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Pseudo threshold pressure gradient (PTPG) is one of the main factors affecting the oil recovery of heterogeneous low-permeability and tight reservoirs. When the pressure gradient between the supply boundary and the bottom hole is less than PTPG, the crude oil in the formation cannot flow. In order to accurately measure the relationship between PTPG and permeability, a novel experimental device has been designed and a series of core flooding experiments using brine and oil have been carried out. The new experimental device eliminates the influence of rubber sleeve in core holder and core end-effect on the results, and greatly improves the accuracy of pressure measurement. The experimental results show the PTPG has a power function relationship with permeability, and has no obvious relationship with the viscosity of the fluid. Based on the equation for PTPG and permeability of crude oil and brine fitted by the experimental data, a new heterogeneous reservoir mathematical model considering PTPG were established. The influence of the coefficient of permeability variation, average permeability, and the production rate on oil recovery factor have been studied by this model. The results clearly show that the coefficient of permeability variation has the greatest influence on oil recovery factor, which represents inhomogeneity in low-permeability and tight reservoirs. Also, when the coefficient of permeability variation is less than a certain value (about 0.2 when average permeability is 1mD, in our model), there is only a slight decline in oil recovery factor, and when coefficient of permeability variation is larger than this value, the oil recovery factor decreases rapidly. The finding is consistent with oil field production and helpful to determine whether to take EOR(enhanced oil recovery) measures for a low-permeability heterogeneous reservoirs.

Water collection by dew condensation emerges as a sustainable solution to water scarcity. However, the transient condensation process that involves droplet nucleation, growth, and transport imposes conflicting requirements on surface properties. It is challenging to satisfy all benefits for different condensation stages simultaneously. By mimicking the structures and functions of moss Rhacocarpus, here, we report the attainment of dropwise condensation for efficient water collection even on a hydrophilic surface gated by a liquid suction mechanism. The Rhacocarpus-inspired porous surface (RIPS), which possesses a three-level wettability gradient, facilitates a rapid, directional, and persistent droplet suction. Such suction condensation enables a low nucleation barrier, frequent surface refreshing, and well-defined maximum droplet shedding radius simultaneously. Thus, a maximum ∼160% enhancement in water collection performance compared to the hydrophobic surface is achieved. Our work provides new insights and a design route for developing engineered materials for a wide range of water-harvesting and phase-change heat-transfer applications.

Although it is established that the force-induced electric polarization field of piezoelectric semiconductors can be used to tune the transfer rate of photoexcited charge carriers, there is still a lack of successful strategies to effectively improve the photocatalytic reactivity and solar-to-chemical conversion efficiency (SCC) of piezoelectric materials. Here, we are the first to prepare and study a kind of catalyst based on nanopiezoelectric heterostructures of LiNbO3-type ZnTiO3·TiO2 and tetragonal BaTiO3 with Pt or FeOx nanoparticle modification (i.e., ZBTO-Pt or ZBTO-FeOx) for reactive species generation. With respect to the production of •OH and •O2- radicals, higher amounts were observed in piezophotocatalysis relative to those for individual piezo- and photocatalysis. Benefiting from the charge transfer resistance decreases by the deposition of Pt and FeOx, the amounts of •OH radicals formed on ZBTO-Pt and ZBTO-FeOx were approximately 48 and 21% higher than that on isolated ZBTO during piezophotocatalysis, and for the amounts of •O2- radicals the enhancements were approximately 11 and 6%, respectively. Furthermore, the concentrations of H2O2 formed on ZBTO-Pt and ZBTO-FeOx under piezophotocatalysis reached approximately 315 and 206 μM after 100 min of reaction (and was still increasing) corresponding to 0.10 and 0.06% SCCs, respectively, which were also much higher than the concentrations and SCCs observed for piezo- and photocatalysis. The enhancements of piezophotocatalytic activities with these piezoelectric materials were related to the mechanical strain exerted on ZBTO, which generated a larger electric polarization field than those on ZnTiO3·TiO2 and BaTiO3 as analyzed by a finite element method. This high-intensity electric polarization field accelerated the separation and transportation of photoexcited charge carriers in the highly sunlight responsive nanopiezoelectric heterostructures based on ZBTO-Pt and ZBTO-FeOx.

Lead-free (1−x)Bi0.5Na0.5TiO3–x(Sr0.7Bi0.2□0.1)TiO3 (x = 0.0, 0.1, 0.2 and 0.3, denoted as BNT–xSBT) thin films were deposited on Pt(111)/Ti/SiO2/Si substrates by the sol–gel method, and their microstructure and dielectric, ferroelectric and piezoelectric properties were investigated in detail. All thin films present a single perovskite structure as demonstrated. In particular, appropriate Mn doping modifies the concentration of oxygen vacancies in thin films, resulting in a marked decline in leakage current. In this way, an ultra-high inverse piezoelectric coefficient (d33* ∼144.11 pm V−1) can be obtained from a 0.8BNT–0.2SBT thin film, and a maximum polarization Pm of 46.88 μC cm−2 is observed under an electric field of 700 kV cm−1. Meanwhile, a BNT–SBT thin film has flexible dielectric tunability. All results strongly suggest that the ultra-high piezoelectric property of BNT–0.2SBT is derived from the ferroelectric-to-relaxor transition. As described, this work indicates that the BNT–SBT thin film is an ideal lead-free piezoelectric substituted material. Moreover, BNT–SBT is a novel system of thin films, which has a great development prospect.

In recent years, sodium bismuth titanate (Bi0.5Na0.5TiO3, BNT) -based relaxor ferroelectrics have attracted more and more attention for energy storage applications owing to their high power density, large saturated polarization (PS)/maximum polarization (Pmax) as well as meeting the needs of environment-friendly society. However, the recoverable energy storage density (Wrec) and energy storage efficiency (η) of most BNT-based relaxor ferroelectric ceramics are lower than 3.5 ​J ​cm−3 and/or 80%, respectively, in recently. In this work, the relaxor ferroelectric ceramics of 0.75Bi(0.5+x)Na(0.5-x)TiO3-0.25SrTiO3 (BNST-x) were constructed via A-site defect engineering and prepared by tape-casting method. It is worth noting that an ultrahigh Wrec of 5.63 ​J ​cm−3 together with outstanding η of 94% can be achieved simultaneously at a relative high electric field of 535 ​kV ​cm−1 with the composition of BNST-0.08, Meanwhile, for BNST-0.08 ceramic, the η is higher than 90% and the variation of Wrec is less than ±2% and ±5% within the frequency range of 1–100 ​Hz and temperature range of 30–130 ​°C, respectively. The Wrec is always higher than 3 ​J ​cm−3 and did not deteriorate significantly after 104 fatigue cycles. In addition, the BNST-0.08 ceramic also possesses ultrafast discharge speed (t0.9, less than 125 ​ns) and ultrahigh power density (PD, higher than 147 ​MW ​cm−3) within the temperature range of 30–130 ​°C at 300 ​kV ​cm−1. Therefore, the BNST-0.08 ceramic is promising candidate environment-friendly materials for advanced pulsed power capacitor applications and the energy storage properties of BNT-based relaxor ferroelectrics can be enhanced significantly via A-site defect engineering.

Wettability plays a vital role in fundamental researches and practical applications. Wettability control and patterning have been widely studied in various fields. Although researches have grown rapidly, the methods are still restricted by limitations including complicated processes, high equipment requirements and shortage of methods to treat complex surfaces. Here we report a simple, low cost, array-based wettability control and patterning method via in-situ modification by flexible plasma stamp. Wettability control and patterning on surfaces of superhydrophobic aluminum, superhydrophobic PDMS and silicon, even plant leaf and fruit are achieved. The relationships between the wettability and the treatment time are investigated. We elucidate that the wetting states can also be reversible. The surface modification mechanism of in-situ plasma treatment is further investigated. Utilizing the step by step treatment, gradient and arbitrary wettability patterning on surfaces have been obtained. Notably, the patterned wettability on the inner surface of a tube has been realized, which has never been reported. Finally, in-situ wettability patterning is applied to achieve microfluidics channels on the inner surface of superhydrophobic tube. This work will bring new insights into the study of wetting field and stimulate more applications on wettability control and patterning.

Extensive efforts have been made to harvest energy from water in the form of raindrops1–6, river and ocean waves7,8, tides9 and others10–17. However, achieving a high density of electrical power generation is challenging. Traditional hydraulic power generation mainly uses electromagnetic generators that are heavy, bulky, and become inefficient with low water supply. An alternative, the water-droplet/solid-based triboelectric nanogenerator, has so far generated peak power densities of less than one watt per square metre, owing to the limitations imposed by interfacial effects—as seen in characterizations of the charge generation and transfer that occur at solid–liquid1–4 or liquid–liquid5,18 interfaces. Here we develop a device to harvest energy from impinging water droplets by using an architecture that comprises a polytetrafluoroethylene film on an indium tin oxide substrate plus an aluminium electrode. We show that spreading of an impinged water droplet on the device bridges the originally disconnected components into a closed-loop electrical system, transforming the conventional interfacial effect into a bulk effect, and so enhancing the instantaneous power density by several orders of magnitude over equivalent devices that are limited by interfacial effects. A device involving a polytetrafluoroethylene film, an indium tin oxide substrate and an aluminium electrode allows improved electricity generation from water droplets, which bridge the previously disconnected circuit components.

Nickel cobalt sulfide (NiCo2S4) is a promising battery-type material for electrochemical energy storage. However, the slow charge transfer kinetics and ion diffusion as well as the deficiency of electrochemically active sites hinder the practical application of NiCo2S4. Defect engineering at the atomic level is adopted to improve charge storage kinetics, through the incorporation of P dopants and S vacancies onto the surface of a NiCo2S4 nanotube (P-NiCo2S4−x). Experimental results reveal that the introduction of these defects effectively increases the electrical conductivity and induces the formation of low oxidation state Ni and Co species, accelerating the charge transfer kinetics and enabling rich faradaic redox chemistry. Moreover, the partial substitution of S sites with P improves the covalent nature of P-NiCo2S4−x, facilitating surface electroactivity. The as-prepared P-NiCo2S4−x shows a high specific capacity of 1806.4 C g−1 at 1 A g−1 and a 95.5% capacity retention after 5000 cycles at a high current density of 30 A g−1. Flexible solid-state asymmetric supercapacitors with P-NiCo2S4−x and activated carbon as the positive and negative electrodes, respectively, deliver a high energy density of 68.2 W h kg−1 at 800 W kg−1 and excellent cycling stability. Moreover, the device exhibits good mechanical flexibility with negligible capacitance decay under different bending states.

Based on the principle of sustainable development theory, lead-free ceramics are regarded as an excellent candidate in dielectrics for numerous pulsed power capacitor applications due to their outstanding thermal stability and environmental friendliness. However, the recoverable energy storage density (Wrec) and energy storage efficiency (η) of most lead-free ceramics are less than 4 J cm−3 and 80%, respectively, due to their low electric breakdown strength (Eb), large remnant polarization (Pr) and/or small maximum polarization (Pmax). In order to dramatically enhance the Wrec and η of lead-free ceramics, the macro-structure design strategy (construction of the ceramics with a sandwich structure comprising the large Pmax of ferroelectrics as the outer layer and the large Eb of the linear-like dielectric as the middle layer) was adopted to synergistically optimize the polarization and Eb in this study. Interestingly, the prepared ceramics exhibited a clear sandwich structure and the ultra-high Wrec of 6.78 J cm−3, together with a very high η of 89.7%, could be achieved at a high electric field of 572 kV cm−1, which are superior to the previously reported lead-free ceramics. Meanwhile, the energy storage properties also exhibited outstanding stability. In particular, the η was higher than 86% and the variation of Wrec was less than ±3% within 1–100 Hz and 30–120 °C. Therefore, the founding of this study opened up a novel and efficient guideline for exploring new environmentally friendly ceramics with superior energy storage properties.

Alloy Sb as an anode material for Li ion batteries (LIBs) suffers from severe volume expansion and structural breakdown during lithiation process, leading to a abrupt drop of battery cycle performance. The density functional theory is used to explore the adsorption and diffusion of Li atom in the two dimensional graphene/β-antimonene (G/Sb) heterostructure. Our calculation results reveal that the G/Sb heterostructure possesses excellent thermodynamic and dynamic stability with the 0.06 eV band gap, which is much smaller than that of monolayer Sb (1.24 eV) and can insure fast electron transport in the electrode during lithiation/delithiation process. The calculated smaller Li diffusion energy barrier and volume expansion, together with the larger Li diffusion coefficient at 300 K explore greater charge/discharge performance for the G/Sb heterostructure than the corresponding parent bulk, monolayer, and bilayer materials. This is mainly because the monolayer β-Sb within the G/Sb heterostructure can render larger strain compared with that of the pristine β-Sb. We also evaluate the performance of the G/Sb heterostructure as the anode of LIBs by charge analysis and density of states. These results provide conclusive evidence to explore that the G/Sb heterostructure should be a promising candidate anode for flexible and wearable LIBs.

A facile chemical vapor deposition method to prepare VS2 with different nano-micro structures for the high absorption of long wavelength is reported. It is demonstrated in this research that the VS2 with nanowire-like structure can enable absorbing >92% across the wavelengths from 400 nm to 2.5 μm and above 94.5% for the mid-infrared regime (2.5 μm–10 μm), demonstrating it a very high and efficient absorber reported to date. The improved anti-reflection and pronounced light absorption properties make the black absorber an ideal material in applications such as biomedical and electro-optical devices for the military purposes.

Flexible micro-supercapacitors (MSCs) featured with high storage capacity and mechanical stability are essential and indispensable for the development of wearable devices. Since the active materials physically deposited on the current collectors are rigid and will be desquamated under the mechanical cycling, the performance of flexible MSCs is still limited by the weak interfacial adhesions between materials and collectors. The effective strategy to strengthen the interfacial adhesion is one important key to achieve high-performance flexible MSCs. In this work, a flexible symmetrical micro-supercapacitor with a bioinspired hierarchically topological interlocking interfacial enhancement strategy was presented. Based on the high stability metal current collectors on the polyimide substrate, two-level 3D interlocking structures between the active materials and the current collectors were further utilized, which was inspired by the structures of a gecko's feet and a tree's roots in rock cracks, respectively. Through these 3D interlocking structures, the effective contact areas and the adhesion strengths of two interfaces, that is, the active material/current collectors and the current collector/substrate interfaces, are significantly enhanced. The energy density of the interfacial enhanced active carbon symmetrical MSC (IE SMSC) has been improved over 3 times in comparison with the in-plane active carbon SMSC (SMSC). The capacitance of IE SMSC can remain 92.9% even after 5000 cycles of bending treatment. Even more remarkable, the potential window of the IE SMSC can expand to 1.6 V in the aqueous electrolyte. The results show that the hierarchically topological interlocking strategy can not only ensure the mechanical stability of the flexible MSC but also improve its energy efficiency. Our strategy provides a new perspective for the study of flexible supercapacitors and various flexible devices to achieve high adhesion, high flexibility, and high electrical capacitive performance.

Energy harvesting devices that prosper in harsh environments are highly demanded in a wide range of applications ranging from wearable and biomedical devices to self-powered and intelligent systems. Particularly, over the past several years, the innovation of triboelectric nanogenerators (TENGs) that efficiently convert ambient kinetic energy of water droplets or wave power to electricity has received growing attention. One of the main bottlenecks for the practical implications of such devices originates from the fast degradation of the physiochemical properties of interfacial materials under harsh environments. To overcome these challenges, here we report the design of a novel slippery lubricant-impregnated porous surface (SLIPS) based TENG, referred to as SLIPS-TENG, which exhibits many distinctive advantages over conventional design including optical transparency, configurability, self-cleaning, flexibility, and power generation stability, in a wide range of working environments. Unexpectedly, the slippery and configurable lubricant layer not only serves as a unique substrate for liquid/droplet transport and optical transmission, but also for efficient charge transfer. Moreover, we show that there exists a critical thickness in the liquid layer, below which the triboelectric effect is almost identical to that without the presence of such a liquid film. Such an intriguing charge transparency behavior is reminiscent of the wetting transparency and van der Waals potential transparency of graphene previously reported, though the fundamental mechanism remains to be elucidated. We envision that the marriage of these two seemingly totally different arenas (SLIPS and TENG) provides a paradigm shift in the design of robust and versatile energy devices that can be used as a clean and longer-lifetime alternative in various working environments.

Wafer-to-wafer hybrid bonding technology is used to realize a DRAM array wafer and a logic wafer face-to-face connected with the advantages of a high density integration for high bandwidth and energy efficiency. With the proposed stacked embedded DRAM (SEDRAM), the electromagnetic crosstalk and the electrothermal performance of hybrid bonding via (HBV) are studied using the proposed Meshless radial point interpolation method (M-RPIM) to reduce the electromagnetic crosstalk and the thermal crosstalk of the array. A parallelogram layout which arranges the signal HBVs and the ground HBVs in parallelogram shows the crosstalk noise and the maximum temperature is reduced by 10% and 11% respectively. In addition, an advanced honeycomb arrangement with dummy HBVs array and the interleaving stacking TSV-HBV structure are also proposed to further improve the performance of the SEDRAM.

Manifested from the "tears of wine" to the "coffee-ring effect", the directional transport of a liquid governed by the Marangoni effect is highly pervasive in our daily life and has brought a great number of applications. Similar to this surface tension gradient-dominated process, the fluid preferentially flows from the hot region to the cold region. In contrast to this perception, in this study, we report that water liquid deposited on a specially designed topological surface can flow from the low-temperature region to the high-temperature region in a spontaneous, long-range, and unidirectional manner. We show that such a behavior is mainly owing to a strong topological effect that outweighs the thermal gradient imposed along the surface. Moreover, the specific temperature range applied on the topological surface for the occurrence of such a unidirectional liquid transport phenomenon is also identified. Our findings would find important insights for developing next-generation cooling devices where a rapid flow from the condensation region to the evaporation/boiling region is preferred.

Selective conversion of CO2 to formate with high current densities is highly desirable but still challenging. Copper hollow fibers with interconnected pore structures were fabricated via a facile method and used as a stand-alone cathode for highly efficient electrochemical reduction of CO2 to formate. Our studies revealed that delivering the reactant CO2 gas to the inner space of the hollow fiber could build up a higher CO2 partial pressure in the pores and presumably reduce the concentration of H[Formula: see text] from the electrolyte to effectively suppress the major competing reaction, hydrogen evolution reaction (HER), from 46.9% faradaic efficiency (FE) to 15.0%. A high selectivity for CO2 reduction to formate with a maximum FE of 77.1% was achieved with a high current density of 34.7[Formula: see text]mA cm[Formula: see text], which is one of the highest FEs on Cu-based materials. Mechanistic studies suggest that the abundant active sites along with the unique crystal facets induced by the high pressure of CO2 at the pore surface in the “gas in” mode are attributed to the superior electroactivity and selectivity for the CO2 reduction to formate. The Cu hollow fiber electrodes exhibit an outstanding long-term stability at high current density, showing great potential for large-scale practical applications.

Metallic tungsten disulfide (WS2) monolayers have been demonstrated as promising electrocatalysts for hydrogen evolution reaction (HER) induced by the high intrinsic conductivity, however, the key challenges to maximize the catalytic activity are achieving the metallic WS2 with high concentration and increasing the density of the active sites. In this work, single-atom-V catalysts (V SACs) substitutions in 1T-WS2 monolayers (91% phase purity) are fabricated to significantly enhance the HER performance via a one-step chemical vapor deposition strategy. Atomic-resolution scanning transmission electron microscopy (STEM) imaging together with Raman spectroscopy confirm the atomic dispersion of V species on the 1T-WS2 monolayers instead of energetically favorable 2H-WS2 monolayers. The growth mechanism of V SACs@1T-WS2 monolayers is experimentally and theoretically demonstrated. Density functional theory (DFT) calculations demonstrate that the activated V-atom sites play vital important role in enhancing the HER activity. In this work, it opens a novel path to directly synthesize atomically dispersed single-metal catalysts on metastable materials as efficient and robust electrocatalysts. Ru is one of the most active metals for oxygen evolution reaction, but it quickly dissolves in acidic electrolyte particularly in nanosized form. Here the authors show that coral-like solid-solution Ru‒Ir consisting of 3 nm-thick sheets with only 6 at% Ir is a long-lived catalyst with high activity

The ultrafast electron transport is central to the requirement of all-electrically controlled spintronics in metallic collinear antiferromagnetic (AFM) ${\mathrm{Mn}}_{2}\mathrm{Au}$ thin films within the terahertz (THz) range. Here we use the THz time-domain spectroscopy to measure the conductivity spectra of ${\mathrm{Mn}}_{2}\mathrm{Au}$ thin films with different thicknesses and temperatures. We demonstrate an onset of carrier localization in ${\mathrm{Mn}}_{2}\mathrm{Au}$ with decreasing the film thickness from 15 to 5 nm. By using optical pump-THz probe spectroscopy, we found the surface trapping states in the thinnest ${\mathrm{Mn}}_{2}\mathrm{Au}$ film limit its photoconductivity significantly. The DC conductivity and scattering time become larger and longer with decreasing temperature for all samples, which suggests that ${\mathrm{Mn}}_{2}\mathrm{Au}$ behaves in a typical metallic fashion. The THz optical and conductivity properties of ${\mathrm{Mn}}_{2}\mathrm{Au}$ films will advance our understanding of ultrafast electronic transport processes in AFM ${\mathrm{Mn}}_{2}\mathrm{Au}$ thin films.

In recent years, the open electrowetting on dielectric (EWOD) device has been widely used in biomedical detection, chemical synthesis analysis, and so on. However, the cost of using ITO glass as surface material is difficult to meet the requirement for large-scale array chip production. So, a low-cost, easy-to-manufacture open EWOD platform is designed in this paper. In hardware platform, an operation platform is prepared by using a printed circuit board (PCB) as a substrate. The electrode shape is designed as zigzag, and its surface is optimized by organic solderability preservatives (OSP). In addition, Parafilm M and silicone oil are used as a dielectric hydrophobic layer to prepare the open platform. In software, the system program is designed by C programming language, including initialization program, serial port communication program, high-voltage output port program, and interrupt program, which can be used to drive droplets. The system can achieve an effective driving voltage of 180–240 V. The moving speed of droplets can reach 15 mm/s when the droplet volume is 1850 μL and the electrode voltage output frequency is 10 Hz.

ZnO/NiO composite photoanodes for dye-sensitized solar cells (DSSCs) were synthesized by an all solid state mothed. The effect of as-prepared NiO with NiCl2·6H2O and Ni(NO3)2·6H2O precusor was investigated using X-ray diffraction (XRD), field-emission scaning electron microscope (FESEM), energy dispersive X-ray analysis (EDAX), UV–visible absorption spectra (UV–vis), electrochemical impedance spectroscopy (EIS), and open circuit voltage decay (OCVD) characterization techniques. NiO enhanced the performance of DSSCs because of the energy level potential difference between NiO and ZnO, which accelerated the electron transfer at the ZnO/dye/electrolyte interface. Using ZnO/NiO composite photoanodes attained the maximum power conversion efficiency (PCE) of 6.60% in DSSCs. Moreover, saturated Zn(Ac)2 ethanol solution-processed ZnO/NiO composite photoanodes showed excellent optical characteristic and prolonged carrier lifetime to contrast unprocessed ones. This post-processed photoanodes exhibited a short-circuit current density (JSC) of 22.34 mA cm−2 and a PCE of 7.01%, and these values were higher than those of the isolated ZnO/NiO photoanodes. These results pave the way to further improve the performance and potential application of DSSCs.

An interesting subject of non-fuel utilization of coal is the synthesis of high-performance coal-based carbon (CBC) materials to replace expensive Pt counter electrodes (CEs) in dye-sensitized solar cells (DSSCs). Selection of coal source, treatment, and structural optimization of coal should be considered to obtain high-performance CBC CEs. In this study, a coal-based porous carbon material with low cost and high performance was synthesized from three kinds of pulverized coal (collected from different regions of Xinjiang, China) through chemical activation followed by acid washing oxidation treatment. The prepared porous CBC material exhibited higher catalytic activity for the reduction of I−/I3− than Pt. The use of carbon nanotubes (CNTs) plus prepared porous CBC/CNTs composite materials as CEs for DSSCs led to a VOC of 0.62 V, a JSC of 21.92 mA cm−2, an FF of 0.42, and a conversion efficiency of 5.75%, which is higher than those of CEs made of porous CBC, CNTs, or Pt. The improvement in the conversion efficiency could be attributed to the synergistic effect of the good catalytic activity of the prepared CBC materials and the good conductivity of CNTs. Moreover, the double-layer structure played an important role in improving the adhesion and electron transport capacity. Results provide a theoretical basis for the possible use of cheap CBCs as CEs for thin-film solar cells. We use the ZnO as photoanode; the dye is N719.

The secondary structure transitions of regenerated silk fibroin (RSF) under different external perturbations have been studied extensively, except for pressure. In this work, time-resolved infrared spectroscopy with the attenuated total reflectance (ATR) accessory was employed to follow the secondary structure transitions of RSF in its wet film under low pressure. It has been found that pressure alone is favorable only to the formation of β-sheet structure. Under constant pressure there is an optimum amount of D2 O in the wet film (D2 O : film = 2:1) so as to provide the optimal condition for the reorganization of the secondary structure and to have the largest formation of β-sheet structure. Under constant amount of D2 O and constant pressure, the secondary structure transitions of RSF in its wet film can be divided into three stages along with time. In the first stage, random coil, α-helix, and β-turn were quickly transformed into β-sheet. In the second stage, random coil and β-turn were relatively slowly transformed into β-sheet and α-helix, and the content of α-helix was recovered to the value prior to the application of pressure. In the third and final stage, no measurable changes can be found for each secondary structure. This study may be helpful to understand the secondary structure changes of silk fibroin in silkworm's glands under hydrostatic pressure.

Charge recombination at the ZnO photoanode/electrolyte interface is one of the major limitations for high performance dye-sensitized solar cells (DSSCs) toward their theoretical power conversion efficiency (PCE). Here, we proposed an efficient approach for reducing this interfacial losses and consequently facilitating charge transfer by decorating a hydrophobic thin-film on the surface of the dye-coated zinc oxide photoanode via 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) hexane solution immersing. As a result, a high PCE of 8.22% was obtained, which far exceeded the efficiency of 5.40% in a conventional DSSC without PFDTES treatment. Furthermore, PFDTES treatment also largely elongated the lifetime of photogenerated electrons, and maintained a good photo-response at the photoelectrode. This work provides a comprehensive explanation of electron injection, transfer and recombination at the ZnO photoanode/electrolyte interface, and a promising strategy to explore high efficiency ZnO-based DSSCs.

Density functional calculations are used to investigate the effective approach to prevent the degradation of black phosphorus (BP). For the few-layer BP, it is found that the Sc atom monodoped the 3 × 3 unit cell with a doping ratio of 1.4%, which can retain the semiconductor character with a moderate band gap (Egap) of 0.84 eV. Obviously, the two layer BP(2MLBP) with one Sc atom binding to three P atoms on the upmost layer has the lowest formation energy (−4.57 eV), exploring its greatest stability. Moreover, the calculated binding energy of Sc above the three P atoms is the largest (4.24 eV) energy, which is larger than the experimental cohesive energy of bulk Sc (3.90 eV), indicating that the clustering of Sc atoms on the surface of BP can be avoided. Importantly, the Sc atom adsorbed 2MLBP structure (2MLBP-Sc) has a conduction band minimum (CBM) value of −4.18 eV, which is below the redox potential of O2/O2– (−4.11 eV). When the O2 molecule is adsorbed on the 2MLBP-Sc, although the Sc–O and O–P bonds ...

With the rapid development of electronic information technology and the rising environmental concerns as well as the tendency of electronic devices towards miniaturization and integration, enhancing the energy storage properties of lead-free ceramic capacitors is one of the imperative issues. Although a large number of efforts have been contributed to optimize the energy storage properties of lead-free ceramics, the conflict between the polarization and electric breakdown strength seriously impedes the improvement of energy storage density significantly. Herein, inspired by the layered composites of sandwich, the sandwich structured lead-free ceramics based on Bi0.5Na0.5TiO3 were designed and fabricated to overcome the above challenge effectively. The theoretical simulations and experiment results demonstrate that the polarization and electric breakdown strength can be optimized synchronously via the sandwich structured design. An ultrahigh recoverable energy storage density of ~ 6 J cm−3 and a nearly ideal energy conversion efficiency of ~ 95% can be obtained for the prepared sandwich structured lead-free ceramics. Meanwhile, the maximum applied electric field can be enhanced to more than 500 kV cm−1. The energy storage capabilities also exhibit outstanding stability over a broad temperature range, frequency range and cycle numbers. These results reveal that the Bi0.5Na0.5TiO3-based lead-free ceramics of this study have a great potential for high energy storage capacitors applications.

Pitting damage severely degrades the mechanical properties of the main force-bearing member of a circular tube; it can also change its failure mode. Offshore high-strength seamless steel pipes with steel grade X52Q certified by ABS were selected for a pressure test and research. The constraint conditions of one hinged end and one fixed end were adopted to investigate the effect of the bending moment of the nodes so that any section of the circular tube can be subjected to the superposition of axial force and bending moment. Pitting craters were generated using mechanical processing methods; the effect of pitting parameters such as diameter, depth, and distribution on the mechanical properties and failure modes of circular pipes was explored. Pitting corrosion damage caused local stress concentration and the local cross-section weakening of the tube. In addition to the decline of the bearing capacity under the action of axial compression load, the failure mode of the pitting corrosion damage tube also showed differences. Increased local damage caused by the increase in the diameter of the pitting corrosion was likely to cause plastic hinges on the pits of the tube, and this changed stress conditions, failure modes, and failure locations of the components. An increase in the depth of the pitting craters resulted in a significant drop in the overall load-bearing capacity caused by local buckling. The location of pitting corrosion had negligible effect on the mechanical performance of the tube; the end distribution was more unfavourable than the centre distribution. The stress–strain distribution characteristics of the pitting area of the specimen were considerably different, and the stress concentration on the inner side of the pitting corrosion were serious and uneven. The results of the experimental analysis and several numerical examples indicated that pitting corrosion causes the pressure-bearing circular pipes with lower strength buckling to more likely suffer from an instability failure.

Droplets are ubiquitous in nature and the preferential control of droplet transport offers limitless potential for efficient mass and momentum transfer as well as energy conversion. In this work, we show that even without the need for any external energy input, the self-propelled motion of droplets driven by a surface wetting gradient can lead to reliable electricity generation. Simple analytical analysis demonstrates that the output voltage results from the modulation of the surface charge distribution on the dynamically changing solid/liquid interfaces, which can be programmed by tailoring the wetting gradient and the size of the droplet. We demonstrate that a self-propelled 25 μL droplet can generate a peak current of 93.5 nA and a maximum output power of 2.4 nW. This work provides a new angle for optimizing energy harvesting devices based on liquid-solid interfaces.

Recent experimental and theoretical studies have demonstrated that two-dimensional (2D) transition metal dichalcogenide (TMDC) nanoflakes are one of the most promising candidates for non-noblemetal electrocatalysts for hydrogen evolution reaction (HER). However, it is still challenging to optimize their conductivity and enrich active sites for highly efficient electrochemical performance. Herein, we report a chemical vapor deposition (CVD) and thermal annealing two-step strategy to controllably synthesize hybrid electrocatalysts consisting of metallic NbS2 nanoflake backbones and a highly catalytic active MoSx nanocrystalline shell on polished commercial glass carbon (GC). In addition, the amount of MoSx in the hybrids can be easily adjusted. We first demonstrate that a small amount of MoSx significantly promotes the HER activity of 2D NbS2 nanoflakes, which is in good agreement with the density functional theory (DFT) calculation results. Moreover, the optimized MoSx@NbS2/GC electrocatalyst displays superior HER activity with overpotential of −164 mV at −10 mA cm−2, a small Tafel slope of 43.2 mV dec−1, and prominent electrochemical stability. This study provides a new path for enhancing the HER performance of 2D TMDC nanoflakes.

Wave energy is one of the most promising renewable energy sources. The approaches for wave energy harvesting have been attracting more and more attentions all over the world. Although triboelectric nanogenerators (TENGs) based on liquid-solid interface have offered a new method for wave energy harvesting, some challenges still remain such as the relatively low energy power density and energy conversion efficiency. Here, we introduce a liquid-solid generator with electrode arrays that allows for improved wave energy harvesting compared to conventional TENG. The design of 3D electrodes above dielectric layer engenders a bulk effect that connect the electrode array, the polymer layer and bulk water into a closed-looped system. The arrayed generator can also be assembled easily and the instantaneous output power density can be enhanced from 2.7 W/m2 to 11.7 W/m2 with the 3D electrodes. We envision that this bulk effect generator based on liquid-solid interface will open new insight in blue energy harvesting in the future.

For the purpose of meeting the requirements of protecting environment and sustainable development, bismuth ferrite (BiFeO3, BF)-based lead-free ceramics have gained immense attention for pulsed power capacitor applications due to their large spontaneous polarization, low sintering temperature as well as non-toxic and harmless. However, the low energy storage properties (ESPs) and unstable performance of BF-based ceramics are not good for practical applications. In this work, novel bismuth ferrite-based lead-free ceramics of (1-x)(0.67BiFeO3-0.33BaTiO3)-xNa0.73Bi0.09NbO3 ((1-x)BFBT-xNBN) were designed and fabricated successfully by optimizing the polarization and electric field. With increasing the content of NBN, the remnant polarization decreased rapidly as well as the slim and pinched polarization-electric field loops together with high electric field can be observed. Notably, ultrahigh ESPs with the total energy storage density (Wtot) of 6.65 J cm−3 and the recoverable energy storage density (Wrec) of 5.57 J cm−3 can be achieved at high electric field of 410 kV cm−1. At the same time, the η is greater than 80% and the variation of Wrec is less than ±5% over a broad frequency range (1–100 Hz) and temperature range (30–150 °C). In addition, the η is stabilized around 89% and the variation of Wrec is less than ± 2% after 104 cycles. Therefore, the (1-x)BFBT-xNBN lead-free ceramics not only possess ultrahigh ESPs but also the ESPs exhibit outstanding stability, which is promising candidates for high performance pulsed power capacitor applications.

Over the past several years, the development of triboelectric nanogenerator (TENG) has blossomed owing to many advantages such as the simple structure, high conversion efficiency and wide material selectivity. Currently, most of TENG devices are constructed with micro-structured surfaces using complicated manufacturing processes. Owing to the lack of high-volume manufacturing scalability, it still remains a bottleneck to apply TENG into the commercial products. In this work, we report the development of a novel TENG, which leverages on the regenerated, flexible, biocompatible, and highly transparent silk-fibroin as a triboelectric layer and can be deposited on a PET/ITO substrate (SF/PET/ITO) using a simple spray-coating process. The as-fabricated TENG exhibits a maximum voltage of 213.9 V and a high power density of 68.0 mW/m 2 as a result of the ability of losing electrons and rough surface rendered by the silk-fibroin. We further demonstrate that this generator can charge a capacitor (10 μF) to 4.5 V in 6 mins, and instantaneously light up as many as 100 commercial LED bulbs. We anticipate that the large-scale fabrication of silk-fibroin-based TENGs will serve as a promising system for electricity generation with an extremely low cost to commercial applications.

Cuprite Cu 2 O particles with different morphologies and very narrow band gap were synthesized through combining a hot water bath process with a post calcination process. The ZnO was prepared by using a simple solid-state method. When using the ZnO/Cu 2 O composite as the photoanode, the ZnO/Cu 2 O-based dye-sensitized solar cells (DSSCs) yielded a conversion efficiency of 6.94% at the optimized polyhedron Cu 2 O addition amounts of 0.25 wt%, which is improved by 23.93% compared with the performance of the pure ZnO-based DSSCs (5.60%). After introducing a ZnO buffer layer, the obtained bilayer ZnO/Cu 2 O-based DSSCs achieved a significantly elevated efficiency up to 7.02%, which corresponds to a 24.03% improvement compared with the pure bilayer-based one. This improvement can be attributed to the large specific surface area and pore structure of ZnO/Cu 2 O composite materials and the conductivity of Cu 2 O, which offsets the inherent shortages of ZnO of lower anchoring site density and poor conductivity, and generates some additional advantages, such as a lower charge transfer resistance, higher dye-loading quantity, longer electron lifetime, and reduced charge recombination.

The ability to control cell patterning on artificial substrates with various physicochemical properties is of essence for important implications in cytology and biomedical fields. Despite extensive progress, the ability to control the cell-surface interaction is complicated by the complexity in the physiochemical features of bioactive surfaces. In particular, the manifestation of special wettability rendered by the combination of surface roughness and surface chemistry further enriches the cell-surface interaction. Herein we investigated the cell adhesion behaviors of Circulating Tumor Cells (CTCs) on topographically patterned but chemically homogeneous surfaces. Harnessing the distinctive cell adhesion on surfaces with different topography, we further explored the feasibility of controlled cell patterning using periodic lattices of alternative topographies. We envision that our method provides a designer's toolbox to manage the extracellular environment.

A series of Al-containing mesostructured cellular silica foams (Al-MCFs) with different Si/Al molar ratios ( x ; x = 10, 20, 30, 40, or 50) were prepared by a post synthetic method using aluminum isopropoxide as an alumina source. The corresponding NiMo catalysts supported on Al-MCFs were prepared and evaluated using dibenzothiophene (DBT) as the probe reactant. All the synthesized samples were characterized by small-angle X-ray scattering, scanning electron microscopy, nitrogen adsorption-desorption, UV-Vis diffuse reflectance spectroscopy, H 2 temperature-programmed reduction, 27 Al MAS NMR, temperature-programmed desorption of ammonia, pyridine-FTIR, Raman spectroscopy, HRTEM, and X-ray photoelectron spectroscopy to analyze their physicochemical properties and to gain a deeper insight of the interrelationship between the structures and the catalytic performance. The synthesis mechanism was proposed to involve the formation of Bronsted acid and Lewis acid sites through the replacement of Si 4+ with Al 3+ . Aluminum introduced into MCFs by the post synthetic method has a negligible influence on the mesostructure of the parent MCFs but can form silicoaluminate materials with moderate Bronsted acidity. For Al-MCFs( x ) materials, the detection of tetrahedrally coordinated Al 3+ cations demonstrated that the Al species had been successfully incorporated into the silicon frameworks. Furthermore, the DBT hydrodesulfurization (HDS) catalytic activity of the NiMo/Al-MCFs( x ) catalysts increased with increasing Si/Al molar ratio, and reached a maximum at a Si/Al molar ratio of 20. The interaction of Ni and Mo species with the support became stronger when Al was incorporated into the MCFs supports. The high activities of the NiMo/Al-MCFs catalysts for the DBT HDS were attributed to the suitable acidity properties and good dispersions of the Ni and Mo active phases.

The directional and long-range droplet transportation is of great importance in microfluidic systems. However, it usually requires external energy input. Here we designed a wettability gradient surface that can drive droplet motion by structural topography. The surface has a wettability gradient range of over 150° from superhydrophobic to hydrophilic, which was achieved by etching silicon nanopillars and adjusting the area of hydrophilic silicon dioxide plane. We conducted force analysis to further reveal the mechanism for droplet self-propulsion, and found that the nanostructures are critical to providing a large driving force and small resistance force. Theoretical calculation has been used to analyze the maximal self-propulsion displacement on different gradient surfaces with different volumes of droplets. On this basis, we designed several surfaces with arbitrary paths, which achieved directional and long-range transportation of droplet. These results clarify a driving mechanism for droplet self-propulsion on wettability gradient surfaces, and open up new opportunities for long-range and directional droplet transportation in microfluidic system.

Mechanical flexible electronic skin has been focused on sensing various physical parameters, such as pressure and temperature. The studies of material design and array-accessible devices are the building blocks of strain sensors for subtle pressure sensing. Here, we report a new and facile preparation of a graphene hybrid structure with an ultrafast dynamic pressure response. Graphene oxide nanosheets are used as a surfactant to prevent graphene restacking in aqueous solution. This graphene hybrid structure exhibits a frequency-independent pressure resistive sensing property. Exceeding natural skin, such pressure sensors, can provide transient responses from static up to 10 000 Hz dynamic frequencies. Integrated by the controlling system, the array-accessible sensors can manipulate a robot arm and self-rectify the temperature of a heating blanket. This may pave a path toward the future application of graphene-based wearable electronics.

A comparative study of two methods for the synthesis of hierarchical structural CuBi2O4 particles was performed and the prepared samples were used in ZnO-based dye-sensitized solar cells (DSSCs) as an inorganic photosensitizer and additive for the ZnO anode. The structure, morphology, and light absorption were characterized by X-ray diffraction, scanning electron microscopy, and UV–Visible diffuse reflectance spectra. The photovoltaic performance was also investigated. Results indicate that this new type of thin-film solar cell, namely, ZnO/CuBi2O4/Pt (with CuBi2O4 instead of dye), yielded an overall light conversion efficiency of 0.45%. This result suggests that CuBi2O4 is highly likely to develop into a promising inorganic photosensitizer through further structural optimization and adjustment. By contrast, CuBi2O4 was also added into the ZnO to form a composite photoanode and sensitized by N719 dye thereafter. Results show that the addition of a minimal amount of CuBi2O4 (0.3 wt%) improves the photovoltaic efficiency by 25% compared with that of the pure ZnO-based DSSCs. The reason for such improvement was discussed with an interfacial charge transfer mechanism.

Quaternary chalcopyrite sulfide semiconductors Cu 2 XSnS 4 (X = Mn, Fe, Co, Ni, Zn and Cd) are successfully prepared by using a solvothermal method. Crystal structure, elemental composition and morphology of the as-synthesized nanoflowers are characterised using XRD, XPS, EDS, TEM and SEM. Photovoltaic and catalytic performances based on prepared samples as counter-electrode (CE) materials in ZnO-based dye-sensitised solar cells (DSSCs) are investigated based on N719 dye and iodide/triiodide electrolyte. Notably, Cu 2 XSnS 4 (X = Mn, Fe, Co, Ni, Zn, Cd) all show excellent catalytic activity for the reduction of I 3 − to I − in the electrolyte. In addition, Cu 2 MnSnS 4 and Cu 2 NiSnS 4 are explored as CE materials for DSSCs for the first time. Cu 2 MnSnS 4 and Cu 2 NiSnS 4 exhibit power conversion efficiency values of 6.18% and 6.12%, respectively, which are comparable to the photovoltaic performance of the DSSCs using a Pt CE (6.09%).

There exists a strong demand to replace expensive noble metal catalysts with efficient and earth-abundant catalysts for hydrogen evolution reaction (HER). Recently the Co- and Mo-based sulfides such as CoS2, Co9S8, and MoSx have been considered as several promising HER candidates. Here, a highly active and stable hybrid electrocatalyst 3D flower-like hierarchical Co9S8 nanosheets incorporated with MoSx has been developed via a one-step sulfurization method. Since the amounts of Co9S8 and MoSx are easily adjustable, we verify that small amounts of MoSx promotes the HER activity of Co9S8, and vise versa. In other words, we validate that symmetric synergy for HER in the Co- and Mo-based sulfide hybrid catalysts, a long-standing question requiring clear experimental proofs. Meanwhile, the best electrocatalyst Co9S8-30@MoSx/CC in this study exhibits excellent HER performance with an overpotential of −98 mV at −10 mA/cm2, a small Tafel slope of 64.8 mV/dec, and prominent electrochemical stability.

Humidity sensors are indispensable for various electronic systems and instrumentations. To develop a new humidity sensing mechanism is the key for the next generation of sensor technology. In this work, a novel flexible paper-based current humidity sensor is proposed. The developed alternating current electroluminescent devices (ACEL) consist of the electroless plating Ni on filter paper and silver nanowires (AgNWs) as the bottom and upper electrodes, and ZnS:Cu as the phosphor layer, respectively. The proposed humidity sensor is based on ACEL with the paper substrate and the ZnS:Cu phosphor layer as the humidity sensing element. The moisture effect on the optical properties of ACELs has been studied firstly. Then, the processing parameters of the paper-based ACELs such as electroless plated bottom electrode and spin-coated phosphor layer as a function of the humidity-sensitive characteristics are investigated. The sensing mechanism of the proposed sensor has been elucidated based on the Q ~ V analysis. The sensor exhibits an excellent linearity ( R 2 = 0.99965 ) within the humidity range from 20% to 90% relative humidity (RH) and shows excellent flexibility. We also demonstrate its potential application in postharvest preservation where the EL light is used for preservation and the humidity can be monitored simultaneously through the current.

Efficient electrical switching of antiferromagnets (AFMs) is key to their use in high-density, ultrafast, nonvolatile spintronic memory. Mn${}_{2}$Au, an AFM with opposite spin sublattices, is a unique metallic material, in that fieldlike spin torque can switch its AFM moments. However, switching induced by antidamping torque remains to be verified in metallic AFMs. Here the authors demonstrate current-induced switching of AFM moment in both a (103)-oriented Mn${}_{2}$Au single layer and a Mn${}_{2}$Au/Pt heterojunction by fieldlike torque and antidamping torque respectively. The simultaneous realization of both torque types in metallic Mn2Au makes it a promising candidate for AFM spintronics.

Current-driven domain-wall motion has attracted intense attention, due to its rich physics and promising application in ``racetrack'' nonvolatile memory. However, the interplay between antiferromagnetic/ferromagnetic (AFM/FM) phase boundaries and current has remained elusive. To investigate, the authors use pulses of current to induce the formation of anisotropic FM domains in an AFM matrix. The phase boundaries can be reversibly oriented by the applied (writing) current, giving rise to the orthogonal alignment of phase boundaries and current, which could pave the way for multistage digital memory based on AFM/FM boundaries.

Current-induced spin-orbit torque (SOT) is attracting increasing interest and exciting significant research activity. We aim to provide a comprehensive review of recent progress in SOT in various materials. The intrinsic correlation between the heterostructure and SOT behaviors is emphasized. We first present a brief summary of the spin-orbit coupling in inversion-asymmetric magnetic systems and describe the discovery, classification and development of SOT. Then we focus on the characterization techniques and classification of SOT from the viewpoint of materials, including both spin sources and magnetic functional layers. In the third part, the mechanisms of SOT are discussed in detail, including spin Hall effect, Rashba effect, and emerging new mechanisms. The fourth part illustrates SOT in subdivided magnetic systems, including heavy metal combined with ferromagnets, ferrimagnets and antiferromagnets, and systems with topological insulators and single layer magnets. The fifth part presents typical performances of SOT, including the modulation, improvement, and field-free switching through material design, and discusses its promising applications for non-volatile SOT-magnetic random access memory and other device configurations. We conclude with a discussion of the challenges and future prospects of SOT, which will inspire more in-depth research and advance the practical applications.

Harvesting water kinetic energy is a prospective way to obtain sustainable power. However, conventional water energy harvesting technologies are restricted by specific operating locations and fabrication materials. These techniques urgently need to be improved and supplemented with new methods. Here, we report a novel and universal single electrode droplet-based electricity generator (SE-DEG) that allows converting water droplet kinetic energy into electricity power on any surfaces of artificial or natural materials such as PTFE, glass, wood, aloe, cicada wing, stone and etc. This functionality is endowed by a special configuration characterized by the location of the electrode on the top of dielectric material rather than underlying as in the conventional triboelectric nanogenerator (TENG). Such special configuration can effectively harness the triboelectric charges generated without going through the electrostatic induction process between bottom electrode and the surface in the case of TENG. We envision that SE-DEGs represent a new dimension in ability to harvest abundant hydrodynamic energy everywhere.

The low permeability reservoirs is difficult to be economically developed by conventional water flooding. In this work, five enhancing oil recovery (EOR) methods including water flooding, modified water flooding, CO2 flooding, water alternating CO2 flooding (WAC) and surfactant alternating CO2 flooding (SAC) are systematically evaluated by core-injection experiments. In addition, the microscopic oil-displacement mechanism for these EOR methods are revealed by nuclear magnetic resonance (NMR) technique. The experiment indicates that the SAC performs the best among the five flooding methods, which not only effectively improves the oil recovery (recovery factor up to 50%), but also effectively decreases the water cut. By using this method, gas phase can recovery more oil from smaller pores due to the reduction of interfacial tension and easy accessibility of these pores, while surfactant reduces oil-water interfacial tension and generates foam, significantly improving the oil displacement efficiency in larger pores. Therefore, SAC combines the advantage of gas and water which can recovery the oil both within smaller pores and larger pores in a higher proportion. The results of this work provides us fundamental understandings of the mechanisms in enhancing oil recovery of the CO2 associated EOR methods.