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This study provides an insight into the structure-property relationship of graphene network (GN) reinforced metal matrix composites (MMCs). Molecular dynamics results show that the interlocking structure improves the deformation compatibility between the GN and matrix, as well as increases the load-sharing of GN. And the mechanical interlocking can be further enhanced by the dislocation-GN interactions as the GN being straightened. The straightening of GN also enables itself to release its stress concentrations through overall deformation, which helps the GN perform better in dislocation-blocking than graphene sheets. Besides, curved portions of GN contribute more to dislocation-GN interactions while the straight portions do better in load-sharing. With the hole-like defects on whether straight or curved portions of GN, both the strength and Young's modulus of the imperfect GN reinforced composites are reduced. However, these defects enable the matrix to be connected into a continuous body, by which the ductility of imperfect GN reinforced Ni matrix composites is improved since their failures are mainly dictated by the fracture of Ni matrix, while the rupture of GN determines the failure of composites reinforced by the GN without hole-like defects.

In acoustic logging, most published studies of extracting array data characteristics are difficult to avoid the interference from the false modes. The false modes contribute little to the acoustic waveforms but makes the true modes hard to identify. We introduce a threshold of the energy spectrum into the pole-calculation method to remove the false modes, thereby eliminating their interferences to the true modes. To avoid the separation of multiple crossings of pole distribution, we directly acquire the slowness dispersion of multiple modes by superposing the single-mode results calculated from the weighted spectral semblance method. We processed the slowness-frequency snapshot and design an extreme-point extraction formula to generate the multi-mode scatterplot, which provide a precise slowness dispersion result. In terms of four synthetic cases of acoustic logging, it has demonstrated that the proposed algorithm can provide a high-resolution slowness dispersion profile for multiple modes. Even for acoustic logging while drilling with strong tool wave components, the aliases and interferences of false modes do not exist. Finally, a test proves that the proposed algorithm also has a good anti-noise ability.

Urban land subsidence is a slow-density geology disaster caused by the withdrawal of groundwater or the application of water at the land surface. Developing a method of effectively monitoring, predicting and preventing land subsidence has become an urgent urban disaster issue and a great challenge. Traditional mathematical statistics prediction models lack physical meaning. Thus, in this paper, an improved third-order gray prediction GM(1, 3) model that combines terrain factors and neural network error corrections is proposed for urban land subsidence prediction. First, the correlation between land subsidence and terrain factors is verified through a correlation analysis. Second, a geospatial weight matrix based on the terrain factors is presented for auxiliary variable selection. Finally, a neural network is used to model the prediction errors to improve the model accuracy. Precision levelling data for Haiyan County, Zhejiang Province, China from 1999 to 2016 are used as the experimental data. The results show that the proposed method can achieve the same accuracy level as precision levelling. The average absolute error of three-phrase prediction is less than 10 mm, and the relative error can reach 0.4%. The proposed method can be expected to replace precision levelling for the prediction of long-term land subsidence and provide decision support for urban settlement disaster prevention.

Traditional positive electrode materials consisting of transition metal oxides, sulfides, hydroxides, and conductive polymers exhibit ultra-high capacitances for asymmetric supercapacitors. However, negative electrode materials are rather poor. Herein, we report a simple but efficient template carbonization method to covalently graft p-phenylenediamine molecules onto a hollow “bubble-like” carbon sphere (PPD–BC) surface as the negative electrode for high performance asymmetric supercapacitors. In this strategy, the “bubble-like” carbon spheres can not only act as “reservoirs” to physically store pseudocapacitance additive p-phenylenediamine (PPD) molecules through a spatially constrained behavior, but also chemically confine the PPD using CO–NH chemically covalent bonds. As a result, the specific capacitance of PPD–BC (451 F g−1) is about three times higher than that of hollow bubble carbon (166 F g−1) due to the extra addition of faradaic reactions. More importantly, the as-assembled PPD–BC//Ni(OH)2 asymmetric supercapacitor exhibits a remarkably high energy density of 94 W h kg−1 at a power density of 423 W kg−1, as well as outstanding cycling performance with 88% capacitance retention after 1000 cycles. Therefore, the design of organic molecule modified carbon materials holds great promise for ultrahigh energy density storage devices.

A simple rhodamine-based fluorescent probe L1, which exhibits good response to Fe3+ in CH3CN/Tris-HCl buffer (v:v = 9:1, pH 7.00) solution. With the experimental conditions optimized, the probe L1 could be used as a fluorescent and colorimetric probe for Fe3+ with the detection limit as low as 0.29 μM. The binding constant (Ka) of Fe3+ binding to the probe L1 were calculated to be 1.4 × 1010 M−2, respectively from a Benesi-Hildebrand plot. With the addition of Fe3+, the CH3CN/Tris-HCl buffer (v:v = 9:1, pH 7.00) solution of the probe L1 exhibited a obviously color change from transparent to pink with distinctive changes. More importantly, the recognition process of the probe L1 for Fe3+ was chemically reversible on the addition AcO−.

Nickel hexacyanoferrate (NiHCF) with rigid open framework is promising for energy storage devices, yet still suffer from inferior conductivity and low energy density. Herein, NiHCF supported on diallyldimethylammonium chloride (PDDA) modified graphene (PRGO-NiHCF) was successfully synthesized via a facile co-precipitation method. The size of NiHCF nanoparticals decreased from 50 nm to 20 nm with the introduction of PDDA-induced reduced graphene oxide. The unique structure can not only reversibly accommodate hydrated alkali cations with 3D open-framework, but also facilitate the electrons transportation through the graphene basal plane. Consequently, the as-obtained PRGO-NiHCF exhibits higher specific capacitances of 294 F g−1 at 2 mV s−1 compared to pure NiHCF (176 F g−1). Moreover, under the combination of PRGO-NiHCF positive electrode and the interconnected sandwiched graphene carbon (SGC) negative electrode, the as-assembled asymmetric supercapacitor delivers a wide operation potential of 1.8 V and a high energy density of 25.4 Wh kg−1.

Harmful metal ions have received intense attention. In particular, palladium, a rare inner transition metal, is the subject of intense research in light of its catalytic capabilities and the restrictions on the levels of residual harmful metal ions in end products，has attracted wide spread interest from chemists. A near-infrared Pd2+ probe Cy202 has been synthesized that exhibits pronounced fluorescence enhancement in the presence of Pd2+. The Pd2+ recognition properties were examined by using UV–Vis spectroscopy and fluorescence spectroscopy in DMSO/PBS buffer solution (pH 7.40, 8/2, v/v). The solution of the probe exhibits color change turned from yellow to brown upon the addition of Pd2+ while no significant response to other metal ions. The detection limit was calculated as low as 0.52 μM. The probe could be useful for imaging Pd2+ in palladium-containing catalyst and samples.

A ratiometric fluorescent probe for Pd2+ has been constructed through appending indole to rhodamine B. The response process of Pd2+ to probe was also verified by UV-vis, fluorescence, ESI-MS, 1H NMR and density functional theory calculation. Moreover, the highly sensitive and selective probe was successfully applied to monitor Pd2+ in living cells.

Atrazine as a kind of herbicide could cause damage to the sensitive plants. Though plant growth promoting rhizobacteria (PGPR) have been proven with the potential to enhance the resistance of plants against various abiotic stresses, whether it could alleviate phytotoxicity caused by atrazine is sill unclear. In present study, the effects of strain Pseudomonas chlororaphis PAS18, a kind of PGPR enable to produce indole-3-acetic acid (IAA), on the growth and physiological responses of Pennisetum americanum (L.) K.Schum seedlings were investigated under three different levels (0, 20 and 100 mg kg−1) of atrazine in pot experiment. The results suggest that strain PAS18 could alleviate the growth and physiological interference caused by 20 mg kg−1 of atrazine. Physiological analysis showed strain PAS18 could further decrease the damaged extent of photosystem II, superoxide radical level and malondialdehyde content of test plant via up-regulating psbA expression, enhancing superoxide dismutase activity and reducing atrazine accumulation in the test plant. Moreover, ion flux measurements suggest that IAA could alleviate the Ca2+ exflux state of the test plant which caused by atrazine stress. Hence, it is plausible that strain PAS18 could alleviate atrazine-induced stress to P. americanum by enhancing the photosystem II repair and antioxidant defense ability as well as balancing the Ca2+ flux.

Due to its chemical stability, excellent reversibility and high pseudocapacitance, polyaniline (PANI) has attracted extensive attention for supercapacitors. However, the poor rate performance of PANI-based materials limits their large-scale application. Here, we report a facile strategy to fabricate PANI nanofibers confined into graphene oxide architecture (PGA50) through the adsorption of aniline onto stacked graphene oxide sheets and consequent in-situ polymerization. Benefited from the synergistic effect of PANI nanofibers and graphene oxide sheets, the sandwiched PGA50 has efficient electron/ion transfer pathways with stable structural framework. As a result, PGA50 electrode shows a high capacitance of 780 F g−1 at 0.5 A g−1 and excellent rate performance (521 F g−1 at 50 A g−1) compared to PANI (323 F g−1 at 0.5 A g−1 and 120 F g−1 at 50 A g−1). Significantly, the assembled PGA50//PGA50 supercapacitor achieves a high energy density of 30 Wh kg−1 at a power density of 216 W kg−1.

There are crucial demands for high power density and long-term cycling performance of Li-ion batteries (LIBs), and the development of stable electrode material operating at high current densities still remains a challenge. Here we develop a novel strategy for the synthesis of flexible N-doped carbon nanofiber/CoFe2O4 film (CoFe2O4@N-CNF) with a double-layer carbon protection by electrospinning, which possesses stable carbon shell and honeycomb-like core with CoFe2O4 nanosheets embedded into conductive and interconnected carbon nanosheets. The unique structure is beneficial for providing robust structural stability upon long-term cycling, and offering nitrogen-rich interconnected mesoporous and conductive carbon matrix for fast charge and ion transport. As a consequence, the optimized CoFe2O4@N-CNF exhibits a high reversible capacity of 858 mAh g−1 at 0.1 A g−1, excellent rate capability (306 mAh g−1 at 30 A g−1), and superior cycling stability up to 10,000 cycles with almost no capacity loss at 10 A g−1. We believe that this proposed methodology has a profound impact on drastic improvements of various flexible energy storage devices.

The requirements on volumetric and gravimetric performances of lithium-ion batteries have been more and more urgent for their applications in miniaturized consumer electronics. Herein, we report a simple synthesis strategy of densely stacked graphene/MnO architecture anode for lithium-ion batteries. Through a simply modified Hummers method, the MnO2 nanofibers are homogeneously confined in-between the graphene oxide sheets, which can form a three-dimensional layered dense structure that can be easily reduced to densely stacked graphene/MnO architecture during annealing process. More importantly, the integration of MnO nanosheets and graphene sheets with dense architecture is beneficial for the enhanced electron/ion transfer kinetics, and the improved structural and interfacial stability during charge-discharge process. As a result, the graphene/MnO architecture electrode exhibits ultra-high gravimetric/volumetric capacities (1000 mA h g−1/2288 mA h cm−3 at 0.1 A g−1), excellent rate performance (270 mA h g−1/618 mA h cm−3 at 8.0 A g−1), ultra-low volume expansion (18%) and outstanding cycling stability (118% of capacity retention after 300 cycles).

Traditional positive electrode materials such as transition metal oxides/hydroxides/sulfides exhibit high capacitances for asymmetric supercapacitors. However, their rate performance and cycling stability are rather poor. Herein, we develop a novel strategy for the design of Fe(CN)63− ions confined into porous pillared-carbon nanosheets (F–OPPCNs) as a positive electrode material for high energy density asymmetric supercapacitors. As a result, the specific capacitance of the F–OPPCNs (363 F g−1) is about three times higher than that of pillared-porous carbon nanosheets (PPCNs, 126 F g−1) due to the existence of the additional faradaic reaction. Benefiting from the high performances of the positive electrode, the as-assembled asymmetric supercapacitor delivers a high energy density of 48 W h kg−1 at 960 W kg−1, much higher than those of previously reported asymmetric supercapacitors in neutral aqueous electrolytes, as well as excellent cycling stability with 91% capacitance retention over 10 000 cycles. Therefore, the introduction of a redox mediator into porous carbons is a versatile approach for constructing high-performance asymmetric supercapacitors.

With the increasing energy demand of electronic devices and electric vehicles, the achievement of anode materials for lithium-ion batteries with high specific capacity and superior rate capability and cycling stability still remains a challenge. Herein, we report a novel strategy to prepare the core–shell mesoporous single-crystalline MnOx nanofibers@graphene (PSCMnOx@G) through a “spraying–rapid freezing” process. The elastic graphene shell not only improves the conductivity of the electrode but can also substantially inhibit the collapse of MnOx nanofibers (NFs) over continuous discharge–charge cycles. Moreover, the double-exchange interaction of manganese mixed-valence ions further improves the conductivity of manganese oxide, and Li ion diffusion is significantly enhanced by the vertically aligned single-crystalline and mesoporous structure of MnOx NFs. As a result, the PSCMnOx@G exhibits an ultrahigh rate performance (1072 mA h g−1 at 0.1 A g−1 and 419 mA h g−1 at 10 A g−1), which is among the best ever reported for MnOx based anodes, as well as excellent cycling stability (1162 mA h g−1 at 2 A g−1 over 500 cycles).

A simple chemosensor, namely, ethyl 5-(isonicotinoylimino)methyl-2,4-dimethyl-pyrrole-3-carboxylate (1), was synthesized and characterized. Probe 1 exhibited great selectivity when used as an off–on fluorescent sensor for Zn2+. Moreover, 1 can be used as a colorimetric probe for the detection of Cu2+ in semiaqueous media. The putative binding mechanism of 1 with its target analytes was confirmed through UV-Vis absorption analysis, fluorescence measurements, mass spectroscopy, 1H NMR analysis, and density functional theory calculations. In addition, the resulting 1 + Cu2+ complex can be used as a colorimetric sensor for pyrophosphate. Probe 1 is successfully applied in monitoring intracellular Zn2+ in the glioma cell line U251.

Achieving high electrochemical energy density while retaining high power density still remains a great challenge for porous carbons as the electrodes for supercapacitors. We report a facile and scalable synthesis of N-doped aligned carbon nanosheet network (N-ACN10) with high surface area and efficient 3D ion and electron transport pathways. Moreover, 3D interconnected nanochannels parallel to the graphene planes are beneficial for the increased ion accessible surface area and fast ion diffusion. Benefiting from fast ion and electron transport kinetics, the N-ACN10 electrode exhibits excellent frequency response with a scan rate up to 5 V s −1 , high capacitance of 331 F g −1 at 2 mV s −1 and superior rate capability (203 F g −1 at 5 V s −1 ), as well as excellent cycling stability (98% of capacitance retention after 10,000 cycles) in 6 M KOH. More importantly, the assembled N-ACN10//N-ACN10 supercapacitors exhibit outstanding electrochemical performances in 1 M Na 2 SO 4 and EMIMBF 4 electrolytes with maximum energy densities of 20.6 and 120.4 Wh kg −1 based on the mass of total active material, respectively.

To further improve the capacity of Cu 2 O to absorb I − anions from solution, and to understand the difference between the adsorption mechanisms of Ag/Cu 2 O and Cu/Cu 2 O adsorbents, bimetallic AgCu was doped into Cu 2 O through a facile solvothermal route. Samples were characterized and employed to adsorb I − anions under different experimental conditions. The results show that the Cu content can be tuned by adding different volumes of Ag sols. After doping bimetallic AgCu, the adsorption capacity of the samples can be increased from 0.02 mmol g −1 to 0.52 mmol g −1 . Moreover, the optimal adsorption is reached within only 240 min. Meanwhile, the difference between the adsorption mechanisms of Ag/Cu 2 O and Cu/Cu 2 O adsorbents was verified, and the cooperative adsorption mechanism of the AgCu/Cu 2 O hybrid was proposed and verified. In addition, the AgCu/Cu 2 O hybrid showed excellent selectivity, e.g., its adsorption efficiencies are 85.1%, 81.9%, 85.9% and 85.7% in the presence of the Cl − , CO 3 2− , SO 4 2− and NO 3 − competitive anions, respectively. Furthermore, the AgCu/Cu 2 O hybrid can worked well in other harsh environments (e.g., acidic, alkaline and seawater environments). Therefore, this study is expected to promote the development of Cu 2 O into a highly efficient adsorbent for the removal of iodide from solution.

The graphene network (GN) reinforced Ti6Al4V composites with concurrently enhanced strength and ductility are fabricated based on powder metallurgy, in which the GN interlocks with the matrix intimately via the in-situ generation of interfacial TiC. The strengthening and toughening mechanisms of the composites are investigated through experiments and molecular dynamics (MD) simulations. Grain refinement, deformation compatibility, dislocation blocking, together with the restraint and bridging of cracks are provided by the embedded GN, improving both the strength and ductility of the composites. Interestingly, with a better ductility than Ti6Al4V, the composites possess a more brittle-like fracture surface. With the introduction of GN, the fracture mode of the composites is diverted from the transgranular fracture in Ti6Al4V to the mix of intergranular and quasi-cleavage fracture. The intergranular fracture is mainly ascribed to the brittle fracture of the TiC shell. And the propagation of cracks along cleavage plane in the matrix, working together with the impediment of cracks by GN, results in the quasi-cleavage fracture. Despite the brittle-like fracture surface, the restraint of crack propagation by dislocation-GN interactions, as well as the crack-bridging of GN, postpones the failure of the composites and thereby conduces to a good ductility.

In this work, a feasible strategy to fabricate graphene nanoplatelets (GNP) reinforced nickel (Ni) matrix composites is developed, in which the in-situ exfoliation and dispersion of GNP are synchronized. This strategy consists of preparing composite powders by three dimensional (3D) vibration milling Ni powders with graphite bulks and consolidation process by spark plasma sintering (SPS). Characterization results show that GNPs are stripped from the graphite bulk and homogeneously distributed on Ni powders surfaces. Compared with pure Ni, the 0.1 wt % GNP/Ni composites demonstrate a yield strength of 338 MPa and ultimate tensile strength of 593 MPa, achieving improvement by 29.5% and 24.8% respectively, and preserve good ductility simultaneously. Due to the grain refinement and efficient load transfer, the obtained GNP/Ni composites exhibit superior strengthening efficiency. This strategy can be disseminated to simple and economical preparation of other metal matrix composites reinforced with GNP.

Supercapacitors based on microporous carbons face some contradictory and competitive challenges such as relatively high specific capacitance and low charge rates. Previously, the mesopores in these carbons can effectively enhance the ion transport, but their charge and discharge rates are often less than 1 V s −1 . Here, we have demonstrated “brick-and-mortar” sandwiched porous carbon building by using MOF-5 derived porous carbon film as “mortar” and the graphene nanosheet as “brick”. The confined mesoporous channels between-in graphene sheets provide efficient ion transport pathways for fast ion diffusion, and the existence of graphene can effectively maintain the conductivity and structural stability of the carbon building. As a result, the obtained porous carbon building exhibits fast frequency response with an ultrahigh rate up to 2 V s −1 , high specific capacitance of 345 F g −1 at 2 mV s −1 , and outstanding cycling stability of 99% capacitance retention after 10,000 cycles. More importantly, the as-assembled symmetric supercapacitor in aqueous electrolyte can deliver a high energy density of 30.3 Wh kg −1 at a power density of 137 W kg –1 and superior cycling life (94% capacitance retention after 10,000 cycles). Even at a high power density of 11.9 kW kg –1 , it still remains an energy density of 10.6 Wh kg –1 , higher than those of previously reported carbon-based symmetric supercapacitors and other asymmetric supercapacitors.

A facile and one-step method is demonstrated to prepare carbon nanofibers (CNFs)-bridged porous carbon nanosheets (PCNs) through carbonization of the mixture of bacterial cellulose and potassium citrate. The CNFs bridge PCNs to form integrated porous carbon architecture with high specific surface area of 1037 m 2 g −1 , much higher than those of pure PCNs (381 m 2 g −1 ) and CNFs (510 m 2 g −1 ). As a consequence, the PCN/CNF composite displays high specific capacitance of 261 F g −1 , excellent rate capability and outstanding cycling stability (97.6% of capacitance retention after 10000 cycles). Moreover, the assembled symmetric supercapacitor with PCN/CNF electrodes delivers an ultrahigh energy density of 20.4 Wh kg −1 and outstanding cycling life (94.8% capacitance retention after 10000 cycles) in an aqueous electrolyte.

The fluorescent probes with good water-solubility, long-wavelength emission and large Stokes shift are greatly desirable for in vivo detection. Herein, we designed a novel 1,8-naphthalimide-based near-infrared (NIR) optical and fluorescent probe (NTC) for sensing cysteine (Cys). Using acrylate as the recognition site, the probe demonstrated high selectivity and sensitivity for Cys with a low detection limit (0.093 μM) in aqueous buffer solution due to the excellent water-solubility. Upon the reaction with Cys, the recovery of intramolecular charge transfer (ICT) in the probe led to about 40-fold fluorescence enhancement. Furthermore, the reaction result was investigated by 1H NMR, and HRMS analyses, and the sensing mechanism was validated by quantum calculations. Finally, NTC was applied to image exogenous and endogenous Cys in HeLa cells and zebrafish selectively, implying that the probe possessed great potential application in biological fluorescence sensing.

For the shale gas transport model in nanopores, researchers recently pay more and more attention to the existence of water phase. However, the effect of water film on the gas transport is still not clearly understood. In this paper, we considered the existence of water film on inorganic shale pore surface and introduced the adsorption mechanism of methane-water film-shale clay three-phase (gas-liquid-solid) to the shale gas transport model. Then, we modified the expression of porosity and derived a new transport equation of shale gas considering the adsorption mechanism of three-phases in nanopores. Using the finite element method, we solved the equation and analyzed the effect of water film. Finally, the range of water film effect was analyzed by defining the offset ratio. The results show that: (1) The existence of water film has negative effects on physical quantities, such as effective porosity and apparent permeability. When the water molecular coverage ratio reaches to 1, the decrease of porosity can be about 18.1%; (2) The existence of water film reduces the gas production rate and accumulative gas production. When the water molecular coverage ratio reaches to 1, the gas accumulative production decreases about 49.6%; (3) The pore radius which has significant water film effect is very small. Furthermore, the smaller of the pore size, the more significant the water film effect is. Also, it can be found that the effect of water film on porosity can be ignored with when pore radius exceeds 29 nm. When the pore radius is larger than 11 nm, the effect of water film on kapp/kd can be ignored.