Search

Electrocatalytic water splitting, as a sustainable, pollution-free and convenient method of hydrogen production, has attracted the attention of researchers. However, due to the high reaction barrier and slow four-electron transfer process, it is necessary to develop and design efficient electrocatalysts to promote electron transfer and improve reaction kinetics. Tungsten oxide-based nanomaterials have received extensive attention due to their great potential in energy-related and environmental catalysis. To maximize the catalytic efficiency of catalysts in practical applications, it is essential to further understand the structure–property relationship of tungsten oxide-based nanomaterials by controlling the surface/interface structure. In this review, recent methods to enhance the catalytic activities of tungsten oxide-based nanomaterials are reviewed, which are classified into four strategies: morphology regulation, phase control, defect engineering, and heterostructure construction. The structure–property relationship of tungsten oxide-based nanomaterials affected by various strategies is discussed with examples. Finally, the development prospects and challenges in tungsten oxide-based nanomaterials are discussed in the conclusion. We believe that this review provides guidance for researchers to develop more promising electrocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Li et al. [[3]] fabricated a CoFe SB 2 sb O SB 4 sb /g-C SB 3 sb N SB 4 sb composite catalyst with CoFe SB 2 sb O SB 4 sb particles supported on the flaky g-C SB 3 sb N SB 4 sb using a scalable facile method. However, currently, Li-S batteries suffer from low volumetric energy density and poor cycling stability due to the intrinsic low conductivity of sulfur and its discharge product, lithium polysulfide shuttle effect, and so on. Developing efficient and low-cost energy conversion and storage devices and technologies is all-important issue in order to achieve a low-carbon society, whose performance essentially depends on the properties of materials. Zhao et al. [[8]] designed a single-atom catalyst Au/WSSe by filling the single Au atom at the S vacancy site in the Janus WSSe monolayer. [Extracted from the article]

Atomically thin two-dimensional transition metal dichalcogenides (TMDCs) have been regarded as ideal and promising nanomaterials that bring broad application prospects in extensive fields due to their ultrathin layered structure, unique electronic band structure, and multiple spatial phase configurations. TMDCs with different phase structures exhibit great diversities in physical and chemical properties. By regulating the phase structure, their properties would be modified to broaden the application fields. In this mini review, focusing on the most widely concerned molybdenum dichalcogenides (MoX2: X = S, Se, Te), we summarized their phase structures and corresponding electronic properties. Particularly, the mechanisms of phase transformation are explained, and the common methods of phase regulation or phase stabilization strategies are systematically reviewed and discussed. We hope the review could provide guidance for the phase regulation of molybdenum dichalcogenides nanomaterials, and further promote their real industrial applications. [ABSTRACT FROM AUTHOR]

Two ferromagnetic transitions have been found by temperature dependence ac susceptibility experiments on as-prepared bulk polycrystalline La0.9Ba0.1MnO3. Investigation indicates that the higher temperature transition (TCh) can be attributed to the oxygen excessive phase La0.9Ba0.1MnO3+δ at the surface, while the lower temperature transition (TCl) can be attributed to the interior stoichiometric phase La0.9Ba0.1MnO3 of the samples. Softening of ferromagnetic system near TCl has been observed in La0.9Ba0.1MnO3, which can be explained by the freezing of misorder of metal ion at higher temperature. [ABSTRACT FROM AUTHOR]

In this paper, we consider an optimal investment-consumption-insurance purchase problem for a wage earner. We assume that the price of the risky asset is governed by a continuous-time, finite state self-exciting threshold model. In this model, the state space of the price of the risky asset is partitioned by a set of thresholds and the parameters depend on the region which the current value of the price falls in. The wage earner's objective is to find the optimal investment-consumption-insurance strategy that maximizes the expected discounted utilities. The optimal strategy for power utility function is derived by the martingale approach and the dynamic programming approach. Numerical examples are also provided to illustrate the effect of the thresholds. [ABSTRACT FROM AUTHOR]

Abstract: Background and Aim: The aim of this study is to investigate the impact of hepatitis B virus (HBV) S gene integration on serum hepatitis B surface antigen (HBsAg) levels in chronic hepatitis B with long‐term nucleos(t)ide analogue (NUC) therapy. Methods: Chronic hepatitis B patients who performed liver biopsy at baseline and treated with long‐term NUC therapy were recruited. The integration of HBV S gene in baseline liver biopsy specimen was detected by Alu polymerase chain reaction method. Serum HBsAg levels were measured at baseline and the second year and the fourth year after NUC therapy by Roche reagent, respectively. Serum HBsAg levels between HBV S gene integrated group and nonintegrated group were compared and analyzed. Results: Seventy patients were eligible for this study. Among them, 11 (15.7%) were found to have HBV S gene integration in their baseline liver biopsy specimens. Similar significant decrease of HBsAg levels was found in both integrated and nonintegrated groups (2.63 vs 2.65 log IU/mL, P = 0.478) after the first 2 years of NUC therapy. Thereafter, the decrease of HBsAg level from 2 to 4 years after therapy was largely unchanged in integrated group as compared with that of nonintegrated group (0.1 vs 2.53 log IU/mL, P = 0.002), with statistical difference. Conclusions: Serum HBsAg could be originated from the expression of the integrated HBV S gene in patients with S gene integration, which implicated the limitations when regarding HBsAg as a surrogate biomarker of covalently closed circular DNA activity and as an indicator of safe NUC discontinuation. [ABSTRACT FROM AUTHOR]

This paper considers the optimal investment–consumption problem with liability subject to a maximum Value-at-Risk (denoted by MVaR ) constraint. The model also contains regime-switching market modes, whose states are interpreted as the states of the economy. In each state of economy state, we constrain a VaR value for the portfolio in a short time duration, and MVaR is defined as the maximum value of the VaR s in all economy states. We suppose that both the price dynamics of the risky asset and the liability value process are governed by a Markov-modulated geometric Brownian motion. With the objective of maximizing the discounted utility of consumption, we obtain a system of HJB equations corresponding to the economy states by using the dynamic programming principle. Then, by adopting the techniques of Chen et al. (2010), we get explicit expressions of value functions. Moreover, with the help of Lagrange multiplier method, we derive the optimal investment and the optimal consumption. Finally, a numerical example is investigated, and the effects of many parameters on the optimal investment, on the optimal consumption and on VaR value are studied. Furthermore, we also explore how VaR value affects the optimal investment and the optimal consumption. [ABSTRACT FROM AUTHOR]

We consider the valuation of a correlation option, a two-factor analog of a European call option, under a Hull-White interest rate model with regime switching. More specifically, the model parameters are modulated by an observable, continuous-time, finite-state Markov chain. We obtain an integral pricing formula for the correlation option by adopting the techniques of measure changes and inverse Fourier transform. Numerical analysis, via the fast Fourier transform, is provided to illustrate the practical implementation of our model. [ABSTRACT FROM AUTHOR]

This article supposes that a large insurance company can control its surplus process by reinsurance, paying dividends, or injecting capitals. The exponential premium principle and proportional reinsurance are adopted in business activities. We investigate the general situation that the company needs to pay both proportional and fixed costs for dividends and capital injections. The object of the company is to determine an optimal joint reinsurance–dividend–capital injection strategy for maximizing the expected present value of dividends less capital injections until the time of bankruptcy. In both cases of non cheap and cheap reinsurance, we obtain the explicit solutions for value function and optimal strategy. [ABSTRACT FROM AUTHOR]

In this paper, we consider the dividends and equity issuances control problem in the perturbed dual model under a penalty for ruin. Transaction costs are incurred by these business activities: dividend is taxed and fixed costs are generated by equity issuance. The objective is to maximize the expected present value of dividends minus the discounted costs of equity issuances and the discounted penalty until the ruin time. We find the joint optimal dividend and equity issuance strategy by solving the control problems of two categories of suboptimal model. Furthermore, we derive the explicit closed solutions for the value functions and the optimal strategies when the jumps are mixed exponential. In particular, we investigate the effects of the penalty, the proportional and fixed transaction costs, the expense rate and the force of interest on the optimal strategies by numerical calculations, and give some interesting economic insights. [ABSTRACT FROM AUTHOR]

This paper investigates an optimal dividend and capital injection problem in the dual model with a random horizon. Both fixed and proportional costs from the transactions of capital injection are considered. The objective is to maximize the total value of the expected discounted dividends and the penalized discounted capital injections during the horizon, which is described by the minimum of the time of ruin and an exponential random variable. By the fluctuation theory of Lévy processes, the optimal dividend and capital injection strategy is obtained. We also find that the optimal return function can be expressed in terms of the scale functions of Lévy processes. Besides, numerical examples are studied to illustrate our results. [ABSTRACT FROM AUTHOR]

An efficient enantioselective Michael addition of benzofuran-2(3 H )-ones to alkylideneindolenines generated in situ from arenesulfonylalkylindoles has been described, and a series of optically active C-3 alkyl-substituted benzofuran-2(3 H )-one derivatives containing indole skeleton with two adjacent stereocenters have been obtained. The resulting adduct can readily be converted to chiral o -hydroxyphenylacetic acid derivative with indole motif. [ABSTRACT FROM AUTHOR]

This article considers the pricing of equity-indexed annuity (EIA). By employing the change of measure technique, we derive the closed-form solutions for the prices of both point-to-point and annual reset equity-indexed annuities. We also provide numerical results to illustrate the method and computational efficiency of our simulation scheme and the effects of various model parameters on the participation rate. [ABSTRACT FROM AUTHOR]

Two porous metal–organic frameworks (1 and 2) with a fsc topology based on mixed ligands have been assembled and characterized. The different pillared ligands (pyrazine for 1 and 4,4′-bipyridine for 2) significantly influence the pore size of the frameworks. Gas uptake measurements reveal that complex 1 possesses higher H2, CO2, and CH4 uptake capacities than 2, although the surface area of 1 is lower than that of complex 2. These results further experimentally prove that the pore size plays an important role in gas uptake in porous MOFs, and the slit pore with a size of ∼6 Å exhibits stronger interactions with gas molecules. [ABSTRACT FROM AUTHOR]

In this article, we discuss about the stochastic comparisons and optimal allocation for policy limits and deductibles. We order the total retained losses of a policyholder in the usual stochastic order under more general conditions ofXi(i = 1,…,n), based on which the optimal allocation of policy limits and deductibles are achieved in some special cases. Several results in Cheung (2007) and Lu and Meng (2011) are generalized here. [ABSTRACT FROM AUTHOR]

Highly efficient photoluminescence (PL) emission is obtained from flower-like silicon oxide (SiOx)–Au nanostructures that were synthesized by annealing silicon substrates coated with Au thin film under Ar–H2 atmosphere at 1100 °C via the vapour–liquid–solid process. The morphologies and structures of the SiOx–Au nanoflowers were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and helium ion microscopy. The results revealed that the silicon oxide–Au nanoflowers were amorphous with an Au nanoparticle core at the centre. As compared to simple SiOx nanowires, the SiOx–Au nanoflowers show a 5-fold enhancement in intensity of room temperature photoluminescence, which can be attributed to the unique nanostructures, the strong coupling between the photoluminescence emission of the SiOx nanoflowers and the local surface plasmon resonance of the Au nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Bimetallic nanomaterials consisting of magnetic metals and noble metals have attracted much interest for their promising potentials in fields such as magnetic sensors, catalysts, optical detection and biomedical applications. Bimetallic nanomaterials synthesized by wet-chemical methods with different architectures including nanoparticles, nanowires or nanotubes and their assemblies are summarized in this review. The particular properties of bimetallic nanomaterials, especially their magnetic, catalytic and optical properties, are presented. The advance in electron microscopy makes it possible to understand the nanostructural materials at much higher level than before, which helps to disclose the relationship between the microstructures and properties qualitatively and quantitatively. [Copyright &y& Elsevier]

Abstract: ZnS nanomaterials at different dimensions, from nanoparticles, nanobelts to nanotetrapods have been synthesized in the same solvothermal system, which is kinetically controlled by ethylenediamine. Microscopy analysis reveals that the four arms of tetrapod are grown from Zn-terminated surfaces of an octahedral core by alternately stacking zinc blende and wurtzite structures along [111]/[0001] direction, while the ZnS nanobelts are self-assembled along [0001] direction by ultra-small wurtzite nanocrystals. These nanobelts can be transformed into their single-crystal counterparts and ZnO/ZnS heterostructures by thermal treatment. Uv–visible analysis demonstrates that the heterostructure presents a strain-induced staggered Type-II band structure. These investigation results suggest an efficient approach for phase-controlled synthesis of nanostructures in group II–VI semiconductors. [Copyright &y& Elsevier]

Abstract: By maximizing the expected utility, we study the optimal allocation of policy limits and deductibles from the viewpoint of a policyholder, where the dependence structure of losses is unknown. In Cheung (2007) [K.C. Cheung, Optimal allocation of policy limits and deductibles, Insurance: Mathematics and Economics 41 (2007) 382–391], the author had considered similar problems. He supposed that a policyholder was exposed to random losses, and the losses were general risks there, i.e., the loss on each policy was just a random variable. In this paper, the model is extended in two directions. On one hand, we assume that policies of the losses are effected by random environments. For each policy, the loss under a fixed environment is characterized by a random variable, so the loss on each policy is a mixture of some fundamental random variables. On the other hand, loss frequencies, which are stochastic, are also considered. Therefore, the whole model is equipped with mixture risks and discount factors. Finally, we get the orderings of the optimal allocations of policy limits and deductibles. Our conclusions also extend the main results in Hua and Cheung (2008) [L. Hua, K.C. Cheung, Stochastic orders of scalar products with applications, Insurance: Mathematics and Economics 42 (2008) 865–872]. [Copyright &y& Elsevier]

Abstract: A novel metal-organic framework, [Zn2(OH)(Hcht)(4,4′-bpy)] n ·4nH2O (1) (H4cht=cyclohexane-1,2,4,5-tetracarboxylic acid and 4,4′-bpy=4,4′-bipyridine), was synthesized by the hydrothermal reaction of Zn(NO3)2·6H2O, 4,4′-bipyridine, and cyclohexane-1,2,4,5-tetracarboxylic acid in the presence of sodium carbonate. The complex was obtained by controlling the ratio of the starting materials and a reaction temperature at 120°C and was characterized by IR, X-ray powder diffraction, thermogravimetric analysis, fluorescent spectrum, and single crystal X-ray diffraction. Single-crystal X-ray investigation reveals that the structure features a two-dimensional framework with novel coordination mode of Hcht ligand and all Hcht ligands exclusively convert to a sole conformation in the complex. IR spectrum reveals the characteristic absorption peaks of asymmetric stretching vibrations that result from the protonated and deprotonated carboxyl groups. Thermogravimetric analysis shows four clear courses of weight loss, which corresponds to the decomposition of different ligands. Fluorescent spectrum displays that complex 1 is a potential blue-luminescent material. [Copyright &y& Elsevier]

Abstract: TbMnO3/n-Si (n–N) and TbMnO3/p-Si (p–n) heterojunctions were fabricated under identical conditions. Good rectifying characteristics were found with almost the same forward current–voltage behavior in a temperature range from 150 to 300 K. Such intriguing superposed rectifying behaviours at the interfaces between TbMnO3 and Si of two different doped types can be explained by a similar Schottky barrier diode behavior with its current–voltage dependence generally dominated by only one type of carrier. This work will favor both electronic transport analysis and future device applications. [Copyright &y& Elsevier]

Abstract: A new dinuclear iron nitrosyl complex [Fe2(C14H12N3S)2(NO)4] (1) (C14H12N3S=2-mercapto-1-[2-(4-pyridyl)-ethyl]-benzimidazolyl) has been obtained by the reaction of Fe(NO)2(CO)2 with 2-mercapto-1-[2-(4-pyridyl)-ethyl]-benzimidazole in CH3OH under moderate condition. Complex 1 was characterized by IR, UV–vis, electrochemistry and single crystal X-ray diffraction. IR spectrum displays two strong characteristic NO stretching frequencies (ν NO) in solution and in solid state. Cyclic voltammetry shows one irreversible, two quasi-reversible and two reversible one-electron reductions and irreversible oxidizations. This result is consistent with the fact that complex 1 is very unstable and ready to lose NO in the air. As showing in the single crystal X-ray diffraction, complex 1 forms a “chair-shape” structure by the connections of two iron centers and S–C–N frames of benzimidazole. The dihedral angle of benzimidazole ring and 2Fe–2S plane is 73.6°. The crystal data are the following: 1, monoclinic, space group P2(1)/c, a =10.43940(10)Å, b =16.0900(2)Å, c =10.13240(10)Å, α =90°, β =111.0940(10)°, γ =90°, V =1587.89(3)Å3, Z =4. [Copyright &y& Elsevier]

In contrast with the classical Cramer-Lundberg model where the premium process is a linear function of time, we consider the ruin probability under the risk model where the aggregate premium consists of both a compound Poisson process and a linear process of time. Moreover, a constant interest force is also taken into account in our model. We restrict ourselves to the case where the claim size is heavy-tailed, i.e., the equilibrium distribution function of the claim size belongs to a wide subclass of the subexponential distribution. An asymptotic formula for the ruin probability is obtained by using the similar method of Kalashnikov and Konstantinides (2000). The asymptotic formula we get here is the same as the one in Asmussen (1998), Kluppelberg and Stadtmuller (1998), and Kalashnikov and Konstantinides (2000) which did not consider the stochastic premium. [ABSTRACT FROM AUTHOR]

In this paper, ruin problems in the risk model with stochastic premium incomes and stochastic return on investments are studied. The logarithm of the asset price process is assumed to be a Lévy process. An exact expression for expected discounted penalty function is established. Lower bounds and two kinds of upper bounds for expected discounted penalty function are obtained by inductive method and martingale approach. Integro-differential equations for the expected discounted penalty function are obtained when the Lévy process is a Brownian motion with positive drift and a compound Poisson process, respectively. Some analytical examples and numerical examples are given to illustrate the upper bounds and the applications of the integro-differential equations in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Low-frequency (102–105 Hz) dielectric properties of TbMnO3 (TMO) composites adding different cations were investigated from 360 to 77K. Compared to the parent TMO, it was found that cation addition could reduce dissipation factor, while very high dielectric constant almost remained. Especially addition of Ti ion reduced dissipation factor remarkably. And the additions of Sr ion and Ti ion at the same time resulted in the increase of dissipation factor. It is interesting that dissipation factor decreased again when Sr ion was partly substituted by Ba ion. [Copyright &y& Elsevier]

Abstract: The infrared (IR) spectroscopic data and Raman spectroscopic properties for a series of 13 “pinwheel-like” homoleptic bis(phthalocyaninato) rare earth complexes M[Pc(α-OC5H11)4]2 [M=Y and Pr–Lu except Pm; H2Pc(α-OC5H11)4 =1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine] have been collected and comparatively studied. Both the IR and Raman spectra for M[Pc(α-OC5H11)4]2 are more complicated than those of homoleptic bis(phthalocyaninato) rare earth analogues, namely M(Pc)2 and M[Pc(OC8H17)8]2, but resemble (for IR) or are a bit more complicated (for Raman) than those of heteroleptic counterparts M(Pc)[Pc(α-OC5H11)4], revealing the decreased molecular symmetry of these double-decker compounds, namely S 8. Except for the obvious splitting of the isoindole breathing band at 1110–1123cm−1, the IR spectra of M[Pc(α-OC5H11)4]2 are quite similar to those of corresponding M(Pc)[Pc(α-OC5H11)4] and therefore are similarly assigned. With laser excitation at 633nm, Raman bands derived from isoindole ring and aza stretchings in the range of 1300–1600cm−1 are selectively intensified. The IR spectra reveal that the frequencies of pyrrole stretching and pyrrole stretching coupled with the symmetrical C of –CH3 groups are sensitive to the rare earth ionic size, while the Raman technique shows that the bands due to the isoindole stretchings and the coupled pyrrole and aza stretchings are similarly affected. Nevertheless, the phthalocyanine monoanion radical Pc′ − IR marker band of bis(phthalocyaninato) complexes involving the same rare earth ion is found to shift to lower energy in the order M(Pc)2 >M(Pc)[Pc(α-OC5H11)4]>M[Pc(α-OC5H11)4]2, revealing the weakened π–π interaction between the two phthalocyanine rings in the same order. [Copyright &y& Elsevier]

Bicrystalline nanowires of hematite (α-Fe2O3) have been successfully synthesized by the oxidation of pure iron. The product was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM in combination with focal series reconstruction, energy-dispersive X-ray spectroscopy, and electron energy-loss spectroscopy. The bicrystalline nanowires have diameters of 20−80 nm and lengths up to 20 μm. All of the investigated materials are found to be α-Fe2O3 with a rhombohedral crystal structure. Investigations indicate that most of the bicrystalline nanowires are nanotwins with ellipsoidal heads. The orientation relationship between the nanotwins can be described as (1̄110)M//(1̄110)T, [110]M//[1̄1̄0]T. An energy-filtered TEM investigation indicates that the ellipsoidal head is iron-rich. The growth mechanism of such unique nanostructures is considered to be a solid-phase growth via surface and internal diffusions of molecules from base to tip. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) were synthesized using hot-filament chemical vapor deposition on Ni film-coated Si substrate. The CNTs were well-aligned perpendicular to the substrate. The as-grown CNTs were bamboo-like in their morphology, and were investigated using SEM and high-resolution transmission electron microscopy (HRTEM). The SEM and HRTEM studies show that the both ends of a CNT contain metallic catalytic particles, which is different from results previously reported. Our analysis results provide strong evidence that the metallic catalyst remains in a liquid state during nanotube growth. The upward-growth pulling force of the CNT layer elongates the liquid nanoparticles, which are finally broken into two parts. One part remains at the substrate surface (base of the CNTs) and is responsible for the catalytic growth of the CNTs. The other part is enclosed at the tip of the CNTs and is inactive during CNT growth. [Copyright &y& Elsevier]

Two-dimensional (2D) layered materials are assembled through the intralayer covalent bonds and interlayer van der Waals (vdWs) interactions. The relatively weak interlayer vdWs interactions result in the weak interlayer mechanical coupling between layers, which strongly impacts the overall mechanical properties of multilayer 2D materials or heterostructures. Experimentally probing the interlayer mechanical coupling is of vital importance on the accumulation of fundamental parameters for their applications in flexible and stretchable devices, yet there are hardly comprehensive reviews in this research field. In this review, we firstly introduce the probing methods of interlayer mechanical coupling, including high-frequency and ultralow-frequency Raman characterizations, nanoindentation of multilayer 2D materials or heterostructures, surface indentation, pressurized blister test, characterization of spontaneously formed nanoblisters, and nano-friction tests. Based on the analysis and comparison of the existing methods and results, we also discuss the advantages and limitations of each method. Finally, the challenges and opportunities in this promising field are discussed. This review summarizes the recent progress in the probing of interlayer mechanical coupling of 2D layered materials and will provide important reference for the rational design of flexible and stretchable devices. [Display omitted] • The interlayer interactions strongly impact the mechanical properties of multilayer 2D materials or heterostructures. • Probing the interlayer mechanical coupling of 2D materials is very important for the accumulation of fundamental parameters. • The current experimental methods of probing the interlayer mechanical coupling of 2D layered materials are summarized. [ABSTRACT FROM AUTHOR]

We introduce a “solution‐processing‐transformation” strategy, deploying solvent vapor as scaffolds, to fabricate high‐quality hydrogen‐bonded organic framework (HOF) membranes. This strategy can overcome the mismatch in processing conditions and crystal growth thermodynamics faced during the facile solution processing of the membrane. The procedure includes the vapor‐trigged in situ transformation of dense amorphous supramolecules to crystalline HOF‐16, with HOF‐11 as the transient state. The mechanism involves a vapor‐activated dissolution‐precipitation equilibrium shifting and hydrogen bonding‐guided molecule rearrangement, elucidated through combined experimental and theoretical analysis. Upon removal of the molecular scaffolds, the resulting HOF‐16 membranes showcase significant improvement in hydrogen separation performance over their amorphous counterparts and previously reported HOF membranes. The method's broad applicability is evidenced by successfully extending it to other substrates and HOF structures. This study provides a fundamental understanding of guest‐induced ordered supramolecular assembly and paves the way for the advanced manufacture of high‐performance HOF membranes for gas separation processes. [ABSTRACT FROM AUTHOR]

Interface strain significantly affects the band structure and electronic states of metal‐nanocrystal‐2D‐semiconductor heterostructures, impacting system performance. While transmission electron microscopy (TEM) is a powerful tool for studying interface strain, its accuracy may be compromised by sample overlap in high‐resolution images due to the unique nature of the metal‐nanocrystals‐2D‐semiconductors heterostructure. Utilizing digital dark‐field technology, the substrate influence on metal atomic column contrasts is eliminated, improving the accuracy of quantitative analysis in high‐resolution TEM images. Applying this method to investigate Pt on MoS2 surfaces reveals that the heterostructure introduces a tensile strain of ≈3% in Pt nanocrystal. The x‐directional linear strain in Pt nanocrystals has a periodic distribution that matches the semi‐coherent interface between Pt nanocrystals and MoS2, while the remaining strain components localize mainly on edge atomic steps. These results demonstrate an accurate and efficient method for studying interface strain and provide a theoretical foundation for precise heterostructure fabrication. [ABSTRACT FROM AUTHOR]

Abstract: Effects of moisture absorption on capacitance–loss and current–voltage characteristics of LaMnO3+ δ /SrTiO3:Nb heterojunction had been investigated after the heterojunctions were exposed to ambient air. The moisture-absorption-induced increases in loss tangent and breakdown voltage were observed, whereas no changes were found on capacitance and diffusion voltage. These results were discussed by the decrease of oxygen ions in LaMnO3+ δ and the generation of hydroxide ions at grain boundaries. This work will favor both electronic transport analysis and future device applications. [Copyright &y& Elsevier]

The Au/Nb-1.0 wt %-doped SrTiO3 junctions were successfully fabricated by magnetic controlled sputtering and annealing process. Backward diodelike behaviors were observed in as-prepared junction and the one annealed at 350 °C. Transition to Schottky behavior was found in the junction annealed at 750 °C; the Schottky junction shows linear capacitance-voltage (C-2-V) relationship in the reverse condition with barrier heights determined to be 1.6 eV. The results of current-voltage (I-V) measurements reveal that high temperature annealing can alter interface barrier and thereby ameliorate the stability of leakage current remarkably. [ABSTRACT FROM AUTHOR]

Short-range order in amorphous intergranular films in SiC hot pressed with Al, B, and C additives was recognized with autocorrelation processing of high-resolution electron microscopy images. The short-range order corresponds to Al–O–C tetrahedra formed near the SiC matrix grains. In situ heating high-resolution transmission electron microscopy study demonstrated that the amorphous-to-crystalline transformation in the amorphous Al–O–C intergranular films started from nucleation and local growth of the short-range order structure. [ABSTRACT FROM AUTHOR]

MXenes, a family of 2D transition metal carbides, are considered promising high‐rate pseudocapacitive materials because of their metallic‐like conductivity and transition metal oxide‐like surfaces. Currently, nearly 50 stoichiometric MXenes have been synthesized. However, only a few MXenes, such as Ti3C2, have shown stable pseudocapacitive charge storage so far. Further improving the inherent pseudocapacitance of MXenes without losing their cyclability remains a challenge. Herein, a mild method is reported to produce highly stable bimetallic solid‐solution MXene Ti2VC2 using a solution of potassium fluoride and hydrochloric acid. The electrochemical properties of resulting multilayered clay‐like and delaminated Ti2VC2 films are investigated, exceeding the performance of typical Ti3C2 in acidic electrolytes. These electrodes deliver up to 2000 F cm−3 and retain more than 90% of their initial capacitance after 20 000 cycles, surpassing most state‐of‐the‐art supercapacitor materials known. The pseudocapacitive charge storage of Ti2VC2 is deeply investigated through in situ and ex situ experimental studies, confirmed the pseudocapacitive mechanism is a combination of hydrated H+ intercalation and surface redox. This work provides a practical route toward future rational design on the atomic scale for high‐performance pseudocapacitive materials. [ABSTRACT FROM AUTHOR]

The construction of interfacial electric field (IEF) in semiconductor heterojunction is of great significance in boosting photocatalytic hydrogen evolution through efficient separation of photogenerated charge‐carriers. However, the exploitation of IEF in type‐I heterojunction has not been proposed for designing photocatalysts. Herein, based on the density functional theory prediction, p‐SnS with different work functions modulated by Sn‐vacancy are compounded with n‐ZnIn2S4 containing S‐vacancy to form type‐I heterojunction. The optimized SnS/ZnIn2S4 photocatalyst without co‐catalysts exhibits an impressive hydrogen evolution rate of 22.75 mmol g−1 h−1, 6.23 times of ZnIn2S4. Systematic investigations reveal that the interfacial Sn‐S bond acts as a transport channel that accelerates the interface charge‐carriers transfer under the promotion of IEF originating from the significant Fermi level difference. A large difference in the surface photovoltage signal of SnS/ZnIn2S4 and ZnIn2S4 is achieved from effective photogenerated charge‐carriers separation by IEF. The new p‐n type‐I scheme of SnS/ZnIn2S4 induced by the interfacial mediation can separate the photogenerated charge‐carriers, and retain the highly reductive electrons of ZnIn2S4 for hydrogen evolution, overcoming the disadvantage of reduction potential decline in the typical type‐I scheme. This study will afford a new theoretical basis for the achievement of high‐efficiency photocatalytic hydrogen evolution through interface modulation. [ABSTRACT FROM AUTHOR]

Metal-semiconductor heterostructure nanoparticles (NPs) have attracted much interest and extensively been investigated due to their promising potentials in the fields of catalysis, energy conversion and storage. Due to the synergistic effect and coupling effect between metal and semiconductor, designing and controlling the interface structure of metal-semiconductor NPs and understanding the structure-property relationship have great significance for optimizing their physicochemical performances. Metal NPs coupled with semiconductors forming several kinds of interface structures, including core-shell, yolk-shell, Janus and oligomer-like structures are summarized in this review. The controllable synthesis methods to obtain metal-semiconductor heterostructure NPs with fantastic properties are presented in detail. Moreover, the structure-property relationship and their applications in the fields of catalysis, energy conversion and storage are also exhibited. A brief outlook is given on the challenges and possible solutions in future development of metal-semiconductor NPs. Image 1 • Forming metal-semiconductor heterostructure is an effective way to improve the properties of semiconductor materials. • Structure design and controllable synthesis methods for metal-semiconductor heterostructure nanoparticles are summarized. • The interface structure of metal-semiconductor nanoparticles is a key factor that influence their performances. [ABSTRACT FROM AUTHOR]

Nanoclusters involve finite metal atoms are of great importance in chemical synthesis and catalysis due to their unique structure-dependent properties. Knowing how nanoclusters work in reaction conditions is no doubt one of the most important challenges, which requires deep insight into atomic-scale dynamics during the process. State-of-the-art in-situ transmission electron microscope (TEM) can realize the real-time study, which is expected to reveal insights into the underlying mechanisms of catalysis and design efficient catalysts. In this minireview, we aim to give a critical review and recent progress on nanocluster dynamics unveiled by in-situ and environmental TEM from two aspects: evolutions of metal single atoms and nanoclusters in high-temperature reaction conditions and the well-defined molecular clusters in confined space. We emphasize the cluster-environment interaction and the cluster structure–property relationships. In the end, we also summarize the present achievements and propose future challenges. We expect this review will fuel the excitement and stimulate research in the fields of cluster and catalysis. [ABSTRACT FROM AUTHOR]

Abstract Forward osmosis (FO) is an emerging membrane process driven by the osmotic pressure gradient for freshwater production. Low water flux, reverse solute diffusion, and membrane biofouling are three major issues affecting the FO performances, and the membrane material is one of the keys to solve them. The graphene oxide (GO) membrane exhibits high water flux, indicating its promising potential for application in the field of water purification. However, precisely control of the pore size of the GO membranes is necessary for efficient ion sieving. In this work, the hydrophilic metal-organic framework (UiO-66) nanoparticles, as the microporous fillers, are intercalated into the GO layers to form ultrathin "sandwich" membranes for improving the FO performances. The incorporated UiO-66 introduces uniform and suitable nanochannels that can effectively allow water to permeate through, while hinder the solutes of Na+ ions. Furthermore, the GO layers form the matrix of nanometer-thick membranes possess the antimicrobial activity (bacteriostasis of 90%), which would prevent the biofouling. In the FO model, the UiO-66/GO membrane exhibits a water flux of 29.16 LMH, which was 270% higher than the pristine GO membrane, while the reverse solute diffusion was reduced by 83.5% (12.86 gMH). Graphical abstract By the incorporation of UiO-66 into GO matrix, a sandwich membrane was obtained with highly improved FO performance compared with the pristine GO membrane. Image 1 [ABSTRACT FROM AUTHOR]

The title process allows the synthesis of a series of optically active indole derivatives with enantioselectivities up to 94%. [ABSTRACT FROM AUTHOR]

The long–term stability of proton conductors is one of the most important factors in evaluating materials. Guest molecules can act as "bridges" for proton conduction channels and reside in the channels of covalent organic frameworks, but they are prone to leakage. Therefore, it is important to develop proton conductors with intrinsic proton conductivity. In this paper, we synthesized an intrinsically sulfonated covalent organic framework, TpPa–SO3H, which has a more stable proton conducting performance than that of TpPa@H2SO4 by loading guest molecules. Meanwhile, the proton conductivity of TpPa–SO3H was further improved by coating a superabsorbent polymer through an in situ reaction to obtain PANa@TpPa–SO3H (PANa: sodium polyacrylate). As a result, the modified composite exhibits an ultrahigh proton conductivity of 2.33 × 10−1 S cm−1 at 80 °C under 95% relative humidity (RH). The stability of PANa@TpPa–SO3H makes it an efficient proton transport platform with excellent proton conductivity and long–term durability. [ABSTRACT FROM AUTHOR]

Interfacial atomic configuration plays a vital role in the structural stability and functionality of nanocomposites composed of metal nanoparticles (NPs) and two−dimensional semiconductors. In situ transmission electron microscope (TEM) provides a real−time technique to observe the interface structure at atomic resolution. Herein, we loaded bimetallic NiPt truncated octahedral NPs (TONPs) on MoS2 nanosheets and constructed a NiPt TONPs/MoS2 heterostructure. The interfacial structure evolution of NiPt TONPs on MoS2 was in situ investigated using aberration−corrected TEM. It was observed that some NiPt TONPs exhibited lattice matching with MoS2 and displayed remarkable stability under electron beam irradiation. Intriguingly, the rotation of an individual NiPt TONP can be triggered by the electron beam to match the MoS2 lattice underneath. Furthermore, the coalescence kinetics of NiPt TONPs can be quantitatively described by the relationship between neck radius (r) and time (t), expressed as rn = Kt. Our work offers a detailed analysis of the lattice alignment relationship of NiPt TONPs on MoS2, which may enlighten the design and preparation of stable bimetallic metal NPs/MoS2 heterostructures. [ABSTRACT FROM AUTHOR]

A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission). [ABSTRACT FROM AUTHOR]

Constructing a heterogeneous interface using different components is one of the effective measures to achieve the bifunctionality of nanocatalysts, while synergistic interactions between multiple interfaces can further optimize the performance of single-interface nanocatalysts. The non-precious metal nanocatalysts MoS2/NiSe2/reduced graphene oxide (rGO) bilayer sandwich-like nanostructure with multiple well-defined interfaces is prepared by a simple hydrothermal method. MoS2 and rGO are layered nanostructures with clear boundaries, and the NiSe2 nanoparticles with uniform size are sandwiched between both layered nanostructures. This multiple-interfaced sandwich-like nanostructure is prominent in catalytic water splitting with low overpotential for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and almost no degradation in performance after a 20 h long-term reaction. In order to simulate the actual overall water splitting process, the prepared nanostructures are assembled into MoS2/NiSe2/rGO||MoS2/NiSe2/rGO modified two-electrode system, whose overpotential is only 1.52 mV, even exceeded that of noble metal nanocatalyst (Pt/C||RuO2~1.63 mV). This work provides a feasible idea for constructing multi-interface bifunctional electrocatalysts using nanoparticle-doped bilayer-like nanostructures. [ABSTRACT FROM AUTHOR]

As a typical planar 4-connected ligand that possesses D4h symmetry, the squarate ligand is expected to construct some interesting topologies. Here, we report that the assembly of the squarate ligand with rare-earth ions can produce a series of (4, 8)-connected frameworks with the "smallest" scu type topology. Among these compounds, the Tb based analogue not only possesses a good proton conductivity, but also exhibits luminescence responses toward MnO4− and Cr2O72−, making it a candidate for multifunctional materials. [ABSTRACT FROM AUTHOR]

Cu 2 O is an ideal template material for the preparation of transition metal hydroxide/oxyhydroxides with oxygen evolution reaction (OER) enhanced catalytic performance. Here, inspired by Pearson's principle, Cu 2 O wires were prepared and used as a sacrificial template to prepare Ni(OH) 2 ·0.75H 2 O hollow tubes (Ni(OH) 2 HTs) with highly improved surface roughness. Benefiting from unique structural advantages, the Ni(OH) 2 HTs showed excellent catalytic activity, rapid kinetics and a long-term stability as the OER catalyst, where an overpotential of only 207 ​mV was required to drive a current density of 10 ​mA ​cm−2, an ideal kinetics with a Tafel slope as 79.8 ​mV dec−1 was calculated, and no obvious attenuation in chronoamperometry was discovered after operation for 24 ​h. This paper provides a novel template-assisted strategy to prepare high-performance transition metal-based OER catalysts possessing hollow and tubular structures. [Display omitted] • For the first time , we used Cu 2 O wires as hard template to prepare hollow tubular Ni(OH) 2. • The Ni(OH) 2 HTs possess novel morphologies with stable hollow one-dimensional structure and rough surface. • As OER catalyst, the Ni(OH) 2 HTs showed excellent electrochemical performances for overpotential, kinetics and stability. [ABSTRACT FROM AUTHOR]

A 2D wave-like layered framework based on benzotriazole-5-carboxylic acid (H2btca), 2,2′-bipy and zinc ions – [Zn(btca)(2,2′-bipy)]n (1) – has been resoundingly designed and synthesized by a solvothermal method. By changing the solvent from DMF to DMA, a 3D porous framework – [Zn2(btca)2(bpy)(H2O)]n·n(DMA) (2) – was obtained. Complexes 1 and 2 have been determined by single-crystal X-ray diffraction analysis and further characterized by powder X-ray diffraction (PXRD), elemental analysis, IR spectroscopy, and thermogravimetric (TG) analysis. Complex 1 shows an AA packing 2D layered structure and complex 2 displays a 3D open honeycomb framework with a (3,4)-connected 2-nodal fsc topology. Moreover, gas adsorption of 2a (the activated form of 2) and the luminescence properties of 1, 2 and 2a have also been investigated intensively. [ABSTRACT FROM AUTHOR]

Herein, Cu 2 O microcrystals are found to perform efficiently in hydrogen generation and formaldehyde degradation at room temperature, with MgO as a sacrificial agent, while other photocatalytic semiconductors such as TiO 2 , ZnO, Bi 2 O 3 , Fe 2 O 3 and CuO exhibit poor capability under the same condition. This peculiarity of Cu 2 O microcrystals is comprehensively analyzed, focusing on exploring the formation of [Cu + ]· paramagnetic during the reaction, which is first proposed as a principal factor for the hydrogen generation and formaldehyde degradation. Even more exciting, abundant hydroxyl radicals produced during this reaction process are detected via electron paramagnetic resonance spectrometry, which are particularly efficient in oxidizing formaldehyde and producing hydrogen. [ABSTRACT FROM AUTHOR]