Search

Herein, Ag1-3xSmxNbO3 (0 ≤ x ≤ 0.025) antiferroelectric ceramics were successfully synthesized by solid state methods. The effect of Sm3+ doping on the structure, property and energy storage performance were studied. With the increasing Sm3+ concentrations, the average grain size decreased. Meanwhile, the stability of high temperature M phases (i.e., the structure between Tf and T3) was expanded, which led to low loss for energy storage. Both of structure analysis and ferroelectric tests revealed the existence of weakly polar/AFE-like phase below Tf. The Sm3+ doping tended to suppress the ferroelectric behavior and expand the stability of antiferroelectricity. Consequently, a significantly enhanced energy storage performance (Wrec = 3.8 J/cm3, η = 73 %) could be achieved in Ag0.97Sm0.01NbO3 ceramic, which was almost 1.5 times larger than that in non-doped AgNbO3 (Wrec = 2.4 J/cm3, η = 45 %) under the similar applied field of 1705 kV/cm ± . In particular, the performance of the ceramic showed great temperature stability with variation of ± 5 % from 25 °C to 125 °C. These results indicated that the Ag0.97Sm0.01NbO3 ceramic could be an ideal lead-free candidate used in the energy storage field.

Based on the hole-drilling strain sensing method, a ring Fiber Bragg Grating (FBG) array is proposed to realize comprehensive and convenient measurement of residual stress for homogeneous or inhomogeneous materials. All FBG sensors are arranged tangentially along the edge of the ring. With the ring array around the drilled hole, more detailed information of the residual stress can be obtained such as the location and the degree of inhomogeneity. The tangential arrangement of FBG sensors can achieve comparable measurement results to the radial arrangement but it brings convenience for the drilling process without any overlap upon the hole position. This method promotes the application of the FBG sensors in the residual stress measurement field.

Exploring high-efficiency metal-free electrocatalysts towards N2 reduction reaction (NRR) is of great interest for the development of electrocatalytic N2 fixation technology. Herein, we combined boron nitride quantum dots (BNQDs) and graphitic carbon nitride (C3N4) to design a metal-free BNQDs/C3N4 heterostructure as an effective and durable NRR catalyst. The electronically coupled BNQDs/C3N4 presented an NH3 yield as high as 72.3 μg h−1 mg−1 (-0.3 V) and a Faradaic efficiency of 19.5% (-0.2 V), far superior to isolated BNQDs and C3N4, and outperforming nearly all previously reported metal-free catalysts. Theoretical computations unveiled that the N2 activation could be drastically enhanced at the BNQDs-C3N4 interface where interfacial BNQDs and C3N4 cooperatively adsorb N2 and stabilize *N2H intermediate, leading to the significantly promoted NRR process with an ultra-low overpotential of 0.23 V.

To improve dispersion stability and magnetorheological (MR) characteristics of carbonyl iron (CI) particles, we proposed novel hydrogel magnetic microspheres (MPs) dual-coated with alginate (AL) and chitosan (CTS) for the first time. The double-network structures formed by biological crosslinking and chelation reactions are capable to enhance its own structural stability and mechanical properties. The structural characterization, MR properties, and dispersion stability for different MPs were investigated. Additionally, the swelling behaviors were studied by swelling the dried MPs in the deionized water and sodium chloride solution, respectively. The results showed that the AL/CTS hydrogel core/shell MPs displayed the advantages of simple manufacturing, superior MR properties and deformability compared to pure micron-sized CI particles, indicating the improved dispersion stability of the MR fluids compared to that of the pure CI particles-based MR fluids. The introduction of double network structures with natural biopolymers will provide a new thought for the development of MR materials.

High permittivity materials for a gigahertz (GHz) communication technology have been actively sought for some time. Unfortunately, in most materials, the dielectric constant starts to drop as frequencies increase through the megahertz (MHz) range. In this work, we report a large dielectric constant of ∼800 observed in defect-mediated rutile SnO2 ceramics, which is nearly frequency and temperature independent over the frequency range of 1 mHz to 35 GHz and temperature range of 50-450 K. Experimental and theoretical investigations demonstrate that the origin of the high dielectric constant can be attributed to the formation of locally well-defined Zn2+-Nb4+ defect clusters, which create hole-pinned defect dipoles. We believe that this work provides a promising strategy to advance dipole polarization theory and opens up a direction for the design and development of high frequency, broadband dielectric materials for use in future communication technology.

Imaging the vibrations of nanomechanical resonators means measuring their flexural mode shapes from the dependence of their frequency response on in-plane position. Applied to two-dimensional resonators, this technique provides a wealth of information on the mechanical properties of atomically-thin membranes. We present a simple and robust system to image the vibrations of few layer graphene (FLG) resonators at room temperature and in vacuum with an in-plane displacement precision of ≈0.20 μm. It consists of a sturdy vacuum enclosure mounted on a three-axis micropositioning stage and designed for free space optical measurements of vibrations. The system is equipped with ultraflexible radio frequency transmission lines to electrically actuate resonators. With it we characterize the lowest frequency mode of FLG resonators by measuring its frequency response as a function of position on the membrane and by extracting its effective mass. We use the background noise of the undriven vibrational spectrum to calibrate in-plane displacement. Finally, we measure the first three vibration modes of a resonator whose membrane is partially folded and find that folds locally suppress vibrations.

The behavior of room temperature phosphorescence quenching and fluorescence enhancing of gadolinium labeled sinoporphyrin sodium (Gd-DVDMS) in the aqueous solution were studied. Gd-DVDMS was characterized by various techniques including mass spectra, Fourier transform infrared spectra and transmission electron microscopy. The optical behavior was monitored through UV–vis absorption spectra and photoluminescence spectra. The result shows that the phosphorescence intensity gradually quenches, almost disappears after dissolved 120 min, meanwhile the fluorescence intensity enhances 5 times. The above behavior is attributed to the decreased population of Gd-DVDMS as first excited triplet state (T1). Based on the time-invariant of both absorption spectra and phosphorescence decay curves at 710 nm of Gd-DVDMS in different dissolution time, the reason for the decreased population of Gd-DVDMS in T1 state is that the intersystem crossing from first excited state (S1) to T1 is prevented. In addition, the fluorescent decay curves of Gd-DVDMS initially dissolved in the aqueous solution and dissolved for 120 min were also measured for comparison. The big change in fluorescent lifetime further proves the conclusion that intersystem crossing is prevented, meanwhile, the increase in fluorescence intensity is demonstrated. In this work, the possibility of decomposition of Gd-DVDMS is excluded because the phosphorescence decay curve in Gd-DVDMS aqueous solution is sensible to DVDMS.

Based on magnetic medium theory, a newly invited magnetic corrosion detector (MCD) showed great potential in quantitative monitoring the corrosion process of steel rebar in concrete. To furtherly explore the application performance of MCD, a numerical model was established to simulate the magnetic induction intensity variation caused by corrosion of steel rebar. And the influence of the length and the positioning variance of steel rebar on the measurement were discussed based on experimental and numerical investigation. The research results indicate that the numerical simulation is a valid approach to reveal the essential performance of MCD in measuring the corrosion ratio of steel rebar in concrete. Based on the geometric and physical properties of MCD, the corrosion ratio of the steel rebar can be effectively measured. And the positioning variance of steel rebar has significant influence on the precision and sensitivity of MCD. It is suggested that the steel rebar should be placed right at the center of the test area during the measurement to achieve a high accuracy.

As a lead-free material, AgNbO3 has received a lot of attention for its potential application in the field of energy storage. Herein, AgxNbO2.5+x/2 ceramics were successfully synthesized via solid state reaction with the x ranged from 1 to 0.92. The effect of silver deficiency on structure, dielectric properties and energy storage performance was investigated. As x value decreased from 1 to 0.94, the unit volume of AgxNbO2.5+x/2 ceramics contracted. Meanwhile, all the compositions displayed double hysteresis loops with reduced Pmax, Pr and enhanced transformation fields (EF and EB) as functions of silver deficiency. Silver deficiency stabilized the antiferroelectric state in the FIE (-like) phase and improved the energy storage performance of AgNbO3 ceramics. Hence, an enhanced energy storage performance (Wrec = 3.1 J/cm3, η = 49%) were achieved in Ag0.94NbO2.97 ceramic.

The combustion characteristics of a hydrogen-fueled scramjet combustor were investigated experimentally and numerically. One nonreacting case (case 1), and two different equivalence ratio (ER) reacting cases (cases 2 and 3) were compared. The combustion process of each reacting case was divided into three phases. In the first phase, the monitor pressure in case 2 (ER = 0.1) reached a higher level due to the fuel injected before the hydrogen was ignited, whereas the change in case 3 (ER = 0.3) was the opposite, being less than that in the nonreacting flow. Almost all of the hydrogen in case 2 was in the front of the cavity, and that in case 3 was both throughout the whole cavity and near the top wall behind the cavity. In the second phase, the ignition times were about 0.010 s in case 2 and about 0.022 in case 3; a larger ER of hydrogen might be difficult to ignite. Finally, in the last phase, the hydrogen combustion was stable. The shock train in case 3 was pushed into the isolator, and the disturbing distance was about 0.08 m, in accordance with the wall pressure distribution. The higher static temperature in case 2 was mainly in the back of the cavity and that in case 3 was in the cavity shear layer, in line with the hydroxyl planner laser-induced fluorescence (OH-PLIF) results. The combustion mode in case 2 was supersonic combustion and that in case 3 was subsonic combustion.

Herein, we report the high De-NOx performance of the A-site defective perovskite-based Pd/La0.5Sr0.3MnO3 catalyst. The formation of the defective perovskite structure can be proved by both the increased Mn4+/Mn3+ ratio and serious lattice contraction due to cationic nonstoichiometry. It promotes the Sr doping into perovskite lattice and reduces the formation of the SrCO3 phase. Our results demonstrate that below 300 °C the A-site defective perovskite can be more efficiently regenerated than the SrCO3 phase as NOx storage sites due to the latter's stronger basicity, and also exhibits the higher NO oxidation ability than the A-site stoichiometric and excessive catalysts. Both factors promote the low-temperature De-NOx activity of the Pd/La0.5Sr0.3MnO3 catalyst through improving its NOx trapping efficiency. Nevertheless, above 300 °C, the NOx reduction becomes the determinant of the De-NOx activity of the perovskite-based catalysts. A-site defects can weaken the interactions between perovskite and Pd, inducing activation of Pd sites by in-situ transformation from PdO to metallic Pd in the alternative lean-burn/fuel-rich atmospheric alternations, which boosts the De-NOx activity of the Pd/La0.5Sr0.3MnO3 catalyst. The Pd/La0.5Sr0.3MnO3 catalyst exhibits the high sulfur tolerance as well. These findings provide insight into optimizing the structural properties and catalytic activities of the perovskite-based catalysts via tuning formulation, and have potential to be applied for various related catalyst systems.

Here, we report (C4H9)4NCuCl2 single crystals with a luminous intensity that remains largely the same after soaking in water for 24 h. (CH9)4NCuCl2 has a new type zero-dimensional framework, in which the isolated [CuCl2]- anions are wrapped by organic (C4H9)4N+ cations. As expected, (C4H9)4NCuCl2 shows a broad emission band at 508 nm with a photoluminescence quantum yield of approximately 82% at room temperature, stemming from self-trapped exciton (STE) emission. Temperature-dependent photoluminescence measurement reveals that there is an energy barrier ΔE (24.0 meV) between the intrinsic state and STE state, which leads to the increase in emission intensity with an increase in temperature (98-278 K), while the emission intensity begins to decrease when the temperature is higher than 278 K due to the effects of both thermal quenching and carrier scattering. Our findings provide a new idea for the design of lead-free anti-water stability metal halide materials.

For supported metal catalyst systems, the impact on catalysis originates from the interaction between metal nanoparticles and their support. Metal-support interactions (MSI) can change electronic properties, geometric morphologies, or chemical compositions of metal nanoparticles to make active sites have specific properties and catalytic activities. Fischer-Tropsch synthesis (FTS) is one of the most effective ways to convert cheap non-petroleum-based carbon sources into high value-added chemicals or ultra-clean liquid fuels. In this review, we summarize and classify the impact of MSI on the catalytic activity, selectivity and stability of FTS catalysts. The strategies to tune MSI are introduced in detail, and the recent development of high-efficiency FTS catalysts through the manipulation of SMI strategies has been highlighted. It is emphasized that the active metal sites, which are endowed with special functions by MSI, can change the strength of adsorption bond of adsorbates, consequently controlling the product distribution.

Based on the excellent sodium ion mobility of sodium superionic conductor structures, Na3V2(PO4)3 materials have become promising cathode materials in sodium-ion batteries (SIBs). However, inadequate electronic transport of Na3V2(PO4)3 limits the cycling stability and rate performances in SIBs. In this work, high-performance conductive carbon-coated Na3V2(PO4)3 materials are obtained via a simple and facile ball-milling assisted solid-state method by utilizing citric acid as carbon sources. The carbon-coated composite electrodes display a high initial specific capacity of 111.6 mAh·g−1, and the specific capacity could retention reach 92.83% after 100 cycles at 1C with the high coulombic efficiency (99.95%). More importantly, the capacity of conductive carbon-coated nano-sized Na3V2(PO4)3 can remain 48.5 mAh·g−1 at 10C after 3000 cycles (initial capacity of 101.2 mAh·g−1). At the same time, high coulombic efficiency (near 100%) has little decay even at a high rate of 20C during 1000 cycles, demonstrating the excellent cycling stability and remarkable rate performances, and showing potential in large-scale productions and applications. 基于钠超离子导体结构的优异钠离子迁移速率, Na3V2(PO4)3材料已成为钠离子电池 (SIBs) 中极有发展前景的正极材料。然而, Na3V2(PO4)3的导电性不佳会限制钠离子电池的循环稳定性和速率性能。在这项工作中, 利用柠檬酸作为碳源, 通过一种简单而又容易的球磨辅助固相法, 制备了高性能导电碳包覆的Na3V2(PO4)3材料。碳包覆复合电极的初始比容量高, 为111.6 mAh•g-1。在1C的电流密度下, 循环100次后, 容量保持率达到92.83%, 库仑效率高达99.95%。更重要的是, 在10C下经过3000次循环后, 导电碳涂覆纳米级Na3V2(PO4)3的容量仍可保持48.5 mAh•g-1 (初始容量为101.2 mAh•g-1)。同时, 即使在20C的高倍率下循环1000次, 高库仑效率 (接近100%) 也几乎没有衰减, 证明该材料具有优异的循环稳定性和出色的倍率性能, 并在大规模生产和应用中展现出潜力。

Summary Most simulators currently use the advection/diffusion model (ADM), where the total flux comprises Darcian advection and Fickian diffusion. However, significant errors can arise, especially for modeling diffusion processes in fractured unconventional reservoirs, if diffusion is modeled by the conventional Fick’s law using molar concentration. Hence, we propose an improved multicomponent diffusion model for fractured reservoirs to better quantify the multiphase multicomponent transport across the fracture/matrix interface. We first give a modified formulation of the Maxwell-Stefan (MS) equation to model the multicomponent diffusion driven by the chemical potential gradients. A physics-based modification is proposed for the ADM in fractured reservoirs, where fracture, matrix, and their interface are represented by three different yet interconnected flow domains to honor the flux continuity at the fracture/matrix interface. The added interface using a more representative fluid saturation and composition of the interface can hence better capture the transient mass fluxes between fracture and matrix. The proposed approach is also implemented in an in-house compositional simulator. The multicomponent diffusion model is validated with both intraphase and interphase diffusion experiments. Then, the improved model for fracture/matrix interaction is compared with a fine-grid model. The proposed multiple interacting continua (MINC) model with three continua (MINC3) can better match the fine-grid model’s result than the double-porosity (DP) model, which only obtains a fair match at an early time. Then, we simulate a gas huff ‘n’ puff (HnP) well in the Permian Basin to investigate the effect of diffusion within the fractured tight oil reservoir. The simulation reveals that diffusion has a minor effect on the performance of depletion when oil is the dominant phase. For gas HnP, the simulation neglecting diffusion will underestimate the oil recovery factor (RF) but overestimate the gas rate. The DP approach tends to overestimate the RF of heavy components but leads to a similar cumulative oil RF compared with MINC3. With the diffusion included in the simulation, gas HnP performance becomes more sensitive to the soaking time than the model without diffusion. Although increasing the soaking time will lead to a higher RF after considering diffusion, the incremental oil is not sufficiently large to justify a prolonged soaking time.

Chalcopyrite (CuFeS2), a natural copper–iron bimetallic sulfide, has shown great promise as an active material for lithium-ion batteries because of its superior electrochemical performance, high ab...

DNA origami technology has proven to be an excellent tool for precisely manipulating molecules and colloidal elements in a three-dimensional manner. However, fabrication of single crystals with well-defined facets from highly programmable, complex DNA origami units is a great challenge. Here, we report the successful fabrication of DNA origami single crystals with Wulff shapes and high yield. By regulating the symmetries and binding modes of the DNA origami building blocks, the crystalline shapes can be designed and well-controlled. The single crystals are then used to induce precise growth of an ultrathin layer of silica on the edges, resulting in mechanically reinforced silica-DNA hybrid structures that preserve the details of the single crystals without distortion. The silica-infused microcrystals can be directly observed in the dry state, which allows meticulous analysis of the crystal facets and tomographic 3D reconstruction of the single crystals by high-resolution electron microscopy., DNA origami is a valuable tool for precise manipulation of molecules in a three dimensional manner, but the design and assembly of origami units into single crystals is challenging. Here, the authors report successful fabrication of DNA origami single crystals with Wulff shapes, and regulation of their shapes by changing the symmetry and binding modes of DNA origami building blocks.

Herein, Cu-modified SAPO-34 catalysts with various copper loadings are synthesized via a pH-controlled ion-exchange method. Cu exists predominantly as isolated cations at lower loadings, located at octahedrally coordinated sites in the ellipsoidal cavity of SAPO-34 zeolites, while CuO is gradually generated on the external surface at higher loadings. Our results reveal that the isolated Cu cations are the active sites for C₃H₆-SCR. The presence of CuO species enhances the C₃H₆ activation ability of the catalysts, which thus, improves the C₃H₆-SCR performance at medium and low temperatures (below 400 °C). At high temperatures, however, the formation of CuO accelerates the nonselective oxidation of C₃H₆ and causes activity decline. These findings suggest that the active temperature window for hydrocarbons-selective catalytic reduction (HC-SCR) reactions over Cu/SAPO-34 catalysts can be tailored by tuning the proportion of various copper species to fit the need in real applications, which provide new insights into understanding and designing highly efficient Cu-based zeolite catalysts.

The crystallization methodology of DNA origami frames has found salient utility in large-scalely integrating multifarious functional components following organized arrangements, thus opening up the possibilities for optical, biological, and other interdisciplinary applications. However, the single strand-dominated spacing region between adjacent DNA origami units has extremely restricted the adjustment of DNA origami separations, leading the soft crystals susceptible to environmental influences. Herein, we developed a cocrystallization pathway by incorporating rigid DNA rods into a DNA origami assembly system to achieve mutually ordered bridging on a three-dimensional scale. The intervention of DNA rods significantly improved the rigidity and crushing resistance of entire cocrystals and rendered DNA origami units exhibiting different spacing distances within the obtained crystal phase when varying DNA rod structures artificially. Such a tuning strategy that uses DNA rods as allosteric factors would provide a rational method for accessing diverse crystalline states and even modulating the tailorable properties of materials on demand.

The self-assembly of block copolymers in a confined space has been proven to be a facile and robust strategy for fabricating assembled structures with various potential applications. Herein, we employed a new pH-responsive polymer self-assembly method to regulate ion transport inside artificial nanochannels. The track-etched asymmetric nanochannels were functionalized with PS22k-b-P4VP17k/hPS4k blend polymers, and the ionic conductance and rectification properties of the proposed system were investigated. The pH-actuated changes in the surface charge and wettability resulted in the selective pH-gated ionic transport behavior. The designed system showed a good switching property to the pH stimulus and could recover during the repetitive experiments. The gating ability of the polymer-nanochannel system increased with increasing the weight of the homopolymer, and the proposed platform demonstrated robust stability and reusability. Numerical and the dissipative particle dynamics simulations were implemented to emulate the pH-dependent self-assembling behavior of diblock copolymers in a confined space, which were consistent with the experimental observations. As an example of the self-assembly of polymers in nanoconfinements, this work provides a facile and robust strategy for the regulation of ion transport in synthetic nanochannels. Meanwhile, this work can be further extended to design artificial smart nanogates for various applications such as mass delivery and energy harvesting.

Dispersions of magnetic nanoparticles (MNPs) can exhibit paramagnetic ferrofluid or ferromagnetic liquid behavior. By modifying the surface functionality of MNPs, ferrofluids have been used to fabricate novel magnetically actuated devices. If the surface-functionalized MNPs interact with complementary ligands at a fluid-fluid interface, MNP surfactants form and in situ assemble at the interface. When jammed interfacially, MNP surfactants give rise to ferromagnetic behavior of the liquid (droplet), which is endowed with permanent magnetic dipoles while maintaining all of the characteristics of a fluid system. Here, we give a brief overview of the developments in the dispersion of MNPs in liquids from ferrofluids to ferromagnetic liquid droplets, their responses to external fields, and the manipulation of these responses for end uses. The reversible room-temperature para-to-ferro transformation of magnetic liquids is highlighted. We discuss challenges in the synthesis and characterization of these unusual liquids along with potential technological applications.

Zero-dimensional lead-free organic-inorganic hybrid metal halides have drawn attention as a result of their local metal ion confinement structure and photoelectric properties. Herein, a lead-free compound of (Gua)3Cu2I5 (Gua = guanidine) with a different metal ion confinement has been discovered, which possesses a unique [Cu2I5]3- face-sharing tetrahedral dimer structure. First-principles calculation demonstrates the inherent nature of a direct band gap for (Gua)3Cu2I5, and its band gap of ∼2.98 eV was determined by experiments. Worthy of note is that (Gua)3Cu2I5 exhibits a highly efficient cool-white emission peaking at 481 nm, a full-width at half-maximum of 125 nm, a large Stokes shift, and a photoluminescence quantum efficiency of 96%, originating from self-trapped exciton emission. More importantly, (Gua)3Cu2I5 single crystals have a reversible thermoinduced luminescence characteristic due to a structural transition scaled by the electron-phonon coupling coefficients, which can be converted back and forth between cool-white and yellow color emission by heating or cooling treatment within a short time. In brief, as-synthesized (Gua)3Cu2I5 shows great potential for application both in single-component white solid-state lighting and sensitive temperature scaling.

Ultraviolet photoacoustic microscopy (UV-PAM) has been investigated to provide label-free and registration-free volumetric histological images for whole organs, offering new insights into complex biological organs. However, because of the high UV absorption of lipids and pigments in tissue, UV-PAM suffers from low image contrast and shallow image depth, hindering its capability for revealing various microstructures in organs. To improve the UV-PAM imaging contrast and imaging depth, here we propose to implement a state-of-the-art optical clearing technique, CUBIC (clear, unobstructed brain/body imaging cocktails and computational analysis), to wash out the lipids and pigments from tissues. Our results show that the UV-PAM imaging contrast and quality can be significantly improved after tissue clearing. With the cleared tissue, multilayers of cell nuclei can also be extracted from time-resolved PA signals. Tissue clearing-enhanced UV-PAM can provide fine details for organ imaging.

Cobalt sulfide is favorable for supercapacitors, but its application is inhibited by the inherent slow charge transfer kinetics and poor stability in alkaline solution. Herein, zeolitic imidazole f...

Unraveling the morphology of the sensing material is of paramount in realizing the better sensitivity. For this purpose, the Bi2Ti2O7:Yb3+/Er3+ nanofibers (0:1, 4:1, 8:1, 15:1, 20:1) and nanoparticles were synthesized via an electrospinning and sol–gel route, respectively. Subsequently, the temperature sensing properties based on the fluorescence intensity ration were studied within Bi2Ti2O7:Yb3+/Er3+ nanofibers and particles in the range of 298–538 K. The maximum relative sensitivity value was 1.53% at 298 K for Bi2Ti2O7:Yb3+/Er3+ (4:1) nanofibers. As was expected, Bi2Ti2O7:Yb3+/Er3+ nanofibers demonstrated an enhanced temperature sensitivity than that of the individual nanoparticles, exhibiting the champion values among all the reported Yb–Er pairs. To exploit the potential for practical application, the Bi2Ti2O7:Yb3+/Er3+ nanofibers were utilized to measure the surface temperature of a heating object. An improved surface temperature resolution was realized compare with the infrared thermal camera. All the presented results confirmed that the novel upconversion Bi2Ti2O7:Yb3+/Er3+ nanofibers could be an outstanding candidate for temperature sensors. Our work has proven to be a reliable alternative for exploring contactless temperature sensing at a higher resolution.

Exploring a convenient method to solve the stability problem of all-inorganic halide perovskite nanocrystals (NCs) has become an urgent task in their practical application. In recent years, cesium ...

To accurately assess the combustion fluctuation for a scramjet, a new method based on indium tin oxide (ITO) thin-film thermocouples (TFTCs) and time–frequency analysis (TFA) was developed in this study. ITO TFTCs were used to measure the transient wall-temperature change of the combustor, and the combustion fluctuation features were extracted from the temperature signal via TFA. The combustion fluctuation-resolving abilities of different TFA methods, including the short-time Fourier transform (STFT), continuous wavelet transform (CWT), and Hilbert–Huang transform (HHT), were investigated using a reconstruction signal. The results indicated that the CWT can provide an excellent global view and that the HHT is useful for localizing the frequency features in the time domain. Then, the effect of the equivalence ratio (ER) on the supersonic combustion fluctuation was researched. The total energy of the fluctuation was strongly correlated with the increase in the ER. Meanwhile, the frequency of main fluctuation was always concentrated at approximately 395 Hz, just like an intrinsic characteristic of the combustor. Additionally, the fuel type affected the energy of the combustion fluctuation, rather than the frequency.

In this study, the effects of five different ionic and nonionic surfactants on the physical properties and microstructures of a metakaolin-based geopolymer (MKG) were investigated. It is the first comprehensive comparative study of the effects of sodium lauryl sulfonate (SLS), alkyl polyglycoside (APG), benzalkonium chloride (BAC), sucrose fatty acid esters (SE), and stearic acid (STA) on MKG. Viscosity, densities, apparent water absorption, and compressive strength were measured, and pore structures, micro-defects, and gels observed through scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). In the MKG slurry, a high affinity of surfactants to liquid-air interfaces increased viscosity and promoted the generation of bubbles. Based on both the ionic types and molecular configurations of the surfactants, stronger adsorption of a surfactant on the surface of the metakaolin resulted in better dispersion of metakaolin particles and a denser microstructure of the MKG. The surfactants with weaker adsorption (SLS and APG) caused higher porosity, a larger pore size, and more micro-defects, while those with stronger adsorption (BAC, SE, and STA) led to relatively lower porosity and denser microstructures. Density, water absorption, and compressive strength were closely related to the total intrusion porosity of the MKG. The mechanisms underlying surfactant adsorption to the surface of metakaolin are proposed.

Recently, zero-dimensional (0D) metal halides have made remarkable achievements in the field of optoelectronics due to their diverse structures and optical performances. Here, we report 0D (TBA)2Cu2I4 (TBA+ = tetrabutylammonium cation) single crystals (SCs), which shows a dual-emission band at 473 and 699 nm and a bright cool-white emission with a high photoluminescence quantum yield (PLQY) of 72.5% at room temperature (RT). The temperature-dependent emission spectra and Raman spectra show that a dual self-trapped exciton (STE) is present in this compound, and the external thermal energy can effectively regulate the population of STEs in the two emitting states, and thus the emission color can be changed from blue at a low temperature (78 K) to a cool-white emission at RT. More specifically, (TBA)2Cu2I4 SCs possess high anti-water stability, and can maintain highly efficient emission even if immersed in water for 24 hours. Also noteworthily, the high thermal stability, air stability and photostability of this component have also been proved.

As a highly safe and low-cost cathode material for lithium-ion batteries, LiFePO4 predominately suffers from undesirable rate performance, arising from its inferior conductivity, during practical applications. Herein, LiFePO4 modified with a modulated band structure, as theoretically predicted, was successfully designed to overcome this deficiency. Notably, replacing the Li sites with Ti4+ led to tuned band structures, giving rise to an effective reduction of the forbidden bandwidth and the activated delocalization of the d-orbital electrons, as clearly observed using density functional theory calculations. Importantly, it also induces the shrinkage of the particle size, reducing the transport distance for Li+ inside the particles, as verified using Rietveld refinement of the X-ray diffraction spectra. As expected, electronic transfer and Li+ transport are synchronously accelerated thanks to the appropriate doping of Ti4+ in the olivine lattice, confirmed based on the measurement of the conductivity and calculations of the Li+ diffusion coefficient. Hence, the as-optimized cathode (0.5% Ti4+-LFP/C) exhibits an excellent rate capacity (135 mA h g−1 at 10C within 2.5–4.2 V) with superior long-term cycling stability (78% capacity retention after 3000 cycles). Based on these results, the dramatic improvement in the rate performance achieved via modulating the band structures and the ionic diffusion may provide novel opportunities for the development of olivine cathode materials.

Piezoelectric sensors with good flexibility and high sensitivity have attracted extensive interest in wearable electronics. Here, we report a novel frequency-response behaviour of piezoelectric voltage of a sensor that is based on a piezoelectric enhanced composite film of P(VDF-TrFE) and BaTiO3. The piezoelectric voltage enhances with the increase of frequency and becomes stable beyond the critical frequency. Such a demonstrated sensing characteristic of the piezoelectric sensor depends on the inner resistance of the voltmeter, which is determined by whether the loading of stimuli can be completed within the period of piezoelectric voltage measurement in the testing circuit. By utilizing the frequency-response behaviour in different frequency ranges, the flexible piezoelectric device exhibits excellent capabilities to quantitatively detect the magnitude and loading rate of stimuli. As a proof-of-concept demonstration, a flexible pressure sensor is successfully integrated with a bionic bee to monitor the flight status (i.e., strain rate and strain) of the vibrating wings. This work demonstrates that flexible piezoelectric sensors have great prospects for application in the field of bionic flying robots, thus paving the way forward for the development of smart self-sensing flexible electronics.

Laser-induced breakdown spectroscopy (LIBS) has been successfully developed into the oceanic chemical sensor for deep-sea exploration. However, the LIBS signals will be affected by marine environmental factors, and this effect has yet to be revealed in practice. In this work, the effects of oceanic pressure and temperature on in situ LIBS measurements were synthetically investigated according to the seawater spectra obtained by a LIBS system at different depths during sea trials. It is shown that the spectral features vary dramatically with depth. An approximately linear increase of line broadening with increasing depth was obtained. The emission intensities of the Na I and K I lines first increase with depth, followed by a decrease, while the emission intensity of the Ca I line gradually increases with depth. In addition, the emission intensity changes less significantly at depths less than 400 m, as the rapid decrease in seawater temperature above the thermocline slows the increase in emission intensity, while below the thermocline, it is mainly influenced by pressure. Especially, we initially modeled the relationship between LIBS signals and oceanic depth and temperature using exponential fitting, which not only deepens the understanding of the comprehensive influence of the marine environment on LIBS detection, but also facilitates the better application of LIBS technology in marine in situ qualitative and quantitative analysis.

Highly efficient semiconductor photocatalysis technology is widely used for water purification. Herein, we prepared carbon quantum dots (CQDs)/graphitic carbon nitride (g-C3N4) on carbon cloth (CC). After the addition of CQDs, the visible light absorption characteristics and electron–hole separation rate of g-C3N4 are improved. The g-C3N4/CQDs/CC composite material has photocatalytic activity and good recyclability under visible light irradiation and can be used for the photodegradation of rhodamine B (RhB). The introduction of carbon cloth facilitates recycling and improves the cycle life of the photocatalyst. This work can be extended to the manufacture of high-performance photocatalysts supported by other recyclable carbon cloth.

As a promising cathode material for high performance lithium ion batteries, olivine LiMnxFe1−xPO4 (LMFP) combines the high safety of LiFePO4 and the high energy density of LiMnPO4. However, there are still obstacles to overcome for achieving higher rate performance, especially its inherent low electronic conductivity and Li+ diffusion coefficient. Here, the restricting factors for realizing high rate performance LMFP cathode materials are reviewed systematically. The bulk properties that affect the internal ion transport and electronic conduction are thoroughly expounded, particularly the phase transition mechanism, lattice distortion, point defects, element doping, Fe/Mn ratio and particle morphology. Moreover, the effect of utilizing a carbon-based/non-carbon material coating for improving the interface structure on rate performance is discussed comprehensively. A particular emphasis is placed on the design of LMFP-based batteries with high rate capability as well from the aspect of cell preparation technology, including the electrolyte selection and electrode design. Finally, on the basis of state-of-the-art understanding of bulk properties, the interface structure and cell preparation engineering, several technical challenges and research trends in improving the rate performance of LMFP cathode materials are proposed.

There has been great interest in the fabrication of solid surfaces with desirable under-liquid wettability, and especially under-liquid dual-lyophobicity, because of their potential for widespread use. However, there remains the lack of a general principle to modulate the under-liquid wettability in terms of surface energy (SE). Herein, we found that the relative proportion between the polar and dispersive components in SE that reflects the competition between hydrophilicity and lipophilicity governs the under-liquid wettability of the solid surface. For the first time, we introduced hydrophilic–lipophilic balance (HLB) calculated solely based on the amount and type of hydrophilic and lipophilic fragments in surface molecules to rapidly predict the under-liquid wettability of a solid surface, thereby guiding the fabrication of solid surfaces with desirable under-liquid wettability. Accordingly, the under-liquid dual superlyophobic surfaces in a nonpolar oil–water-solid system were fabricated by grafting molecules with appropriate HLB values (e.g., 6.341–7.673 in a cyclohexane–water–solid system) onto porous nanofibrous membranes, which were able to achieve continuous separation of oil–water mixtures. This work provides reasonable guidance for the fabrication of solid surfaces with targeted under-liquid wettability, which may lead to advanced applications in oil–water–solid systems., Hydrophilic–lipophilic balance calculated based on the component of surface molecules is introduced to predict the under-liquid wettability of solid surfaces, thereby guiding the fabrication of solid surface with desirable under-liquid wettabilities.

A chirp compensation method of fiber Bragg grating (FBG) is proposed to improve the residual stress measurement accuracy in the hole-drilling method. The effects of the radii of the hole, the distance between the FBG and the hole, the Young’s modulus of the material, and the residual stress on the FBG chirped spectra are analyzed. The relationship between radii of the hole, the distance between the FBG and the hole, the full-width at half maximum (FWHM), and the peak wavelength are established. The feasibility of the method is verified through experiments, which shows that the residual stress measurement error can be reduced by the compensation method.

Designing van der Waals' heterostructures with prominent properties is crucial to improve the performance of nanoscale optoelectronic devices. In this article, the structural stability and electronic properties of Sb/AlAs heterostructures were investigated by comprehensive first-principles calculations. It is worth noting that Sb/AlAs heterostructures have good thermal stability and a small lattice mismatch. Owing to suitable direct-gap and intrinsic type-II band alignment, effective separation of photogenerated carriers occurs at the interface, which has numerous optoelectronic properties suitable for use in photodetectors. Furthermore, the heterostructure undergoes transition from indirect-gap to direct-gap under vertical strain. When an external electric field is applied, the charge transfer is significantly enhanced and a semiconductor–metal transition is accomplished. The biaxial strain can induce indirect–direct–indirect transition, and the effective mass of electrons and holes exhibit notable anisotropy, which can be modulated by tensile and compressive strain. The above-mentioned results provide valuable theoretical guidance for designing high-quality Sb-based heterostructures and specify an orientation for high-performance photodetector applications.

Laser-induced breakdown spectroscopy (LIBS) has been successfully applied for in situ detection in the sea, and the water pressure is found to be the main influence on the LIBS signal compared to temperature or salinity. In this study, we explored self-absorption to evaluate the pressure effects on LIBS detection. By using fast imaging and spectroscopic technique, it is proved that self-absorption (SA) was significantly enhanced with increased pressure, and the severe inhomogeneity of plasma distribution might be the reason. With this SA model, the LIBS intensity could be well-estimated according to the simulation results. Moreover, the self-absorption of LIBS underwater was more likely determined by the plasma temperature when the detection was carried out in a low-pressure regime. The obtained results would be helpful for the signal correction of LIBS in the deep sea.

Low-dimensional organic–inorganic hybrid metal halides have drawn intense attention due to their flexible structures and outstanding optical properties. However, the toxicity of lead halides hinders their future application in optoelectronic devices. Herein, we report a zero-dimensional (0D) lead-free compound of (TPA)2SbCl5 (TTA+ = tetrapropylammonium cation) single crystals (SCs), which crystallizes in a triclinic system with P symmetry. Interestingly, (TPA)2SbCl5 exhibits a single broad orange emission band at 610 nm under low-energy excitation (e.g., 375 nm) with a high photoluminescence quantum yield (PLQY) of 95.3%, while it shows a dual-band emission profile with an additional narrow emission band at 466 nm at high-energy excitation (e.g., 300 nm), which is formed by the transformation of the doublet of spin–orbit interactions into two individual STEs. The Raman spectra supplied clear evidence for the self-trapped exciton (STE) with clear multiphonon modes in (TPA)2SbCl5, which reflects its strong nonlinear electron–phonon coupling. The emission mechanism for the temperature-dependent dual emission can be attributed to the radiative transitions of singlet STEs and triplet STEs in [SbCl5]2− clusters. Moreover, a white-light-emitting diode (WLED) was also fabricated by mixing (TPA)2SbCl5 with green (Ba2SiO4:Eu2+) and blue (BaMgAl10O17:Eu2+) phosphors, which exhibited CIE coordinates of (3.48, 3.50), a correlated color temperature (CCT) of 4900 K, and a color rendering index (CRI) of 93.2. Our achievements illustrate that the lead-free compound of (TPA)2SbCl5 has great potential in solid-state lighting.

Constructing step-scheme (S-scheme) heterojunctions is one of the efficient strategies to enhance photocatalytic processes, but unfortunately their synthesis requires complex procedures. Here, we develop a facile methodology for one-pot synthesis of defect-engineered S-scheme WO3/g-C3N4 heterojunctions. The as-synthesized sample (15.0WCN) exhibits a remarkable photocatalytic hydrogen generation rate (1034 μmol h−1 g−1), which is 1.7 and 4.5 times higher than that of normal S-scheme WO3/g-C3N4 heterojunctions (15.0W + CN) and pure g-C3N4, respectively. We discover that surface oxygen vacancies can improve the separation efficiency of photogenerated carriers by acting as a mediator between the valence band of g-C3N4 and the conduction band of WO3, while bulk oxygen vacancies mainly enhance visible light absorption through narrowing the band gap in the S-scheme system. In addition, our studies show that surface oxygen vacancies are more effective than bulk ones in S-scheme heterojunctions for photocatalytic hydrogen production. This work affords a new insight into coupling strategies of defect-engineering and S-scheme heterojunctions, which is helpful for designing other efficient photocatalytic systems.