Strong Separation Research Articles

Hollow Zn0.01Co0.99 Se2/ZnIn2S4 Z-scheme heterogeneous photocatalyst with Strong internal electric field and Excellent surface electron transfer capability for Efficient Hydrogen Production

Reasonable design and optimization of photocatalyst structure is an important strategy to realize sustainable hydrogen production. The rational design and interfacial tuning of Z-scheme heterojunctions remain challenging. Herein, a series of hollow cage-like Zn0.01Co0.99Se2/ZnIn2S4 Z-scheme heterojunction photocatalysts templated by cobalt-based bimetallic organic frameworks is successfully obtained via a hydrothermal approach. As expected, the optimized catalysts exhibit excellent hydrogen production performance without noble metal co-catalysts, which is mainly attributable to the synergistic effect of abundant active sites, strong light trapping and effective charge separation. Spectroscopic characterization and density functional theory (DFT) calculations indicate that the doping of Zn ions leading to more photogenerated carriers and faster charge transfer rates inside the heterojunction is another key factor in improving the catalytic performance. This work provides a feasible strategy for the optimization and design of Z-scheme heterojunctions through structural and interfacial engineering.

Multiblock copolymers with disulfonated bis(phenylsulfonylphenyl) sulfone group for polymer electrolyte membrane water electrolysis

Hydrogen, a zero-emissions fuel, is increasingly being targeted as a source of renewable energy. However, hydrogen production by electrolysis is limited by the characteristics of the hydrogen-separating membrane. Here, a series of multiblock copolymers composed of a hydrophilic block based on disulfonated bis(phenyulfonylphenyl) sulfone groups, and a hydrophobic block based on bis(p-phenoxyphenyl) ether groups is developed for application as a proton exchange membrane for water electrolysis. The multiblock copolymers combining stiff hydrophilic block and flexible hydrophobic block are expected to have reduced water swelling and low hydrogen permeability even under full-wet and high-temperature conditions in water electrolysis. Microscopy and X-ray scattering analyses of the multiblock copolymer-based membranes reveal strong nanophase separation and well-developed ion transport channels. The as-synthesized membranes exhibit advantages including low swelling, high proton conductivity, good mechanical and thermal properties, high oxidative stability, and reduced hydrogen permeability. A membrane electrode assembly employing the multiblock copolymer membrane achieved a current density above 3 A cm−2 at 1.8 V, far surpassing that of Nafion 212, and a long-term operating stability exceeding 500 h, demonstrating the suitability of the membrane for practical water electrolysis.

B-TiO2/CuInS2 photocatalyst based on the synergistic effect of oxygen vacancy and Z-scheme heterojunction for improving photocatalyst CO2 reduction

Photocatalytic reduction CO2 into valuable solar fuels is a promising strategy to alleviate the greenhouse effect and the energy crisis on Earth. In this work, a B-TiO2/CuInS2 photocatalyst has been synthesized through a simple hydrothermal-calcination method for efficient reducing CO2 into CO and CH4. Boron doping and sensitization of CuInS2 ensure the excellent visible light response capacity of the composite catalyst. The synergistic effect between oxygen vacancies and Z-scheme heterojunction also endow the photocatalyst with strong carrier separation capability. Consequently, the optimized B-TO/CIS-2.5 sample exhibited the best CO (21.39 μmol g−1 h−1) and CH4 (4.83 μmol g−1 h−1) production, approximately 9 and 14 times higher than that of TO and B-TO, respectively. This study provides a reliable approach for developing photocatalysts with boosted CO2 reduction activity and high stability.

PbTiO3 Based Single-Domain Ferroelectric Photocatalysts for Water Splitting

ConspectusSolar-driven photocatalytic water splitting paves a way to produce green hydrogen for building a sustainable clean energy system, particularly within the framework of the carbon-neutral initiative. However, to date, the solar-to-hydrogen (STH) conversion efficiency of particulate photocatalysts falls far short of the demand of over 10% for industrial applications. Single-domain ferroelectric semiconductor materials with amazing unidirectional spontaneous polarization penetrating the bulk are promising candidates as photocatalysts for water splitting. Their existing inherent internal field set up by polarization can cause both two oppositely charged surfaces (namely, polar surfaces) and spatial separation of photogenerated charge carriers between them upon light excitation. These unique properties provide sufficient new room for flexibly engineering of bulk and surface/interface structures to enhance photocatalytic water splitting.In this Account, we offer a systematic overview of the exploration of PbTiO3 based single-domain ferroelectric photocatalysts for efficient solar water splitting. In detail, the controlled growth, surface modification, heterostructures, and Z-scheme system of single-domain PbTiO3 ferroelectrics are discussed by considering polar surfaces, spatial separation of the photoexcited charges, selective distribution of defects, and selective adsorption of reactive species. We start with the controlled synthesis of single-domain ferroelectric PbTiO3 nanoplates to realize the opposite directional transport of photoexcited charges driven by the polarized internal electric field, which can be verified by the fact that photochemical reduction/oxidation deposits occur on opposite polar surfaces. Then, we move to the selective modification of the specific polar surface to promote the transfer of photoexcited charges by applying the spatial separation effect of photoexcited charges and defects related internal screening mechanism. Furthermore, asymmetric heterostructures and Z-scheme systems are rationally designed by selective adsorption of reactive species on charged surfaces to promote charge separation and suppress redox mediator side reactions, respectively. Although significant advances have been achieved, many efforts remain needed toward the industrial production target. Based on single-domain ferroelectric photocatalysts, we present the following perspectives on the utilization of a wide solar spectrum for improving solar energy conversion efficiency. First, proper dopants can be incorporated homogeneously in the bulk to reduce the bandgap without obviously weakening ferroelectricity. Second, the epitaxial growth of narrow bandgap semiconductors on the ferroelectrics is feasible to induce additional polarization in the region close to their interface. These two aspects are anticipated to enable strong visible light absorption and charge separation efficiency. Third but not least, the assembly of Z-scheme systems with two narrow bandgap ferroelectrics is desirable to mimic natural photosynthetic systems with quantum yield approaching one unit.

Metagenomic analysis of gut microbiome from tilapia species across several regions in Japan

Tilapia is one of the most widely cultured fish species in the world. The host-associated microbiota plays essential roles in growth, metabolism, immunological responses, and adaptation. We used the 16S rRNA Illumina MiSeq sequencing to investigate the microbial composition, structure, and functions of tilapia species gut microbiota from five distinct regions in Japan. Our findings showed that the gut microbial community in fish was more strongly shaped by habitat water source than by tilapia species. The bacterial community of fish differs significantly from groundwater to river water. The beta diversity analysis indicated a strong separation of samples based on their water source. The fish gut microbiota was dominated by Fusobacteriota (25%), Proteobacteria (22%), Firmicutes (14%), and Cyanobacteria (12%) across all samples. Contrarily, the relative abundance of Cyanobacteria was higher in the groundwater group than in the river group, with a shift in the functional features of the community. Cetobacterium and Romboutsia were the most prevalent genera across all samples. This study sheds light on the gut microbiota of tilapia species in Japan. It contributes to our understanding of tilapia adaptability, which may aid in developing future tilapia aquaculture strategies in Japan.

Promoting photocatalytic nitrogen reduction for aqueous nitrogenous fertilizer from organic wastewater over p-BiOBr/n-Bi2MoO6 hetero-nanofibers

Photocatalytic nitrogen reduction (PNR) is a potential routine for producing aqueous nitrogenous fertilizer via a green chemistry process but is still limited by a relatively poor efficiency. Considering the dynamic coupling of excited electrons and holes, we introduced organic wastewater oxidation process to substitute the sluggish water oxidation for promoting the PNR reaction. We developed p-BiOBr/n-Bi2MoO6 Z-scheme hetero-nanofibers and experimentally studied their interface charge transfer mechanism in detail. Their strong redox ability and high charge separation efficiency enabled efficient PNR with simultaneous organic pollutant degradation. They have exhibited a PNR rate of up to 911.6 µmol g−1 h−1 L−1 in Rhodamine B (RhB) solution, about 2.5 times higher than that in pure water. Meanwhile, their RhB removal rate reached ∼91.2% in the PNR process (i.e., in N2 saturated solution), close to that in the air (∼96.6%) due to the strong oxidation ability of valence band holes. The proper loading ratio of BiOBr on the hetero-nanofibers and their super-long one-dimensional structures were essential for tuning the charge separation and photocatalytic activity. Moreover, the dual-functional system exhibited efficient photocatalytic performance in a natural water matrix and simulated flowing wastewater scene. Based on a comparative plant cultivation study, the system could effectively convert pollutant solutions into aqueous nitrogenous fertilizers that could promote the healthy growth of nitrogenous sensitive plants. The green and sustainable strategy of PNR for aqueous nitrogenous fertilizer from organic wastewater would have broad applications in energy conservation and environmental remediation.

Sensitivity Enhancement for Separation-Based Analytical Techniques Utilizing Solid-Phase Enrichment Approaches and Analyte Derivatization for Trace Analysis in Various Matrices

Despite the fact that strong routine separation methodologies can give reliable specificity and validity at usual working pharmaceutical concentrations, they may fail at very low concentration levels. This poses considerable challenges for researchers investigating product purity and therapeutic drug monitoring. Sensitivity enhancement procedures are thus required to maximize the performance of separation techniques. Solid-phase extraction/solid-phase enrichment (SPE/SPEn) and pre-, post-, and in-column derivatization, as well as the use of sensitive detection devices, are the simplest strategies for improving sensitivity of separation-based analytical techniques. Large-volume injection of samples with online SPE/SPEn coupled with separation techniques increased sensitivity and improved detection as well as quantification limits without affecting peak shape and system performance. Although the primary purpose of derivatization is to improve sensitivity and selectivity, greener derivatization is growing in popularity and should be considered in analytical chemistry. In general, two strategies are essential for accomplishing greener derivatization goals. The first is the search for and use of ecologically acceptable derivatizing reagents, solvents, and reaction conditions. The second is miniaturization and automation of analytical methods. This review discusses significant advances in separation-based analytical techniques, specifically enrichment approaches and detector signal improvement for pharmaceutical quantification in various matrices at very low concentration levels. As a result of improved analytical systems setup in drug assays, the possibility of high-throughput analyses was also highlighted.

A new smoothed particle hydrodynamics method based on high-order moving-least-square targeted essentially non-oscillatory scheme for compressible flows

In this study, we establish a hybrid high-order smoothed particle hydrodynamics (SPH) framework (MLS-TENO-SPH) for compressible flows with discontinuities, which is able to achieve genuine high-order convergence in smooth regions and also capture discontinuities well in non-smooth regions. The framework can be either fully Lagrangian, Eulerian or realizing arbitary-Lagrangian-Eulerian (ALE) feature enforcing the isotropic particle distribution in specific cases. In the proposed framework, the computational domain is divided into smooth regions and non-smooth regions, and these two regions are determined by a strong scale separation strategy in the targeted essentially non-oscillatory (TENO) scheme. In smooth regions, the moving-least-square (MLS) approximation is used for evaluating high-order derivative operator, which is able to realize genuine high-order construction; in non-smooth regions, the new TENO scheme based on Vila's framework with several new improvements will be deployed to capture discontinuities and high-wavenumber flow scales with low numerical dissipation. The present MLS-TENO-SPH method is validated with a set of challenging cases based on the Eulerian, Lagrangian or ALE framework. Numerical results demonstrate that the MLS-TENO-SPH method features lower numerical dissipation and higher efficiency than the conventional method, and can restore genuine high-order accuracy in smooth regions. Overall, the proposed framework serves as a new exploration in high-order SPH methods, which are potential for compressible flow simulations with shockwaves.

Separation and purification of glycosides from medicinal plants based on strong polar separation medium with online closed-loop mode

Natural glycosides widely distributed in medicinal plants are valuable sources of therapeutic agents, showing various pharmacological effects. The separation and purification of natural glycosides are meaningful for their pharmacological research, which face with great challenges due to the complex of medicinal plants samples. In this work, two kinds of functional monolithic separation mediums A and S were fabricated and fully applied in the online extraction, separation and purification of active glycoside components from medicinal plants with a simple-procedure closed-loop mode. Chrysophanol glucoside and physcion glucoside were detected and separated from Rhei Radix et Rhizoma using separation medium A as a solid-phase extraction adsorbent. Rhapontin was isolated and purified from Rheum hotaoense C. Y. Cheng et Kao using separation medium S as the stationary phase of high-performance liquid chromatography. Compared to the reported literatures, high yield of 5.68, 1.20 and 4.76 mg g−1 of these three products were obtained with high purity. These two online closed-loop mode methods were carried out using high-performance liquid chromatography system, in which the sample injection, isolation and purification procedures are all online mode, and reduced loss compared to offline extraction and purification procedures, thus achieving high recovery and high purity.

The In Situ Optimization of Spinterface in Polymer Spin Valve by Electronic Phase Separated Oxides.

Tailoring the interface between organic semiconductor (OSC) and ferromagnetic (FM) electrodes, that is, the spinterface, offers a promising way to manipulate and optimize the magnetoresistance (MR) ratio of the organic spin valve (OSV) devices. However, the non-destructive in situ regulation method of spinterface is seldom reported, limiting its theoretical research and further application in organic spintronics. (La2/3 Pr1/3 )5/8 Ca3/8 MnO3 (LPCMO), a recently developed FM material, exhibits a strong electronic phase separation (EPS) property, and can be employed as an effective in situ spinterface adjuster. Herein, we fabricated a LPCMO-based polymer spin valve with a vertical configuration of LPCMO/poly(3-hexylthiophene-2,5-diyl) (P3HT)/Co, and emphasized the important role of LPCMO/P3HT spinterface in MR regulation. A unique competitive spin-scattering mechanism generated by the EPS characteristics of LPCMO inside the polymer spin valve was discovered by abstracting the anomalous non-monotonic MR value as a function of pre-set magnetic field (Bpre ) and temperature (T). Particularly, a record-high MR ratio of 93% was achieved in polymer spin valves under optimal conditions. These findings highlight the importance of interdisciplinary research between organic spintronics and EPS oxides and offer a novel scenario for multi-level storage via spinterface manipulation.

Numerical and experimental investigation of quantitative relationship between secondary flow intensity and inviscid blade force in axial compressors

The secondary flow attracts wide concerns in the aeroengine compressors since it has become one of the major loss sources in modern high-performance compressors. But the research about the quantitative relationship between secondary flow and inviscid blade force needs to be more detailed. In this paper, a database of 889 three-dimensional linear cascades was built. An indicator, called Secondary Flow Intensity (SFI), was used to express the loss caused by secondary flow. The quantitative relationship between the SFI and inviscid blade force deterioration was researched. Blade oil flow and Computation Fluid Dynamics (CFD) results of some cascades were also used to cross-validate. Results suggested that all numerical cascade cases can be divided into 3 clusters by the SFI, which are called Clusters A, B and C in the order of the increasing SFI indicator. The corner stall, known as the strong corner separation, only happens when the SFI is high. Both calculations and oil flow experiments show that the SFI would stay at a low level if the vortex core at the endwall surface does not appear. The strong interaction of Kutta condition and endwall cross-flow is considered the dominant mechanism of higher secondary flow losses, rather than the secondary flow penetration depth on the suction surface. In conclusion, the inviscid blade force spanwise deterioration is strongly related to the SFI. The correlation of the SFI and spanwise inviscid blade force deterioration is given in this paper. The correlation could provide a quantitative reference for estimating secondary flow losses in the design.

Imparting High Conductivity to 3D Printed PEDOT:PSS

Complex 3D geometry and high conductivity have generally been mutually exclusive characteristics for conducting polymers. For instance, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), a benchmark conducting polymer, typically exhibits conductivity 1 to 2 orders of magnitude lower in 3D-printed forms compared to 2D-processed thin films, due to its sensitivity to processing conditions. Here, we investigate the main causes of this reduced conductivity, which are found to be (1) the ink formulation strategy and (2) the strong lateral phase separation of the printed filaments. Processing approaches that overcome these factors have produced significant conductivity enhancement to 1200 S/cm, higher than the typical 2D-processed PEDOT:PSS. Our study also unveils a set of guiding principles for optimizing the conductivity of direct ink writing (DIW)-printed PEDOT:PSS, including printing orientation, print bed temperature, and nozzle diameter. With the combination of high conductivity and 3D geometric freedom, potential applications such as omnidirectionally deformable LED devices with strain-independent electrical behavior and bespoke electronics that replicate the shape of human body parts have been demonstrated.

Transient simulation of reversible pump turbine during pump mode's starting up

A pumped storage power station is an electric power system that utilizes low-peak electricity to pump water into a high-altitude reservoir and releases water to generate electricity during high-peak electricity demand. The pump mode's starting up impacts the operational stability and lifespan of the reversible pump turbine (RPT). Especially, the pressure pulsation signal during the pump mode's starting up is a typical non-stationary signal in RPT, which is an important basis for judging the operation status of the unit. In this study, the time-varying boundary conditions are used to calculate the pressure fluctuation and flow pattern evolution for a prototype RPT. This paper analyzed and compared the time-frequency characteristics of pressure fluctuations by continuous wavelet transform (CWT) and by variational mode decomposition (VMD). And the internal flow of RPT was also visualized using entropy generation theory. In this study, the effect of the penalty coefficient on the VMD algorithm is investigated in the form of a signal-noise ratio (SNR). With the increase of the penalty coefficient, the SNR of the signal gradually decreases and tends to be stable. Several modal components with strong physical significance and center frequency separation are obtained. Influenced by the boundary conditions that change with time, the pressure fluctuation presents a five-stage trend of “descending - ascending - descending - ascending - descending”. There are three main types of high-flow energy dissipation (FED) areas during this process of the RPT. The research and analysis in this paper will provide a good reference for the stable and safe operation of RPT and pumped storage power stations.

Light Control-Induced Oxygen Vacancy Generation and In Situ Surface Heterojunction Reconstruction for Boosting CO2 Reduction.

The weak adsorption of CO2 and the fast recombination of photogenerated charges harshly restrain the photocatalytic CO2 reduction efficiency. The simultaneous catalyst design with strong CO2 capture ability and fast charge separation efficiency is challenging. Herein, taking advantage of the metastable characteristic of oxygen vacancy, amorphous defect Bi2O2CO3 (named BOvC) was built on the surface of defect-rich BiOBr (named BOvB) through an in situ surface reconstruction progress, in which the CO32- in solution reacted with the generated Bi(3-x)+ around the oxygen vacancies. The in situ formed BOvC is tightly in contact with the BOvB and can prevent the further destruction of the oxygen vacancy sites essential for CO2 adsorption and visible light utilization. Additionally, the superficial BOvC associated with the internal BOvB forms a typical heterojunction promoting the interface carriers' separation. Finally, the in situ formation of BOvC boosted the BOvB and showed better activity in the photocatalytic reduction of CO2 into CO (three times compared to that of pristine BiOBr). This work provides a comprehensive solution for governing defects chemistry and heterojunction design, as well as gives an in-depth understanding of the function of vacancies in CO2 reduction.

Optimality Conditions for Multiobjective Optimization Problems via Image Space Analysis

In this article, optimality conditions on (weak) efficient solutions in multiobjective optimization problems are investigated by using the image space analysis. A class of strong separation functions is constructed by oriented distance functions. Simultaneously, a generalized Lagrange function is introduced by the class of strong separation functions. Then, generalized Karush-Kuhn-Tucker (KKT for short) necessary optimality conditions are established without constraint qualifications or regularity conditions. Under the suitable assumptions, Lagrangian-type sufficient optimality conditions are also characterized. Moreover, the difference between strong separation and weak separation methods is explained.

Interfacial Polymerization on Polyethersulfone Ultrafiltration Membrane to Prepare Nanofiltration Layers for Dye Separation.

Nanofiltration membranes are of great significance to the treatment of dye wastewater. Interfacial polymerization is a widely used method to fabricate nanofiltration membranes. In this study, the interaction of tannic acid-assisted polyethylene polyamine (PEPA) with terephthalaldehyde (TPAL) was performed on PES ultrafiltration membranes using novel nitrogen-rich amine monomers and relatively less reactive aldehyde-based monomers. A new nanofiltration membrane ((T-P-T)/PES) was prepared by interfacial polymerization. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy were used to analyze the elemental composition, bonding state, and surface morphology of the membrane surface. The effects of the PEPA deposition time, TPAL concentration, interfacial reaction time, and curing time on the nanofiltration layer were investigated. The modified membrane, prepared under optimal conditions, showed strong dye separation ability. The permeation of the modified membrane could reach 68.68 L·m-2·h-1·bar-1, and the rejection of various dyes was above 99%. In addition, the (T-P-T)/PES membrane showed good stability during long-term dye separation.

Spatial distribution modulation of laser-accelerated charged particles with micro-tube structures

We present experimental studies on the spatial distribution of charged particles using a linearly polarized femtosecond laser interacting with a micro-structure target composed of micro-tube structure and planar foil. For protons, a six-lobed structure was observed in the low-energy region, while a smaller angular divergence was measured in the high-energy region. Electron distribution exhibits a circular distribution at low energies and double-lobed structure at high energies. These results are well reproduced by 3D particle-in-cell simulations, showing that the profile of electrons driven by a laser pulse is manipulated by the micro-tube structure, which maps into the spatial distribution of protons via a strong charge separation field. These results demonstrate the effect of micro-structures on laser-driven particle sources and provide a possible approach for spatial manipulation of the particle beams.

A Carbon-Free and Free-Standing Cathode From Mixed-Phase TiO2 for Photo-Assisted Li-CO2 Battery.

Li-CO2 battery provides a new strategy to simultaneously solve the problems of energy storage and greenhouse effect. However, the severe polarization of CO2 reduction and CO2 evolution reaction impede the practical application. Herein, anodic TiO2 nanotube arrays are first introduced as carbon-free and free-standing cathode for photo-assisted Li-CO2 battery, and the photo-assisted charge and discharge mechanism is first clarified from the perspective of photocatalysis. Mixed-phase TiO2 exhibits a long cycling life of 580h (52 cycles) at 0.025mA cm-2 and delivers a high discharge specific capacity of 3001 µAh cm-2 under UV illumination. The charge voltage dramatically reduces from 4.53 to 3.03V under UV illumination. The improvement of photo-assisted Li-CO2 battery performance relies on the synergistic effect of the hierarchical porous structure, strong UV absorption, efficient separation, and transfer of photo-generated electrons and holes at hetero-phase junction, and the facilitation of photo-generated electrons and holes on CO2 reduction and CO2 evolution reaction. This work can provide useful guidance for designing efficient photocathode for photo-assisted Li-CO2 battery and other metal-air batteries.

Digital units and digital innovation: Balancing fluidity and stability for the Creation, Conversion, and Dissemination of sticky knowledge

The creation and dissemination of knowledge is critical for enabling digital innovation in firms. Yet, many digital units fail to do so. We analyze multiple interviews with functional experts and digital unit members from eight firms to explore how digital units enable organizational digital transformation. Findings emphasize that strong structural separation and poor strategizing of the digital unit solidify existing schemes while not reducing organizational rigidities. This leads to knowledge becoming difficult or sticky to exchange. Successful digital innovation depends on knowledge creation and exchange among experts, non-experts, and managers. Digital units must find and integrate experts from digital technology and functional domains and convert their tacit knowledge into digital innovation requirements. We highlight the need for balance between fluidity and stability, as sticky knowledge conversion requires long-term relationships, while digital innovation demands fluid knowledge inflows and outflows. Thus, we contribute to digital unit research which emphasizes strong cross-functional exchanges.

On the Fractal Measures and Dimensions of Image Measures on a Class of Moran Sets

In this work, we focus on the centered Hausdorff measure, the packing measure, and the Hewitt–Stromberg measure that determines the modified lower box dimension Moran fractal sets. The equivalence of these measures for a class of Moran is shown by having a strong separation condition. We give a sufficient condition for the equality of the Hewitt–Stromberg dimension, Hausdorff dimension, and packing dimensions. As an application, we obtain some relevant conclusions about the Hewitt–Stromberg measures and dimensions of the image measure of a τ-invariant ergodic Borel probability measures. Moreover, we give some statistical interpretation to dimensions and corresponding geometrical measures.