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Laboratory hydrate formation process simulation provides a theoretical support for determining the dynamic revolution behaviors of actual hydrate reservoirs. In view of this, based on the ITS electrical resistance tomography (ERT) module, a dedicated apparatus was developed to simulate the in-situ core-scale distribution of natural gas hydrate directly during the process of hydrate formation and dissociation in artificial sediments. Beach sand was used as porous media to simulate the formation of methane hydrate and assess the 2-D ERT evolution characteristics simultaneously. The findings were obtained. (1) The apparent average resistance values of hydrate-bearing sediment system are determined by the combination of hydrate forming rate and salt-removing effect, showing fluctuation rise behaviors during the process of hydrate formation. (2) When the hydrate forming rate is high enough, hysteresis influence of salt-removing effect on apparent average resistance value is observed. After the hydrate formation, there still exists a mass transfer process controlled by the difference of salt ion concentration. (3) Difference between original and real-time ERT distribution indicates a heterogeneous formation process of hydrate within the sediments. In conclusion, initial gas–water contact relationship and distribution is the virtual factors for hydrate heterogeneous distribution behaviors, while that of spatial difference of ion concentration caused by the salt-removing effect plays a key role in promoting local hydrate formation position change.

Sulfur-doped two-dimensional (2D) graphitic carbon nitride nanosheets (2D-SCN) with efficient photocatalytic activity were synthesized via (1) polycondensation of thiourea to form bulk sulfur-doped graphitic carbon nitride (SCN) and (2) followed by thermal oxidative treatment of the prepared SCN via an etching strategy to form 2D-SCN. Sulfur was doped in situ into SCN by using thiourea as the precursor, and the 2D nanosheet structure was obtained during the thermal oxidative etching process. The structural, morphological, and optical properties of the 2D-SCN sample were investigated in detail. Herein, it is shown that the thermal oxidative etching treatment and sulfur doping induced a 2D nanosheet structure (2D-SCN-3h) with a thickness of about 4.0 nm and exposure of more sulfur elements on the surface. The surface area increased from 16.6 m

Colorimetric assays have drawn increasing research interest with respect to the quantitative detection of hydrogen peroxide (H2O2) based on artificial enzymes because of their advantages with respe...

The current natural gas hydrate extraction experimental research has always been carried out in a small-scale simulation test device, and the resulted boundary effect is so obvious due to the small size of samples in the reaction kettle that the experimental results will be difficult to apply in the field. In this paper, an integrated experimental system for drilling and exploitation of gas hydrate is developed innovatively based on the idea of depressurization method and the technological process. This experimental system consists of high-pressure vesselmodule, drilling & extraction module, liquid supply module, gas supply module, confining pressure loading module, back-pressure control module, three-phase separation module, temperature control module, data acquisition module and an operational platform. The hydrate-bearing samples similar to marine hydrate formations were prepared inthe experimental system with the actual geological surroundings simulated. The electrical resistance tomography was used to real-time monitor the dynamic distribution of gas hydrate in sediments inside the high-pressure vessel (521 L). This experimental system can also simulate the process of wellbore drilling in hydrate reservoirs and depressurization extraction, and realize the real-time monitoring of parameters in the whole production process such as gas production, water production, sand production, temperature, pressure, etc. We carried out a preliminary experiment on the CO2 hydrate extraction via depressurization by using this experimental system. Fundamental procedures for data acquisition and analysis were established and verified. The variations of temperature and pressure fields and gas/water output behaviors in the reservoirs were both achieved. The results show that (1) the gas and water production rate fluctuate greatly even at a constant backpressure; (2) the reservoir temperature distribution is uneven during hydrate decomposition, and the maximum temperature is decreased by 5 °C, suggesting that the hydrate decomposition is heterogeneous and stochastic. The abundant and credible experimental results based on this system are expected to provide important data support for marine gas hydrate production tests. Keywords: Natural gas hydrate, Experimental system, Drilling and production integration, Real-time monitoring, Depressurization method, CO2 hydrate, Production behavior, Electrical resistance tomography

Bismuth vanadate (BiVO4) has been widely used as a photocatalytic semiconductor for oxygen evolution in artificial photosynthesis. In this study, one-dimensional mesoporous BiVO4 nanofibers (BiVO4 NFs) were fabricated by the electrospinning strategy. The NFs were then deposited with NiCo layered double hydroxides (NiCo LDHs) to improve their reaction kinetics, charge transfers, and water oxidation activities. The obtained BiVO4/4 wt%NiCo LDHs composite exhibits enhanced photocatalytic oxygen oxidation activity that is approximately 1.6 times higher than that of BiVO4 NFs, due to the synergistic effects between BiVO4 NFs and NiCo LDHs, which can accelerate the transfer of holes between their surfaces. This design is a promising approach for fabricating large-scale nanofibers with good photocatalytic performance.

Small molecule tyrosine kinase inhibitors (TKIs) targeting at epidermal growth factor receptor (EGFR) in recent years have made great progress in the treatment of advanced non-small cell cancer (NSCLC). Although as the first-line treatment for sensitizing EGFR mutation-positive metastatic NSCLC, gefitinib has also behaved quite a lot of side effect and EGFR tolerance. Herein, a novel series of 7-bromo-1,4-dihydrothieno[3’,2’:5,6]thiopyrano[4,3-c]pyrazole-3-carboxamide derivatives were designed and synthesized, and screened for their inhibitory activity on the EGFR high-expressing human lung adenocarcinoma cell line A549 and human large cell lung cancer cell line NCI-H460 by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide colorimetric assay. The calculated IC50 values were reported. Compound 8h demonstrated the most potent inhibitory activity (IC50 = 9.57 ± 2.20 μmol L–1 for A549 and IC50 = 13.04 ± 1.21 μmol L–1 for NCI-H460), comparable to the positive-control gefitinib (IC50 = 8.58 ± 1.65 μmol L–1 for A549 and IC50 = 18.66 ± 5.01 μmol L–1 for NCI-H460). Conclusively, 7-bromo- 1,4-dihydrothieno[3’,2’:5,6]thiopyrano[4,3-c]pyrazole-3-carboxamide derivatives as the EGFR–TKIs were discovered, and could be used as potential leading compounds for further research.

The molecular and carbon and hydrogen isotope compositions associated with the aerobic consumption of methane (Cl), ethane (C2) and propane (C3) were determined from incubations of marine sediments collected from the seafloor surface of the gas- and oil-bearing Bohai Bay in eastern China. The fresh sediment samples were incubated aerobically at 28 °C and treated with three types of hydrocarbon gas mixtures as follows: mixture I (C1:C2:C3 = 100:0:0), II (C1:C2:C3 = 99.00:0.70:0.30) and III (C1:C2:C3 = 79.96:10.04:10.00), corresponding to incubations i, ii and iii, respectively. All the hydrocarbons are of thermogenic origin, except C1 (microbial) in incubation ii. The oxidation of C1-C3 was observed in all three treatments, with variations in carbon isotope fractionation factors (eC) of C1 and average values of −10.5 ± 0.1, −5.7 ± 1.6, and −10.9 ± 2.9, respectively. The hydrogen isotope fractionation factors (eH) of C1 in the three incubations also display variation, with average values of −118.4 ± 3.0, −68.3 ± 15.0 and −56.3 ± 8.4, respectively. Experiments with thermogenic C1 display greater carbon fractionation than those with microbial C1. The eC and eH values for C2 and C3 were obtained only in incubation iii. Compared to C1, C2 and C3 exhibit weaker carbon isotope fractionation but stronger hydrogen isotope fractionation. The fractionation factors presented in this study can be applied to estimate the extent of C1-C3 oxidation in natural environments, especially at seafloor and terrestrial seeps where aerobic microbes are commonly present. Our study has important implications in oil and gas exploration, with an alert for exercising caution when using the molecular and isotopic characteristics of hydrocarbon gases to evaluate the gas sources because these are susceptible to aerobic microbial oxidation.

The development of highly efficient and long-term durable electrocatalyst for oxygen evolution reaction is still a great challenge to attain renewable and clean energy. Herein, CoSe2@N-Doped-carbon-nanorods named as CoSe2@NC nanorods have been conveniently synthesized by in-situ selenization of a novel N-doped metal organic frameworks under N2 atmosphere . CoSe2@NC nanorods show highly efficient electrocatalytic performance for oxygen evolution reaction at a low overpotential of 310 mV for 10 mA cm−2 current density in 1.0 M KOH aqueous solution, which are comparable to the state-of-the-art RuO2 and IrO2 catalysts. The remarkable electrocatalytic performance can be attributed to the unique N-doped MOFs derived well-defined architecture with large active surface area, high conductivity of carbon and well-distributed active sites. In addition, CoSe2@NC nanorods exhibit long-term stability without obvious decay after 1000 cyclic voltammetry cycles.

Optimization of the depressurization pathways plays a crucial role in avoiding potential geohazards while increasing hydrate production efficiency. In this study, methane hydrate was formed in a flexible plastic vessel and then gas production processes were conducted at constant confining pressure and constant confining temperature. The CMG-STARS simulator was applied to match the experimental gas production behavior and to derive the hydrate intrinsic dissociation constant. Secondly, fluid production behavior, pressure-temperature ( P ‐ T ) responses, and hydrate saturation evolution behaviors under different depressurization pathways were analyzed. The results show that integrated gas-water ratio (IGWR) decreases linearly with the increase in depressurizing magnitude in each step, while it rises logarithmically with the increase in the number of steps. Under the same initial average hydrate saturation and the same total pressure-drop magnitude, a slow and multistage depressurization strategy would help to increase the IGWR and avoid severe temperature drop. The pore pressure rebounds logarithmically once the gas production is suspended, and would decrease to the regular level instantaneously once the shut-in operation is ended. We speculate that the shut-in operation could barely affect the IGWR and formation P ‐ T response in the long-term level.

Hematite is recognized as an excellent photocatalyst for photoelectrochemical photoanodes for water oxidation because of its favorable band gap, excellent anti-photocorrosion and structural stability in alkaline solution. However, slow charge transport and fast carrier recombination in the bulk and at the hematite photoanode/electrolyte interface, have limited its applications for water splitting. Herein, we report a highly efficient hematite/ferrhydrite (Fh) core-shell photoanode system, consisting of hematite (α-Fe2O3) semiconductor nanorods which dramatically enhance light harvesting, and ferrhydrite as the hole-storage shell. Our integrated hematite/ferrhydrite core-shell photoanode shows 2.7 times increased photo-current density under simulated sun light irradiation.

Hydraulic properties of hydrate-bearing sediments are largely affected by the maximum size of pores occupied by fluids. However, effects of host particle properties on the maximum size of fluid-occupied pores within hydrate-bearing sediments remain elusive, and differences in the maximum equivalent, incircle, and hydraulic diameters of fluid-occupied pores evolving with hydrate saturation have not been well understood. In this study, numerical simulations of grain-coating and pore-filling hydrate nucleation and growth within different artificial porous media are performed to quantify the maximum equivalent, incircle, and hydraulic diameters of fluid-occupied pores during hydrate formation, and how maximum diameters of fluid-occupied pores change with hydrate saturation is analyzed. Then, theoretical models of geometry factors for incircle and hydraulic diameters are proposed based on fractal theory, and variations of fluid-occupied pore shapes during hydrate formation are discussed. Results show that host particle properties have obvious effects on the intrinsic maximum diameters of fluid-occupied pores and introduce discrepancies in evolutions of the maximum pore diameters during hydrate formation. Pore-filling hydrates reduce the maximum incircle and hydraulic diameters of fluid-occupied pores much more significantly than grain-coating hydrates; however, hydrate pore habits have minor effects on the maximum equivalent diameter reduction. Shapes of fluid-occupied pores change little due to the presence of grain-coating hydrates, but pore-filling hydrates lead to much fibrous shapes of fluid-occupied pores.

The HotDisk thermal constants analyzer based on the transient plane source (TPS) technique can be used to measure the hydrate thermal conductivity. In order to improve the measurement accuracy, the HotDisk setting parameters, the sample preparation and measurement method are investigated in this paper. Firstly, the evaluation criteria are proposed to determine the optimal setting parameters, mainly the output power and measurement time. Four kinds of method of the sample preparation and thermal conductivity measurement in situ are proposed and discussed. The used samples include pure Tetrahydrofuran (THF) hydrate, ice and THF hydrate or ice bearing silica sand. The results show that the optimal parameters of the output power and measurement time depend on the sample. A high purity of sample can be obtained using the temperature oscillation-aging method and the accuracy of measurement can be further improved using the “increasing temperature-decreasing temperature” method.

A series of novel visible light driven all-solid-state Z-scheme BiOBr0.3I0.7/Ag/AgI photocatalysts were synthesized by facile in situ precipitation and photo-reduction methods. Under visible light irradiation, the BiOBr0.3I0.7/Ag/AgI samples exhibited enhanced photocatalytic activity compared to BiOBr0.3I0.7 and AgI in the degradation of methyl orange (MO). The optimal ratio of added elemental Ag was 15%, which degraded 89% of MO within 20 min. The enhanced photocatalytic activity of BiOBr0.3I0.7/Ag/AgI can be ascribed to the efficient separation of photo-generated electron–hole pairs through a Z-scheme charge-carrier migration pathway, in which Ag nanoparticles act as electron mediators. The mechanism study indicated that ·O2 − and h+ are active radicals for photocatalytic degradation and that a small amount of ·OH also participates in the photocatalytic degradation process.

In this work, a series of efficient visible-light-driven WO3/Cu (II) nanofiber photocatalysts, with superior photocatalytic activities for the degradation of dyes and aniline, were prepared by electrospinning and impregnation methods. The impregnation method brought about homogeneous distribution of Cu (II) species on the surface of WO3 nanofibers. The prepared WO3/Cu (II) nanofiber photocatalysts exhibited enhanced visible-light absorption and reduced charge recombination, as compared to pure WO3 nanofibers, due to the interfacial charge transfer (IFCT) effect between the Cu (II) species and WO3. The combined benefits of the grafting Cu (II) species on the surface of WO3, in terms of optical, surface, and texture properties, led to a significant improvement in the photocatalytic activity for the degradation of Rhodamine B (Rh B) and aniline under conditions of visible light irradiation. Upon the irradiation with visible light in the presence of WO3/Cu (II)-2% photocatalyst, the concentration of Rhodamine B (Rh B) decreased from 10 mg/L to 1.5 mg/L, and that of aniline solution decreased from 5 mg/L to 0.728 mg/L over a period of 3 h. And after running five cycles, the concentration of aniline solution could decrease from 5 mg/L to 0.89 mg/L by WO3/Cu (II)-2% photocatalyst.

3,5-Bis(arylidene)piperidin-4-one derivatives (BAPs) display good antitumour activity because of their double α,β-unsaturated ketone structural characteristics. Reported BAPs have generally been symmetric and asymmetric BAPs have been little documented. Three asymmetric BAPs, namely (5E)-3-(4-tert-butylbenzylidene)-5-(4-fluorobenzylidene)-1-methylpiperidin-4-one, C24H26FNO, (5), (5E)-3-(4-tert-butylbenzylidene)-5-(3,5-dimethoxybenzylidene)-1-methylpiperidin-4-one, C26H31NO3, (6), and (5E)-3-{3-[(E)-(2,3-dihydroxybenzylidene)amino]benzylidene}-5-(2-fluorobenzylidene)-1-methylpiperidin-4-one, C27H23FN2O3, (12), were generated by Claisen–Schmidt condensation. They are characterized by NMR and FT–IR spectroscopies, and elemental analysis. Single-crystal structure analysis reveals that the two arylidene rings on both sides of the BAP structures adopt an E stereochemistry of the olefinic double bonds and the compounds are E,E isomers. Molecules of (5) and (12) generate one-dimensional chains through intermolecular hydrogen bonds, while compound (6) generates a two-dimensional network through hydrogen bonds. Preliminary cytotoxicities toward human liver hepatocellular carcinoma cell line (HepG2), human acute mononuclear granulocyte leukaemia (THP-1) and human normal hepatical cell line (LO2) were evaluated.

Thermal conductivity and thermal diffusivity of pure methane hydrate samples, formed from compacted granular ice (0–75 μm), and were measured simultaneously by the transient plane source (TPS) technique. The temperature dependence was measured between 263.15 and 283.05 K, and the gas-phase pressure dependence was measured between 2 and 10 MPa. It is revealed that the thermal conductivity of pure methane hydrate exhibits a positive trend with temperature and increases from 0.4877 to 0.5467 W·m−1·K−1. The thermal diffusivity of methane hydrate has inverse dependence on temperature and the values in the temperature range from 0.2940 to 0.3754 mm2·s−1, which is more than twice that of water. The experimental results show that the effects of gas-phase pressure on the thermal conductivity and thermal diffusivity are very small. Thermal conductivity of methane hydrate is found to have weakly positive gas-phase pressure dependence, whereas the thermal diffusivity has slightly negative trend with gas-phase pressure.

Si nanowires (SiNWs) and graphite-like carbon nitride (g-C3N4) are highly promising materials for solar water splitting. In this work, n-type SiNWs (n-SiNWs) are obtained via metal-catalyzed electroless etching. To improve the photoelectrochemical performance of the n-SiNWs, g-C3N4 is deposited on their surface as a coating layer (n-SiNW/g-C3N4). Furthermore, to increase the density of active sites in g-C3N4, barbituric acid (BA) is introduced into precursors before the layer deposition. The n-SiNW/g-C3N4 photoanode shows a negative shift of the onset potential as compared to the bare n-SiNWs. Moreover, a 50% enhancement in the photocurrent density at 1.6V vs. RHE is achieved on the BA-modified n-SiNW/g-C3N4 as compared to the pristine n-SiNW/g-C3N4. Keywords: Water splitting, Si nanowires, Graphite-like carbon nitride, Core/shell nanostructure, Copolymerization modification

A series of barbituric acid doped carbon nitride (CN-BA) photocatalysts were successfully prepared by copolymerizing dicyandiamide with barbituric acid (BA). Under AM1.5 simulated sunlight, CN-BA photocatalysts exhibit enhanced photocatalytic activity compared to pure carbon nitride for the degradation of aniline. The highest activity is obtained with 2% doped CN-BA photocatalyst. Results on the photodegradation of aniline indicate that for the optimized CN-BA photocatalyst, the concentration of aniline solution was reduced gradually from 16 mg/L to 1.354 mg/L in 2 h. This corresponds to a 6 times higher photodegradation efficiency than pure carbon nitride samples. The enhanced photocatalytic activity of CN-BA relies on the enhanced surface area, the higher light absorption and the reduced recombination of the photo-generated electron-hole pairs. This interpretation results from multiple characterizations with EPR, BET, N2 adsorption, Solid-state 13C NMR, UV–vis DRS, FESEM, and TEM. Under simulated sunlight irradiation, CN-BA is excited and generates electron-hole pairs. The photo-generated electrons in the CN-BA conduction band react with the molecular oxygen to form O2−. Part of the O2− transforms into OH, which further oxides aniline. Meanwhile, photo-generated holes in the valence band of CN-BA can benefit to the formation of OH or directly oxide aniline.

In this study, a series of visible-light-driven BiOBrxI1-x solid solution nanoplates photocatalysts are successfully prepared by an ultrasound-assisted hydrolysis method, which does not use organic reagents, with advantages of cost-effectiveness and non-toxicity. Under visible-light irradiation, all of the as-prepared BiOBrxI1-x nanoplates exhibit superior photocatalytic activities compared to those of pure BiOBr and BiOI for the degradation of methyl orange (MO). BiOBr0.3I0.7 exhibits the highest photocatalytic activity, corresponding to the degradation of 92% MO in 40 min under visible-light irradiation. The structures and elemental composition of the as-prepared BiOBrxI1-x nanoplates samples are characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. From the results obtained from X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy, and transient time-resolved luminescence decay, it is suggested that the enhanced photocatalytic activity of BiOBrxI1-x is possibly related to the narrowing of the band gap and high separation of the photo-generated electron–hole pairs. Electron paramagnetic resonance and mechanistic experiments indicated that O2− and h+ are active radicals for photocatalytic degradation. In conclusion, an ultrasound-assisted hydrolysis method which is free of organic reagents is developed for synthesizing BiOBrxI1-x nanoplates photocatalysts with tunable bandgap and enhanced photocatalytic activity.

Nuclear magnetic resonance (NMR) is an effective method used for measuring and predicting the properties of methane hydrate (MH)-bearing sediments. In this work we present the results of MH-related interface evolution during the MH dissociation process obtained by X-ray computed tomography (CT) imaging technique. Some implications of interface evolution for the NMR-based property predictions are analysed based on the experimental measurements. The results show that the areas of MH surface and MH-brine interface decrease slowly in the early stage of dissociation, but turns to decrease rapidly in the later stage. A conceptual model for determining the NMR transverse surface relaxivity (ρ2) in the hydrate-bearing sediment is proposed by considering these changes of MH-related interface. Predictions based on this model show that the NMR transverse surface relaxivity and effective permeability are both influenced by the influencing weight and surface area proportions of the MH-brine surface and sand-brine surface.

Using two trans-dicyanidechromium(III) precursors K[Cr(bpdmb)(CN)2] (bpdmb2− = 1,2-bis(pyridine-2-carboxamido)-4,5-dimethyl-benzenate), K[Cr(bpClb)-(CN)2] (bpClb2− = 1,2-bis(pyridine-2-carboxamido)-4-chloro-benzenate) and one Cu(II) complex of a 14-membered macrocycle as ancillary organic ligand as assembling segments, two one-dimensional cyanide-bridged CrIII–CuII complexes {{[Cu(cyclam)][Cr(bpdmb)(CN)2]}ClO4} n ·nCH3OH·nH2O (1) and {{[Cu(cyclam)][Cr(bpClb)(CN)2]}ClO4} n ·nCH3OH (2) (cyclam = 1,4,8,11-tetraazacyclotetradecane) have been synthesized and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. Single X-ray diffraction analysis shows that their similar one-dimensional cationic single-chain structures consist of alternating units of [Cu(cyclam)]2+ and [Cr(bpdmb)(CN)2]−/[Cr(bpClb)(CN)2]− with free ClO4 − as balancing anions. Investigations of the temperature dependences of magnetic susceptibility and the field-dependent magnetization reveal that both complexes have overall ferromagnetic coupling between the neighboring Cr(III) and Cu(II) centers through the bridging cyanide groups.

The characteristics of the hydrate-bearing layer are important parameters for gas hydrate exploration and exploitation, which can be provided by laboratory analysis. We have carried out a systematic analysis of modern instruments, including the laser grain size analyzer, X-ray computed tomography, scanning electron microscopy, X-ray diffraction (XRD), Raman spectroscopy, gas chromatography, and isotope mass spectrometry, on the hydrate-bearing sediment samples recovered from the Shenhu area in the South China Sea in 2016. We focused on the structure, hydration number, and gas composition of the gas hydrate samples. We also evaluated the effects of sediments on the occurrence and distribution of gas hydrate. Our results showed that the sediments are much finer than those recovered from the Shenhu area in 2007. Some samples are found to contain calcareous microfossils and foraminifera, which are beneficial for dispersed gas hydrate formation. Whereas the only visible hydrate sample (FC4) has not found any bioclast in the sediments. Based on the Raman data and the XRD analysis, the gas hydrates demonstrate typical structure I (sI) hydrates, with cage occupancies of methane molecules higher than 99.3% in large cages and 81.5%–91.4% in small cages, respectively. The crystal lattice parameter is 11.89 Å with the hydration number being approximately 6.0. Methane is obviously the dominant component, ranging from 97.6% to 99.95% in these samples. Comprehensive study of carbon and hydrogen isotopes suggests that the hydrate-bound gases are from biogenic and thermogenic gases in the study area.

Carbon Nitride is considered as a promising photocatalyst material because of its unique properties such as environment-friendly, suitable band gap and high stability. However, the photocatalytic activity of pristine g-C3N4 was greatly hindered by the recombination of photo-generated electron-hole pairs. In this work, we provide an alternative method to address this problem by the construction of g-C3N4 isotype heterojunction (CNH−T/CNH−U) structure, which was successfully synthesized by a facile protonation assisted hydrothermal method. Under the irradiation of visible light (λ > 420 nm), the CNH−T/CNH−U isotype heterojunction photocatalyst displays much higher photodegradation activity of organic dyes degradation and H2-production activity than the pure CNH−T or CNH−U sample. This remarkably improved photocatalytic performance is attributed to the successful construction of CNH−T/CNH−U isotype heterojunction associated by protonation, which results in larger surface area and the more efficient separation of photo-generated electron-hole pairs, further investigated by electron paramagnetic resonance, photoluminescence, photocurrent measurement, and a series of active species trapping experiments.

Ocotillol-type saponins are one kind of tetracyclic triterpenoids, sharing a tetrahydrofuran ring. Natural ocotillol-type saponins have been discovered in Panax quinquefolius L., Panax japonicus, Hana mina, and Vietnamese ginseng. In recent years, the semisynthesis of 20(S/R)-ocotillol-type saponins has been reported. The biological activities of ocotillol-type saponins include neuroprotective effect, antimyocardial ischemia, antiinflammatory, antibacterial, and antitumor activities. Owing to their chemical structure, pharmacological actions, and the stereoselective activity on antimyocardial ischemia, ocotillol-type saponins are subjected to extensive consideration. In this review, we sum up the discovery, semisynthesis, biological activities, and metabolism of ocotillol-type saponins.

In the current study, a mediator-free solid-state BiVO4/pyridine-doped g-C3N4 nano-Z-scheme photocatalytic system (BDCN) with superior visible-light absorption and optimized photocatalytic activity was constructed via an in situ hydrothermal method for the first time. The pyridine-doped g-C3N4 (DCN) nanosheets show strong absorbance in the visible-light region by pyridine doping, and the BiVO4 (∼10 nm) nanoparticles are successfully in situ grown on the surface of DCN nanosheets by the controlled hydrothermal method. Under the irradiation of visible light (λ > 420 nm), the BiVO4/DCN nanocomposite photocatalysts efficiently degrade phenol and methyl orange (MO) and display much higher photocatalytic activity than the individual DCN, bulk BiVO4, or the simple physical mixture of DCN and BiVO4. The greatly improved photocatalytic ability is attributed to the construction of the direct Z-scheme system in the BiVO4/DCN nanocomposite free from any mediator, which leads to enhanced separation of photogenerated electron–hole pairs, as confirmed by the photocurrent analysis. The possible Z-scheme mechanism of the BiVO4/DCN nanocomposite photocatalyst was investigated by transient time-resolved luminescence decay spectrum, active species trapping experiments, electron paramagnetic resonance (EPR) technology, and hydrogen evolution test.

A large Ho 3+ :Li 3 Ba 2 La 3 (MoO 4 ) 8 crystal with high optical quality and well-developed appearance was grown by the flux method. The main spectral properties of the crystal, including the absorption spectra, fluorescence spectra and fluorescence decay curves were recorded at room temperature. The Judd-Ofelt (J-O) theory was applied to calculate the oscillator strength parameters Ω t ( t =2, 4, 6), spontaneous emission probabilities, fluorescence branching ratios, and radiative lifetimes of Ho 3+ ions undergoing transitions from ground state 5 I 8 to the excited states. The stimulated emission cross-section for the 5 I 7 → 5 I 8 transition was estimated to be 1.32×10 −20 cm 2 at 2045 nm by Fuchtbauer-Ladenburg (F-L) equation and the quantum efficiency of the 5 I 7 level was calculated to be 89%.

In this work, we have prepared a series of efficient visible-light-driven WO3/Fe(III) nanofiber photocatalysts by electrospinning and impregnation method. The physical and optical properties of the prepared photocatalysts were characterized by field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the nitrogen adsorption analysis. Under the irradiation of visible light, all the prepared WO3/Fe(III) nanofiber photocatalysts exhibit much higher activity for degrading methyl orange (MO) solution than the pristine WO3 nanofibers, and reaches 94.6% under visible light irradiation for 3 h when the relative grafting amount of Fe(III) ions was 0.003 by mass percentage. Grafting of Fe(III) ions on the surface of WO3 nanofiber could enhance its visible-light absorption and reduce the photo-generated electron-hole pairs recombination due to the interfacial charge transfer (IFCT) effect, and thus improve its photocatalytic activity, which were further verified by the ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence (PL) and the ns-level time-resolved fluorescence decay spectrum measurements.

A photoelectrochemical (PEC) cell made of metal-free carbon nitride (g-C3N4) @siliconnanowire(Si NW) arrays (denoted as Si NWs/g-C3N4) is presented in this work. The as-prepared photoelectrodes with different mass contents of g-C3N4 have been synthesized via a metal-catalyzed electroless etching (MCEE), liquid atomic layer deposition (LALD) and annealing methods. The amount of g-C3N4 on the Si NW arrays can be controlled by tuning the concentration of the cyanamide solution used in the LALD procedure. The dense and vertically aligned Si NWs/g-C3N4 core/shell nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In comparison with FTO/g-C3N4 and Si NW samples, the Si NWs/g-C3N4 samples showed significantly enhanced photocurrents over the entire potential sweep range. Electrochemical impedance spectroscopy (EIS) was conducted to investigate the properties of the charge transfer process, and the results indicated that the enhanced PEC performance may be due to the increased photo-generated interfacial charge transfer between the Si NWs and g-C3N4. The photocurrent density reached 45 μA/cm2 under 100 mW/cm2 (AM 1.5 G) illumination at 0 V (vs. Pt) in neutral Na2SO4 solution (pH ∼ 7.62). Finally, a systematical PEC mechanism of the Si NWs/g-C3N4 was proposed.

Graphene nanoplatelets with excellent electrical conductivity in polymer matrices are highly promising for the industrial application of electrical conductive materials, however, poor dispersion results in high contents of graphene nanoplatelets being required for electrical property enhancement. In this study, graphene nanoplatelets (GNP)@polyaniline (PANI) nanocomposites were synthesized by in situ polymerization whereas the compatibility between GNP@PANI nanocomposites and the polymer matrix improved significantly due to graphene nanoplatelet encapsulation with polyaniline. GNP@PANI nanocomposites were utilized to prepare a permanent antistatic high-density polyethylene (HDPE) composite through solution blending and press forming in order for GNP@PANI nanocomposites to be dispersed homogeneously in the HDPE. The dispersion and compatibility of GNP@PANI nanocomposites in the HDPE were verified by morphology characterization, resulting in significant improvement of the electrical properties of the GNP@PANI/HDPE composites. It was observed that surface resistivity (ρs) and volume resistivity (ρv) decreased sharply with a 10 wt% GNP@PANI addition of nanocomposites. The results displayed that in situ polymerization and solution blending were effective methods for a conductive network establishment by addition of only 2 wt% of GNP and 8 wt% of PANI.

C25H23Br2ClN3NaNiO9, monoclinic, P21/n (no. 14), a = 15.595(4) Å, b = 10.993(3) Å, c = 18.660(5) Å, β = 114.536(4), V = 2910.2(14) Å3, Z = 4, R gt(F) = 0.0390, wR ref(F 2) = 0.0998, T = 293 K.

To explore the photocatalytic performances and optoelectronic properties of pure and doped bismuth oxyhalides D-doped BiOX (D = Ag, Pd, X = F, Cl, Br, I) compounds, their atomic properties, electronic structures, and optical properties were systematically investigated using first-principles calculations. In previous experiments, the BiOX (X = Cl, Br) based system has been observed with enhanced visible light photocatalytic activity driven by the Ag dopant. Our calculations also show that the potential photocatalytic performance of Ag-doped BiOCl or BiOBr systems is enhanced greatly under visible light, compared with other Pd-doped BiOX (X = Cl, Br) compounds. Furthermore, it is intriguing to find that the Pd-doped BiOF compound has strong absorption over the infrared and visible light spectrum, which may offer an effective strategy for a promising full spectrum catalyst. Indicated by various Mulliken charge distributions and different impurity states in the gap when Ag or Pd was doped in the BiOX compounds, we notice that all D-doped BiOXs exhibit a p-type semiconductor, and all impurity levels originated from the D-4d state. The charge transfer, optoelectronic properties, and absorption coefficients for photocatalytic activities among D-doped BiOX photocatalysts caused by the electronegativity difference of halide elements and metal atoms will finally affect the photocatalytic activity of doped BiOX systems. Therefore, it is significant to understand the inside physical mechanism of the enhanced Ag/Pd-doped BiOX photocatalysts through density functional theory.

Modification of a photocatalyst with single-atom noble metals can improve its activity while a remaining challenge is the stabilization of single atoms. As a proof of concept, g-C3N4 with desired amount of carbon defects was fabricated to manipulate the distribution of single-atom Pd by taking advantage of its affinity with carbon vacancy-resulted nitrogen atoms. The single-atom Pd was produced by photo-reduction, preferentially located on the carbon vacancy sites as supported by HAADF-STEM and XAFS analyses. As obtained photocatalyst showed high and stable photocatalytic activity in NO conversion; its activity is about 4.4 times higher than that of the pristine g-C3N4. The improved photoactivity was attributed to the preferential separation and transportation of the photo-generated charge carriers due to the introduction of single-atom Pd as evidenced by UV–vis, static and time-resolved photoluminescence spectroscopic analyses. The present work underlines the impetus of surface defect chemistry in the fabrication of single-atom catalysts.

Photofragmentation mechanisms of gas-phase lanthanide tris(isopropylcyclopentadienyl) complexes, Ln(iCp)3, were studied through experimental photoionization time-of-flight mass spectrometry (PI-TOF-MS). A DFT-based time-dependent excited-state molecular dynamics (TDESMD) algorithm, under standard approximations, was used to simulate the photofragmentation process. Two competing reaction pathways, intact ligand stripping and ligand cracking within the metal–ligand complex, were hypothesized based on experimental data. It was evident that intramolecular hydrogen, methyl, and isopropyl abstraction play an important role in the ligand-cracking reaction pathway, leading to metal carbide and metal hydrocarbide products. The TDESMD simulations also produced branching reaction pathways for ligand ejection and ligand cracking and further suggested that both pathways are initiated by ligand-to-metal charge transfer. Although the simulations reproduced several of the proposed reactions and several of the products of...

MIL-53(Al) was synthesized in a mixture of aluminum nitrate, 1,4-benzenedicarboxylic acid, and water using the hydrothermal and reflux methods. A metal–organic-framework-supported Au-based heterogeneous catalyst (Au/MIL-53(Al)) was prepared using the impregnation method under mild conditions with HAuCl4·4H2O as the Au precursors. The physicochemical properties of the samples were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TG), transmission electron microscopy (TEM), and inductively coupled plasma atomic emission spectroscopy (ICP–AES). MIL-53(Al) indicates excellent chemical stability without structure degradation during the loading and catalysis process. The XPS spectra indicate that the catalyst Au/MIL-53(Al) contains coexisting Au0 and Au3+ ions. The catalytic performance of the catalyst was examined in one-pot synthesis of structurally divergent propargylamines via three component coupling of aldehyde, alkyne, and amine (A3) in 1,4-dioxane. The results showed that the catalyst Au/MIL-53(Al) displayed high activity without any additives or an inert atmosphere (the yield reached 97.9 % for 5 h at 120 °C). Au/MIL-53(Al) has proven to be applicable to a wide range of substrates. Various aromatic/aliphatic aldehydes, aromatic alkynes, and piperidine were able to undergo A3 coupling on the catalyst Au/MIL-53(Al). In addition, the catalyst could be recovered easily by centrifugation and reused three times.

Two C24 epimeric 3-acetylated ocotillol-type sapogenins, 20 R,24 S-epoxy-dammarane-3β,12β,25-triol acetate and 20 R,24 R-epoxy-dammarane-3β,12β,25-triol acetate have been achieved from 20( R)-protopanaxadiol. Their structures were confirmed by HRMS, 1H NMR, 13C NMR and single crystal X-ray diffraction which showed that their configurations were (20 R, 24 S) and (20 R, 24 R), respectively. In the crystal structure of the 24 ( S)-epimer, there were two intramolecular hydrogen bonds and a left-handed helical chain whilst in the 24 ( R)-epimer there was one intramolecular hydrogen bond and a right-handed helical chain.

A novel dinuclear Cu(II) coordination polymer, [Cu(BCPPO)H2O]n (1) [H2BCPPO = bis -4-carboxyphenyl phenyl phosphine oxide], has been synthesized and structurally characterized by single crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis, elemental analysis and infrared spectroscopy. As revealed by the single crystal X-ray diffraction, in complex 1, two paddle-wheel-type Cu2 units were connected by two BCPPO ligands to form one-dimensional infinite chain. The A3 coupling reaction of phenylacetylene, aldehyde and amine (piperidine) in the presence of the dinuclear Cu(II) coordination polymer as an efficient heterogeneous catalyst has also been studied. Complex 1 displayed high activity and afforded the corresponding propargylamines with moderate yields.

The structures of coordination polymers are strongly influenced by the organic ligands and metal ions used for their construction, so it is important to choose suitable ligands and metal ions and appropriate synthetic processes. Two noveld10coordination polymers, namely poly[[diaquabis(2,2′-bipyridine)[μ4-4,4′-(1,4-phenylenedioxy)bis(benzene-1,2-dicarboxylato)]dizinc(II)] dihydrate], {[Zn2(C22H10O10)(C10H8N2)2(H2O)2]·2H2O}n, (1), and poly[[diaquabis(1,10-phenanthroline)[μ4-4,4′-(1,4-phenylenedioxy)bis(benzene-1,2-dicarboxylato)]dicadmium(II)] dimethylformamide disolvate], {[Cd2(C22H10O10)(C12H8N2)2(H2O)2]·2C3H7NO}n, (2), have been synthesized from 4,4′-(1,4-phenylenedioxy)bis(benzene-1,2-dicarboxylic acid) (H4L) and two different N-containing auxiliary ligands through a mixed-ligand synthetic strategy under a solvothermal environment. The structures were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis and IR spectroscopy. Compounds (1) and (2) both present one-dimensional chain structures and two-dimensional supramolecular layer structures constructed by weak hydrogen bonds. It is interesting to note that the carboxylate ligands reveal stabletransconfigurations in both compounds. The fluorescence properties of (1) and (2) in the solid state were also investigated.

Deltamethrin is used widely in Eriocheir sinensis aquaculture to remove wild fish and parasites. The residual deltamethrin greatly affects the growth and quality of E. sinensis. In this study, the LC50 of deltamethrin against E. sinensis at 24, 48 and 96 h was determined to be 6.5, 5.0 and 2.8 μg/L, respectively. The enzyme activity and gene transcription of SOD, CAT, and PO in the hepatopancreas of E. sinensis after deltamethrin stimulation showed an increasing tendency, and these enzymes reached their maximum activities at 6–10 d. The MDA content accumulated with increased time of deltamethrin stress. After 15 d of deltamethrin stress, the hepatopancreas of E. sinensis was found to be damaged based on HE staining. These results showed that deltamethrin is highly toxic to E. sinensis. But the half-life of deltamethrin is long and mainly relies on biodegradation. To resolve the pollution of residual deltamethrin, a strain of deltamethrin-degrading bacteria, P-2, was isolated from the sediment of an E. sinensis culture pond. Through morphological observation, physiological and biochemical identification and 16S rDNA sequence analysis, we found that this strain belonged to Paracoccus sp. When the pH was 7, the substrate concentration was low, the inoculation amount was high, and the deltamethrin degradation effect of Paracoccus sp. P-2 was good. The deltamethrin residue in the hepatopancreas and muscle of E. sinensis decreased significantly when Paracoccus sp. P-2 was added at 6.0 × 108 CFU/L. The degradation efficiency of Paracoccus sp. P-2 in the hepatopancreas and muscle was more than 70%. These results showed that Paracoccus sp. P-2, the first deltamethrin-degrading bacterium in aquaculture, could be used to remove residual deltamethrin and improve the food safety of E. sinensis.

Hydrate occupancy, morphology and spatial distribution in sediment pore can significantly affect the physical properties of hydrate-bearing sediment, but their evolutions with hydrate dissociation under various brine saturations are not well understood. X-ray micro-CT is employed to image the pore-scale dynamic process of methane hydrate dissociation in both sediments with different brine saturations. On the basis of processing and statistical analysis of X-ray CT images, several topological parameters, including volume, shape factor, fractal dimension and Euler characteristic of individual hydrate cluster, are selected to quantify hydrate occupancy, morphology and microstructure evolution with hydrate dissociation in the host sediments. Results show that the degree of brine saturation within the sediments can exert a significant impact on hydrate pore occupancy, morphology and microstructure connectedness during hydrate dissociation. In contrary to those of fully brine-saturated sediment, the topological parameters of individual hydrate cluster usually experience more dramatic changes with hydrate dissociation in partially brine-saturated sediment. It is inferred that in partially brine-saturated sediment the isolated hydrate clusters occupying in pore bodies are dissociated earlier in the initial experimental stage, and the dissociation of interpore hydrate frameworks interconnected through pore throats get dominated when hydrate saturation declines below a critical threshold value. On the other hand, in fully brine-saturated sediment the kinetics of pore-scale hydrate dissociation exhibit a completely opposite trend.

Atomically modified graphitic carbon nitride quantum dots (QDs), characterized by strongly increased reactivity and stability, are developed. These are deposited on arrays of TiO2 nanopillars used as a photoanode for the photoelectrochemical water splitting. This photoanode shows excellent stability, with 111 h of continuous work without any performance loss, which outperforms the best‐reported results by a factor of 10. Remarkably, our photoanode produces hydrogen even at zero bias. The excellent performance is attributed to the enhancement of photoabsorption, as well as to the promotion of charge separation between TiO2 nanopillars and the QDs.

Herein, we synthesized BiOBr/ultrathin g-C3N4/ternary heterostructures modified with black phosphorous quantum dots using a simple water bath heating and sonication method. The ternary heterostructure was then used for the photocatalytic degradation of tetracycline in visible light, with an efficiency as high as 92% after 3 h of irradiation. Thus, the photodegradation efficiency is greatly improved compared to that of ultrathin g-C3N4, BiOBr, and black phosphorous quantum dots alone. The synthesized ternary heterostructure improves the charge separation efficiency, thus increasing the photodegradation efficiency. This work provides a new and efficient method for the degradation of antibiotics in the environment.

Taxonomic classification of Eriocheir hepuensis was ambiguous, and it has long been controversial. In this study, the whole mitochondrial genome of E. hepuensis was determined to be 16,397 bp, including 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 1 control region. A total of 20 intergenic gaps were detected, and the AT content of whole mitochondrial genome was 71.78%. Phylogenetic analysis confirmed that the evolutionary relationship of E. hepuensis, E. sinensis, and E. japonica are most likely to be three species with the same taxonomic status. The whole mitogenome of this species will be useful for the future animal evolutionary, phylogenetic relationship, phylogeny and genomic studies in the genus Eriocheir.

A 3D porous framework ([Co1.5(tib)(dcpna)]·6H2O) (1) with a Wei topology has been synthesized by solvothermal reaction of 1,3,5-tris(1-imidazolyl)-benzene (tib), 5-(3′,5′-dicarboxylphenyl)nicotinic acid (H3dcpna) and cobalt nitrate. The electrocatalytic activity for water oxidation of 1 has been investigated in alkaline solution. Compound 1 exhibits good oxygen evolution reaction (OER) activities in alkaline solution, exhibiting 10 mA·cm−2 at η = 360 mV with a Tafel slope of 89 mV·dec−1. The high OER activity can be ascribe to 1D open channels along b axis of 1, which expose more activity sites and facilitate the electrolyte penetration.

In recent years, BiVO4 has drawn much attention as a novel photocatalyst given its excellent ability to absorb visible light. This work reports the development of Ag-modified BiV1-xMoxO4 composites through a facile hydrothermal synthesis with the subsequent photoinduced reduction of Ag+ at almost neutral pH conditions. Metallic Ag nanoparticles were deposited on the (040) facet of Mo-doped BiVO4 powders. The crystal structure and morphology of the as-prepared samples were studied by XRD and SEM analyses. Moreover, the photocatalytic performance of BiVO4, Ag/BiVO4, and Ag-modified BiV1-xMoxO4 were evaluated by the degradation of rhodamine B (RhB). The Ag/BiV0.9925Mo0.0075O4 composite exhibited the most efficient photocatalytic performance. The present work provides greater insight into the application of BiVO4 in the field of photocatalysis.

This study compares two competing pathways of photoexcitations in gas-phase metal-organic complexes: first, a sequence of phonon-assisted electronic transitions leading to dissipation of the energy of photoexcitations and, second, a sequence of light-driven electronic transitions leading to photolysis. Phonon-assisted charge carrier dynamics is investigated by combination of the density matrix formalism and on-the-fly nonadiabatic couplings. Light-driven fragmentation is modeled by a time-dependent excited-state molecular-dynamics (TDESMD) algorithm based on Rabi theory and principles similar to the trajectory surface hopping approximation. Numerical results indicate that, under the medium intensity of the laser field, light-driven electronic transitions are more probable than phonon-assisted ones. The formation of multiple products is observed in TDESMD trajectories. Simulated mass spectra are extracted from TDESMD simulations and compared to experimental photoionization time-of-flight (PI-TOF) mass spectra. It is found that several features in the experimental mass spectra are reproduced by the simulations.

Unimolecular gas-phase laser-photodissociation reaction mechanisms of open-shell lanthanide cyclopentadienyl complexes, Ln(Cp)3 and Ln(TMCp)3, are analyzed from experimental and computational perspectives. The most probable pathways for the photoreactions are inferred from photoionization time-of-flight mass spectrometry (PI-TOF-MS), which provides the sequence of reaction intermediates and the distribution of final products. Time-dependent excited-state molecular dynamics (TDESMD) calculations provide insight into the electronic mechanisms for the individual steps of the laser-driven photoreactions for Ln(Cp)3. Computational analysis correctly predicts several key reaction products as well as the observed branching between two reaction pathways: (1) ligand ejection and (2) ligand cracking. Simulations support our previous assertion that both reaction pathways are initiated via a ligand-to-metal charge-transfer (LMCT) process. For the more complex chemistry of the tetramethylcyclopentadienyl complexes Ln(TMCp)3, TMESMD is less tractable, but computational geometry optimization reveals the structures of intermediates deduced from PI-TOF-MS, including several classic “tuck-in” structures and products of Cp ring expansion. The results have important implications for metal–organic catalysis and laser-assisted metal–organic chemical vapor deposition (LCVD) of insulators with high dielectric constants.

Global warming and increased nutrient fluxes cause cyanobacterial blooms in freshwater ecosystems. These phenomena have increased the concern for human health and ecosystem services. The mass occurrences of toxic cyanobacteria strongly affect freshwater zooplankton communities, especially the unselective filter feeder Daphnia. However, the molecular mechanisms of cyanobacterial toxicity remain poorly understood. This study is the first to combine the established body growth rate (BGR), which is an indicator of life-history fitness, with differential peptide labeling (iTRAQ)-based proteomics in Daphnia magna influenced by microcystin-producing (MP) and microcystin-free (MF) Microcystis aeruginosa. A significant decrease in BGR was detected when D. magna was exposed to MP or MF M. aeruginosa. Conducting iTRAQ proteomic analyses, we successfully identified and quantified 211 proteins with significant changes in expression. A cluster of orthologous groups revealed that M. aeruginosa-affected differential proteins were strongly associated with lipid, carbohydrate, amino acid, and energy metabolism. These parameters could potentially explain the reduced fitness based on the cost of the substance metabolism.

Hydrogen sulfide (H2S) has been considered as the third biologically gaseous messenger (gasotransmitter) after nitric oxide (NO) and carbon monoxide (CO). Fluorescent detection of H2S in living cells is very important to human health because it has been found that the abnormal levels of H2S in human body can cause Alzheimer’s disease, cancers and diabetes. Herein, we develop a cyclodextrin-based metal-organic nanotube, CD-MONT-2, possessing a {Pb14} metallamacrocycle for efficient detection of H2S. CD-MONT-2′ (the guest-free form of CD-MONT-2) exhibits turn-on detection of H2S with high selectivity and moderate sensitivity when the material was dissolved in DMSO solution. Significantly, CD-MONT-2′ can act as a fluorescent turn-on probe for highly selective detection of H2S in living cells. The sensing mechanism in the present work is based on the coordination of H2S as the auxochromic group to the central Pb(II) ion to enhance the fluorescence intensity, which is studied for the first time.

We report the first demonstration of a high-efficiency photoelectrochemical (PEC) water splitting reaction using a novel Si NWs/WO3 core/shell photoanode prepared by a mild and inexpensive metal-catalyzed electroless etching process followed by dip-coating, airing and annealing methods. The dense and vertically aligned Si NWs/WO3 core/shell nanostructure were characterized by scanning electron microscopy, transmission electron microscopy and x-ray diffraction. In comparison to planar n-Si, Si NWs and planar Si/WO3, the Si NWs/WO3 samples showed significantly enhanced photocurrent over the entire potential sweep range. More significantly, the Si NWs/WO3 samples have an exceptionally low photocurrent onset potential of -0.6393 V versus reversible hydrogen electrode (RHE), indicating very efficient charge separation and charge transportation processes. The as-prepared electrode also has a photocurrent density of 2.7 mA cm-2 at 0.6107 V versus RHE in 0.5 M Na2SO4 solution under simulated solar light irradiation (100 mW cm-2 from 300 W Xenon lamp coupled with an AM 1.5 G filter). An optimal solar-to-hydrogen efficiency of about 1.9% was achieved at 0.2676 V versus RHE. Electrochemical impedance spectroscopy was conducted to investigate the properties of the charge transfer process, and the results indicated that the enhanced PEC performance may due to the increased charge separation. The x-ray photoelectron spectroscopy measurements indicated the chemical composition of the Si NWs/WO3 nanostructure. Our work has provided an efficient strategy to improve the energy conversion efficiency and photocurrent of water splitting materials.