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Low-cost yet high-efficiency oxygen evolution reaction (OER) catalysts have attracted ardent attention to speed up the development of water electrolysis. Recent researches have shown that layered double hydroxides (LDH) are promising candidates towards OER, but further improvement is still highly demanded for its large-scale practical application in water splitting. Herein, we report a 3D P-doped MoO3/FeCo LDH/NF (P–MoO3/FeCo LDH/NF) ultrathin nanosheet heterostructure electrocatalyst with an extremely low overpotentials of 225 mV for delivering a current density of 10 mA cm−2 for OER and a great durability for at least 80 h by a simple one-step hydrothermal method. Extraordinarily, the P–MoO3/FeCo LDH catalyst achieves a high current density of 300 mA cm−2 and even 350 mA cm−2 at an extremely low overpotential of 297 mV and 302 mV, respectively, which is crucial for the water electrolysis industry. The remarkable performance may be attributed to that the heterostructure between P–MoO3 and FeCo LDH not only optimizes electronic structure, thus inducing electron transfer from P–MoO3 to FeCo LDH and then realizing fast electron transfer rates, but also produces more catalytic active sites. Moreover, the synergetic effect between MoO3 and FeCo LDH also plays an essential role for enhancing the catalytic performances. This work explores the effect of phosphomolybdic acid on the structure, composition and performances of FeCo LDH catalysts, and also provides a simple and cost-effective way to prepare high-efficiency and low-cost layered double hydroxide electrocatalysts for OER.

NiFe LDH (layered double hydroxide) is currently attracting increasing attention as a type of promising electrocatalyst for oxygen evolution reaction (OERs); however, the biggest obstacle to its large-scale practical application is its poor conductivity and limited active sites. Herein, we report a three-dimensional NiFe LDH with high conductivity and dense active sites, where amorphous NiFe LDH nanosheets are directly electrodeposited on the surface of a hierarchical porous NiCoP@NC derived from the calcination and phosphorization of metal-organic frameworks (ZIF-67) in situ grown on nickel foam. Based on the 3D porous structure, abundant exposed active sites, fast electron and mass transfer rates and strong synergetic effects between NiCoP@NC and NiFe LDH, the resultant NiFe LDH/NiCoP@NC/NF catalysts exhibited significantly enhanced OER catalytic performances compared with NiFe LDH on nickel foam and most of the reported NiFe LDH-based catalysts: a low overpotential of 210 mV for yielding a current density of 10 mA cm-2, an extremely small Tafel slope (35 mV dec-1) and excellent durability. For overall water splitting, with NiFe LDH/NiCoP@NC/NF as the anode and NiCoP@NC/NF as the cathode, the assembled two-electrode system only required 1.54 V to obtain a stable current density of 10 mA cm-2 in 1 M KOH for at least 40 h. This research provided a simple and facile way to develop non-noble-metal oxygen evolution catalysts for replacing high-cost noble metal catalysts.

Herein, a novel label-free photoelectrochemical (PEC) sensing platform with near-zero background noise was developed for M.SssI CpG methyltransferase (M.SssI MTase) activity assay based on a new Schottky junction of Bi2S3/Ti3C2 nanosheets. The proposed PEC sensor exhibited a low detection limit and a high signal-to-noise ratio for M.SssI MTase assay.

Herein, 2D siloxene terminated by surface functional groups of Si-H and Si-OH is demonstrated to be an effective support for the spontaneous deposition of iridium nanoparticles (Ir NPs) to promote HER electrocatalysis. With ultra-low Ir loading, the obtained Ir NPs/siloxene electrocatalyst shows superior electrocatalytic activity toward the HER.

Herein, based on DNAzyme-induced disassembly of the "Z-scheme" TiO2/Au/CdS QDs system, a facile and sensitive photoelectrochemical biosensor was developed for lead ion assay and a low detection limit of 0.13 pM was obtained.

Here, based on a newly developed “Z-scheme” CdSe QD/afGQD heterojunction and multiple signal amplification strategies, a sensitive photoelectrochemical methyltransferase activity assay was carried out and a low detection limit of 0.046 U mL−1 was obtained.

The development of non-platinum catalysts for the oxygen reduction reaction (ORR) to substitute state-of-the-art but expensive Pt catalysts is essential for the development and practical application of fuel cells. Here, combining the self-assembly and coordination interaction between graphene oxide (GO) with g-C3N4 and iron phthalocyanine (FePc), FeNx atom clusters supported on three-dimensional porous nitrogen-enriched graphene carbon aerogels were successfully prepared by one facile solution method. The obtained FeNx atom cluster catalyst (FeNx-CN/g-GEL) exhibited superb catalytic performance (E1/2 = 0.90 V) toward the ORR, which is superior to that of commercial Pt/C (E1/2 = 0.835 V) and the currently reported non-noble nanocatalysts. Additionally, the catalyst displayed a high metal utilization rate with a mass specific activity of 840 mA mgFe−1 at 0.80 V, excellent long-term stability with only a little decline after the 28 000 s test and remarkable tolerance to methanol and SCN−.

In order to utilize the low-concentration gas directly discharged into the atmosphere from 1.1% to 1.50% in coal mine production, the heat storage and oxidation equipment of gas was improved, and the heat storage and safety of gas under high-temperature environment were tested. The experimental results show that the regenerative oxidation system could provide a high-temperature oxidation environment of 1000°C for gas oxidation after changing the heating mode and enhancing the sealing property. The pressure curves of air and gas in the burner were similar. With the increase of gas concentration, the pressure difference between inlet and outlet tended to increase linearly with a minimum pressure differential of 4 kPa (air) and a maximum pressure differential of 11 kPa (1.50% gas). The internal pressure was relatively stable without an instantaneous pressure surge or explosion. The result of this study provides a reference for further research on the low-concentration gas regeneration oxidation unit at high temperatures.

A modified Gilbert down-conversion mixer for 77-GHz automotive radar application is presented in this paper. By replacing the resistive loads with active loads composed of resistors and PMOSs, the output DC voltage becomes stabler, and the suppression of even-order components is improved. Fabricated in 40-nm CMOS technology, the proposed mixer occupies a core chip area of $0.25 \times 0.26$ mm2. The DC power consumption is only 1.5 mW with a 1-V supply. The measured maximum voltage conversion gain is 4.8 dB at LO frequency of 78.5 GHz and IF frequency of 20 MHz. The input 1-dB compression point is 0.8 dBm. Measured results also show that the reflection coefficient of the RF port is less than -11 dB from 74 to 83 GHz.

A nonwoven fabric adsorbent loaded with 2-ethylhexyl hydrogen-2-ethylhexylphosphonate (EHEP) was developed for the separation and recovery of dysprosium (Dy) and neodymium (Nd) from an aqueous solution. The adsorbent was prepared by the radiation-induced graft polymerization of a methacrylate monomer with a long alkyl chain onto a nonwoven fabric and the subsequent loading of EHEP by hydrophobic interaction and chain entanglement between the alkyl chains. The adsorbent was evaluated by batch and column tests with a Dy (III) and Nd (III) aqueous solution. In the batch tests, the adsorbent showed high Dy (III) adsorptivity close to 25.0 mg/g but low Nd (III) adsorptivity below 1.0 mg/g, indicating that the adsorbent had high selective adsorption. In particular, the octadecyl methacrylate (OMA)-adsorbent showed adsorption stability in repeated tests. In the column tests, the OMA-adsorbent was also stable and showed high Dy (III) adsorptivity and high selectivity in repeated adsorption&ndash, elution circle tests. This result suggested that the OMA-adsorbent may be a promising adsorbent for the separation and recovery of Dy (III) and Nd (III) ions.

Nitrogen doped porous carbon nanopolyhedra (N-PCNPs) were prepared from direct carbonization of ZIF-8 nanopolyhedra. The N-PCNPs showed uniform morphology, narrow pore-size distribution centered at 3.7 nm, high surface area (2221 m2 g−1) and good electrochemical properties and were used to modify a glassy carbon electrode to electrochemically detect ascorbic acid (AA), dopamine (DA) and uric acid (UA). Compared with the bare GC electrode and reduced graphene oxide modified glassy carbon (rGO/GC) electrode, the N-PCNPs modified GC electrode (N-PCNPs/GC) was found to perform better toward electrocatalytic oxidation of AA, DA and UA. For simultaneous sensing of three analytes, three well-separated voltammetry peaks were obtained using the N-PCNPs/GC electrode in differential pulse voltammetry measurements, and the corresponding peak separations between AA and DA, DA and UA were 228 mV, 124 mV respectively. The linear response ranges for the determination of AA, DA and UA were 80–2000 μM, 0.5–30 μM and 4–50 μM, respectively, and the detection limits (S/N = 3) were 740 nM, 11 nM and 21 nM, respectively. Furthermore, the N-PCNPs/GC electrode showed good reproducibility and stability. The attractive features of N-PCNPs provided potential applications in the simultaneous determination of UA, AA and DA.

In order to meet the application of the flexible wings of the submersible, nanocomposite hydrogels(NC gels) was prepared. Preparation of polyglycidyl methacrylate (PGMA) microspheres and correspondingly NC gels were reported. PGMA microspheres were prepared and modified by N-Methyl-D-glucamine, followed by free radical polymerization of acrylamide in the presence of microspheres to construct nanocomposite hydrogel. FT-IR, XPS and DLS verified a successful introduction of hydroxyl groups during modification. The effects of the particle size and content of the microspheres on the swelling properties of the composite hydrogels were investigated. Hydrogen bonds between hydroxyl groups and polyacrylamide molecular chains play important roles to the swelling property of NC gels. The intermolecular interaction and the crosslinking density were enhanced by the hydrogen bonds, and resultantly, swelling ratio of NC gels decreases.

To achieve efficient utilization of low-concentration mine gas, reduce resource waste, and alleviate environmental pollution, high-temperature oxidation of low-concentration gas at a concentration range of 1.00% to 1.50% that is directly discharged into the atmosphere during coal mine production was oxidized to recover heat for reuse. The gas oxidation equipment was improved for the heating process, and the safety of low-concentration gas oxidation under high-temperature environment was evaluated. Experimental results showed that the reactor could provide a 1000 ℃ high-temperature oxidation environment for gas oxidation after installing high-temperature resistant ceramics. The pressure variation curves of the reactor with air and different concentrations of gas were similar. Due to the thermal expansion, the air pressure slightly increased and then returned to normal pressure. In contrast, the low-concentration gas exhibited a stable pressure response in the high-temperature environment of 1000 ℃. The outlet pressure was significantly greater than the inlet pressure, and the pressure difference between the inlet and outlet exhibited a trend to increase with the gas concentration. The explosion limit varied with the temperature and the blend with oxidation products. The ratio of measured gas pressure to air pressure after oxidation was below the explosion criterion, indicating that the measured concentration gas is still safe after the shift of explosion limit, which provides a safe concentration range for efficient use of low-concentration gas in the future.

Microencapsulated phase change materials (MePCMs) based on swelling polymerization in Pickering emulsion were demonstrated. Monodisperse poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate) P(GMA-co-HEMA) particles were prepared by dispersion polymerization. The introduction of hydrophilic monomer HEMA endowed the obtained particles with suitable surface hydrophilicity for stabilizing Pickering emulsion. MePCMs with PGMA–polystyrene interpenetrating composite shell were formed when non-crosslinked particles were employed as stabilizer, while MePCMs with particles-embedded shell were prepared with crosslinked particles as Pickering stabilizer. Phase change property, thermal stability and thermal reliability of two kinds of MePCMs were investigated by TGA, FT-IR, DSC and cycling test. The temperature of 10% weight loss of MePCMs with interpenetrating shell was 11 °C higher than that of MePCMs with particles-embedded shell. After cycling test, the percentage of leached core materials from MePCMs with interpenetrating shell was approximately one-third of that from MePCMs with particles-embedded shell. The results showed that MePCMs with an integral shell presented better thermal stability, tightness and thermal reliability than MePCMs with particles-embedded shell. The research developed a simple process for MePCMs with excellent performance.

In this work, high-performance non-enzymatic catalysts based on 3D hierarchical hollow porous Co3O4 nanododecahedras in situ decorated on carbon nanotubes (3D Co3O4-HPND/CNTs) were successfully prepared via direct carbonizing metal-organic framework-67 in situ grown on carbon nanotubes. The morphology, microstructure, and composite of 3D Co3O4-HPND/CNTs were characterized by scanning electron microscopy, transmission electron microscopy, micropore and chemisorption analyzer, and X-ray diffraction. The electrochemical characterizations indicated that 3D Co3O4-HPND/CNTs present considerably catalytic activity toward glucose oxidation and could be promising for constructing high-performance electrochemical non-enzymatic glucose sensors and glucose/O2 biofuel cell. When used for non-enzymatic glucose detection, the 3D Co3O4-HPND/CNTs modified glassy carbon electrode (3D Co3O4-HPND/CNTs/GCE) exhibited excellent analytical performance with high sensitivity (22.21 mA mM−1 cm−2), low detection limit of 0.35 μM (S/N = 3), fast response (less than 5 s) and good stability. On the other hand, when the 3D Co3O4-HPND/CNTs/GCE worked as an anode of a biofuel cell, a maximum power density of 210 μW cm−2 at 0.15 V could be obtained, and the open circuit potential was 0.68 V. The attractive 3D hierarchical porous structural features, the large surface area, and the excellent conductivity based on the continuous and effective electron transport network in 3D Co3O4-HPND/CNTs endow 3D Co3O4-HPND/CNTs with the enhanced electrochemical performance and promising applications in electrochemical sensing, biofuel cell, and other energy storage and conversion devices such as supercapacitor.

Herein, a photocurrent polarity switching platform for highly selective assay of mucin 1 (MUC1) was developed based on target-induced hemin transfer from ZrO2 hollow spheres (ZrO2 HSs) to G-quadruplex nanowires (G wires). In this system, SiO2 spheres were used as templates to synthesize the uniform and mesoporous ZrO2 HSs. As nanocontainers, ZrO2 HSs could load hemin in its cavity via pores. Then, the aptamers of MUC1, as bio-gates, blocked the pores of ZrO2 HSs based on the specific binding of Zr4+ and the phosphate groups of aptamer. In the presence of MUC1, the aptamer could specifically recognize and bind with MUC1, and then leave away from the surface of ZrO2 HSs, which resulted in the opening of the bio-gates and releasing of hemin. Assisted with the G wires formed on the Au NPs/In2S3/ITO, the released hemin was captured on the electrode through the formation of hemin/G-quadruplex structure, leading to the switch of the photocurrent polarity of the electrode from anodic photocurrent to cathodic photocurrent. The proposed photoelectrochemical biosensor showed outstanding performance for MUC1 assay with high selectivity, wide linear response range (1 fg mL−1 -10 ng mL−1) and lower detection limit (0.48 fg mL−1). And the strategy could be easily extended to a triple-mode detection of MUC1 because the hemin/G-quadruplex structure was widely used in electrochemical and colorimetric methods as a hydrogen peroxide mimetic enzyme, which might provide wide applications in biological or clinical studies.

High-performance supercapacitors as the promising energy storage devices have attracted considerable research interests, due to the apparent merits of high power density, fast charge/discharge, and long lifetime. However, their further practical applications are still greatly hindered by the limited energy density, as well as low capacitance, inferior rate capability and poor cycling performance of the electrode materials. Herein, three-dimensional (3D) hierarchical NiCoP@CoS tree-like core-shell nanoarrays (NAs) on nickel foam (NF) are obtained with the vertically grown NiCoP nanowires as core via phosphorization of NiCo2O4 nanowires arrays, and the subsequently electrodeposited CoS nanosheets as shell. The 3D hierarchical tree-like core-shell nanoarrays take advantages of one-dimensional (1D) core as “hyperchannel” for electron transfer, coupling with two-dimensional (2D) vertical shell for fast ion diffusion meanwhile enhancement of cycling stability. The proposed NiCoP@CoS NAs/NF electrode exhibits superior battery-type electrochemical supercapacitor performance via the synergy of NiCoP nanowires and CoS nanosheets, which delivers a high specific capacitance of 1796 F g−1 at 2 A g−1, outstanding rate capability and good cycling stability with high capacitance retention of 91.4% after 5000 cycles even at 10 A g−1. Furthermore, the asymmetric supercapacitor assembled by NiCoP@CoS NAs/NF and activated carbon achieves a high energy density (35.8 Wh kg−1) at a power density of 748.9 W kg−1. The as-fabricated NiCoP@CoS tree-like core-shell nanoarrays hold great promise as novel battery-type electrodes for high-performance supercapacitor applications.

The recently emerging renewable energy industry has boosted a research hot in searching for bifunctional electrocatalysts for water splitting. CoSe2, as one of transition-metal chalcogenides, has attracted particular attention because of its abundant resource, low cost, high efficiency and stability. However, further enhancing catalytic activity of CoSe2 to meet the large-scale application requirements of hydrogen energy remains an important challenge. Herein, three-dimension (3D) Mo-doped porous CoSe2 nanosheet array was directly formed on commercial Ni foam (Mo-CoSe2 NS@NF) electrode through a three-step process including electrodeposition, hydrothermal and subsequent selenylation. Systematically experimental research and density functional theory calculations confirmed that, based on active site and intermediate modulation effect of Mo doping, the obtained 3D Mo-CoSe2 NS@NF electrodes were provided with enlarged electrochemical active surface area, improved charge transport capability and significantly optimized binding energy for active intermediates of the potential-limiting step, thus exhibiting remarkably boosted bifunctional electrocatalytic ability with a low overpotential of 89 and 234 mV to drive a current density of 10 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, respectively. When the Mo-CoSe2 NS@NF electrode was employed as both a cathode and an anode, an advanced water electrolyzer was fabricated, and a 10 mA cm−2 water splitting current density in 1 M KOH solution could be acquired at a minimal cell voltage of 1.54 V. In addition, we also inferred that the active surface for the OER was O* covered CoSe2, and OER occurred through direct recombination mechanism according to the present first-principles simulation. This work offers an atomistic understanding on the boosted HER and OER electrocatalytical activity of CoSe2 by Mo doping, and develops a promising strategy for exploring advanced low-cost and earth-abundant water splitting electrocatalysts to substitute for the precious-metallic catalysts as well.

The hydrogen evolution reaction (HER) activity in alkaline condition is generally suppressed due to sluggish water dissociation–related Volmer process. Consequently, developing new highly-active and cost-efficient electrocatalysts for the alkaline hydrogen production is greatly desirable for achieving sustainable water splitting in industrial plants. Pyrite-type RuS2 is a potential excellent electrocatalyst for alkaline HER but the related research is still in its infancy. Herein, well-dispersed crystalline RuS2 nanoparticles (c-RuS2 NPs) with ultrasmall particle size anchored on porous nitrogen and sulfur co-doped hollow carbon spheres (NSC) are synthesized for alkaline HER electrocatalysis. The conductive and porous hollow carbon spheres with nitrogen and sulfur doping is used as the effective support to provide abundant anchoring sites and modify the electronic structure of RuS2, beneficial to increasing the active sites and improving the intrinsic activity. Furthermore, the crystallinity modulation of ruthenium sulfide also has a significant impact on HER activity. In 1.0 M KOH solution, the proposed c-RuS2 NPs/NSC catalyst exhibits admirable activity for HER electrocatalysis with a low overpotential of 11 mV at a current density of 10 mA cm−2 and a small Tafel slope of 35.4 mV dec−1. With low Ru loading, superior hydrogen evolution in alkaline media is achieved for c-RuS2 NPs/NSC compared to the commercial Pt/C and the reported ruthenium-sulfide-based electrocatalysts.

Herein, novel photoactive materials, nitrogen-doped porous carbon-ZnO (NPC-ZnO) nanopolyhedra, were prepared by direct carbonization of zeolitic imidazolate framework (ZIF)-8 nanopolyhedra in a nitrogen atmosphere. The morphology, structure, and photoelectrochemical (PEC) properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, nitrogen adsorption–desorption method, and PEC methods. The results showed that the obtained NPC-ZnO nanopolyhedra had a rhombic dodecahedron morphology with uniform particle size of about 100 nm and a high surface area of 609.2 m2 g–1. Under visible-light irradiation, the NPC-ZnO nanopolyhedra showed better PEC performance than ZnO nanorod and the ZIF-8 nanopolyhedra in aqueous media with dissolved oxygen and ascorbic acid. Taking alkaline phosphatase (ALP) as a model, a NPC-ZnO nanopolyhedra-based PEC sensor was developed and showed good performance for ALP assay with a wide linear respo...

Double metal phosphide (NiCoP) with hollow quasi-polyhedron structure was prepared by acidic etching and precipitation of ZIF-67 polyhedra and further phosphorization treatment with NaH2PO2. The morphology and microstructure of NiCoP quasi-polyhedron and its precursors were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and a micropore and chemisorption analyzer. Electrocatalytic properties were examined by typical electrochemical methods, such as linear sweep voltammetry, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy in 1.0 M KOH aqueous solution. Results reveal that, compared with CoP hollow polyhedra, NiCoP hollow quasi-polyhedra exhibit better electrochemical properties for hydrogen evolution with a low onset overpotential of 74 mV and a small Tafel slope of 42 mV dec–1. When the current density is 10 mA cm–2, the corresponding overpotential is merely 124 mV, and 93% of its electrocatalytic activity can be maintain...

This paper presents an analytical model of the electromagnetic vibration and noise for a High Speed Amorphous Alloy Permanent Magnet Synchronous Motor (HSAAPMSM) whose stator cores are made from amorphous alloy magnetic material. Firstly, air gap flux density of HSAAPMSM with different slot width is calculated by two methods of Finite Element Analysis (FEA) and analytical. By comparison, accuracy of the modeling is validated. Then, through the finite element coupling analysis, the electromagnetic force acting on the surface of the stator teeth is obtained. In addition, the space harmonic analysis of air gap flux density and electromagnetic force is carried out. The electromagnetic vibration and noise of HSAAPMSM with different slot width are calculated respectively and the influence of laminating effect is taken into account.

Herein, a novel photoelectrochemical (PEC) sensing platform was developed based on target-induced switching from indirect Z-scheme NPC-ZnO/Au/CdS to direct Z-scheme CdS/hemin systems accompanied by the photocurrent-polarity switching from cathodic to anodic photocurrents. The developed PEC sensor exhibited excellent selectivity and high sensitivity.

Ternary NiCo2O4 has attracted tremendous interest as a type of prospective electrochemical energy storage material. Hence, a facile and economical preparation method for N-doped carbon-coated NiCo2...

Platinum is the most active and commonly used electrocatalyst for hydrogen evolution reaction (HER). However, its expensive price and scarce supply limit its world-wide use for mass production of H2 by water electrolysis. Promising candidates for high-performance hydrogen evolution reaction with exceptionally low Pt loading are urgently required to obtain clean and sustainable chemical fuels. Herein, yolk-shell Pt-CoP polyhedra were prepared to realize low Pt loading on low-cost CoP polyhedral substrates via low-temperature calcination and phosphorization of ZIF-67 combined with a subsequent microwave-assisted platinum reduction process. Owing to the unique yolk-shell structure, large surface area, numerous active sites, trace Pt modification and improved conductivity, the resultant catalyst exhibits highly efficient electrocatalytic activities for the HER with the low overpotentials of only 48 mV and 88 mV at 10 mA cm-2 and excellent stability in the 1 M KOH and 1 M PBS solution, superior to most of the newly reported noble metal-based or transition metal-based catalysts, even the state-of-art Pt/C catalysts.

Highly stretchable silica/polyacrylamide (PAM) nanocomposite hydrogels were synthesized via in situ free radical polymerization in the presence of silica nanoparticles. The effect of particle size and content of silica nanoparticles on tensile properties and swelling behavior were investigated. The hydrogen bond between PAM molecule and silica nanoparticles was evidenced by Fourier transform infrared spectroscopy and the swelling behavior of hydrogels. The tensile strength of silica/PAM hydrogels is 2 times that of PAM gels, and the elongation at break is nearly 2800% when the silica particle size is 15 nm and the content is 10 wt%. This excellent stretching property of hydrogels was ascribed to the presence of hydrogen bond between PAM molecule and silica nanoparticles.

Herein, a new photoelectrochemical (PEC) biosensor based on a photocurrent direction switching system and target-triggered strand displacement amplification strategy was developed for the sensitive detection of microRNA (miRNA)-155, and it showed excellent selectivity and a low detection limit of about 49 aM.

The input-output ratio and comprehensive energy consumption of low concentration coalbed methane cryogenic liquefaction devices are determined by the process parameters in control of the distillation column. In order to accurately control the actual operation process of the distillation column, the effect of the operating temperature of the distillation column on the liquefaction performance of a cold box was studied experimentally, and the optimal control parameters of the distillation column were obtained. The results show that the recovery rate of methane decreases with the increase in temperature at the top of the distillation column, and when this temperature is higher than −178 °C, the methane recovery rate drops sharply to below 90%. When the temperature at the bottom of the distillation column rises from −154 °C to −142.7 °C, the purity of LNG products is improved, and when this temperature is increased to −143.5 °C, the purity of products at the bottom of the distillation column reaches the standard, and can be stored safely. In actual operation, the evaporation temperature at the bottom of the column should not be higher than −140 °C. In the process of industrial plant design, measures should be taken to reduce the interaction of the temperature regulation at the top and bottom of the distillation column. When selecting the refrigerant circulation compressor, the leakage of the refrigerant should be considered to maintain the operating pressure of the refrigeration cycle.

In order to solve the impact of actual construction projects on the existing surrounding environment, the impact and vibration of the impact on the existing railway subgrade stability caused by the construction of the bridge foundation are analyzed. Based on the actual case of the construction project of No. 37 main pier across the Jiaoji Railway Main Bridge at Binlai expressway, the influence of the impact holing on the adjacent railway is analyzed. The influence range of the construction vibration is based on the Chinese Seismic Intensity Scale (GB/T 17742-2008) and Safety Regulations for Blasting (GB6722-2014), and taking the maximum velocity allowable value as criterion, the minimum safety range of impact drilling is obtained. Using the theory of small hole expansion to calculate the influence of the effect of soil compaction, the minimum allowable value of safe distance for the Construction technology of impact forming hole is considered 6.5m; in addition, based on the numerical simulation of nonlinear time history analysis, a reasonable exciting force parameter is given for practical engineering. The influence of impact amplitude A and impact frequency f on construction safety distance is analyzed. The results show that: The minimum safety distance of impact drilling is linear with the increase of impact amplitude A. When the impact frequency f is greater than 10Hz, the minimum safety distance tends to a fixed value as f increases. The results of this study guide the actual construction of the field, it guarantees the normal traffic of the Jiaoji Railway and provides a theoretical support for similar projects.

Owing to the hydrophobic inner cavity and hydrophilic exterior of cyclodextrins (CDs), CDs molecules could exhibit excellent properties in water solubility, molecular recognition and enrichment capability, and CDs-based materials attracted considerable attentions in electrochemical sensing. This review shows the unique advantages and detecting mechanism of electrochemical sensors based on CDs functionalized materials, and recent advances for CDs-based materials (including CDs/carbon nanotubes, CDs/graphene, CDs/conducting polymers and other CDs-based nanomaterials) in electrochemical sensing. Finally, we also discussed some critical challenges and prospects in this field.

In this communication, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) funtionalized graphene nanoribbons (HP-β-CD/GNRs) were prepared for the first time by using a simple wet chemical strategy, and then, the HP-β-CD/GNRs were applied for constructing electrochemical sensors for three representative analytes (p-aminophenol, p-AP; l-tyrosine, Tyr; rhodamine B, RhB). Owing to the synergetic effects of GNRs (excellent electrochemical properties and large surface area) and HP-β-CD (high host–guest recognition and enrichment capability), the highly sensitive electrochemical sensing platforms of three analytes were established by using HP-β-CD/GNRs modified electrode, and the detection limits were 0.0008, 0.003, and 0.001 μM for p-AP, Tyr, and RhB, respectively. Keywords: Graphene nanoribbon, Cyclodextrin, Electrochemical sensor, p-Aminophenol, l-Tyrosine, Rhodamine B

The electrochemical properties of graphene-based supercapacitor electrode materials are closely related to their architecture and chemical nature. Herein, the siloxene-reduced graphene oxide composite hydrogel (SGH) with modified three-dimensional (3D) hierarchical architecture and increased oxygen-containing functional groups are developed via intercalating small amount of layered siloxene between the reduced graphene oxide sheets by a one-step hydrothermal process. Siloxene serves as the “spacers” to form a three-dimensional structure with graphene, resulting in increased specific surface area. More importantly, siloxene is used to modify the surface chemical nature of graphene sheets by introducing additional oxygen-containing functional groups. The abundant oxygen-containing functional groups on SGH contribute to the pseudocapacitance and improve the wettability. Consequently, the proposed SGH exhibits a high specific capacitance of 520 F g−1 at 1 A g−1 in a three-electrode system in 1 M H2SO4 electrolyte, which can be maintained for 76.9% even as the discharging current density increases up to 100 A g−1. Moreover, excellent stability is achieved for SGH with approximately 96.3% retention of the initial specific capacitance value after 15,000 cycles at a high current density of 50 A g−1. Furthermore, the assembled symmetrical supercapacitor of SGH//SGH delivers a high energy density of 24.5 Wh kg−1 at the power density of 399.6 W kg−1. These imply that the siloxene-reduced graphene oxide composite hydrogel may be a promising electrode material for high-performance supercapacitors.

Depended on the target-induced formation of a DNA-linked CdSe quantum dots/amino-functionalized graphene quantum dots (denoted as CdSe QDs/AGQDs) “Z-scheme” system, an ultrasensitive and highly selective PEC sensing platform has been constructed for DNA assay. Firstly, the indium tin oxide (ITO) electrode was modified with the poly(diallyldimethylammonium chloride) (PDDA)-decorated reduced graphene oxide (PDDA-rGO) to fix and disperse CdSe QDs. The obtained ITO/PDDA-rGO/CdSe QDs electrode generated an anode photocurrent. After catalytic hairpin assembly (CHA) and hybridization chain reaction (HCR) processes triggered by target DNA (T-DNA), abundant and long double-strand DNA (dsDNA) were introduced to the sensing platform. And then, numerous AGQDs were intercalated into the dsDNA strands, resulting in the formation of DNA-linked CdSe QDs/AGQDs “Z-scheme” system and the change of the response signal from anodic to cathode photocurrents. Because of the negative background signal and DNA-based amplification strategy, T-DNA was detected sensitively (linear range, 1 aM - 100 pM; detectable limit, 0.1 aM). Importantly, the developed PEC sensing platform can avoid the effects of the initial signal and background noise, and has the enhanced sensitivity and anti-interference ability, which make it may have promising application in bioanalysis and disease diagnosis.

Searching for efficient and durable electrocatalysts toward hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) is highly desirable for the development of sustainable energy conversion technologies, but still remains a great challenge. Here, high-dispersed Rh nanoparticles are successfully encapsulated in the pores of N-doped porous carbon polyhedrons (NPCP) derived from ZIF-8 to avoid their aggregation and detachment, which makes the electrocatalyst (Rh@NPCP) have high activity and good stability. With an accepted metal loading (9.84 wt% Rh), Rh@NPCP exhibits excellent activity for HER electrocatalysis with ultralow overpotentials of 20, 23 and 45 mV to reach a current density of 10 mA cm−2 in alkaline, acidic and neutral media. Besides, remarkable ORR electrocatalytic activity with a half-wave potential of 0.84 V in alkaline media is achieved. Compared to the commercial Pt/C catalyst (20 wt% Pt), the prepared Rh@NPCP catalyst demonstrates significantly superior electrocatalytic performance toward pH-universal HER and alkaline ORR, especially in stability. This work provides a highly efficient, durable and affordable electrocatalyst for HER and ORR, which may have practical applications in water splitting and fuel cells.

Taking beta-cyclodextrin (β-CD) as reducting agent and dispersant, PtRh nanoparticles with varied metal composition were uniformly deposited on the β-CD functionalized carbon nanotubes (β-CD-CNTs) by one-pot hydrothermal synthesis method. Fourier transform infrared spectroscopy and thermogravimetric analysis were used to demonstrate the successful modification of CNTs with β-CD. The morphology, chemical composition and structure of the β-CD-CNTs supported PtRh catalysts (PtRh/β-CD-CNTs) have been characterized by transmission electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy, respectively. Their electrochemical performances were investigated by typical electrochemical technologies. The results indicate that PtRh/β-CD-CNTs catalyst with 1:1 atomic ratio of Pt/Rh (Pt1Rh1/β-CD-CNTs) shows superior electrocatalytic properties towards methanol oxidation. In addition, compared with the acid-treatment CNTs (AO-CNTs) supported PtRh nanoparticles (PtRh/AO-CNTs) prepared by typical NaBH4 reduction, Pt1Rh1/β-CD-CNTs exhibits more excellent electrocatalytic performance for methanol electro-oxidation due to the smaller particle size and more uniform deposition of PtRh nanoparticles.

Nitrogen-doped porous carbon micropolyhedra (N-PCMPs) were successfully prepared by direct carbonization of ZIF-11 polyhedra and further activated with fused KOH to obtain N-PCMPs-A. The morphology and microstructure of samples were examined by scanning electron microscopy, X-ray diffraction, and micropore and chemisorption analyzer. Electrochemical properties were characterized by cyclic voltammetry and galvanostatic charge/discharge method in 1.0 M H 2 SO 4 aqueous solution on a standard three-electrode system. Results show that, compared with N-PCMPs, N-PCMPs-A has higher specific surface area (2188 m 2 g −1 ) and exhibits improved electrochemical capacitive properties (307 F g −1 at 1.0 A g −1 ). The mass specific capacitance of N-PCMPs-A is also higher than that of most MOF-derived carbons, some carbide-derived carbons and carbon aerogel-derived carbons. In addition, the capacitance of the N-PCMPs-A retains 90% after 4000 cycles even at a high current density of 10 A g −1 . These imply that N-PCMPs-A is the promising materials for the construction of a high-performance supercapacitor.

Taking phenylboronic acid as a boron source and ZIF-11 as a carbon template, boron and nitrogen co-doped porous carbon polyhedra (BN-PCPs) were prepared through a simple procedure for the first time. The as-prepared BN-PCPs were characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and typical electrochemical methods. The results show that the developed BN-PCPs possess 10.68 atom% B and 8.1 atom% N with uniform distribution, and excellent electrochemical capacitive properties with high specific capacitance of 262 F g−1 at 20 mV s−1 in 1.0 M H2SO4 aqueous solution and excellent long-term charge–discharge stability (no obvious degradation during 40 000 charge–discharge cycles at 20 A g−1).

Platinum nanoparticles (Pt NPs) encapsulated in nitrogen-doped mesoporous carbons (NMCs) are prepared by direct carbonization of zeolitic imidazolate framework-8 (ZIF-8)-encapsulated Pt NPs, and used as a methanol-tolerant oxygen reduction electrocatalyst. ZIF-8 is used as the carbon and nitrogen precursors and as a matrix for Pt NPs. The obtained Pt NP–NMC hybrids are characterized in detail. The results show that the Pt NP–NMC hybrids possess high surface area (1226 m2 g−1), abundant mesopores with narrow pore size distribution (centered at 3.9 nm), nitrogen doping (5.13 at %), and small and well-dispersed encapsulated Pt NPs (3.7 nm). Furthermore, the prepared Pt NP–NMC catalyst exhibits high electrocatalytic activity, high stability and excellent methanol tolerance in the oxygen reduction reaction.

Because of its advantages such as large power density, small size and high efficiency, high-speed machine has been widely used in aerospace, industrial production and other fields. However, it is easy to cause irreversible permanent magnet demagnetization because of high density and difficult heat dissipation. In view of the above problems, the fluid field simulations of two ventilation systems are carried out, and a detailed fluid field analysis is carried out for the better middle ventilation system. High-speed permanent magnet machine rotor surface speed is very fast, resulting in the friction of the air can not be ignored. But its numerical value is related to many factors, such as machine speed, ventilation system, inlet wind velocity and surface roughness of the rotor. It is difficult to calculate accurately by analytic method. We simulated the 3D fluid model of rotor air friction loss and many factors influence on the high-speed permanent magnet machine is analyzed, and summarizes the corresponding high-speed permanent magnet machine rotor air friction loss law.

Reversible addition-fragmentation chain transfer (RAFT) agent was added into a simultaneous radiation grafting system and its effects on graft polymerization and homopolymerization were investigated. Chloromethylstyrene (CMS) was graft polymerized onto ethylene-tetrafluoroethylene copolymer (ETFE) films under γ-ray sources via simultaneous irradiation. The non-grafted poly(CMS) in the grafted films were extracted by xylene at 120 °C. The poly(CMS) was characterized by NMR and GPC instruments. Addition of the RAFT agent suppressed both graft polymerization and homopolymerization. However, under a high concentration of RAFT agent, the homopolymerization in the monomer solution could occur through a typical RAFT polymerization while polymerization in the ETFE films proceeded via RAFT and conventional radical polymerization, resulting in poly(CMS) in the ETFE films with molecular weight dispersity higher than 1.0 but lower than that without RAFT agent. Furthermore, it was found that the molecular weight of the poly(CMS) in the ETFE films was several times higher than that of the poly(CMS) in the monomer solution.

In this work, filter paper-based SERS substrate was fabricated by soaking the filter paper with concentrated silver colloids, and the time-dependent silver nanoparticles (AgNPs) distribution on filter paper were characterized in detail. SERS spectra of seminal plasma over different soaking time were obtained to optimize the performance for potential application. Our results showed that a more uniform distribution of AgNPs on the surface of filter paper was achieved with the increase of soaking time, and optimum SERS spectra of seminal plasma can be achieved at 12h. Filter paper-based SERS substrate can provide a simple and powerful platform for sensitive and reproducible Raman analysis of seminal plasma as well as other kinds of human body fluids.

Based on the ultrasonic cavitation assisted hydrogen implosion method, Pt nanoparticles (NPs)/nitrogen-doped graphene nanohybrid scrolls (Pt NPs/N-GNSs) were synthesized. As the results of the N-doping and high reduction degree of graphene, and scroll structure of the nanohybrids, the Pt NPs/N-GNSs electrocatalyst shows excellent performance in the direct oxidation of methanol: low onset and peak potentials, high oxidation current, and good long-term cycle stability. The Pt NPs/N-GNSs should have great promising applications in heterogeneous catalysis and fuel cells.

Summary Signal amplification strategies have attracted considerable attention due to the growing demands for ultrasensitive bioassays. Here, we summarize the latest developments in the application of nanomaterials as signal amplification elements in ultrasensitive DNA-based electrochemical detection. Various nanomaterials with different signal amplification routes have been reviewed briefly.

This paper investigates the influences of the initial temperature on the performance of free piston linear generator (FPLG). Based on multi-dimensional combustion model, the effects of initial temperature on in-cylinder pressure, in-cylinder temperature and NO x emissions are studied. The cause of NO x in internal combustion engine is introduced and the NO x formation mechanism of gasoline FPLG is explored. It is found that reducing initial temperature can rapidly increase in-cylinder pressure, including transient pressure, peak pressure and the maximum pressure rising rate. However, the in-cylinder temperature linearly rises up with the increasing initial temperature. And the NO x emissions increases accordingly. In order to improve output power and reduce emissions, it is feasible to decrease initial temperature properly.

This paper is aimed at studying the breakdown voltage and minimum ignition energy of sparking system for the free-piston linear generator (FPLG). Combing the ignition characteristics and demands specifically for the FPLG system, the breakdown voltage and conduction duration of the primary coil are determined theoretically with the Townsend and Paschen Laws. A computational fluid dynamics (CFD) mode is developed to investigate the in-cylinder pressure and temperature at various igniting moments. The theoretical minimum ignition energy is determined with the laminar combustion theory, which contributes to the design and optimization of the sparking system. The effects of the ignition points and initial in-cylinder temperature on the breakdown voltage and minimum ignition energy are analyzed. The results show that advanced ignition contributes to decreasing the breakdown voltage and the conduction duration of the primary coil, meanwhile has no negative influence on the minimum ignition energy. However, rising initial in-cylinder temperature lowers the breakdown voltage, shortens the conduction duration of the primary coil and reduces the minimum ignition energy.

Nitrogen-doped hollow carbon spheres (N-HCS) with uniform size have been synthesized via the hydrothermal method using pyrrole as the precursor. After carbonization at 850 °C, the average diameter of N-HCS is ca. 370 nm with shell thickness of ∼15 nm. The electrochemical capacitive behavior of N-HCS was investigated by cyclic voltammetry and galvanostatic charge–discharge method in 1.0 M H 2 SO 4 aqueous solution. Results show that N-HCS have high specific capacitance (345.2 F g −1 at 0.2 A g −1 ) and high-rate capability with the increase of the scan rate from 10 to 1000 mV s −1 due to the synergetic effects of the unique hollow nanostructure and the N-doped thin carbon shell. In addition, the capacitance retains 98.1% after 1500 cycles even at a high loading current density of 10 A g −1 .

Polythiophene (PTh) was electropolymerized onto multi-walled carbon nanotubes (MWCNT) modified glassy carbon (GC) electrode in ionic liquid bmimPF6 solution successfully. The different electrochemical behavior of thiophene in bmimPF6 solution was studied by cyclic voltammetry. The different morphologies of PTh films on MWCNT/GC and GC electrodes were characterized by scanning electron microscopy. Cyclic voltammetry test displays that PTh/MWCNT composites have better capacitive property than pure MWCNT and pure PTh. The galvanostatic charge–discharge and electrochemical impedance microscopy tests show that the PTh/MWCNT composites possess good capacitive characteristics. The specific capacitance of the supercapacitor is 110 F g−1. The long-term stability of the supercapacitor was also tested, and the result indicates that the specific capacitance still keeps 90% of the initial capacitance after 1000 consecutive charge–discharge cycles.

The direct electropolymerization of pyrrole in [BMIM]PF6 microemulsion was investigated for the first time. The H2O/TX-100/[BMIM]PF6 (W/IL), bicontinuous (BC), [BMIM]PF6/TX-100/H2O (IL/W) subregions can be used as electrolytes for pyrrole electropolymerization. The use of IL microemulsion remarkably reduces the amount of IL. Furthermore, electrochemical measurements indicated that W/IL microemulsion was the optimal medium and its polymerization rate was the fastest. Compared with molecular solvent system (0.25 mol L−1 [BMIM]PF6/acetonitrile) and neat [BMIM]PF6, the resultant films electrodeposited in W/IL microemulsion possessed excellent electrochemical activity and uniform morphology. All the results indicated that the H2O/TX-100/[BMIM]PF6 microemulsion as electrolyte medium is the most suitable for electropolymerization of pyrrole. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012