern, characteristic of functional channel trimers, and pattern of insertion into planar membranes. Both proteins were open at low voltages and displayed two voltage-dependent closure processes, one at positive and the other at negative potentials. Both showed asymmetric voltage dependence such that one gating process occurred at lower voltages (Vo=15 mV) than the other (Vo=25 mV). The sign of the potential that resulted in closure at low voltages varied from membrane to membrane indicating that they may have the property of auto-directed insertion (in analogy to the mitochondrial channel, VDAC). In the case of the recombinant porin, the steepness of the voltage dependence of one gating process was slightly less (n=1.3) than that observed for the other process or for the wild-type channel (n=1.5–1.7). Both channels have a high (40%) probability of closure even at 0 mV. While both channels show a slight selectivity for Cl− over Na+, the selectivity of the recombinant porin is a bit higher (permeability ratio of 2.8 vs. 1.6) as measured using a 2-fold salt gradient. Thus, the method employed to refold the recombinant porin was successful in not only restoring wild-type structure [H.L. Qi, J.Y. Tai, M.S. Blake, Expression of large amounts of Neisserial porin proteins in Escherichia coli and refolding of the proteins into native trimers, Infect. Immun. 62 (1994) 2432–2439; C.A.S.A. Minetti, J.Y. Tai, M.S. Blake, J.K. Pullen, S.M. Liang, D.P. Remeta, Structural and functional characterization of a recombinant PorB class 2 protein from Neisseria meningitidis. Conformational stability and porin activity, J. Biol. Chem. 272 (1997) 10710–10720] but also the overall electrophysiological function.

P-nitrophenol (4-NP) and hydrazine hydrate are considered to be highly toxic pollutants in wastewater, and it is of great importance to remove them. Herein, TiO2-loaded Co0.85Se thin films with heterostructure were successfully synthesized by a hydrothermal route. The as-synthesized samples were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, transmission electron microscopy and selective-area electron diffraction. The results demonstrate that TiO2 nanoparticles with a size of about 10 nm are easily loaded on the surface of graphene-like Co0.85Se nanofilms, and the NH3 · H2O plays an important role in the generation and crystallization of TiO2 nanoparticles. Brunauer-Emmett-Teller measurement shows that the obtained nanocomposites have a larger specific surface area (199.3 m(2) g(-1)) than that of Co0.85Se nanofilms (55.17 m(2) g(-1)) and TiO2 nanoparticles (19.49 m(2) g(-1)). The catalytic tests indicate Co0.85Se-TiO2 nanofilms have the highest activity for 4-NP reduction and hydrazine hydrate decomposition within 10 min and 8 min, respectively, compared with the corresponding precursor Co0.85Se nanofilms and TiO2 nanoparticles. The enhanced catalytic performance can be attributed to the larger specific surface area and higher rate of interfacial charge transfer in the heterojunction than that of the single components. In addition, recycling tests show that the as-synthesized sample presents stable conversion efficiency for 4-NP reduction.

In this paper, a facile and efficient method combined sol–gel method with hydrothermal process was employed for preparing titanium dioxide (TiO[Formula: see text]/reduced graphene oxide (rGO) nanocomposites without using any reductants or surfactants. This approach leads to the reduction of graphene oxide (GO) and the growth of TiO2 nanorods simultaneously. The results reveal that the TiO2 short nanorods with average size of 15[Formula: see text]nm in length and 10[Formula: see text]nm in diameter were uniformly grown on the rGO sheets with high dispersion. Compared with the pure TiO2 nanoparticles, the TiO2/rGO composites exhibit strong absorption in the visible light range. The photocurrent density of nanocomposites reached 0.826[Formula: see text]mA/cm2 under the simulated sunlight illumination, which is 3.5 times than that of pure TiO2. An enhancement of photocatalytic hydrogen formation rate for the water splitting was observed over the TiO2/rGO composite photocatalysts, the fastest formation rate can reach 889.28[Formula: see text][Formula: see text]mol[Formula: see text]g[Formula: see text]h[Formula: see text] when TiO2 coupling with 1wt.% rGO. Also the hydrogen production rate is about 3.27 times larger than pure TiO2 and 2.23 times than P25 due to the excellent electron trapping and transportation properties of rGO and the synergistic effect between TiO2 and rGO.