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To attain a novel ablation-resistant composite for ultra-high temperature structure application, SiC whiskers reinforced C/C–Cu (C/C–SiCW–Cu) composite was fabricated via chemical vapor deposition and infiltration technologies. Microstructure, mechanical and anti-ablation performances of C/C–SiCW–Cu composite were investigated and compared with those of C/C–SiC–Cu composite. The results show C/C–SiCW–Cu composite has significant advantages in compactness, flexural strength and ablation resistance. Because SiC whisker has a high specific surface area, C/C–SiCW–Cu composite has higher capillary force than C/C–SiC–Cu composite for the infiltration of Cu alloy. Meanwhile, the reinforcement of SiC whisker retards the SiC/Cu interfacial debonding during fracture failure process. Schematic models were built to clarify the structural evolution of ablated surface during oxyacetylene ablation tests, and anti-ablation process of C/C–SiCW–Cu composite can be described: forming a compact SiO2 layer, SiC whiskers pinning anti-ablation layer and Cu alloy transpiration cooling effect.

Solution-phase self-assembly of two-dimensional (2D) networks with a high degree of internal order and long-range periodicity is a great challenge. Herein, we report a rational design to improve 2D...

Perovskite solar cells (PSCs) exhibit large, reversible, and bidirectional light-soaking effects (LSEs); however, these anomalous LSEs are poorly understood, limiting the stability engineering and commercialization. We present a unified defect theory for the LSEs in lead halide perovskites by reconciling their defect photochemistry, ionic migration, and carrier dynamics. We considered typical detrimental defects (IPb, Ii, VI) and observed that two atomic configurations were favored, where the carrier lifetime of one configuration was nearly 1 order of magnitude longer than that in the other. First-principles calculations showed that light illumination promotes ion-diffusion-assisted transitions from energetically stable configurations to metastable configurations, which are converted back to stable configurations in the dark. Fermi-level-dependent formation energies of stable/metastable configurations were used to rationalize contradictory experimental results of anomalous LSEs in PSCs observed in various studies, thus providing insights for minimizing the LSE to achieve high-performance stable PSCs.

The increasingly serious environmental pollution worldwide has posed a great threat to the ecosystem and human health, and yet the development of portable in situ monitoring techniques that are sensitive to gaseous and water pollutants remains incomplete. Herein, we report a highly active surface-enhanced Raman spectroscopy (SERS) substrate fabricated by immobilizing gold nanoparticles (AuNPs) onto a polyvinylidene fluoride (PVDF) membrane for continuous in situ SERS detection of pollutants in water and atmosphere. 4-Mercaptobenzoic acid (4-MBA) was adopted as a probe molecule to evaluate the performance of the substrate, and the results indicate that the polymer-based flexible substrate features high sensitivity, uniformity, and repeatability. The fabricated PVDF/SERS substrate was integrated with a portable Raman spectrometer operating under both passing-by and passing-through modes. The integrated system accomplishes quantitative detection and real-time online monitoring of pH in a liquid environment with a response speed of less than 10 s and the rapid SERS response to gas molecules at a low concentration within 30 s. We also demonstrated the highly sensitive detection for mainstream smoke (MS) and sidestream (SS) of cigarette smoke and verified their differences in the main constituent which contributes to the harmful secondhand smoke in public. The developed portable Raman system has excellent application prospects in online liquid and gas environmental detection.

The lack of cancer cell specificity and the occurrence of multidrug resistance (MDR) are two major obstacles in the treatment of hepatocellular carcinoma (HCC). To tackle these challenges, a novel nanoparticle (NP)-based drug delivery system (DDS) with a core/shell structure consisted of d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS)-galactose (Gal)/polydopamine (PDA) is fabricated. The NP is loaded with doxorubicin (DOX) and a nitric oxide (NO) donor N,N'-di-sec-butyl-N,N'-dinitroso-1,4-phenylenediamine (BNN) sensitive to heat to afford NO-DOX@PDA-TPGS-Gal. The unique binding of Gal to asialoglycoprotein receptor (ASGPR) and the pH-sensitive degradation of NP ensure the targeted transportation of NP into liver cells and the release of DOX in HCC cells. The near-infrared (NIR) light further facilitates DOX release and initiates NO generation from BNN due to the photothermal property of PDA. In addition to the cytotoxicity contributed by DOX, NO, and heat, TPGS and NO act as MDR reversal agents to inhibit P-glycoprotein (P-gp)-related efflux of DOX by HepG2/ADR cells. The combined chemo-photothermal therapy (chemo-PTT) by NO-DOX@PDA-TPGS-Gal thus shows potent anti-cancer activity against drug-resistant HCC cells in vitro and in vivo and significantly prolongs the life span of drug-resistant tumor-bearing mice. The present work provides a useful strategy for highly targeted and MDR reversal treatment of HCC.

Herein, a strategy is proposed to prepare a conductive, self-adhesive, and stretchable agarose gel with the merits of distinct heat resistance, freeze resistance, and long-term moisture retention. To endow the gels with conductivity, monodisperse carbon nanotubes modified by polydopamine are introduced into the gel networks, which promote both conductivity and mechanical strength of the gels. Meanwhile, further addition of glycerol enhances excellent stretchability as well as heating/freezing tolerability and moisture retention of the gels. A wearable biosensor based on the gel is fabricated to record body motions precisely with good biocompatibility, which benefits the development of smart wearable devices.

Oxide double perovskites A2B′B′′O6 are a class of emerging materials in the fields of optoelectronics and catalysis. Due to the chemical flexibilities of perovskite structures, there are multiple elemental combinations of cations A, B′, and B′′, which leading to tremendous candidates. In this study, we comprehensively screened stable oxide double perovskite A2B′B′′O6 from a pool of 2,018 perovskite candidates using a high-throughput computational approach. By considering a tolerance factor (t)–octahedral factor (μ) phase diagram, 138 candidates with F m 3 ¯ m , P21/c, and R3c phases were selected and systematically studied via first-principles calculations based on density functional theory. The screening procedure finally predicted the existence of 21 stable perovskites, and 14 among them have never been reported. Verification with existing experimental results demonstrates that the prediction accuracy for perovskite formability is approximately 90%. The predicted oxide double perovskites exhibit quasi-direct bandgaps ranging from 0 to 4.4 eV with a significantly small direct-indirect bandgap difference, balanced electron and hole effective masses, and strong optical absorptions. The newly predicted oxide double perovskites may enlarge the pool of material candidates for applications in optoelectronics and photocatalysis. This study provides a route for computational screening of novel perovskites for functional applications.

Graphite has become a critical material because of its essential role in the lithium-ion battery (LIB) industry. However, the synthesis of graphite requires an energy-intensive thermal treatment. Also, when used in sodium-ion and potassium-ion batteries (SIBs and PIBs), the graphite anode shows poor capacities and cycling stability, which hinders the development of next-generation battery technologies. Finding suitable anode materials for commercial alkali metal-ion batteries is not only urgent for the energy storage industry, but is also important for economic and sustainable development. In this work, we use fly ash carbon (FAC), a residue of crude oil combustion, as an anode material for alkali metal-ion batteries. The FAC anodes show relatively high capacities and excellent cycling stability. The charge storage mechanism of FAC anode is shown to be intercalation coupled with redox reactions of oxygen functional groups. This work shows that FAC is a promising scalable anode material for alkali metal-ion batteries.

As the intersecting line of three grain boundaries (GBs), triple line is in non-equilibrium state with large stress concentration and extra energy, which makes it the optimal site for twin nucleation. However, it is very difficult to verify this conjecture by direct experiments, so no one has done it so far. In present work, we try to use molecular dynamics (MD) simulation on nanocrystalline Cu to confirm such hypothesis. We found that 25 out of 28 twins were emitted from triple lines. The related atomic micro-mechanism has been analysed. Stress relaxation and energy reduction were considered to be the driving factors for twinning from triple lines. This could be proved by changes of dihedral angles, relative GB energy sum, average atomic von Mises shear stress and average atomic energy. Experimentally, the transmission Kikuchi diffraction (TKD) characterization on nanocrystalline Cu revealed that the fraction of the triple junction-twin intersection was 81.7% in all twinned nanograins. The underestimation of experimental results might be caused by invisible triple lines in the orientation mapping.

A facile synthesis strategy for lignin-derived three-dimensional hierarchical porous carbon (LHPC) was developed in this work. The LHPC was synthesized by a one-step carbonization-activation process using lignin as a carbon precursor and wet KOH as an in situ chemical activation agent. Compared with dry KOH activation agent, the wet KOH shows exfoliation effect on assisting the formation of hierarchical porous structure of LHPC. The H2O plays a key role of an exfoliation agent in forming the hierarchical porous structure of LHPC. The as-prepared LHPC shows a high specific surface area of 2109 m2 g−1 and hierarchical pores. When used as an electrode material for supercapacitor, the LHPC exhibits excellent electrochemical performances, including a high capacitance of 254 F g−1 at 0.5 A g−1 and excellent rate capability with 59% capacitance retention at 20 A g−1. This study offers a convenient and practical approach to produce a high-rate hierarchical porous carbon material for supercapacitors.

Developing high-performance anodes for potassium ion batteries (KIBs) is of paramount significance but remains challenging. In the normal sense, electrode materials are prepared by ubiquitous wet chemical routes, which otherwise might not be versatile enough to create desired heterostructures and/or form clean interfacial areas for fast transport of K-ions and electrons. Along this line, rate capability/cycling stability of resulting KIBs are greatly handicapped. Herein we present an all-chemical vapor deposition approach to harness the direct synthesis of nitrogen-doped graphene (NG)/rhenium diselenide (ReSe2) hybrids over three-dimensional MXene supports as superior heterostructure anode material for KIBs. In such an innovative design, 1T′-ReSe2 nanoparticles are sandwiched in between the NG coatings and MXene frameworks via strong interfacial interactions, thereby affording facile K+ diffusion, enhancing overall conductivity, boosting high-power performance and reinforcing structural stability of electrodes. Thus-constructed anode delivers an excellent rate performance of 138 mAh g−1 at 10.0 A g−1 and a high reversible capacity of 90 mAh g−1 at 5 A g−1 after 300 cycles. Furthermore, the potassium storage mechanism has been systematically probed by advanced in situ/ex situ characterization techniques in combination with first principles computations.

Intrinsic defects in perovskite films strongly influence carrier dynamics by introducing nonradiative recombination centers, limiting the performance of perovskite solar cells. Extensive “trail-and...

To improve electrical conductivity of the carbon-based pantograph strip, a sliding contact material of pyrolytic carbon (PyC) coated-copper foam/carbon composite was fabricated by chemical vapor deposition technology, followed by densifying processes of furan resin impregnation and carbonization. Morphology, electrical conductivity, wear and friction behavior of the composites are investigated to clarify the effect of PyC thickness (from 0 μm to 280 μm) on tribological behaviors and current transfer characteristic. The results show that there is a good interface combination between copper foam and resin carbon matrix in the composites after the improvement of interface wettability by inserting PyC layer. The composite has great advantages in electrical conductivity and density due to the copper foam and PyC layer with three-dimensional structure. With increasing the PyC thickness, both electrical conductivity and wear resistance of the composite have steadily increasing tendency, but friction coefficient has no obvious change. In addition, an analytical model is developed to explore current transfer mechanisms of the PyC-copper foam/carbon composite, and the theoretical predictions are in agreement with the experimental observations, in term of electrical conductivity and porosity of composite preform.

The whole is a collection of parts and fulfills specific functions that the parts do not have. In this work, 50 nm Au NPs were in situ synthesized and close packed into a superorganism-like superstructure by means of microgel 3D networks. The combined microgel is endowed with ultra-wide absorption in visible and near-infrared regions between 500 and 1100 nm in spite of Au NPs not having this property. The strong collective plasmon coupling between neighboring Au NPs induces high photothermal conversion efficiency of the microgel system under irradiation at various laser wavelengths. Due to the good loading capability, microgels with nanocomposites can also load photosensitive drugs simultaneously and be used for combined cancer treatments of photothermal therapy and photodynamic therapy.

The incorporation of a certain amount of Cl ions into methylammonium lead iodide (MAPbI3) perovskite films and how these incorporated Cl ions affect the structural and electronic properties of these films have been an intensively studied topic. In this study, we comprehensively investigated Cl incorporation in MAPbI3 at the atomic scale by a combined study of scanning tunneling microscopy, X-ray photoelectron spectroscopy, ultraviolet and inverse photoemission spectroscopy, density functional theory and molecular dynamics calculations. At a Cl concentration of 14.8 ± 0.6%, scanning tunneling microscopy images confirm the incorporation of Cl ions on the MAPbI3 surface, which also corresponds to the highest surface stability of MAPbI3 found from the viewpoint of both thermodynamics and kinetics by density functional theory and molecular dynamics calculations. Our results show that the Cl concentration is crucial to the surface bandgap and stability of MAPbI3.

To improve the ablation performance of carbon/carbon (C/C) composite materials, a WSi2–ZrSi2 composite-reinforced ZrxHf1–xC/SiC coating was prepared on the substrate surface via patterning strengthening method. The results show that this coating can protect the substrate from failure for 300 s under an oxyacetylene flame at 2600 °C. Owing to the presence of W, an extremely dense oxide layer was formed on the surface of the coating during initial ablation, which progressively led to the expulsion of the product of oxidation (WO3) from the inner layer, as well as to holes and cracks on healing the coating surface, thereby significantly improving the ablation performance of the C/C composites. In addition, the excellent ablative performance and mechanism of the coating were analysed using volatility diagrams.

Sub-stoichiometric silicon oxide (SiOx) is regarded as one of the most promising alternatives to silicon for use in lithium-ion batteries because of its high theoretical capacity, low cost, and abundant reserves. However, the practical application of a SiOx anode is largely limited by the inferior Li+ kinetic characteristics and slow electron transport. Herein, we strategically synthesize sponge-structured SiOx@C@CoO multifunctional composites via spray drying and an electrostatic self-assembly strategy. Ultrathin CoO nanosheets are self-assembled on the surfaces of carbon coated SiOx particles (SiOx@C). The novel design can effectively improve the conductivity of SiOx, shorten the diffusion length and increase surface areas to enhance Li+ diffusion; more importantly the sponge-like structure is capable of accommodating the volume change, contributing to an improved and stable electrochemical performance during the charging/discharging processes. Based on theoretical simulations, it was confirmed that SiOx@C@CoO composites can increase the adsorption energy and reduce the diffusion barrier of Li+ compared with SiOx@C, which enhance the storage capacity and facilitate the Li+ diffusion during cycling processes. Consequently, sponge-like structured SiOx@C@CoO multifunctional composites achieve a reversible specific capacity of up to 1287 mA h g−1 at a current density of 0.1 A g−1, and retain 714 mA h g−1 after 750 cycles at 1 A g−1 with a capacity retention of 98.9%. Remarkably, SiOx@C@CoO composites show great potential in full lithium-ion batteries. Employing LiNi0.8Co0.1Mn0.1O2 (NCM 811) as the cathode, the pouch-type cell exhibits an excellent reversible capacity of 206 mA h g−1 and a long-term cycling stability with a capacity retention of 85.9% after 200 cycles.

The scattered resistive elements residing in a dual-active-bridge (DAB) dc/dc converter can adversely affect its transient performance especially when the load change is large. Conventional phase-shift methods do not take the resistive impact into account in their modeling and analysis. In this paper, a comprehensive analysis of the detrimental influence on the transient performance of a DAB converter due to resistive elements is presented, based on which a modified phase-shift scheme is proposed to further optimize the transient response of the converter. A DAB prototype is designed to verify the resistive impact discussed and validate the proposed phase-shift scheme. The experimental results confirm that better transient response can be effectively achieved with the proposal.

Trap-dominated non-radiative charge recombination is one of the key factors that limit the performance of perovskite solar cells (PSCs), which was widely studied in methylammonium (MA) containing PSCs. However, there is a need to elucidate the defect chemistry of thermally stable, MA-free, cesium/formamidinium (Cs/FA)-based perovskites. Herein, we show that d-penicillamine (PA), an edible antidote for treating heavy metal ions, not only effectively passivates the iodine vacancies (Pb2+ defects) through coordination with the –SH and –COOH groups in PA, but also finely tunes the crystallinity of Cs/FA-based perovskite film. Benefiting from these merits, a reduction of non-radiative recombination and an increase in photoluminescence lifetime have been achieved. As a result, the champion MA-free device exhibits an impressive power conversion efficiency (PCE) of 22.4%, an open-circuit voltage of 1.163 V, a notable fill factor of 82%, and excellent long-term operational stability. Moreover, the defect passivation strategy can be further extended to a mini module (substrate: 4 × 4 cm2, active area: 7.2 cm2) as well as a wide-bandgap (∼1.73 eV) Cs/FA perovskite system by delivering PCEs of 16.3% and 20.2%, respectively, demonstrating its universality in defect passivation for efficient PSCs., Iodine vacancy defects in MA-free perovskite are effectively passivated through the interaction between Pb2+ and the functional groups in d-penicillamine, resulting in an impressive efficiency of 22.4% along with excellent operational stability.

The development of redox-targeting co-catalysts is one of the important tasks in realizing hybrid photocatalytic systems for CO2 reduction reaction (CO2 RR), which has been sought after as a promis...

Organic anodes have attracted increasing attention for alkali metal ion batteries. In this work, we discovered that cyclized polyacrylonitrile (cPAN) can serve as an excellent anode for alkali metal ion batteries. Upon activation cycling, as an anode of lithium-ion battery, cPAN exhibits a reversible capacity as high as 1238 mAh g

Chemical vapor deposition (CVD) has become a promising approach for the industrial production of graphene films with appealing controllability and uniformity. However, in the conventional hot-wall CVD system, CVD-derived graphene films suffer from surface contamination originating from the gas-phase reaction during the high-temperature growth. Shown here is that the cold-wall CVD system is capable of suppressing the gas-phase reaction, and achieves the superclean growth of graphene films in a controllable manner. The as-received superclean graphene film, exhibiting improved optical and electrical properties, was proven to be an ideal candidate material used as transparent electrodes and substrate for epitaxial growth. This study provides a new promising choice for industrial production of high-quality graphene films, and the finding about the engineering of the gas-phase reaction, which is usually overlooked, will be instructive for future research on CVD growth of graphene.

Quasi-two-dimensional (quasi-2D) perovskite is rising as a promising luminescent material for blue perovskite light-emitting diodes (PeLEDs). However, typical quasi-2D perovskites show a wide distr...

Symbolic regression (SR) is an approach of interpretable machine learning for building mathematical formulas that best fit certain datasets. In this work, SR is used to guide the design of new oxide perovskite catalysts with improved oxygen evolution reaction (OER) activities. A simple descriptor, μ/t, where μ and t are the octahedral and tolerance factors, respectively, is identified, which accelerates the discovery of a series of new oxide perovskite catalysts with improved OER activity. We successfully synthesise five new oxide perovskites and characterise their OER activities. Remarkably, four of them, Cs0.4La0.6Mn0.25Co0.75O3, Cs0.3La0.7NiO3, SrNi0.75Co0.25O3, and Sr0.25Ba0.75NiO3, are among the oxide perovskite catalysts with the highest intrinsic activities. Our results demonstrate the potential of SR for accelerating the data-driven design and discovery of new materials with improved properties., Symbolic regression holds big promise for guiding materials design, yet its application in materials science is still limited. Here the authors use symbolic regression to introduce an activity descriptor predicting new oxide perovskites with improved oxygen evolution activity as corroborated by experimental validation.

The intrinsic material instability and toxicity of organic-inorganic hybrid perovskite CH3NH3PbI3 are the main challenges for the large-scale deployment of perovskite solar cells, propelling the se...

Summary The pump dynamometer card is a direct reflection of the operating conditions of the downhole pump, which is important for the diagnosis of sucker-rod pumping systems. In this paper, we propose a novel diagnostic method based on the estimation of the parameters from the polished-rod load vibration signal of sucker-rod pumping systems in a vertical well. In this study, we deduce a new analytic solution of the 1D wave equation of the sucker-rod string, which can be used for the predictive and diagnostic analyses. The relationship between the polished-rod load vibration and the pump equivalent impulse load based on the analytic solution is studied, and the diagnostic parameter estimating method is proposed. Therefore, the pump dynamometer card calculated method based on the surface dynamometer card is realized. This study shows that the method is efficient.

The figure of merit is of crucial importance in materials design to search for candidates with optimal functionality. In the field of photovoltaics, the bandgap ( E g) is a well-recognized figure of merit for screening solar cell absorbers subject to the Shockley-Queisser limit. In this paper, the bandgap as the figure of merit is challenged since an ideal solar cell absorber requires multiple criteria such as stability, optical absorption, and carrier lifetime. Multiple criteria make the quantitative description of material candidates difficult and computationally time-consuming. Taking halide perovskites as an example, we combine thermodynamic stability (Δ H d) and E g into a unified figure of merit and use Bayesian optimization (BO) to accelerate materials screening. We have found that, in comparison to an exhaustive search via multiple parameters, BO based on the unified figure of merit can screen optimal candidates ( E g,PBE between 0.6– 1.2 eV, Δ H d>− 29 meV per atom) more efficiently. Therefore, the proposed method opens a viable route for the search of optimal solar cell absorbers from a large amount of material candidates with less computational cost.

Engineering the band gap chemically by organic molecules is a powerful tool with which to optimize the properties of inorganic 2D materials. The obtained materials are however still limited by inhomogeneous compositions and properties at nanoscale and small adjustable band gap ranges. To overcome these problems in the traditional exfoliation and then organic modification strategy, an organic modification and then exfoliation strategy was explored in this work for preparing 2D organic metal chalcogenides (OMCs). Unlike the reported organically modified 2D materials, the inorganic layers of OMCs are fully covered by long-range ordered organic functional groups. By changing the electron-donating ability of the organic functional groups and the electronegativity of the metals, the band gaps of OMCs were varied by 0.83 eV and their conductivities were modulated by 9 orders of magnitude, which are 2 and 107 times higher than the highest values observed in the reported chemical methods, respectively., Here, the authors report a new class of 2D materials with inorganic metal chalcogenide layers covered by long-range ordered organic groups. The range of modulation on their band gaps and electrical conductivities are two times and 7 orders of magnitude better than the highest values reported so far.

Despite the rapid development of power conversion efficiencies, the commercialization of the emerging organic–inorganic hybrid perovskite solar cells still faces significant challenges. The major issues are their poor long-term stability and toxicity. In light of this, materials design and screening of novel stable perovskites is becoming a surging research direction. In contrast to conventional trial-and-error processes, materials genome techniques and high-throughput calculations have been prevalently applied in this area and accelerated materials discovery. Here, we present a review that summarizes recent progress in this field, which mainly focuses on four classes of perovskites including AM2+X3 halide single perovskites, AM4+Y3 chalcogenide single perovskites, A2M+M3+X6 halide double perovskites and A2M3+M5+Y6 chalcogenide double perovskites. The stability, electronic, optical, and defect properties are extensively discussed for each class of these perovskites, and their applicability as solar cell absorbers has also been commented on.

Aqueous zinc ion batteries are regarded as ideal candidates for stationary energy storage systems due to their low cost and high safety. However, zinc can readily grow into dendrites, leading to limited cycling performance and quick failure of the batteries. Herein, we propose a novel strategy to mitigate this dendrite problem, in which selectively-polarized ferroelectric polymer material (poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))) is employed as a surface protective layer on zinc anodes. Such a polarized ferroelectric polymer layer could enable a locally-concentrated zinc ion distribution along the coated surface and thus enable the horizontal growth of zinc plates. As a result, symmetrical zinc batteries using such anodes exhibits long cycling lifespan at 0.2 mA cm-2 , 0.2 mAh cm-2 for 2000 hours, and a high rate performance up to 15 mA cm-2 . Also, the full cell (including Zn-MnO2 battery and zinc ion capacitor) based on this anode has been demonstrated. This work provides a novel strategy to protect the zinc anode and even other metal anodes exploiting polymer ferroelectricity. This article is protected by copyright. All rights reserved.

In this article, efficiency performance of blue GaN/InGaN micro light emitting diodes (μ-LEDs) are investigated as functions of chip sizes, quantum barrier doping level and the number of quantum wells (QWs) by simulation. Internal quantum efficiency (IQE) and external quantum efficiency (EQE) drastically decrease with decreasing mesa sizes of μ-LEDs. The simulation indicates that μ-LEDs with n-doped quantum barriers can effectively suppress the Shockley-Read-Hall (SRH) nonradiative recombination and improve the efficiency compared to those with intrinsic quantum barriers in small μ-LEDs. The simulated results also show that decreasing the number of QWs can improve the IQE of μ-LEDs with higher radiative recombination rate in a single QW. An optimized design for 5×5 μm2 GaN/InGaN μ-LEDs with n-doped barriers and a single QW shows around 367% efficiency improvement at 1 A/cm2 comparing to the conventional intrinsic multiple QWs-based design in simulation.

We developed a density functional theory (DFT)-free approach for crystal structure prediction, in which a graph network (GN) is adopted to establish a correlation model between the crystal structure and formation enthalpies, and Bayesian optimization (BO) is used to accelerate the search for crystal structure with optimal formation enthalpy. The approach of combining GN and BO for crystal structure searching (GN-BOSS) can predict crystal structures at given chemical compositions with and without additional constraints on cell shapes and lattice symmetries. The applicability and efficiency of the GN-BOSS approach is then verified by solving the classical Ph-vV challenge. The approach can accurately predict the crystal structures with a computational cost that is three orders of magnitude less than that required for DFT-based approaches. The GN-BOSS approach may open new avenues for data-driven crystal structural predictions without using expensive DFT calculations.

The interesting physical and chemical properties of carbon nanotubes (CNTs) have prompted the search for diverse inorganic nanotubes with different compositions to expand the number of available nanotechnology applications. Among these materials, crystalline inorganic nanotubes with well-defined structures and uniform sizes are suitable for understanding structure–activity relationships. However, their preparation comes with large synthetic challenges owing to their inherent complexity. Herein, we report the example of a crystalline nanotube array based on a supertetrahedral chalcogenide cluster, K3[K(Cu2Ge3Se9)(H2O)] (1). To the best of our knowledge, this nanotube array possesses the largest diameter of crystalline inorganic nanotubes reported to date and exhibits an excellent structure-dependent electric conductivity and an oriented photoconductive behavior. This work represents a significant breakthrough both in terms of the structure of cluster-based metal chalcogenides and in the conductivity of crystalline nanotube arrays (i.e., an enhancement of ~4 orders of magnitude)., Interesting properties of carbon nanotubes prompt a search for diverse inorganic nanotubes. Here, the authors report a supertetrahedral chalcogenide cluster-based semiconducting nanotube array that exhibits high electric conductivity and oriented photoconductive behavior.

Two-dimensional Dion-Jacobson (DJ) perovskites have shown improved structure stability in comparison with Ruddlesden-Popper (RP) perovskites. However, the mechanism behind the improved stability is still largely unexplored. Here a multifluorinated aromatic spacer, namely, 4F-PhDMA, has been successfully developed for 2D DJ perovskites. It is found that the 2D DJ perovskite with a 4F-PhDMA spacer exhibits a high dissociation energy due to the multiple noncovalent interactions. The optimized 2D DJ device based on the 4F-PhDMA spacer (n = 4) exhibits a champion efficiency of 16.62% with much improved light and thermal stability. This efficiency is much higher than that of the control device using an unfluorinated spacer (n = 4, PCE = 10.11%) and is among the highest efficiencies in aromatic-spacer-based 2D DJ perovskite solar cells (PSCs). Our work highlights the importance of incorporating multiple noncovalent interactions in the 2D DJ perovskite by employing a multifluorinated aromatic spacer to achieve DJ PSCs with both high efficiency and high stability.

P–O–H polycondensation −O–Cu–O– ion-bonded bridges were formed in copper phosphate thermal insulation materials by mixing Al(OH)3 dissolved in H3PO4 with CuO filler and Al2O3, SiC, ZrC, and Cr2O3 as curing accelerators, alone or in combination. The effects of different additive combinations on the curing behavior and thermal stability of the copper phosphate thermal insulation material matrixes were compared using thermogravimetry/differential scanning calorimetry, X-ray diffractometry, and scanning electron microscopy. The copper phosphate materials exhibit good thermal stabilities and low thermal conductivities. The thermal weight losses before and after ceramic reinforcement were 4–19.8 and 3.8–9.4%, respectively, and the thermal conductivities of the P–O–H polycondensation −O–Cu–O– ion-bonded bridges formed in the copper phosphate thermal insulation materials were in the range of 0.656–1.824 W/(m·K).

Tin-based compounds are deemed as suitable anode candidates affording promising sodium-ion storages for rechargeable batteries and hybrid capacitors. However, synergistically tailoring the electrical conductivity and structural stability of tin-based anodes to attain durable sodium-ion storages remains challenging to date for its practical applications. Herein, metal-organic framework (MOF) derived SnSe/C wrapped within nitrogen-doped graphene (NG@SnSe/C) is designed targeting durable sodium-ion storage. NG@SnSe/C possesses favorable electrical conductivity and structure stability due to the “inner” carbon framework from the MOF thermal treatment and “outer” graphitic cage from the direct chemical vapor deposition synthesis. Consequently, NG@SnSe/C electrode can obtain a high reversible capacity of 650 mAh·g−1 at 0.05 A·g−1, a favorable rate performance of 287.8 mAh·g−1 at 5 A·g−1 and a superior cycle stability with a negligible capacity decay of 0.016% per cycle over 3,200 cycles at 0.4 A·g−1. Theoretical calculations reveal that the nitrogen-doping in graphene can stabilize the NG@SnSe/C structure and improve the electrical conductivity. The reversible Na-ion storage mechanism of SnSe is further investigated by in-situ X-ray diffraction/ex-situ transmission electron microscopy. Furthermore, assembled sodium-ion hybrid capacitor full-cells comprising our NG@SnSe/C anode and an active carbon cathode harvest a high energy/power density of 115.5 Wh·kg−1/5,742 W·kg−1, holding promise for next-generation energy storages.

In this work the interactions of an edge dislocation with Cu precipitates of different diameters in α-Fe were investigated by molecular dynamics simulation. The influence of Fe atoms or outer Ni shell on the interactions was also studied. It is found that the dislocation stress field assists a structure transformation of the precipitates from BCC to FCC/HCP during the gliding of the dislocation. For the Cu precipitates with diameters less than 4 nm, most of the atoms return to BCC structure after the dislocation leaves away. The structure transformation of Cu-Fe precipitates is identical with pure Cu precipitates with diameters less than 4 nm. The outer Ni shells contribute the precipitate transformation to FCC/HCP structure and reduce the critical diameter of structure transformation. The critical resolved shear stress (CRSS) has been calculated for the precipitates and it is demonstrated that the FCC/HCP fraction of the precipitate contributes to the CRSS in this interaction.

Metal–organic framework (MOF) membranes exhibit enormous potential for molecular mixtures’ sieving with high permeance, as well as high selectivity. Current MOF composite membranes suffer from unduly thick MOF layer and poor adhesion to the porous support. By a simple multiple seeded growth method, the ultrathin (less than 200 nm) and defect-free MOF layer is prepared on a ZIF-8 in-situ embedded PSf substrate. On the one hand, the nano-sized ZIF-8 crystals embedded on substrate surface act as anchors linking the ZIF-8 layer with the substrate. On the other hand, these ZIF-8 crystals also act as seeds to promote the formation of the ZIF-8 layer and reduce the crystallization time, leading to a thin and continuous ZIF-8 layer. The obtained ultrathin ZIF-8 membrane shows superior gas molecular sieving performance, with a high gas permeance of 24.5 × 10−7 mol/m2/s/Pa for H2 and selectivity of 4.5, 23.2, and 31.5 for H2/CO2, H2/N2, and H2/CH4, respectively. In addition, neither the permeance or the selectivity shows a noticeable change after 3% elongation, which indicates high mechanical integrity of the MOF layer on the ZIF-8 in-situ embedded PSf substrate. We believe that the utilization of MOF in-situ embedded polymer substrate offers a universal and simple strategy strengthening and thinning the MOF layer of its composite membranes.

We reported a facile analysis and reduction of oxygen vacancy ( V O • • ) in 0.7Bi(Fe1-xScx)O3-0.3BaTiO3 (0≤x≤0.08) ceramics. The leakage current mechanism was investigated intensively. Our results indicated that oxygen vacancies are the main cause for the high conductivity in BF-BT ceramics, and their concentration was quantitatively estimated from the Bi3+ content and the average oxidation state of iron. The V O • • concentration was effectively suppressed and the insulation resistance was enhanced by almost two orders of magnitude after doping 2%mol Sc3+. The enhanced insulation resistance contributed to excellent piezoelectric properties with d33 = 165 pC/N, TC = 505 °C, and kp = 26%. The proposed analysis method used to quantify the V O • • concentration provides valuable indications to reduce the leakage current density and improve the piezoelectric properties of BF-BT based ceramic.

Ni segregation at the interfaces of Cu-rich precipitates in Fe–Cu–Ni alloys is investigated using ab initio based models with Monte Carlo simulations and density functional theory calculations. It is demonstrated that Ni segregation decreases with increasing temperature and increases in proportion to global Ni concentration. The predicted Ni segregation profiles are in quantitative agreement with experiments. Analysis show that both the temperature dependent alloy energetics and the configurational entropy are important for predicting Ni segregation. The results also reveal that Ni segregation reduces the interfacial structure stability, especially at low temperatures and with high global Ni concentrations, which could be used to explain the Ni enhanced hardening in Fe–Cu–Ni alloys.

In this work, a facile strategy is proposed to construct stretchable electronics based on agarose hydrogels. The hot agarose solution is casted onto a template with patterned Ag nanowires, endowing agarose hydrogel with patterned conductive surface. After further heating treatment, Ag nanowires can be embedded into the agarose hydrogel, which improves the stability of Ag pattern and has no obvious effect on the conductivity of hydrogels. The agarose hydrogel with patterned Ag nanowires is certified to be an effective stretchable electrode to record the motion of joints, which has great potential applications in the field of wearable devices.

Although Sn-Pb perovskites sensing near-ultraviolet-visible-near-infrared light could be an attractive alternative to silicon in photodiodes and imaging, there have been no clear studies on such devices constructed on metal/silicon substrates, hindering their direct integration with complementary metal-oxide semiconductor (CMOS) and silicon electronics. Typically, high surface roughness and severe pinholes of Sn-rich binary perovskites make it difficult for them to fulfill the requirements of efficient photodiodes and imaging. These issues cause inherently high dark current and poor (dark and photo-) current uniformity. Herein, we propose and demonstrate the room-temperature crystallization in the Sn-rich binary perovskite system to effectively control film crystallization kinetics. With experimental and theoretical studies of the crystallization mechanism, we successfully tune the density and location of nanocrystals in precursor films to achieve compact nanocrystals, which coalesce into high-quality (smooth, dense, and pinhole-free) perovskites with intensified preferred orientation and decreased trap density. The high-quality perovskites reduce dark current and improve (dark and photo-) current uniformity of perovskite photodiodes on CMOS-compatible metal/silicon substrates. Meanwhile, self-powered devices achieve a high responsivity of 0.2 A/W at 940 nm, a large dynamic range of 100 dB, and a fast fall time of 2.27 μs, exceeding those of most silicon-based imaging sensors. Finally, a 6 × 6 pixel integrated photodiode array is successfully demonstrated to realize the imaging application. The work contributes to understanding the fundamentals of the crystallization of Sn-rich binary perovskites and advancing perovskite integration with Si-based electronics.

In this work, the effects of mixing sequence of graphene oxide (GO) and warm mix additives on the mechanical properties of the composite modified asphalt binder (CMAB) were evaluated. The warm mix additives included Sasobit® and waste cooking oil (WCO). The experimental results indicated that the combination of GO and Sasobit® can greatly improve the high-temperature performance of asphalt, and the blending of GO and WCO can significantly enhance the fatigue and low-temperature properties of the asphalt. Statistical analysis results suggested that different GO and Sasobit® mixing sequences have significant influence on the workability, mechanical properties, and chemical reaction characteristics of the CMABs, while the influence of different GO and WCO mixing sequences on these properties of asphalt is not significant. In conclusion, GO is suggested to be added first to achieve the better performance of the nano-modified asphalt binder.

A novel sliding contact material of pyrolytic carbon (PyC)-coated copper foam/carbon composite was fabricated by a chemical vapor deposition (CVD) technology, followed by several densifying processes of furan resin impregnation and carbonization. Microstructure, electrical and thermal conductivities and current-carrying tribological performance were investigated. The results show PyC crystallites are evenly arranged on the copper foam surface after the CVD process. Because interface wettability between the copper foam and resin carbon matrix is improved by the PyC layer, the composite has a dense structure and a good interface bonding. The composite has obviously more advantages than the carbon-based pantograph strips in the density, electrical and thermal conductivities, due to the copper foam with three-dimensional structure. Friction and wear behaviors were investigated using a current-carrying friction tester. As the electrical current increases, wear rate and wear surface temperature continually increase, and friction coefficient changes from wildly fluctuating to stable. The high electrical current causes high temperature of wear surface and severe wear of oxidization and arc erosion. Copper oxide particles can improve wear surface roughness and change the sliding friction to the rolling friction between the friction couples. In addition, two physical models are schematically illustrated to understand wear mechanism during the current-carrying friction tests.

Chalcogenide perovskites ABX3 (A = Ca, Sr, or Ba; B = Ti, Zr, or Hf; and X = O, S, or Se) have been considered as promising candidates for overcoming the stability and toxic issues of halide perovskites. In this work, we unveil the disparity of the nature of the band gap between halide and chalcogenide perovskites. First-principles calculations show that the prototype cubic phase of chalcogenide perovskites exhibits indirect band gaps with the valence band maximum and the conduction band minimum located at R and Γ points, respectively, in the Brillion zone. Therefore, the optical transitions near band edges of chalcogenide perovskites differ from those of its halide counterparts, although its stable orthorhombic phase embodies a direct band gap. We have further found that the direct-indirect band gap difference of chalcogenide perovskites in the cubic phase demonstrates a linear correlation with t + μ, where t and μ are the tolerance and octahedral factor, respectively, thereby providing a viable way to search chalcogenide perovskites with a quasi-direct band gap.

Two dimensional (2D) materials-based plasmon-free surface-enhanced Raman scattering (SERS) is an emerging field in nondestructive analysis. However, impeded by the low density of state (DOS), an inferior detection sensitivity is frequently encountered due to the low enhancement factor of most 2D materials. Metallic transition-metal dichalcogenides (TMDs) could be ideal plasmon-free SERS substrates because of their abundant DOS near the Fermi level. However, the absence of controllable synthesis of metallic 2D TMDs has hindered their study as SERS substrates. Here, we realize controllable synthesis of ultrathin metallic 2D niobium disulfide (NbS2) ( 160 μm). We have explored the SERS performance of as-obtained NbS2, which shows a detection limit down to 10-14 mol·L-1. The enhancement mechanism was studied in depth by density functional theory, which suggested a strong correlation between the SERS performance and DOS near the Fermi level. NbS2 features the most abundant DOS and strongest binding energy with probe molecules as compared with other 2D materials such as graphene, 1T-phase MoS2, and 2H-phase MoS2. The large DOS increases the intermolecular charge transfer probability and thus induces prominent Raman enhancement. To extend the results to practical applications, the resulting NbS2-based plasmon-free SERS substrates were applied for distinguishing different types of red wines.

Multi-walled carbon nanotube (MWCNT) and carbon fiber and flaky graphite reinforced copper foam/furan resin composite for a novel sliding contact material was fabricated using an acid purify and ultrasonic dispersion technology, followed by a mold pressing process. The microstructure, electrical resistivity, impact strength and current-carrying friction performances of the composites were measured to investigate the effect of the different MWCNT contents. The results showed that the MWCNTs had a good dispersion state in the composite and the percolation threshold was approximate 0.074–0.185 vol%. As addition of the MWCNTs, the impact strength and wear resistance of the composites could be raised by 45% and 22%, respectively.