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Silver nanodisks (AgNDs) have been successfully synthesized by using ferric chloride as an auxiliary agent in the presence of polyvinylpyrrolidone and

In this paper, the efficient magnetic dummy molecular imprinted polymers were firstly synthesized by dummy template (raffinose). The dummy molecularly imprinted layer was polymerized on the surface of Fe3O4 nanoparticles modified with NH2 group. The micromorphology and chemical composites of prepared polymers were detailed characterized. Their adsorption and desorption conditions including extraction time, adsorbent dosage, solution pH, washing solvent, and elution solvent were carefully evaluated. The results showed that the obtained magnetic dummy template molecularly imprinted polymers showed uniform sizes, high magnetic responsivity, core–shell structure, and selectively recognition capacity towards five aminoglycoside antibiotics. Under optimum conditions, magnetic solid-phase extraction coupled high performance liquid chromatography-tandem mass spectrometry for enriching and determining aminoglycoside antibiotics in milk samples was developed. This method showed good linearity (50–1000 μg/kg) with r2 larger than 0.9923. The limits of detection (S/N = 3) were from 3.6 to 9.6 μg/kg. With spiked at three different concentration levels, the recoveries fell into 82.6–114.1% with relative standard deviation from 2.8 to 13.2%. The established method based on magnetic dummy molecular imprinted polymers proved to be highly sensitive and repeatable, providing the promising adsorbent for aminoglycoside antibiotics analysis in the complex samples.

To realize an embedded online diagnosis system for accurate detection of internal defects in high voltage polymeric insulators, a novel ultra-wideband (UWB) microwave diagnostic system for fault detection is proposed in this article. The UWB system is based on the multimode transferring theory on dielectric waveguides, where the level difference of transmission signals of mode transferring has been employed to detect internal defects, such as cracks. First, an investigation by simulations is performed regarding the interfacial millimeter-order cracks in both transverse and longitudinal orientations. Differences of 30–50 and 20–40 dB in receiving signals of mode-transferring between non-crack and crack cases have been observed over 3–10 GHz to transverse and longitudinal oriented cracks, respectively. Then, a test prototype is designed and manufactured for experimental verification. The measurement results have a significant 40–60 dB receiving signal level difference between the non-crack reference case and the crack case. The proposed method is promising for further development of online systems to detect millimeter-order cracks in energized polymeric insulators.

Synthesis of silver nanowires (Ag NWs) has been studied for decades. However, Ag NWs with diameters below 20 nm synthesised by simple and robust approaches are still rarely reported. In this work, Ag NWs with an average diameter of ∼15 nm and an aspect ratio of over 1000 have been prepared by using a Grignard reagent 5-chloro-2-thienylmagnesium bromide as an assistant additive. In particular, the presence of 5-chloro-2-thienylmagnesium bromide is proven to be beneficial for the in situ formation of smaller AgBr and AgCl particles step by step in comparison with traditional inorganic halide ions, and then promote the final growth of ultrafine Ag NWs.

In this paper, a flower-like molybdenum disulfide material was prepared by hydrothermal method and firstly used as adsorbents in solid-phase extraction process for enriching N-nitrosoamines. Molybdenum disulfide exhibited three-dimensional petal-like microspheres with about 500 nm in diameter. The relevant analyte extraction and elution parameters (sample volumes, solution pH, washing solvents, elution solvents and elution volumes) were optimized to improve the solid-phase extraction efficiency. The solid-phase extraction process coupled with high-performance liquid chromatography tandem mass spectrometry for determining N-nitrosoamines in environmental water samples was established. The limits of detection were in the range of 0.01-0.05 ng/mL. The satisfactory recoveries (68.9%-106.1%) were obtained at three different spiked concentrations (2, 5 and 8 ng/mL) in water samples, and the relative standard deviations were between 1.96% and 8.38%. This proposed method not only showed high sensitivity and good reusability, but also provided a new adsorbent for enriching trace N-nitrosoamines in environmental water samples. This article is protected by copyright. All rights reserved.

Porcelain insulators are basic and important insulation components on overhead transmission lines, in which mechanical deterioration can pose serious threat to the safety and stability of power grid in China. In this paper, the mechanical characteristics of a fallen large-tonnage porcelain insulator are investigated with respect to frontal, back and side falling scenarios. The stress and deformation of porcelain insulator are calculated by the finite element method under free falling motion and rigid ground boundary conditions. The results reveal that the porcelain disc is more easily to be damaged in the side and frontal falling scenarios, while the steel cap is more easily to be damaged in the back falling scenario. In comparison, the steel foot as well as cement has much lower risk of damage in all falling scenarios.

Chemical modification of graphdiyne (GDY) can achieve the synthesis of GDY derivatives which also can exhibit excellent electrochemical properties. Here, we demonstrate a unique strategy to drill h...

In this paper, magnetic zeolitic imidazolate framework-8 composites were synthesized by a simple in situ method and then used for the first time as an adsorbent in magnetic solid-phase extraction for extracting multiple strobilurin fungicides. The magnetic composites were characterized in detail. The results showed that Fe3O4 nanoparticles were attached on the surface of zeolitic imidazolate framework-8 with a uniform particle size of 150-200 nm and that the magnetic composites possessed a perfect molecular transfer rate towards strobilurin fungicides. The parameters of the magnetic solid-phase extraction process, including solution pH, adsorption time, solution volume, elution solvent, and elution volume, were investigated. Under the optimum conditions, the recoveries of all five fungicides fell within the range 80.8-109.0% with spiking levels of 10, 20 and 50 ng mL-1. A magnetic solid-phase extraction-high performance liquid chromatography-tandem mass spectrometry method based on the magnetic composites was established and confirmed to be simple, time-efficient and highly sensitive.

In order to improve the energy efficiency ratio (EER) of central air conditioning system in buildings under different operating conditions, a new hybrid algorithm was established to optimize the key operating parameters of a central air conditioning system in this paper. The new hybrid algorithm includes the following: key operating parameters on the EER of a central air conditioning system are selected by Grey Relational Analysis (GRA); an energy efficiency prediction model between key operating parameters and EER is established by a BP Neural Network (BPNN); association rules among the key operating parameters are obtained through the Apriori Association Rule Algorithm (AARA); the energy efficiency prediction model will be used as the fitness function of Genetic Algorithm (GA), while association rules as chromosome constraints in GA. The proposed hybrid algorithm is thus called GBA-GA algorithm. The key operation parameters of central air conditioning system are optimized by GBA-GA algorithm and an ordinary GA algorithm respectively. The results show that the EER optimized by the GBA-GA algorithm is 2.16%-6.89% higher than that by the GA algorithm under different load rates.

Porcelain suspension insulators are required by utilities to perform regular evaluation on electrical and mechanical properties to ensure safety and reliability of overhead transmission lines in power grids. As an alternative to the conventional insulation resistance test, a novel microwave test method on offline insulator samples is proposed and studied by microwave network analysis, full-wave simulation and experiment. The test described is fast, effective and nondestructive. Hopefully, it can be used as a basis for an improved electrical testbench to ensure high insulation strength of porcelain suspension insulators.

In order to improve the accuracy and efficiency of the delivery inspection on polymeric insulators, a novel ultra-wideband multimode microwave (UWB-MMM) detection method is proposed. This technique makes use of the multimode transferring theory, where the transmission signal level difference can be employed to detect internal defects in an insulating mandrel. A typical millimeter-ordered defect is investigated by simulation and experiment, and 30∼50 dB and 60∼80 dB coupled multimode signal differences have been observed over 0∼8 GHz and 0∼6 GHz, respectively.

High-voltage porcelain insulator has higher permittivity and better electrical erosion resistance when compared with composite insulator, and has been widely used in 220-1000kV power transmission lines for years. In this paper, the three-dimensional finite-element method (FEM) models of insulator strings were built in parallel with the equivalent circuit models. Simulations have been carried out by both of the two methods, with respect to the potential and electric field distributions on the whole insulator string as well as the influence of the number of zero resistance insulators. This study is a stepping stone to the multi-physics simulation on porcelain insulator strings with multiple pieces of zero resistance insulators, which is necessary for the online fault diagnosis by thermal imaging technology.

Porcelain insulators are basic and important insulation components in UHV transmission lines, in which mechanical property deterioration poses serious threat to the operational stability of the power grid. In this paper, the mechanical characteristics of large-tonnage porcelain insulators under running load conditions are investigated. The coupling model of porcelain insulator string and transmission conductor is also established. The mechanical properties of stress and deformation of large tonnage insulator are calculated based on strong wind operation conditions. The results reveal that the steel cap and steel foot possess large stress level and plastic deformation, and the plastic deformation of steel cap is larger than steel foot. Hence, the steel cap is the component which is more easily to be damaged. Maximum tensile stress and stress gradient in porcelain piece can be found at the head region. High stress gradient induces local crack and expansion of the porcelain which cause potential damage of porcelain piece. An existing defect in proximity to the head region also accelerates the deterioration process. In this research, a theoretical basis for the design and manufacture of large tonnage porcelain insulator strings is provided.

A new edge detection operator based on dual parity morphological gradients is proposed, in order to accurately segment a porcelain insulator string in an infrared image before the identification and diagnosis of deteriorated insulators by the extracted thermal information. When applied to the double-shed insulators, the proposed detector is capable of effectively eliminating the blurred region between the upper and lower sheds as well as preventing over-segmentation by combining both odd and even structural elements. Compared with the multiscale morphological gradient algorithm, this technique reduces the size of the maximum structural elements to optimize the computational complexity. A quantitative evaluation using PSNR, IoU, and FPR indexes shows that the new technique outperforms other common edge detectors. In addition, the experiments on thousands of real infrared images demonstrate the detector to be highly effective despite its low complexity.

There is no essential difference in theory between the inner and outer insulating properties of cylindrical and conical head disc suspension porcelain insulators. Compared with a conical head porcelain insulator, a cylindrical head porcelain insulator is significantly lighter in weight, which can effectively reduce the mechanical load of the tower and wire; and it has better dispersion and adjustment capabilities for changes in material properties over time, so that the product is not subject to excessive and uneven stress over a long-term. In order to improve the mechanical performance of cylindrical head insulator products, this paper establishes a parameterized fine simulation model of the steel pin without changing the geometry of the insulator iron cap and porcelain body. The finite element method is used to calculate and analyze how the geometric parameters of the steel pin influence insulator mechanical properties, which can provide design reference for further product optimization.

In this work, in order to enhance the stability, bioavailability and antioxidant activity of insoluble antioxidants used into juice, yoghourt and nutritional supplements, the oligo-hyalurosomes nano-delivery system (CRHs) based on oligo-hyaluronic acid -curcumin (oHC) polymer loaded curcumin(Cur) and resveratrol (Res) was fabricated with new nanotechnolgy. The rosy biodegradable amphiphilic oHC polymer was successfully synthesized and used to fabricate the hyalurosomes containing both Cur and Res, called CRHs. The CRHs can spontaneously self-assemble into nano-sized spherical shape of average particle size 134.5±5.1nm and Zeta potential -29.4±1.2 at pH 7.4 PBS conditions. In vitro gastrointestinal release test showed a perfect stability and outstanding sustained release character. Moreover, compared to the single formulations and liposomes, CRHs showed a dose-dependent manner with a higher radical scavenging activity. Therefore, the novel CRHs nano-food manifested the hopeful properties for the new effective gastrointestinal formulation and promising new nano-food delivery system in the use of juice, yoghourt and nutritional supplements.

Regioselective reactions of methyl pyropheophorbide a (MPPa) with formaldehyde based on hydroxymethylation have been studied. It was found that MPPa can react regioselectively with formaldehyde under different conditions to produce a series of 3-dioxane, 12-, 132- or 20-hydroxymethyl and 12-/132-alkenyl-substituted chlorins via Prins reaction, Blanc chloromethylation and aldol reaction, respectively. The first examples of direct C–C bond formation at 12-position of chlorophyll derivatives were also reported to give a series of 12-vinyl-substituted chlorins. These chlorins showed extend Qy absorptions and efficient singlet oxygen generation property, indicating their potential as photosensitizers for application in photodynamic therapy.

The traditional therapy of cancer has systemic side effects, and many cancers, such as human breast cancer and lung cancer easily metastasize to bones, leading to the formation of secondary tumours. This study was aimed at enhancing the anti-tumour effect of curcumin (CUR) and preventing tumour spread to the bone. A novel multifunctional redox-responsive and CD44 receptor targeting polymer-drug, poly alendronate-hyaluronan-S-S-curcumin copolymer (ALN-oHA-S-S-CUR) based CUR and alendronate (ALN) were synthesized successfully with the disulphide bond linker. The structure of ALN-oHA-S-S-CUR was characterized by

Tandem reactions of methyl pyropheophorbide a with paraformaldehyde, reactive methylene compounds, and/or ammonium acetate provided novel pyrido[2,3-n]chlorophylls in good yields as the first examples of pyridine fused chlorophyll a derivatives, which displayed near-infrared absorptions (748–766 nm) with unusually broadened Q bands and small electrochemical HOMO-LUMO gaps (1.89–2.02 eV).

Molecularly imprinted polymers for strobilurin fungicides were prepared by precipitation polymerization employing azoxystrobin as template molecular together with methacrylic acid monomer and trimethylolpropane triacrylate cross-linker. Morphological characterization showed molecularly imprinted polymers were uniform spherical particles with about 0.2 μm in diameter, while the morphologies of nonimprinted polymers were irregular bulk. The equilibrium binding and selective experiments proved that molecularly imprinted polymers possessed a higher affinity toward four fungicides compared to nonimprinted polymers and heterogeneous binding sites were found in the molecularly imprinted polymers. Molecularly imprinted solid-phase extraction conditions, including sample loading solvents, selective washing, and elution solvents, were carefully optimized. The developed method showed good recoveries (70.0-114.0%) with relative standard deviations in range of 1.0-9.8% (n = 3) for samples (cucumber and peach) spiked at three different levels (10, 50, and 100 μg/ kg). The detection limit (signal/noise = 3) ranged from 0.01 to 0.08 μg/kg. The results demonstrated good potential use of this convenient and highly efficient method for determining trace strobilurin fungicides in agricultural products.

Nowadays polymeric insulators are widely applied, some internal defects could gradually appear due to various complex circumstances. In this paper, a novel ultra-wideband (UWB) antenna system for fault detection is presented. This technique makes use of the multi-mode transferring theory on dielectric waveguides, where the transmission signal level difference can be employed to detect internal defects in the insulating mandrel. An investigation by simulation is performed with regard to the interfacial mm-ordered cracks in transverse and longitudinal orientations, and approximately 20 ~ 30 dB and 20 ~ 40 dB differences have been observed over the same band 0 ~ 8 GHz, respectively.

To achieve online automatic monitoring of high voltage porcelain insulator strings by infrared thermography, it is essential to obtain the temperature information of the iron cap and disc. In order to accurately extract the temperature, this paper proposes a self-constructed convolutional neural network (CNN) for automatic identification of the iron cap and disk area in an infrared image. The sample set of the algorithm consists of insulator images from multiple substations in various regions, without loss of generality. After training, the network finally outputs four classifiers of iron caps, discs, aluminum fittings and cables. Then we use these classifiers to identify the corrected insulator string region image. Finally, we use different colors to identify the target area and extract the temperature of the area with in-house code. By evaluating the relative temperature difference between an individual insulator and its adjacent insulators, we can discriminate whether there is deterioration in the insulator string. The experimental results show that the self-constructed CNN can achieve excellent recognition results for insulator string iron caps and disc surfaces of different voltage levels.

It remains ongoing challenges in the design of printed wideband phase shifters, owing to strict requirements for the bandwidth, insertion loss, phase deviation and size in a variety of applications. In this paper, a wideband 90° differential phase shifter with circular open-circuited stubs is proposed. The transmission line model is used to analyze the circuits, and the full-wave simulation and parametric optimization are performed by CST in combination of Genetic Algorithm MATLAB routines. A phase shifter prototype is manufactured and validated by measurements, which exhibits an operating bandwidth of 90.1% from 2.5 GHz to 6.6 GHz for insertion loss 13 dB and a phase deviation of ±7°.

The uncertainty of electricity price, such as the volatility in the spot market and the influence of the peak-valley time-of-use (TOU) electricity price on the load, are important factors in the loss of risk of electricity purchase and sale to power sales companies (PSC). In order to evaluate the impact of the above two factors on the risk loss of the PSC, this paper establishes a function for measuring the conditional risk loss of PSC based on the conditional value at risk (CVaR) theory considering the peak-valley TOU price. The established model considers both the price volatility of the electricity purchase side and the implementation of the TOU price policy, the demand price elasticity is used to obtain power consumption during peak, flat and valley periods respectively. The proposed model has been verified by the case studies. The results show that the implementation of the peak-valley TOU price policy can effectively reduce the risk of PSC and increase their revenue, and PSC can choose the appropriate price spread ratio or quantity to purchase to avoid risk.

Response surface methodology was used to optimize the ultrasonic-assisted extraction conditions for aflatoxin B1 in peanuts. Box–Behnken center composite optimization was performed with factors including the ratio of sample to extractant, sonication time, and sonication temperature. Response surface methodology was used with three factors and three levels to determine the prime factors on the extraction of aflatoxin B1. High-performance liquid chromatography with fluorescence detector was used for the determination of aflatoxin B1. The optimum conditions were 1 g peanuts to 86 mL extractant, a sonication time of 7 min, and a temperature of 73°C. The mean recoveries in fortified peanuts were between 87.6 and 93.5% with an interday and intraday relative standard deviations below 10.6 and 9.8%, respectively. The developed method was accurate and precise for the determination of aflatoxin B1.

A novel ultrawideband directional flat dipole capped by a planar director is proposed in this letter. The novelty of the antenna is the great improvement of the bandwidth of a flat dipole above an ordinary finite ground plane by using a simple parasitic top patch, referred to as the "director." A linearly polarized prototype has been designed and manufactured, and achieved a nearly 3:1 operating bandwidth (2.2-6.5 GHz) with a return loss higher than 10 dB, nearly constant radiation patterns, and high aperture efficiency over the entire operating band.

In this study, the magnetic flower-like molybdenum disulfide hybrid materials (Fe3O4/MoS2) were successfully synthesized by in-situ fabrication method and utilized in the magnetic solid-phase extraction of organophosphorus pesticides. Fe3O4 nanoparticles with different loading amounts of MoS2 were evaluated and detail characterized. The results showed that MoS2 played a key role with rapid and high adsorption capacity towards organophosphorus pesticides. The higher extraction efficiency and good magnetic performance were obtained with loading amount of 200 mg MoS2. Fe3O4 was attached on the surface of MoS2 with flower-like shape (500 nm in diameter). The parameters (amounts of adsorbents, adsorption time, solution pH, elution solvents and sample volumes) affecting magnetic solid-phase extraction efficiency were optimized. Under the optimum conditions, magnetic solid-phase extraction coupled with high liquid chromatography-tandem mass spectrometry for analyzing organophosphorus pesticides in environmental water samples was established. All the analytes exhibited good recoveries spiked at three different concentration levels (10, 20, 50 ng/mL) in water samples. The relative standard deviations were between 1.4% and 6.8%. The developed method showed high sensitivity and good potential use of this convenient and high efficient method for determining organophosphorus pesticides. More importantly, this study can provide a new magnetic adsorbent with extremely fast mass transfer rate for other potential trace contaminants.

Split aptamers find growing interest as recognition elements for sandwich electrochemical sensors. Here, we report a convenient and highly sensitive sandwich electrochemical sensor based on a new conception of bivalent split aptamer signal probe, which is readily engineered through a simple hybridization of two identical monovalent split aptamers to a DNA template strand. Because of the bivalence cooperativity enhanced sandwich binding to target molecules, this type of DNA-scaffolded bivalent signal probe exhibits significantly increased signal gain for sandwich electrochemical detection of target analytes in comparison with the conventional monovalent signal probe. Through rational optimization of the length of anchor duplex in DNA scaffold and concentration of bivalent signal probe in electrochemical test solution, high signal sensitivity for ATP detection is achieved with a detection limit of 41 nM. The DNA-scaffolded bivalent signal probe based sandwich electrochemical sensor is also specific, selective and applicable for ATP detection in real samples. Due to its simplicity in design and high sensitivity for target recognition, we hope that the conception of DNA-scaffolded bivalent signal probe will provide a useful guide to further developing split aptamer-based sandwich electrochemical sensors for a wide variety of other target analytes.

With the development of the fifth generation (5G) communications, dual-polarization base station antennas have increasingly attracted a lot of attention. In this paper, a broadband high-efficiency dual-polarized capped bow-tie antenna array is presented. Simulation results show that the bandwidth of the proposed antenna is 24-36.8 GHz, with its return loss better than 10 dB and the stable coverage. The directivities vary from 8 to 12dBi and the relative cross-polar level is below −10dB over the most of band. It has a simple and compact structure, and is ready to be extended for large array antennas with massive MIMO performance used in 5G communications.

This letter presents a new directional dual-band slotted trapezoidal inverted-F antenna (IFA) for indoor Wireless Local Area Network (WLAN) applications. The dual-band performance can be obtained by tuning the lengths of the inner symmetrical trapezoidal slots and the outer trapezoidal arms in a nearly independent manner. The measured results show that the proposed antenna can provide two separate impedance bandwidths (return loss better than 10 dB) around 180MHz and 750MHz for 2.4/5.1-5.8 GHz WLAN bands, respectively. Good radiation performance and roughly constant in-band antenna directivities are also observed.

This paper presents a compact 0.92/2.45-GHz dual-band directional circularly polarized (CP) microstrip antenna for handheld radio-frequency identification (RFID) reader applications. The proposed antenna comprises a wideband dual-feed network and two stacked concentric patches assembled by two orthogonally placed vertical probes. The dual-feed network feeds quadrature signals across the RFID bands between 0.92 and 2.45 GHz. The two stacked concentric patches provide resonance frequencies in fundamental mode for lower band and higher band, respectively. Additionally, the antenna features only one connection port and same sense CP radiation at two bands, beneficial to cost and complexity reductions of the dual-band front end of RFID readers. The measurement results show the performances of return loss (RL) ${>} {10}\;{\text{dB}}$ , 3-dB gain variation, and axial ratio (AR) ${ are achieved on the bands 0.911–0.933 GHz and 2.40–2.57 GHz. The measured peak gains are 3.8 dBic at 0.926 GHz and 8.9 dBic at 2.48 GHz. In addition, the antenna provides symmetrical patterns with wide-angle half-power beamwidths and wide-angle 3-dB AR beamwidths. The size of the antenna ${\text{110}} \times {\text{110}} \times {\text{6}}.{6}\;{\text{m}}{{\text{m}}^{\text{3}}}$ is much smaller than reported dual-band one port RFID directional CP reader antennas. The antenna appropriates to both ultra-high frequency (UHF) and industrial scientific and medical (ISM) bands in handheld RFID reader applications.

A series of chlorophyll a-based chlorins conjugated with pyridyl or quinoxalyl group at different positions were synthesized, characterized and evaluated for their photodynamic effect in vitro. It was found that all the pyridyl and quinoxalyl chlorins showed promising photocytotoxicities but nontoxic without irradiation in HeLa cells, and the substituted types and positions had a significant influence on the photocytotoxicities of the chlorophyll a-based chlorins. All the chlorins with a pyridyl group at the C-D ring end exhibited relatively high photocytotoxicity as compared to those with 3(2)-pyridyl. Among them, compound 12 conjugated with a pyridyl group at its C12 position showed the best photodynamic effect in HeLa cells with an IC50 value of 0.033μM. These facts, associated with the relative high long wavelength absorptions of those chlorins may provide valuable ways to design and prepare promising photosensitizers for application in photodynamic therapy.

By taking advantage of a wideband bow-tie antenna in the Yagi configuration, a novel multilayer-stacked ultra-wideband (UWB) Yagi antenna is proposed. First, the fundamental 3-layered UWB Yagi model is studied with respect to a few critical dimensions. Then, several directors are added to form a multilayer-stacked Yagi antenna, where the width of the directors is optimized in a monotonic decreasing manner. A six-layered UWB Yagi antenna is studied by simulations. It covers 3.4–10.6 GHz with its return loss better than 10 dB, and it achieves a high directivity up to 13 dBi and a relative cross-polar level better than −10 dB in the whole band.

Electrochemical aptamer (EA) sensors based on aptamer-cDNA duplex probes (cDNA: complementary DNA) and target induced strand displacement (TISD) recognition are sensitive, selective and capable of detecting a wide variety of target analytes. While substantial research efforts have focused on engineering of new signaling mechanisms for the improvement of sensor sensitivity, little attention was paid to the enhancement of sensor response rate. Typically, the previous TISD based EA sensors exhibited relatively long response times larger than 30min, which mainly resulted from the suboptimal aptamer-cDNA probe structure in which most of aptamer bases were paired to the cDNA bases. In an effort to improve the response rate of this type of sensors, we report here the rational engineering of a quickly responsive and sensitive aptamer-cDNA probe by employing the conception of bivalent interaction in supramolecular chemistry. We design a bivalent cDNA strand through linking two short monovalent cDNA sequences, and it is simultaneously hybridized to two electrode-immobilized aptamer probes to form a bivalent binding (BB) aptamer-cDNA probe. This class of BB probe possesses the advantages of less aptamer bases paired to the cDNA bases for quick response rate and good structural stability for high sensor sensitivity. By use of the rationally designed BB aptamer-cDNA probe, a TISD based EA sensor against ATP with significantly enhanced response rate (with a displacement equilibrium time of 4min) and high sensitivity was successfully constructed. We believe that our BB probe conception will help guide future designs and applications of TISD based EA sensors.

A novel dummy molecularly imprinted polymers (DMIPs) for aminoglycoside antibiotics (AAs) was prepared for the first time by precipitation polymerization using raffinose as template molecule, methacrylic acid as functional monomer and trimethylolpropane triacrylate as cross-linker. The obtained DMIPs were characterized in detail, and their adsorbing and recognition performance were evaluated. The results showed that the DMIPs exhibited specific recognition towards six AAs with large adsorption capacity. The dummy molecularly imprinted solid phase extraction (DMISPE) conditions including elution/washing solutions and sample loading volumes were optimized. Under optimum conditions, a convenient and efficient method for the determination of AAs in environmental water samples based on DMISPE coupling with hydrophilic interaction-high performance liquid chromatography-tandem mass spectrometry was established. The developed method showed good linearity with correlation coefficients higher than 0.9921 for all the analytes and good recoveries (70.8–108.3%) with relative standard deviations from 2.6 to 11.4% spiked at three different concentration levels in water samples. The limit of detection (S/N = 3) ranged from 0.006 to 0.6 ng/mL. The results demonstrated good potential of DMIPs for sample pretreatment of trace AAs in environmental water samples.

Electrochemically reduced graphene oxide (ERGO) films find growing interest as voltammetric sensors for trace detection of electroactive analytes due to their easy preparation and unique electrochemical properties. Here, we demonstrate that the reduction extent of the ERGO film, is a crucial determinant of the concentration detection limits of such ERGO-based voltammetric sensors. To show this, we prepared a series of ERGO films with various reduction extents through electro-reduction at different reduction potentials, examined their background currents and electrocatalytic activities by using dopamine (DA) as a model analyte. Results showed that the background current response on the ERGO modified electrode monotonically increased with increasing reduction extent of the ERGO film, whereas the highest electrocatalytic activity towards the oxidation of DA was observed on the partially electrochemically reduced graphene oxide (pERGO) film. Because of its relatively low background current and high electrocatalytic activity, the pERGO modified electrode exhibited the lowest concentration detection limit for DA and a simple voltammetric sensing platform for trace detection of DA has been developed. These results highlight the important role of the reduction extent of ERGO film in determining the detection limits of ERGO film modified electrodes as voltammetric sensors. We believe that our findings could be also of value in the further developing ERGO-based sensors for trace voltammetric detection of other electroactive analytes.

A simple and compact directional dual-band semi-circular inverted-F antenna for wireless local area network applications is reported. Two pairs of semi-circular slots as well as a pair of arms are employed to generate the dual resonances in the 2.4-2.48 and 5.2-5.8 GHz bands. The measured results show that the proposed antenna can provide two 10 dB impedance bandwidths of 160 MHz (2.40-2.56 GHz) and 900 MHz (4.95-5.85 GHz). Nearly constant directivities (about 4.7 dBi) are observed in the lower band, while directivities in the upper band vary between 6.3 and 8.6 dBi.