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Chloride-based accelerators are widely used to accelerate cement hydration; however, there is no focus on the effect of the interaction between Cl− and SO42− on cement hydration. Hence, the interaction effect between initial gypsum and sodium chloride (NaCl) in the cement hydration process was investigated. Isothermal calorimetry, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction and inductively coupled plasma spectroscopy were used to evaluate the hydration process of cement paste. Moreover, a thermodynamic model and boundary nucleation and a growth model were applied to calculate the hydration products and describe the hydration process, respectively. It is clear that sodium chloride can accelerate cement hydration, but as the incorporated sodium chloride increases, the acceleration effect is weakened. The incorporation of chloride salts will promote the dissolution of minerals and increase the growth rate. In the early stage of hydration, the formation of ettringite precedes formation of Friedel's salt, owing to the fact that tricalcium aluminate (C3A) favours binding with SO42−, which can be demonstrated by the change in ion concentrations and the evolution of hydration products. The formation of Kuzel's salt depends not only on the chloride concentration but also on the hydration time.

Iron-chromium-aluminum (FeCrAl) alloys with different content of niobium (Nb)—0, 0.4 wt%, 0.8 wt%, and 1.2 wt%—were designed and prepared. All samples were then irradiated with 2.4 MeV Fe2+ ion to the dose of 1 and 15 displacements per atom (dpa) at 400 °C. The formations of dislocation loops induced by self-ion irradiation in these alloys were investigated by transmission electron microscopy (TEM). Nano-indentation tests were used to assess the hardness and irradiation hardening of samples. For the samples before irradiation, the (Fe, Cr)2(Nb, Mo) Laves phases density and the nano-indentation hardness increased with increasing Nb content of the samples. After irradiation to 1 and 15 dpa, both of a/2 and a dislocation loops were produced but no voids or αˊ phase were found in all samples. With increasing Nb content of the samples, the size of dislocation loops increased first and then decreased, while the total volume number density decreased and then increased. The fraction of a dislocation loops increased first and then decreased with increasing Nb content, and increased with increasing irradiation dose. Dislocation networks and the amorphization of the Laves phases were observed in the samples with irradiation dose of 15 dpa. Irradiation hardening of Nb free samples was two to four times that of Nb containing samples, and the irradiation hardening increased with increasing Nb content of Nb containing samples. The experimental results indicate that the increase of Nb content in FeCrAl alloys can increase the density of Laves phases, leading to the decrease of Mo content and increase of Cr content in the matrix. The competition between the two types of solutes affects the nucleation and growth of the dislocation loops.

Lithium orthosilicate (Li4SiO4) is regarded as a candidate solid tritium breeding material for the fusion reactors, but the phase control and densification for this ceramic are difficult. Microwave-induced solution combustion synthesis (MSCS) offers an efficient and flexible route for preparing the tritium breeders in a single step. The combustion process can be effectively controlled by the microwave power output and the fuel-to-oxidizer ratio (ϕ), which can be taken advantage of for the phase control of the product. The results show that the combustion temperature increases linearly with the increase of the ϕ value, and the Li4SiO4 becomes the main product when the ϕ value is higher than 0.75. Lithium metasilicate (Li2SiO3) is detected in minimum quantities in the products, and its content can be reduced when the microwave power output is 1100 W, which can be further removed by calcination at 873 K for 2 h. The thermal analysis results show that the redox reaction between the LiNO3 and citric acid provides the heat for the combustion. The ceramic body can be sintered to 84% of the theoretical density at a low temperature of 1073 K, and the relative density is close to 96% with high purity at the sintering temperature of 1373 K.

Purpose High-ductility cementitious composites (HDCC) have an excellent crack controlled capacity and corrosion resistance capacity, which has a promising application in structure engineering under harsh environment. The purpose of this study is to explore the corrosion mechanism of steel bar in HDCC. Design/methodology/approach Intact and the pre-cracked HDCC specimens under the coupled action of different dry–wet cycles and chloride attack were designed, and intact normal concrete (NC) was also considered for comparison. Corrosion behavior of a steel bar embedded in HDCC was analyzed by an electrochemical method, a chloride permeability test and X-ray computed tomography. Findings Steel corrosion probability is related to the chloride permeability of the HDCC cover, and the chloride permeability resistance of HDCC is better than that of NC. Besides, crack is the key factor affecting the corrosion of steel bars, and the HDCC with narrower cracks have a lower corrosion rate. Slight pitting occurs at the crack tips. In addition, the self-healing products and corrosion products fill up the cracks in HDCC, preventing the external aggressive ions from entering and thereby decreasing the steel corrosion rate. Originality/value HDCC has a superior corrosion resistance than that of NC, effects of variable crack width on corrosion behavior of steel bar in HDCC under the coupled actions of different dry–wet cycles and chloride attack are investigated, which can provide the guide for the design application of HDCC material in structure engineering exposed to marine environment.

Sb2Se3 is a promising absorber material for thin-film solar cells owing to its earth-abundant and non-toxic constituents, superior optoelectronic properties, and unique one-dimensional crystal structure. To further increase the power conversion efficiency of the Sb2Se3, we fabricated an n-i-p structure by integrating a solution-processed NiOx hole-transport layer (HTL) into Sb2Se3 solar cells to enhance the carrier collection. In this study, we systematically screen the thickness of NiOx HTL and demonstrate an improved average power conversion efficiency from 6.12% to 7.15% with a 50 nm NiOx HTL. The mechanism associated with the improved device performance was characterized through the microstructure of the material, device physics, and interface electronic behaviors. It is also shown that the low-cost and scalable solution-processed NiOx HTL can improve device stability under an accelerated stress test. Thus, this work paves a way to further improve the performance of antimony chalcogenides-based solar cells via tailoring the inorganic HTL.

Flexible rockfall barriers are commonly constructed on steep hillsides to mitigate rockfall. The evaluation of the dynamic response of proprietary flexible rockfall barriers is conventionally performed using full-scale field tests by dropping a block onto the barriers in accordance with the European test standard ETAG 027. The block typically has a spherical or polyhedral shape and cannot reproduce more complex rockfall scenarios encountered in the field. Little attention has been paid to the effects of the block shape on the impact force and structural response. This paper aims to quantitatively reveal the influence of the block shape on the dynamic response of flexible rockfall barriers. First, an ellipsoidal model is established to approximately simulate the block, and the sphericity is employed as the representative index of the block’s shape. A full-scale test on a typical flexible barrier system is carried out and then used to calibrate an advanced three-dimensional finite element model. Finally, the dynamic responses of flexible rockfall barriers are analyzed and discussed, focusing on the effects of the block’s shape. The numerical results show that the sphericity will obviously influence the maximum elongation of flexible barriers, the peak impact force, the peak force of the upslope anchor cable, the peak force of the lower main support cable, the axial peak force of the post, and the peak shear force at the post foundation. The assumption of spherical or polyhedral blocks in the test standard could lead to the defensive failure of flexible rockfall barriers in some impact scenarios.

The low charge separation efficiency and sunlight utilisation of traditional titanium dioxide (TiO2) nanoparticle photocatalysts greatly limit their applications. Herein, one-dimensional (1D) mesoporous anatase TiO2 nanotubes with engineered surface defects are fabricated using a combination of simple solvothermal synthesis and high-temperature surface hydrogenation strategy. The obtained mesoporous anatase TiO2 nanotubes with mesopores in the nanotube walls and a specific surface area of 110 m2 g−1 decrease the bandgap from 3.18 to 2.98 eV, enhancing the photoresponse to the visible-light region of the solar spectrum. The defective mesoporous anatase TiO2 nanotubes exhibited an excellent photocatalytic hydrogen evolution rate of 9.8 mmol h−1 g−1, which is approximately 2.5 times higher than that of the pristine anatase TiO2 nanotubes. This can be ascribed to the engineered surface defects and 1D mesoporous nanotube structure favouring efficient spatial charge separation on the horizontal–vertical dimensions, enabling visible-light absorption and exposing abundant surface active sites. This study provides a facile and feasible strategy for the fabrication of high-performance 1D mesostructured semiconductor oxide photocatalysts for efficient solar energy conversion.

Direct pull-out method was conducted to explore the bond stress-slip response of ribbed basalt fiber reinforced polymer (BFRP) bars embedded in ecological high ductility cementitious composites (Eco-HDCCs). The effects of the embedment length and cover thickness on the bond properties between Eco-HDCCs and the bars were described. Results indicate that the failure characteristics of the specimens depend on the embedment length and cover thickness of the BFRP bars. As the embedment lengths of the bars increase, the ultimate bond stress decreases while the ultimate slip increases. Besides, both the ultimate bond stress and ultimate slip show an increasing trend if the specimen has a cover thickness of less than 45 mm, while the increasing trend is slower if the specimen has a cover thickness of more than 45 mm. In addition, the strain of the specimen surface depends on the cover thickness, and the strain increases when the cover thickness is in a range of15 mm–35 mm. Moreover, certain embedment lengths and cover thicknesses of the BFRP bars are recommended in the structural design of bridge deck link slabs. The bond stress-slip relationship models of the BFRP bars in Eco-HDCCs are proposed based on the test results.

Phase diagram is a powerful tool to guide the exploitation of thermal energy materials. Heat storage technology of phase-change material (PCM) was widely used to solve major energy utilization problems on large energy consumption and low utilization efficiency. In this work, a novel solid-liquid phase diagram of the binary system octadecanoic acid (C18-acid) + octadecanol (C18-OH) was investigated using the differential scanning calorimeter (DSC). The phase-change temperature and phase-change enthalpies against the composition of C18-acid and C18-OH were determined experimentally, and then the binary phase diagram of T–X (X expresses the mass fraction of C18-OH in the two components of C18-acid and C18-OH) was established for the first time. The phase diagram belongs to a binary simple system with one eutectic point, and the content of C18-OH at eutectic point is 0.4 in mass fraction. Neither solid solution nor copolymer was formed. The thermal chemical properties on the phase-change latent heat (Q), phase-change temperature (Tp), and the thermal conductivity (λ) for the composition at the eutectic point of the binary system are 198.7 J·g−1, 44.2°C, and 0.2352 W·m−1·K−1, respectively. This result indicates that the material at eutectic point has a great potential to be used as energy storage material for supply of heat and scouring bath.

Porous organic polymers (POPs) are an emerging class of porous materials, having many promising applications in a variety of areas. Among them, covalent triazine frameworks (CTFs) featuring conjugated and porous structures can be well applied in optoelectronics. To achieve high optoelectronic performance, usually the design and synthesis of CTFs based on appropriate building blocks is critical. Here we report the synthesis of two fluorescent CTFs based on typical fluorescent building blocks, in which CTF-Py constructed from a pyrene (Py) building block was reported for the first time, showing prospective applications in the sensing of nitroaromatics with high sensitivity, and photocatalytic water splitting and carbon dioxide reduction with high performance in comparison with other porous organic materials.

Robust single spin color centers in solid state systems with telecom wavelength emission are vital to quantum photonics and quantum networks. The nitrogen vacancy (NV) centers in silicon carbide (S...

The cross-linked network of DUT-67/tubular polypyrrole (T-PPY) composites was first synthesized by in-situ growth zirconium - based metal-organic frameworks (DUT-67) with T-PPY. The introduction of T-PPY effectively increases conductivity of DUT-67/T-PPY composites, weakens accumulation of the DUT-67, and exposes more active sites of DUT-67. DUT-67/T-PPY/GCE manifests increased electrocatalytic activity toward reduction of nitrofurazone and ornidazole compared with DTU-67. A novel electrochemical sensor based on DUT-67/T-PPY was established to effectively detect two anti-infective drugs, respectively. Under optimized experimental conditions, the proposed sensor shows a wider linear range for nitrofurazone that is composed by two line segments (9.08–354.08 μM and 354.08–1004.04 μM). Meanwhile, the sensor also displays a linear response to ornidazole in the range of (0.7–100.5 μM and 100.5–250.4 μM) as well as a low LOD as 0.25 μM (S/N = 3). The proposed sensor was used for the detection of nitrofurazone and ornidazole in actual samples, and the satisfactory results were acquired. This research provides an efficient strategy for fabricating novel electrochemical sensor based on cross-linked network structure of T-PPY and MOFs.

The intrinsic hydrophobicity, deficient light absorption of solar energy, and the energy loss from the radiation relaxation of charges that decreases the solar–thermal conversion efficiency, have s...

The evolution of defects with isochronal annealing between 373 and 1273 K in 316L stainless steels, irradiated by helium ions at room temperature (RT), has been studied by the slow positron Doppler broadening spectroscopy (DBS). The results showed that with annealing temperature between RT and 673 K, the S parameters of sample were maintained. It indicates that below 673 K, on the one hand, some vacancies introduced by irradiation were gathered to form vacancy clusters and on the other hand, some vacancies migrated and recovered. From 773 K to 1073 K, there was continuous growth of HenVm cluster, resulting in rapid increasing of S parameter. After 1073 K, unstable HenVm clusters dissociated into vacancies and He atoms. The vacancies were vanished rapidly, which decreases the concentration of vacancy defects, leading to decline of S parameter.

Development of electrocatalysts composed of low cost and abundant elements that exhibit catalytic activity comparable to noble metals is important for water splitting. As such, in this study, a catalyst material with a ginger-like morphology consisting of Co6W6C is synthesized via a hydrothermal reaction and pyrolysis treatment. The Co6W6C catalyst exhibits satisfactory electrochemical properties towards both hydrogen and oxygen evolution reactions in an alkaline electrolyte, with a low overpotential, low Tafel slope, and durable stability. Co6W6C possesses a high activity for the hydrogen evolution reaction in alkaline conditions, with an onset potential and overpotential of −0.024 V and 101 mV, respectively, and low Tafel slope of 80.5 mV dec−1 at a current density of 10 mA cm−2. In addition, Co6W6C achieves a current density of 10 mA cm−2 for the oxygen evolution reaction at an overpotential of only 343 mV. Furthermore, electrochemical stability tests indicate that the Co6W6C catalyst maintains 91% of the original current after 60,000 s for the hydrogen evolution reaction and 95% of the original current after 45,000 s for the oxygen evolution reaction. Moreover, electrochemical splitting of water via a two-electrode system employing this catalyst can hold 89% of the initial current after 40,000 s in 1 M KOH.

Ecological high-ductility cementitious composites (eco-HDCC) are cost-effective high-ductility materials that have promising applications in structural engineering. With an important role in structural design, the bond–slip behaviour of steel bars and basalt-fibre-reinforced polymer (BFRP) bars embedded in an eco-HDCC were investigated using pull-out tests. Factors such as bar type, bar diameter and embedment length were considered, and all these factors were found to have an effect on the failure mode. The bond stress–slip curves of the steel bars and BFRP bars in the eco-HDCC displayed four distinct stages: linear, non-linear, descending and residual stages. Residual bond stress was found to exist at the interface between the BFRP bar and the eco-HDCC. Moreover, the bond stress showed a decreasing tendency for a larger bar diameter or longer embedment length, while the slip displayed the opposite trend. Analytical models were developed to predict bond stress–slip curves based on the experimental data. As a general consideration for structural design, the BFRP bars proved to be a good alternative for structures, showing excellent bond properties at the pull-out stage. A reasonable bar diameter and embedment length need to be selected to prevent specimen splitting and to ensure a certain bond stress or slip.

As one of the alternative insulation gases, C4F7N/CO2 gas mixtures have attracted much attention recently. In this study, the normalized Townsend first ionization coefficient α/N and the normalized attachment coefficient η/N were measured in C4F7N/CO2 gas mixtures by using the Steady-State Townsend (SST) method over a range of electric fields E/N from 100 to 550 Td. The concentrations of C4F7N studied were 4.99, 7.00, 9.00, 13.13 and 20.02%, and the gas pressure were 500 Pa at 20°C. The effective ionization coefficients and the critical electric field were obtained at 500, 1000 and 2000 Pa to investigate the effect of gas pressure on dielectric strength in 9.00%C4F7N/91.00%CO2 respectively. The results indicated that the (E/N)lim have not significant change on the SST experimental conditions. Meanwhile, a comparison with SF6 gas indicates that 20.02% C4F7N/79.98% CO2 has a similar insulation performance with (E/N)lim as 358.82 Td. However, when the liquefaction temperature is considered, the C4F7N/CO2 gas mixtures with 9.00% C4F7N could be considered as an appropriate substitute gas for SF6, because the critical electric field of this gas mixture is over 70% of SF6 gas and could be used under -15°C at 0.7 MPa.

In this study, cobalt-iron selenides embedded in porous carbon nanofibers (CoFe2Se4/PCF), derived from Prussian blue analogues, was prepared as a novel phenolic sensor. The obtained CoFe2Se4/PCF nanocomposites show three-dimensional (3D) networks nanostructures that can supply a desirable conductive network to accelerate electron transfer and avoid the aggregation of CoFe2Se4 nanoparticles. Electrochemical detection of hydroquinone (HQ), catechol (CC) and resorcinol (RS), at CoFe2Se4/PCF modified glassy carbon electrode (GCE) were researched. The results show the obtained 3D CoFe2Se4/PCF/GCE exhibits excellent electrochemical properties towards the simultaneous testing trace of HQ, CC and RS. The obtained electrode provides wide linear ranges of 0.5–200, 0.5–190 and 5–350 μM and low detection limit of 0.13, 0.15 and 1.36 μM for HQ, CC and RS, respectively. The as-prepared phenolic sensor displays satisfied selectivity and long-term storage stability. In addition, the constructed sensor can be used to determine HQ, CC and RS in actual samples.

Electricity retailer is the most critical player in the restructured electricity market. Retailer's electricity procurement problem is a big challenge for them. Electricity retailer can purchase their energy from various options such as pool market, forward contracts, and etc. A relatively new way with a lesser investigation is the demand response exchange market. In this paper, the risk-constrained stochastic power procurement problem of electricity retailers is formulated by modeling the uncertainty of pool-market price and consumers' electricity demand. The Downside risk constraints (DRC) risk-evaluation method is used to obtain risk-based power procurement scheduling of electricity retailers. By using the proposed method, conservative electricity retailer can experience a scenario-independent strategy over the stochastic optimization. In other words, the proposed risk strategy is such that impose more cost for electricity retailer while having an equal cost in all scenarios. Based on the obtained results, the operation cost of electricity retailers in all scenarios is closed to about $4827570, which is a relatively zero-risk strategy due to equality overall scenarios. Besides, results are compared in two cases to demonstrate the advantages of the proposed risk-evaluation method. Also, the Pareto front between risk-in-cost and expected cost can introduce an optimal risk-strategy for electricity retailers in the presence of uncertainties. Finally, the risk-averse strategy of electricity retailer is proposed to obtain the retailer's optimal conservative schedule during power procurement in the presence of uncertainties.

The effect of the concentration of hydrogen (H) atoms on the hydrogen diffusion and evolution of hydrogen bubbles in body-centered cubic iron was investigated using molecular statics and molecular dynamics methods. The simulation results indicate that the local accumulation of H atoms can significantly influence their migration. Compared to the isolated H in a perfect lattice, the H atoms in a high-concentration H-cluster are trapped. After collecting a sufficient amount of hydrogen atoms, the H-vacancy cluster will push out one hydrogen atom instead of a self-interstitial atom, which indicates that loop-punching will not dominate the H-bubble growth in bcc iron. These results will provide a new understanding for the hydrogen-induced radiation damages in nuclear materials.

The evolution of dislocation loops in two types of modified 310S steel under proton irradiation are investigated with rate theory simulations. The growth of dislocation loops is promoted with the increase of irradiation dose and growth rate decreases at high dose, while the number density of the dislocation loops increases first with dose and then tends to be saturated gradually. At the initial stage of irradiation, large number of dislocation loops nucleate and the density increases rapidly. With the development of irradiation, the growth of dislocation loops gradually takes over. Simulation results are in good agreement with the experimental observations of transmission electron microscope. Present study shows that The irradiation resistance of Zr-added steel is slightly better than that of (Nb, Ta, W)-added steel, which may due to the smaller migration energy of interstitials and vacancies in Zr-added steel than that in the (Nb, Ta, W)-added one.

Artificial intelligence methods such as fuzzy logic and particle swarm optimization (PSO) have been applied to maximum power point tracking (MPPT) for solar panels. The P-V curve of a solar panel exhibits multiple peaks under partial shading condition (PSC) when all modules of a solar panel do not receive the same solar irradiation. Although conventional PSO has been shown to perform well under uniform insolation, it is often unable to find the global maximum power point under PSC. Fuzzy adaptive PSO controllers have been proposed for MPPT. However, the controller became computation-intensive in order to adjust the PSO parameters for each particle. In this paper, fuzzy adaptive PSO-based and conventional PSO-based MPPT are compared and evaluated in the aspect of design and performance. A simple fuzzy adaptive PSO controller for MPPT was designed to reach the global optimal point under PSC and uniform irradiation. The controller combines the advantages of both PSO and fuzzy control. The fuzzy controller dynamically adjusts the PSO parameter to improve the convergence speed and global search capability. Since tuning of the PSO parameter is designed to be common for all particles, it reduced the computation complexity. The fuzzy controller’s rule base is designed to obtain a fast transient response and stable steady state response. Design of the fuzzy adaptive PSO-based MPPT is verified with simulation results using a boost converter. The results are evaluated in comparison to the results using a conventional PSO controller under PSC. Simulation shows the fuzzy adaptive PSO-based MPPT is able to improve the global search process and increase the convergency speed. The comparison indicates the settling time using the fuzzy adaptive PSO-based MPPT is 14% faster under PSC on average and 30% faster under uniform irradiation than the settling time using the conventional PSO. Both the fuzzy adaptive and conventional PSO controllers have similar output power tracking accuracy.

Renewable energy sources such as solar and wind provide an effective solution for reducing dependency on conventional power generation and increasing the reliability and quality of power systems. Presented in this paper are design and implementation of a laboratory scale solar microgrid cyber-physical system (CPS) with wireless data monitoring as a teaching tool in the engineering technology curriculum. In the system, the solar panel, battery, charge controller, and loads form the physical layer, while the sensors, communication networks, supervisory control and data acquisition systems (SCADA) and control systems form the cyber layer. The physical layer was seamlessly integrated with the cyber layer consisting of control and communication. The objective was to create a robust CPS platform and to use the system to promote interest in and knowledge of renewable energy among university students. Experimental results showed that the maximum power point tracking (MPPT) charge controller provided the loads with power from the solar panel and used additional power to charge the rechargeable battery. Through the system, students learned and mastered key concepts and knowledge of multi-disciplinary areas including data sampling and acquisition, analog to digital conversion, solar power, battery charging, control, embedded systems and software programing. It is a valuable teaching resource for students to study renewable energy in CPS.

Microstructure and irradiation hardening of V-4Cr-4Ti alloys with different yttrium (Y) contents were studied by self-ion irradiation at 550 °C via TEM and nano-indentation test technology. The peak damage of the V-4Cr-4Ti-xY alloy (x = 0, 0.1, 0.5, and 1, wt.%) irradiated by 2.5 MeV self-ion (V2+) is 8 dpa. Dense dislocation loops were observed in all vanadium alloy samples after irradiation. With the increase of Y content, both average size and number density of dislocation loops using g = &lt, 110&gt, near the pole [001] decreased, while the irradiation hardness increment first decreased and then increased. In order to better reduce the irradiation hardening, it is considered that the addition of 0.1 wt.% Y in V-4Cr-4Ti alloy is reasonable.

The effects of oversized additive atoms on microstructure evolution in 310S stainless steel under irradiation was investigated. Ar ion irradiations were conducted on modified 310S stainless steels at 290 °C and 550 °C. SC-1 was modified with Zr and SC-2 was modified with Nb, Ta and W. Compared with SC-2, lower density, smaller vacancy clusters formed in SC-1 at 290 °C. When irradiation temperature was increased from 290 °C to 550 °C, the average size of vacancy clusters increased while the number density dropped to a lower value in SC-1; however, in SC-2, the average size and number density of vacancy clusters shifted to larger values. At 550 °C, lower density and larger size of vacancy clusters were observed in SC-1 compared with that in SC-2. In addition, precipitates enriched with Ni were observed in SC-1, while Nb- and Ta-enriched precipitates were found in SC-2. A possible mechanism is discussed.

To investigate the nonlinear mechanical behavior of the wire-ring net, this paper presents a new numerical model that can collectively consider equivalence between numerical and actual wire rings. Quasi-static tests, including tensile tests on steel wires and one-ring specimens, and puncturing tests on net specimens were conducted. Based on the test results, the axial constitutive curves of steel wires were obtained. The linear correlation equations for the breaking loads of the one-ring specimens and the puncturing strength of wire-ring nets were established, both of which were related to the number of windings. The wire rings were modeled via an equivalent structure with a single winding and a circular cross section. Equivalence between the numerical and actual wire rings in terms of bending and tensile strength, total mass, contact with sliding friction, and rupture behavior were also derived and presented. In particular, the emphasis was on simulating the flattening effect, a phenomenon rarely accounted for in conventional numerical models. All dominant factors were reflected in a model with the material law by the input of material parameters. The proposed mechanical model was calibrated and verified by the data from the tests of the wire-ring net. The calibrated mechanical model is also shown to successfully simulate a full-scale test of a flexible rockfall protection barrier according to the ETAG027 standard.

In this work, porphyrin-based 2D MOF CuTCPP/platelet ordered mesoporous carbon (pOMC) composites were successfully synthesized by conventional solvothermal reaction. The introduction of pOMC increases conductivity of CuTCPP/pOMC composites, weakens accumulation of the CuTCPP layers, and exposes active sites of CuTCPP. CuTCPP/pOMC composites show high electro-catalytic activity to the oxidation of hydroxylamine and the redox of chlorogenic acid. An electrochemical sensor based on CuTCPP/pOMC was constructed for quantitative determination of hydroxylamine and chlorogenic acid, and relevant mechanisms were discussed. Under optimized conditions, the fabricated sensor displays two wide linear responses in the ranges of 5.8–733.8 μM and 733.8–2933.8 μM for hydroxylamine, with a rapid response time about 1 s. For chlorogenic acid, the sensor presents linear responses in the ranges of 0.1–2 μM and 2–15 μM, with a high sensitivity of 10.18 μA/μM. The sensor was used to detect hydroxylamine and chlorogenic acid in real samples, and satisfactory results were obtained. The synthesis of CuTCPP/pOMC composites provides new strategy for designing electrochemical sensors based on 2D MOFs.

High ductility cementitious composites (HDCCs) exhibit robust tensile ductility accompanied by multiple cracking and a tight crack width. The constitutive relations of fiber/matrix interfacial bonding has a great influence on the mechanical properties of HDCCs. Appropriate interfacial bonding can give full play to the bridging effect of fibers, whereas improper interfacial bonding only achieves inferior, or even no ductility. The purpose of this study is to elaborate on the optimal range of the fiber/matrix interfacial bonding strength based on the micromechanics theory with consideration to fiber rupture. As typical fibers used in HDCCs, like PVA fiber, PET fiber, PE fiber and steel fiber were selected as case studies. Furthermore, a source of confused question is clarified if all the fibers in HDCCs exhibit pullout behavior rather than rupture behavior, which is the optimal case. The analysis results show that moderate volume fractions of fibers ruptured can contribute to obtain stronger fibers bridging capacity and can achieve higher ductility for HDCCs. Finally, the experimental value of fiber/matrix interfacial friction τ 0 is shown to be in an optimal range, and the ductility of the PVA-HDCC and PE-HDCC can reach 2.7 ± 0.3% and 4.8 ± 1.0%, respectively. These research findings can be used as an important guide on fiber surface treatment and fiber/matrix interface tailoring.

Quasi-one-dimensional van der Waals Sb2Se3 compound is a promising absorber material with desired optical properties and has theoretical potential to achieve high power conversion efficiency (PCE) of ∼30%. Here, we report a new window layer, i.e., sputtered CdSe, which can enhance the Sb2Se3 device stability during light soaking and improve the photocurrent collection. Compared to the widely used CdS window layer, CdSe can suppress the interfacial diffusion between the window layer and the Sb2Se3 film, thereby reducing interfacial recombination sites. The dominant degradation mechanism in the CdS/Sb2Se3 devices is found to be the S diffusion instead of the Cd diffusion, as CdSe/Sb2Se3 devices did not show degradation during the 85 °C 120 h 1-Sun light soaking with similar Cd diffusion. Meanwhile, the enhanced photocurrent and reduced series resistivity in the CdSe/Sb2Se3 solar cells lead to an improved PCE of 4.5% with a glass/FTO/CdSe/Sb2Se3/graphite cell architecture. The obtained results suggest that CdSe can be employed as a window layer in the thin-film solar cells made of stable and efficient Sb2Se3-like quasi-one-dimensional van der Waals materials, providing a cost-effective way to integrate into the traditional thin-film solar cell manufacturing process.

A facile, low cost and effective method was used to synthesize porous holey nitrogen-doped graphene (PHNG) with three-dimensional (3D) structure via direct pyrolysis of a mixture of urea and magnesium acetate tetrahydrate, followed by treating with hydrochloric acid to remove magnesium cations. The unique structure of PHNG significantly decreases the irreversible stacking of graphene nanosheet, favors the exposure of active edge sites, and enables more accessibility for reactants/electrolytes. The PHNG shows porous structure with a large surface area and can serve as support for nanoparticles. PtPd nanoparticles with different ratios were deposited on PHNG surface to synthesize PtPd/PHNG. The PtPd/PHNG-2 shows high direct oxidation activity towards the glucose, achieving a high sensitivity (52.526 μA mM−1 cm−2), wide linear range (100–4000 μM), fast response time (

Defects in silicon carbide have been explored as promising spin systems in quantum technologies. However, for practical quantum metrology and quantum communication, it is critical to achieve on-dem...

There is an important connection between the microscopic and macroscopic properties of UHS-UHDCC with compressive strength (more than 160 MPa) and uniaxial tensile ductility (more than 6%). First, some microscopic properties were studied. For the fresh mortar matrix, the plastic viscosity within an optimal range is beneficial to achieve uniform fiber distribution. Compared with the fluorescence analysis, the backscattering analysis more truly displays the fiber distribution situation and cross section shapes of fibers. Based on the mesh size of three-dimensional grid formed by theoretically absolutely uniform distributed fibers, the river sand with an average particle size of 240 μm was selected as the aggregate. The addition of fibers slightly increases the porosity, the larger bubbles are not easy to be excreted due to the isolation of the fiber mesh. With the increasing of silica fume (SF) dosage and the decreasing of the water-binder ratio (w/b), the overall protruded length of fibers on fracture surface of tensile specimen reveals a decreasing trend, the hydration product attached to the fibers first increases and then decreases, and the decreasing accompanies a more severely scraped fiber surface, the fiber shedding changes from being no apparent to gradually increase. Increasing SF dosage or decreasing the w/b, the elastic modulus increases with different degrees, and the difference between the elastic modulus in interfacial transition zone (ITZ) of about 60 μm span and that of mortar matrix gets smaller and smaller. The elastic modulus in ITZ exhibits a gradient that first decreases and then increases. Further, the connection between microscopic and macroscopic (flexural、compressive、tensile) properties was analyzed. The highest fiber dispersion degree at mix proportion 0.4SF + W0.19 + PE and its suitable interfacial bonding strength together create the saturated multi-crack ductility of 6.53% and compressive strength of 163 MPa. When the strength growth benefitting from the increasing of interfacial bonding strength lowers than the strength loss due to the decreasing of the fiber dispersion degree, the ultimate tensile strength and the flexural strength of UHS-UHDCC decrease.

Conjugated microporous polymers (CMPs) with high surface areas, tunable building blocks, and fully conjugated structures have found important applications in optoelectronics. Here, we report a new series of CMPs with tunable band gaps by introducing thiazolo[5,4- d] thiazole as the linkage. Because they are synthetic polymers, the geometries and structures could be rationally designed. Their intrinsic wide visible-light absorption properties and layered architectures endow them with a promising photocatalytic performance. The role of geometries, surface areas, and morphologies of the CMPs in photocatalysis abilities is examined and discussed. The results indicate that geometries have a direct impact on the surface areas and morphologies of the CMPs and thus exert great influence on photocatalysis.

Developing advanced hydrogen evolution reaction (HER) electrocatalysts is of great significance. Herein, we report porous rodlike cobalt–nickel bimetal nitrides (CoxNiyN) as high-efficiency HER electrocatalysts in a wide pH range through nitridation from a bimetal–organic framework (MOF-74) precursor. Thanks to collaborative superiorities of high surface areas, abundant mesoporous structure, perfect metal element dispersion, and electron modulation effect, the as-prepared CoxNiyN possess a superior catalytic ability toward HER at all pH values. In particular, the optimal Co2Ni1N requires overpotentials of 102.6 and 92.0 mV to afford a current density of 10 mA cm–2 in alkaline and acidic solution, respectively. In addition, it also presents favorable activity in neutral media and excellent stability under different pH conditions. The present study not only offers a strategy for the design and synthesis of porous bimetal nitrides derived from binuclear MOF but also brings up new avenues for the development ...

The deterioration of cement based materials in marine and salts lakes environment is complicated problem, due to the presence of chlorides and sulfate simultaneously. The influence of sulfate on the chloride diffusion mechanism was evaluated by scanning electron microscopy (SEM-EDS), mercury intrusion porosimetry (MIP) and X-ray diffraction (XRD). The total chloride profile was also used to illustrate the influence of chloride and sulfate salts concentrations on chloride diffusion. The results show that the chloride binding and formation of Friedel’s salt are inhibited by the presence of sulfate. The presence of sulfate increases chloride diffusion in the short term, while it inhibits the chloride diffusion from a long-term perspective. The aggressive ions penetrate into the mortar causing mortar’s porosity decrease, especially the pore

Designing high-efficiency electrocatalysts for luteolin detection is essential and vital in biological and medical field. Herein, CuCo coated nitrogen-enriched porous carbon polyhedron (CuCo@NPCP) materials are fabricated as a highly sensitive electrochemical luteolin sensor by simple and mild approach. As characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption-desorption isotherms and electrochemical methods, CuCo@NPCP materials possess high specific surface area, 3D porous framework, amounts of available active sites, which all contribute to the adsorption and catalysis for luteolin. Meanwhile, vast mesoporous structure of CuCo@NPCP further affords more mass transport channels and enhances the mass transfer capacity. Thanks to above-mentioned characteristics, optimal Cu1Co3@NPCP presents superior analytical performance: a wide linear range from 0.2 nM to 2.5 μM, a ultrahigh sensitivity of 134.57 μA μM−1 surpassing to other reported catalysts previously, a low detection limit of 0.08 nM, as well as satisfactory selectivity, reproducibility, and long-term stability. This work offers an attractive catalyst derived from MOFs for constructing effective luteolin sensors.

Exploring highly active, inexpensive and robust electrocatalysts for oxygen reduction reaction (ORR) is of great significance as a competitive alternative to noble metal-based catalysts in energy conversion and storage devices. In the present study, we design a novel ORR electrocatalyst of iron-cobalt (FeCo) alloy nanoparticles embedded on N-doped porous carbon nanofibers (FeCo@PCNF-T) by electrospinning of [Polyacrylonitrile (PAN)/Prussian blue analogues/CaCO3] and post-calcination treatment. The obtained catalysts with bimetallic active sites show unique three-dimensional (3D) hierarchical meso/macropores structures. FeCo alloy nanoparticles are encapsulated into graphitic carbon that can increase stability and provide additional catalytic active sites. Under the optimized condition, FeCo@PCNF-800 displays excellent ORR electrocatalytic activity in alkaline solutions, with a more positive half-wave potential (E1/2 of 0.854 V vs RHE) and larger limited-diffusion current density (j of 6.012 mA cm−2) than those of 20 wt% Pt/C (E1/2 of 0.849 V and j of 5.710 mA cm−2). In addition, FeCo@PCNF-800 also exhibits comparable ORR electrocatalytic activity in acidic solutions to those of 20 wt% Pt/C with onset potential and half-wave potential as more positive as 0.843 V vs RHE and 0.739 V vs RHE, respectively. Moreover, FeCo@PCNF-800 exhibits excellent tolerance towards methanol, stability and a four-electron pathway in both basic and acidic solutions. The excellent ORR electrocatalytic activity performance of FeCo@PCNF-800 is attributed to the synergistic effect of the FeCo alloy nanoparticles and N-doped porous carbon nanofibers. The synergistic effect can improve the mass and charge transport capability and increase active sites of FeCo-N-C. Furthermore, this work offers a new insight for the reasonable design and development of efficient non-noble metal electrocatalysts for challenging electrochemical energy-related technologies.

Color centers in silicon carbide have recently attracted broad interest as high bright single photon sources and defect spins with long coherence time at room temperature. There have been several methods to generate silicon vacancy defects with excellent spin properties in silicon carbide, such as electron irradiation and ion implantation. However, little is known about the depth distribution and nanoscale depth control of the shallow defects. Here, a method is presented to precisely control the depths of the ion implantation induced shallow silicon vacancy defects in silicon carbide by using reactive ion etching with little surface damage. After optimizing the major etching parameters, a slow and stable etching rate of about 5.5 ± 0.5 nm min-1 can be obtained. By successive nanoscale plasma etching, the shallow defects are brought close to the surface step by step. The photoluminescence spectrum and optically detected magnetic resonance spectra are measured, which confirm that there were no plasma-induced optical and spin property changes of the defects. By tracing the mean counts of the remaining defects after each etching process, the depth distribution of the defects can be obtained for various implantation conditions. Moreover, the spin coherence time T2* of the generated VSi defects is detected at different etch depths, which greatly decreases when the depth is less than 25 nm. The method of nanoscale depth control of silicon vacancies would pave the way for investigating the surface spin properties and the applications in nanoscale sensing and quantum photonics.

Molecularly imprinted polymers (MIPs) are typically prepared using a single template molecule, which allows selective separation and enrichment of only one target analyte. They are not suitable for determination of complex real samples containing multiple analytes. In order to expand the practical application of MIPs, novel dual-template molecularly imprinted mesoporous silica (DMIMS) was prepared by a simple and facile hybrid dual-template imprinting strategy using bisphenol A (BPA) and diethylstilbestrol (DES) as templates for simultaneous selective recognition and extraction of the two endocrine disruptors in environmental water samples. The structure and morphology of the synthesized DMIMS were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and N2 sorption analysis. The results showed that DMIMS exhibited a spherical morphology, mesoporous structure and favorable thermal stability. More importantly, DMIMS was verified to exhibit fast kinetics, high rebinding capacity and excellent selectivity towards BPA and DES. DMIMS can reach equilibrium within 30 min and the saturated adsorption capacities of DMIMS for BPA and DES are 66.8 mg g−1 and 43.9 mg g−1, respectively. The selectivity coefficients of DMIMS are all far more than 1.0. Theoretical analysis showed that the experimental data fitted well to the pseudo-second-order model, indicating that chemical adsorption might be the rate-limiting step. Furthermore, the high adsorptive capability and selectivity of DMIMS were maintained almost constant after six runs. Finally, water samples were successfully analyzed with DMIMS and high recoveries (95.0–107.1%) and relative standard deviation (1.18–5.63%) were obtained. The limits of detection (3σ) of 3.4 × 10−4 mg L−1 and 5.6 × 10−4 mg L−1 were obtained for BPA and DES, respectively. Overall, these results demonstrated that DMIMS possesses great potential for simultaneous rapid and efficient detection of BPA and DES in environmental water samples.

Development of electrode materials with high capacity, good cycling stability and excellent rate performance is of great importance to promote the applications of Li-ion batteries (LIBs) in electric vehicles and many other electronic devices. Transition metal oxides (TMOs) with metal ions at high valence states are promising anode materials which deliver high energy capacity, since they allow for the storage of a high number of Li ions. They, however, suffer from low electrical conductivity. Here, MnOS@NSC with MnOS microspheres encapsulated in N, S co-doped carbon shells with a core–shell structure synthesized by a sulfurization method has been reported to be a potential anode material for LIBs with high capacity, good cycling stability and excellent rate performance. Specifically, it can deliver a stable reversible capacity of 1400 mA h g−1 at 100 mA g−1. Even at a high current rate of 1.0 A g−1, it still deliver a stable reversible capacity of 1052.3 mA h g−1. The rate performance investigation indicates that the MnOS@NSC can deliver reversible capacities of 1339.3, 1204.1, 1073, 928.2, 734.7, 506.5 and 290.1 mA h g−1 at 0.1, 0.2, 0.5, 1.0, 2.0, 5.0 and 10.0 A g−1, respectively, much higher than those of most transition metal based anodes reported. The in-operando XRD and CV investigations show that the lithiation process of the MnOS@NSC includes the insertion of Li+ ions into the lattice of MnOS and the reduction of MnOS to MnO/MnS and further to Mn0, clearly demonstrating that Mn is at a high valence state of +4. The DFT calculations demonstrate that sulfurization is crucial for the high performance of the MnOS@NSC. First, it increases the valence state of Mn, allowing for the storage of a high number of Li atoms. Second, it improves the electrical conductivity of MnOS, facilitating charge transfer and reducing the energy losses caused by the polarization resistance. Third, it decreases the energy barrier for Li diffusion, which promotes fast lithiation and delithiation, allowing for good rate performance.

Covalent triazine frameworks (CTFs) represent an exciting new type of porous organic material (POP), which have some unique characteristics, i.e., aromatic CN linkage (triazine unit) and the absence of any weak bonds. In particular, the strong aromatic covalent bonds endow CTFs with high chemical stability and rich nitrogen content, which bring great value for many practical applications and the interesting heteroatom effect (HAE). The unique properties make CTFs attractive for various applications, such as separation and storage of gases, energy storage, photocatalysis and heterogeneous catalysis. Based on the current status of research, CTFs can be classified into two categories, i.e., amorphous and crystalline CTFs. Since 2008, a series of synthetic strategies have been developed, i.e., an ionothermal trimerization strategy, a phosphorus pentoxide (P2O5) catalyzed method, amidine based polycondensation methods, a superacid catalyzed method and a Friedel–Crafts reaction method. The advent of these methodologies has prompted researchers to construct well-defined crystalline CTFs. This critical review systematically summarizes the development and challenges in the synthesis and potential applications of CTFs.

High-ductility cementitious composites (HDCCs) with multiple cracking and excellent tensile strain behavior have been widely studied. The fiber component plays a pivotal role and its surface state directly determines the mechanical performances of composites. In this work, micromechanics design theory was used to guide polyvinyl alcohol (PVA) fiber surface treatment. Based on the strength criterion, energy criterion and fracture criterion, the frictional bond strength needs to be limited to an appropriate range. In addition, three different modifying agents (i.e., an oil agent, hydrophilic silica, and nanoscale graphite) were applied as coatings to the PVA fiber surface. The results showed that the hydrophilic silica-treated PVA fibers (S-PVAF) and nanoscale graphite-treated PVA fibers (G-PVAF) exhibited high hydrophobicity and roughness; consequently, the chemical bonding was greatly reduced. However, the S-PVAF still exhibited breakage and abrasion damage during the pullout process, whereas the G-PVAF were pulled out completely. Finally, the fiber bridging stress versus crack opening σ ( δ ) relation was studied by using notched coupon specimens. G-PVA-HDCCs exhibited greater complementary energy. The tensile ductility reached 2.7%, which was higher than that of oiled PVA-HDCC. The results showed the promising advantages of using nanoscale graphite for surface treatment to achieve a higher surface quality.

To enhance the understanding about the utilization of steel slags as a cementitious material, we comparatively studied the chemical, mineralogical and morphological properties of two types of steel slag; basic-oxygen-furnace carbon slag (BOF C) and electric-arc-furnace stainless steel slag (EAF S). Moreover, we studied the standard consistency, setting time and the effect of the slag replacement ratios on the fluidity and compressive strength of blended cement mortar. The experimental results showed that BOF C had higher alkalinity, higher pH value and more hydraulic phases than EAF S. Both types of slag showed water reduction effect due to its high fineness. Neat BOF C paste showed flash set and acceleration in the initial setting time of blended cement especially at high slag proportions. However, EAF S prolonged the setting time of blended cement even at low slag proportions. The pH values for blended cement contained 50% BOF C or EAF S were lower than those of pure cement paste. Despite of slag type, compressive strength gradually decreased with increasing slags content. The strength of BOF C mortar was higher than that of EAF S mortar with the same replacement ratio for the same age. Slag activity index demonstrated that BOF C and EAF S conformed to the Chinese National Standard (GB/T 20491-2006) requirements for steel slag as grade one and grade two, respectively.

In this work, a novel enzyme-free glucose and hydrogen peroxide (H2O2) sensor based on Ni3N nanoparticles on conductive 3D graphene aerogels (Ni3N/GA) has been successfully synthesized by using hydrothermal reaction, freeze-dried and then calcined under NH3 atmosphere. The obtained Ni3N/GA composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption–desorption isotherms and electrochemical methods. The results show the obtained 3D Ni3N/GA composites exhibit excellent electrochemical performance toward glucose oxidation and H2O2 reduction with larger catalytic rate constant Kcat value of 3.75 × 103 M−1 s −1 and 1.24 × 103 M−1 s −1, respectively. As a glucose sensor, the obtained electrode provides a wide detection range of 0.1–7645.3 μM, fast response time within 3 s, high sensitivity of 905.6 μA mM-1 cm-2 and low detection limit of 0.04 μM. For detection of H2O2, this prepared sensor offers a wide detection range (5 μM–75.13 mM), fast response time (within 5 s), sensitivity (101.9 μA mM-1 cm-2) and low detection limit (1.80 μM). This enzyme-free glucose and H2O2 sensor display satisfactory selectivity, reproducibility and long-term storage stability. Additionally, the sensor can also be used for glucose and H2O2 detection in human blood serum. The results demonstrate that 3D GA nanostructures provide an enviable conductive network for efficient charge transfer and avoid Ni3N nanoparticles aggregation, which is advantageous for electrocatalytic applications.

The aim of investigating the annealing effect induced by helium/hydrogen ion irradiation on the micro-defects of ferritic/martensitic (FM) steel is to gain a basic understanding on the development of fusion reactor components. In this study, 250 keV He2+ and 130 keV H+ were used for irradiation. Then, micro-defects were annealed isochronally between 423 K and 673 K, and were monitored by the slow positron beam Doppler broadening technique. The results revealed that the He ions implanted into the steels combined with vacancies to form HenVm clusters, and were likely to grow and form overpressured HenVm clusters by thermal activation. The S-W line of the irradiated specimen deviated the line segment, which indicates the formation of overpressured HenVm clusters in the He-irradiated steel. Moreover, the ΔS-E curves indicate residual vacancies that were induced by He-irradiation at 723 K and later migrated toward the bulk of the sample at 423 K. Subsequently, the vacancies tended to migrate to the sample surface as the annealing temperature increased. The S parameter of the He+H-irradiated sample was much larger than that of all other samples, owing to the synergy effect of H and He. After annealing at 423 K, the H-V clusters decomposed and the hydrogen atoms in the He+H-irradiated sample escaped from the surface leaving a large number of vacancies.

Crystalline covalent triazine frameworks (CTFs) have shown intriguing applications in photoelectric fields. So far, a number of synthetic strategies based on homogeneous nucleation have been report...

Emerging natural-enzyme-based nanocatalytic tumor therapy depending on the high catalytic performance of natural enzymes has inspired great research interest in clinical applications. Nevertheless, the natural-enzyme-based catalytic therapy efficiency is seriously hampered by the low operational stability, poor delivery efficiency, and the short lifetime of enzymes. Herein, a bioreactor based on zeolitic imidazolate framework-8 (ZIF-8) was fabricated through one-pot embedding horseradish peroxidase (HRP) and glucose oxidase (Gox) strategy (ZIF-8@Gox/HRP) for synergistic cancer therapy. Notably, the obtained ZIF-8@Gox/HRP can efficiently consume endogenous glucose to generate gluconic acid and H2O2 for starving tumors, and subsequently, H2O2 was decomposed by encapsulated HRP to release high-toxic •OH radicals, inducing cancer cell apoptosis for oxidation therapy. Importantly, in vivo results showed that ZIF-8@Gox/HRP had an impressive tumor-suppression rate based on cascade catalytic reaction. Therefore, this work paves a new avenue to design smart enzyme-based platforms for safe and efficient cancer therapy.

Simultaneous electrochemical determination of 4-aminophenol (4-AP) and acetaminophen (ACOP) is crucial due to their high toxicity when are overused. Herein, a novel electrocatalyst of nitrogen-doped carbon coated CoNi alloy (CoNi@CN) is derived from bimetallic CoNi(BDC)2(DABCO) for the first time. A series of characterizations demonstrate that composite has been successfully synthesized, and all elements are evenly distributed in the catalyst. The optimal sensor based on Co1Ni1@CN-700 exhibits two wide linear responses for 4-AP (0.05–60 μM and 60–250 μM) and ACOP (0.05–40 μM and 40–150 μM) with the lowest detection limit of 5.2 nM and 3.8 nM compared with current known reports. Moreover, the sensor has superior reproducibility, selectivity and stability. In addition, the wonderful recoveries also are obtained when sensor is used to detect 4-AP and ACOP in real samples, illustrating that electrochemical sensor has great prospect in the clinical application.

Metal–organic framework Ni2(BDC)2(DABCO) (Ni-MOF)/porous graphene aerogel (PGA) composites were fabricated for the first time. The introduction of PGA enhances conductivity of Ni-MOF, prevents Ni-MOF from accumulating, reduces the size of Ni-MOF, and increases the pore size of composites, which improve the electrocatalytic activity of Ni-MOF@PGA-2. The prepared sensors based on Ni-MOF@PGA-2 composite show the highest catalytic current towards electroreduction of 2-nitrochlorobenzene (2-NCB), 3-nitrochlorobenzene (3-NCB), and 4-nitrochlorobenzene (4-NCB) at around − 0.61 V, − 0.56 V, and − 0.57 V (vs. Ag/AgCl) with respect to other sensors. The reaction mechanisms also are discussed. Under optimized experiment conditions, the Ni-MOF@PGA-2/GCE displays the widest linear range (6–1260, 4–980, and 2–1280 μM for 2-NCB, 3-NCB, and 4-NCB, respectively) for determination of individual nitrochlorobenzene isomers (NCBIs) compared to that of recent reports, and relatively low detection limit (0.093, 0.085, and 0.051 μM for 2-NCB, 3-NCB, and 4-NCB, respectively). More importantly, three NCBIs in the mixture were for the first time simultaneously determined by combining differential pulse voltammetry (DPV) based on Ni-MOF@PGA-2/GCE with partial least squares (PLS) chemometrics modeling method. The proposed method was evaluated towards the determination of NCBI mixtures in tap water and Jing lake water, and satisfactory recoveries were obtained.

Rational design and synthesis of multifunctional electrocatalysts with high-efficient activity and robust stability toward the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly desirable, but remain a challenging step. Herein, a novel hollow bimetallic carbide/nitrogen-doped carbon nanotube (Co6Mo6C2@NCNT) is successfully synthesized through the simple pyrolysis of polypyrrole (PPy)-supported metal-organic framework (MOF) composite. Remarkable characteristics of the large surface area, hollow and porous structure, rich active sites and synergistic effect between Co6Mo6C2 and NCNT arouse high catalytic efficiency. Notably, the Co6Mo6C2@NCNT presents excellent ORR catalytic activity (a high half-wave potential of 0.875 V vs. reversible hydrogen electrode (RHE) and diffusion-limited current density of 6.22 mA cm−2) via a four-electron pathway, together with outstanding stability and methanol tolerance over commercial Pt/C in 0.1 M KOH solution. The composite also exhibits superior HER performance, delivering a low overpotential of 122.14 mV at current density of 10 mA cm−2, as well as good catalytic performance for OER in 1.0 M KOH solution. This work may provide some insight in design multifunctional electrocatalysts derived from MOF with advanced performance for sustainable energy technologies.