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This work analyzes the free vibration of a spinning functionally graded graphene platelet-reinforced metal foam (FG-GPLRMF) beam. The differential transformation method is extended to analyze flap-wise bending vibration and chordwise bending vibration with Coriolis force effect for the first time. The beam is modeled using the Euler–Bernoulli beam theory. The Halpin–Tsai micromechanics model is utilized to predict effective material properties. Various types of graphene platelet (GPL) and porosity distributions are considered. The governing equations and corresponding boundary conditions of the FG-GPLRMF beam are obtained via Hamilton’s principle. Results show that the vibration characteristics of the FG-GPLRMF beam are affected by the GPL geometry size, types of porosity, and GPL distributions. Among different types of porosity, the Porosity-A causes the highest fundamental natural frequency, while the Porosity-B corresponds to the lowest one of the spinning FG-GPLRMF beam in most cases. Moreover, the GPL pattern and porosity distribution have a coupled effect on the bending vibration of the spinning FG-GPLRMF beam.

Thermal barrier coatings (TBCs) are facing the challenge of chloride salt hot corrosion in the marine environment. In the manuscript, 7YSZ feather-like columnar structure coatings were prepared by plasma spray-physical vapor deposition (PS-PVD). The Al2O3-modification based on in-situ synthesis was used as the strategy to improve the hot corrosion resistance of the coating. Then, the coatings were subjected to test of 900 °C NaCl thermal exposure and combustion gas-salt spray ablation. The microstructure and phase evolution results of the coatings show that NaCl has a strong corrosive effect on the as-sprayed PS-PVD TBC and leading to catastrophic oxidation. In contrast to this, the Al2O3-modified coating shows good corrosion resistance. In the hot corrosion behavior of NaCl, the metal elements in the bond layer are rapidly oxidized and accumulated on the surface of TGO layer through the electrochemical corrosion mechanism, which makes the TGO thicken rapidly. After combustion gas-salt spray corrosion, the YSZ coatings sintered and the evolution of mechanical properties were analyzed. Compared with the initial sprayed state, the hardness of the as-sprayed coating and the Al2O3-modified coating increased by 13.04 GPa and 11.47 GPa, respectively. And the elastic modulus of as-sprayed coating and Al2O3-modified coating increased by 133.00 GPa and 129.60 GPa, respectively.

Transition metal electrocatalysts with high activity and long durability are desired for methanol oxidation reaction (MOR). Here, the surface fluorinated nickel-graphene nanocomposites (F–Ni–G) are synthesized via the reduction of Si–H bonds produced by silicon and ammonium fluoride in hydrothermal condition. During this process, ionic nickel-F bonds and semi-ionic C–F bonds are introduced to the catalysts as confirmed by X-ray photoelectron spectroscopy. When F–Ni–G nanocomposites are employed as MOR catalysts, the surface fluorination is contributed to the formation of nickelic, which can increase the activity and kinetics for MOR. The onset oxidation potential of F–Ni–G-2 for methanol oxidation is 53 mV lower than that of the Ni/G catalyst without fluorine. The mass activity of F–Ni–G-2 (2493.3 A g−1) is 3.90 folds than that of Ni/G (638.5 A g−1). In addition, the density functional theory calculation indicates that the modified fluorine in graphene results in the decreased reaction energy barrier from ∗CO to ∗COOH step in MOR. The strong electronegativity of F atom makes intermediates easier to attract OH− groups and repel protons, which is conductive to decrease the reaction energy barrier for MOR. Such a facile method for the fabrication of the surface fluorinated catalytic system may be extended to the preparation of other transition metal electrocatalysts.

Post-heat treatment takes a key role for the enhancement of mechanical properties in selective laser melting (SLM) additive manufacturing (AM) of 6xxx series aluminum alloy. To understand the basic mechanism for changes of mechanical properties in the SLM process and the following post-heat treatment, the finite element model and the precipitate evolution (PE) model of SLM AM were established and combined. Results show that the hardness of the fabricated AM component can reach 91.47 HV at 170 °C for 18.8 h, which is 63.1% higher than the as-fabricated state. The comparison of hardness in as-fabricated AM component with experiments shows the validity of the proposed models. Further work on chemical composition shows that the selection of powder particle can greatly affect the hardness of the fabricated AM component. In the selection of 6xxx series aluminum alloy powder, higher Mg and Si contents in their solubility domains lead to higher generation of Mg2Si nano-size precipitates and then cause higher hardness of AM specimen. After the optimal post-heat treatment, the maximum hardness can exceed 100 HV.

The theoretical modeling of a functionally graded (FG) graphene nanoplatelet (GPL)-reinforced assembled beam–plate structure resting on elastic supports is presented for the first time, and its free vibration analysis is performed. Herein, the assembled structure is modeled according to the Kirchhoff plate theory and the Rayleigh beam theory. The graphene nanoplatelets (GPLs) gradiently distribute in the beam’s radial direction and in the plate’s thickness direction, respectively. By adopting the rule of mixture and the Halpin–Tsai model, the effective material properties can be obtained. By employing the Lagrange’s equation and considering the effects of Coriolis force and centrifugal force, the coupled governing equations of the assembled structure are determined. Furthermore, the assumed modes method and substructure modal synthesis method are applied to obtain the frequencies of the assembled beam–plate structure. A comprehensive numerical investigation is carried out to discuss the influence of the structural and material parameters on the vibration behavior of the beam–plate structure.

Highly conductive and elastic three-dimensional (3D) porous carbon materials are ideal platforms to fabricate electrodes for high-performance compressible supercapacitors. Herein, a robust, highly conductive, and elastic carbon foam (CF) hybrid material is reported, which is fabricated by integrating cellulose nanofiber/multiwalled carbon nanotube (CNF/MWCNT) aerogel sheets with a melamine sponge (MS), followed by carbonization. The carbonized CNF/MWCNT aerogel sheets contribute to the high conductivity and specific surface area of the CF, and the 3D network-like skeleton derived from the carbonization of the MS enhances the elasticity and stability of the CF. More importantly, the CF possesses good scalability, allowing the introduction of electroactive materials such as polypyrrole (PPy) and Fe3O4 to fabricate high-performance compressible PPy–CF and Fe3O4–CF electrodes. Moreover, an assembled PPy–CF//Fe3O4–CF device shows reversible charging–discharging at a voltage of 1.6 V and demonstrates a high specific capacitance (172.5 F/g) and an outstanding energy density (59.9 W h/kg). The device exhibits capacitance retention rates reaching 98.3% and stable energy storage characteristics even under different degrees of compressive deformation. This study offers a scalable strategy for fabricating high-performance compressible supercapacitors, thereby providing a new means of satisfying the energy storage needs of portable electronic devices that are prone to deformation.

Excess lead iodide (PbI2) plays a crucial role in passivating the defects of perovskite films and boosting the power conversion efficiency (PCE) of perovskite solar cells (PSCs). However, the photolysis of PbI2 is easily triggered by light illumination, which accelerates the decomposition of perovskite materials and weakens the long-term stability of PSCs. Herein, the high light tolerance of lead iodide (PbI2) is reported by introducing an electron-donor molecule, namely, 2-thiophenecarboxamide (2-TCAm), to strengthen the [PbX6]4- frame. Characterization reveals that the retarded decomposition of PbI2 is attributed to the interactions between Pb2+ and the organic functional groups in 2-TCAm as well as the optimized distribution of PbI2. The crystallization and morphology of 2-TCAm-doped perovskite films are improved simultaneously. The 2-TCAm-based PSCs achieve a 16.8% increase in PCE and nearly 12 times increase in the lifetime as compared to the reference device. The demonstrated method provides insight into the stability of PbI2 and its influence on PSCs.

This paper presents an investigation on vibration characteristics of graphene nanoplatelet (GPL) reinforced disk-shaft rotor with eccentric mass resting on elastic supports. The shaft is made of co...

In the present study, we analyze the nonlinear forced vibration of thin-walled metal foam cylindrical shells reinforced with functionally graded graphene platelets. Attention is focused on the 1:1:1:2 internal resonances, which is detected to exist in this novel nanocomposite structure. Three kinds of porosity distribution and different kinds of graphene platelet distribution are considered. The equations of motion and the compatibility equation are deduced according to the Donnell’s nonlinear shell theory. The stress function is introduced, and then, the four-degree-of-freedom nonlinear ordinary differential equations (ODEs) are obtained via the Galerkin method. The numerical analysis of nonlinear forced vibration responses is presented by using the pseudo-arclength continuation technique. The present results are validated by comparison with those in existing literature for special cases. Results demonstrate that the amplitude–frequency relations of the system are very complex due to the 1:1:1:2 internal resonances. Porosity distribution and graphene platelet (GPL) distribution influence obviously the nonlinear behavior of the shells. We also found that the inclusion of graphene platelets in the shells weakens the nonlinear coupling effect. Moreover, the effects of the porosity coefficient and GPL weight fraction on the nonlinear dynamical response are strongly related to the porosity distribution as well as graphene platelet distribution.

A structure-based modeling of the CaO−‘FeO’−MgO−Al2O3−SiO2 system and its subsystems was investigated based on iron extraction from nickel slag by aluminum dross. Parameters optimization in the present model indicated that the coefficient of free O2− in FeO, $$a_{{{\text{O}}_{{{\text{FeO}}}}^{{2 - }} }}$$ , on the lengths of network linkage had the largest value and $${\text{O}}_{{{\text{FeO}}}}^{{2 - }}$$ (free O2− in FeO) had the largest mobility. The coefficients of bridging oxygen (aSi−O−Al and aAl−O−Al) were lower than those of non-bridging oxygen and free oxygen (O2−). Viscosity prediction for the CaO−‘FeO’−(8 wt.%) MgO−Al2O3−SiO2 system was conducted at a fixed slag basicity, which indicated that the predicted viscosity changed monotonously with the FeO content. However, the non-monotonous evolution with Al2O3 content reflected the amphoteric behavior of Al2O3. In addition, the performances of the present model in predicting viscosity from binary (‘FeO’−SiO2) to quinary (CaO−‘FeO’−MgO−Al2O3−SiO2) system were analyzed and a comparison with the established models was made.

Low back pain associated with degenerative disc diseases has been a major health concern that brings suffering to the patients physically and economically. Many existing therapeutic strategies provide short-term relief of symptoms rather than treatment of the underlying cause. Development of an engineered tissue for disc regeneration is still in its infancy due to the limited autologous healthy disc cell source from the patients. It is also challenging to mimic the complexity of micro-architecture in the native disc tissue that determine their unique structural properties. To date, simple tissue models that mimic the annulus fibrosus (AF) micro-environment for understanding the potential of mesenchymal stem cells (MSCs) in AF tissue engineering are still lacking. In this study, the assembly of a coiled hydrogel microfiber has shown its capability to encapsulate MSCs and create an engineered tissue model that mimics the multiple lamellae of native AF. Using this model, we investigated the potential of MSCs that were previously induced by ascorbic acid (AA). Compared to non-induced MSCs, AA-induced MSCs exhibited significant increase in AF-associated biomarkers during later development in the engineered AF tissue model and also encouraged collagen accumulation through the down-regulated catabolic gene MMP1 and upregulated anti-catabolic gene TIMP1. Furthermore, AA-induced MSCs exhibited a Col2/Col1 ratio closer to that of a native AF tissue. These results suggested that AA-induced MSCs could be a potential cell source for AF tissue engineering and this established tissue model may provide a simple tool for successful AF tissue engineering strategies in the future.

Memristive devices with in-memory computing functions have broad application prospects in the field of artificial intelligence. The development of memristive devices that integrate multi-functions of nonvolatile rewritable memory and biomimicking memristor activity requires the design and preparation of well-tailored memristive materials. In this contribution, MoS2 nanosheets (MoS2 NSs) were modified with polydopamine (PDA) through mussel-inspired chemistry, and then the metal phthalocyanine was covalently tethered onto their surface to form a two-dimensional MoS2-PDA–tBu4PcTiO nanomaterial with a sandwich structure. The fabricated electronic device with the Al/MoS2-PDA–tBu4PcTiO/ITO structure exhibits nonvolatile resistive memory characteristics in a large scanning voltage window and an ON/OFF current ratio of more than 103. Interestingly, the device exhibits history-dependent memristive characteristics in a small scanning voltage window. The potentiation and depression, as well as the “learning–forgetting–relearning” processes of a biological synapse, have been successfully emulated in this biomimicking memristor. This work is expected to provide new insights into the development of multifunctional memristive devices.

Design and fabrication of high-efficiency electrocatalysts are important to generate hydrogen via urea electrocatalysis with the minimum required energy. In this study, in situ growth of a branch-like Mo-doped Ni3S2 nanoforest on Ni foam was achieved through a facile one-pot hydrothermal process. The as-obtained catalyst exhibited excellent activity and robust durability because of its unique hierarchical nanostructures and doping-optimized electronic structural configuration, and required merely 1.33 V (vs. RHE) and 90 mV (overpotential) to attain a current density of 10 mA cm−2 for the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER), without any noticeable loss in activity even after 120 h of operation. On the basis of the experimental results and theoretical calculations, it was confirmed that the incorporation of Mo in Ni3S2 altered the morphology and electronic structure of the catalyst; hence, more active sites were exposed and the Gibbs adsorption energy of the intermediates in the UOR was optimized. Notably, the overall urea electrolysis cell could afford a low voltage of 1.45 V (vs. RHE) to attain a current density of 10 mA cm−2 and showed excellent durability over 120 h. The findings from this study provide new insights into efficient electrocatalysts for urea electrolyzers, which hold great potential in electrochemical energy conversion and sewage treatment applications.

Smaller fibers are welcome in many applications due to larger surface area, but there is a threshold for smallest fibers for a fixed spinning system. In order to further improve surface area, hierarchical structure is considered in this paper using electrospinning. A bi-solvent system is used in our experiment for fast solvent evaporation. Unsmooth nanofibers are obtained, and the formation mechanism is elucidated.

Natural wood has attracted enormous attention in the electrocatalysis field due to its hierarchical porous structure and excellent electrical conductivity after carbonization. Different wood species as a carbon substrate have a significant impact on the electrocatalytic performance. Herein, to fundamentally understand the electrochemical catalytic performance of carbonized natural wood, the oxygen evolution reaction (OER) performances of various carbonized wood (pine, fir, poplar, and balsa) calcined at different temperature were studied. The OER performance of wood carbon was improved with the increase of carbonization temperature, and better OER performance was obtained at a carbonization temperature of 900 °C. The overpotentials of pine carbon, fir carbon, poplar carbon, and balsa carbon are 507 mV, 539 mV, 490 mV, and 651 mV, respectively, at a current density of 10 mA cm−2. The pore structure of wood carbon significantly affected the OER activity. Among the four types of wood carbon, poplar carbon exhibited better electrocatalytic activity due to its cross-distribution of pores and pore diameter. This work is conducive to the selection of suitable wood carbon substrates for the preparation of environmentally friendly electrocatalysts, and is of great significance for improving the efficiency of electrocatalytic water splitting to produce clean and sustainable hydrogen energy.

Organic-inorganic hybrid perovskite has been verified as a suitable semiconductor for hot carrier solar cells via transient absorption spectroscopy. Recently, an internally photoemitted hot carrier (IPHC) solar cell with a novel and innovative structure based on organic-inorganic hybrid perovskite has been achieved. This is a breakthrough in hot carrier study based on perovskite material. To further improve the performance of this newly developed hot electron collection device, a simple and efficient method of adding lithium fluoride (LiF) surface modification layer was applied onto the outmost perovskite layer that benefits both reduction of the trap states and formation of interface dipoles. The IPHC device with LiF modification layer shows a remarkable increase of the short-circuit current density with 20.31% increment. This successful interface engineering proposes a new guideline for further optimizing the performance IPHC and also traditional solar cells based on perovskite.

Metal halide perovskite light-emitting diodes (PeLEDs) have been recognized as emerging candidates for next-generation solution-processed electronic display technology, and great progress has been made in recent years. However, their poor operational stability is yet to be solved. Here, we present a reformative all-inorganic red-emission PeLED based on the passivation effect caused by the incorporation of zinc ions into perovskites for enhancing the efficiency and operational stability. A high-quality quasi-two-dimensional perovskite CsPbI3−xBrx thin film with good crystallinity is obtained, benefiting from the combination of large organic ammonium ions (PEA+ ions) and inorganic salt zinc iodide (ZnI2). As a result, ZnI2-passivated CsPbI3−xBrx PeLEDs emitting at 666 nm show a maximum external quantum efficiency of 9.93% and a maximum brightness of 4258 cd m−2. More importantly, the PeLEDs achieve a long half-lifetime of about 2667 h at an initial luminance of 100 cd m−2. This work provides a facile method to obtain stable and efficient red-emission PeLEDs.

The dropping mechanism in the electrospinning process is elucidated. A moving jet becomes thinner at the initial stage due to the acceleration caused by the electrostatic force. When the jet diameter reaches a threshold, beyond which the jet breaks into drops and daughter jets, dropping occurs. The drops will finally form microspheres. Effects of applied voltage, flow rate, polymer?s concentration, and receptor?s distance on the dropping process are theoretically analyzed and experimentally verified. This paper gives a general strategy for fabrication of smooth fiber, microspheres, and their mixture.

Organic-inorganic hybrid lead halide perovskites are potential candidates for next-generation light-emitting diodes (LEDs) in terms of tunable emission wavelengths, high electroluminescence efficiency, and excellent color purity. However, the device performance is still limited by severe non-radiative recombination losses and operational instability due to a high degree of defect states on the perovskite surface. Here, an effective surface engineering method is developed via the assistance of guanidinium iodide (GAI), which allows the formation of surface-2D heterophased perovskite nanograins and surface defect passivation due to the bonding with undercoordinated halide ions. Efficient and stable red-emission LEDs are realized with the improved optoelectronic properties of GAI-modified perovskite nanograins by suppressing the trap-mediated non-radiative recombination loss. The champion device with a high color purity at 692 nm achieves an external quantum efficiency of 17.1%, which is 2.3 times that of the control device. Furthermore, the operational stability is highly improved, showing a half-lifetime of 563 min at an initial luminance of 1000 cd m-2. The proposed GAI-assisted surface engineering is a promising approach for defect passivation and phase engineering in perovskite films to achieve high-performance perovskite LEDs.

Herein, lignin derived hierarchical porous carbon (LHPC) supported Pd nanoparticles (Pd/LHPC) were synthesized and developed as advanced electrocatalysts for ethanol oxidation. In the Pd/LHPC, the special hierarchical porous carbon with the interconnected micropores and mesopores uniformly distribute on the surface and walls of macropores can provide facile transport for electroactive species and more reaction available surface. The Pd/LHPC exhibits larger specific electrochemically active surface area, higher electrocatalytic activity and better stability toward the oxidation of ethanol than the black carbon (Vulcan XC-72) supported Pd (Pd/XC-72) and commercial Pd/C electrocatalysts. The strategy reported will open a new road to effectively use industrial waste to synthesize advanced carbon material for efficient electrocatalysts and other electrochemical energy-conversion devices.

All-inorganic perovskite cesium lead iodide/bromide (CsPbI2Br) is considered as a robust absorber for perovskite solar cells (PSCs) because of its excellent thermal stability that guarantees its long-term operation stability. Efficient CsPbI2Br PSCs are available when obtaining low energy loss, which needs efficient charge generation, less charge recombination, and balanced charge extraction. However, numerous traps in perovskites hinder the photon-electron conversion process. Herein, hierarchical manipulation of charge recombination is proposed for CsPbI2Br PSCs featuring low energy loss. Nonselective trap reduction and selective halogen vacancy passivation are performed using 2,2'-(ethylenedioxy)diethylamine and phenylbutylammonium iodide for the bottom and top contacts, respectively. Because of all-around suppressed charge recombination, balanced charge extraction and suppressed hysteresis are realized. The champion PSC achieves an open-circuit voltage of 1.30 eV, a fill factor of 80.2%, and a power conversion efficiency of 16.6% that is 28.6% higher than that of the reference device. Moreover, the thermostability of PSCs is simultaneously enhanced because of the limited defect-assisted degradation.

Mixed A-site engineering is an emerging strategy to overcome the difficulties in realizing high-quality perovskite films together with high ambient stability. Particularly, the α-FACsPbI3-based hybrid perovskites have been considered as a promising candidate for solar cell applications. However, the degradation mechanism of α-FACsPbI3 hybrid perovskites induced by light illumination remains unclear. Here, the illumination-caused instability of α-FACsPbI3 hybrid perovskites is investigated using various surface detection technologies, including photoelectron spectroscopy, scanning electron microscopy, and grazing incidence X-ray diffraction. The experimental findings reveal that the A-site vacancies arise from the migration of Cs+ cations from the perovskite surface into the bulk under light illumination, while their content is dependent on the light energy. The visible light enlarges the crystal lattice on the perovskite surface, leading to the Cs+ cation migration along with the lattice distortion of the PbI64- octahedron and phase separation. However, the ultraviolet light further causes a stronger interaction between FA+ and [PbI6]4-, leading to the partial decomposition of [PbI6]4- into Pb0 and I-. These results enrich the photodegradation mechanism, guiding the design of efficient and stable perovskite solar cells through surface passivation to suppress the Cs+ cation migration and to increase the octahedron dissociation energy.

This paper aims to research the high-temperature oxidation behavior of TiC/Mo composite. Adding 5 wt.% TiC, Mo-based composite was prepared by Spark Plasma Sintering. The composite was oxidized at different temperatures (400°C, 600°C, 800°C, 1000°C and 1200°C) and times (5 min, 10 min, 20 min, 30 min and 60 min). When oxidation was at 400-1000°C for 20 minutes, the degree of oxidation intensifies with the increase of temperature, and TiO2 was observed at 1000°C. While the temperature was 1200°C, the oxidation rate gradually decreased with the increase of time. The result shows that the formation of TiO2 can inhibit the oxidation process.

The dissociation of natural gas hydrate is an endothermic reaction controlled by the heat transfer, which is closely associated with the employed exploitation methods and well configurations. The m...

The visual aesthetic that involves color, brightness, and glossiness is of great importance for building integrated photovoltaics. Semitransparent organic solar cells (ST-OSCs) are thus considered as the most promising candidate due to their superiority in transparency and efficiency. However, the realization of high color purity with narrow bandpass transmitted light usually causes the severely suppressed transparency in ST-OSCs. Herein, we present a spectrally selective electrode (SSE) by imitating the integrating strategy of beetle cuticle for achieving narrow bandpass ST-OSCs with high efficiency and long-term stability. The proposed SSE allows for efficient light-selective passage, leading to tunable narrow bandpass transmitted light from violet to red. An optimized power conversion efficiency of 15.07% is achieved for colorful ST-OSCs, which exhibit color purity close to 100% and a peak transmittance approaching 30%. Long-term stability is also improved for ST-OSCs made with this SSE due to the light-rejecting and the moisture-blocking abilities. The realization of bright and colorful ST-OSCs also indicates the application potential of SSEs in light-emitting diodes, lasers, and photodetectors.

In the paper, ZnO-deposited activated carbon composite (ZnO-AC) was firstly prepared in a simple two-step preparation process, and then covered with nano-graphene oxide to give the NGO-ZnOAC composite. The successful deposition of ZnO and NGO on the AC surface was demonstrated by various experiments, and the ZnO nanoparticles showed a mean diameter size mainly within about 10 nm. The specific surface area of the NGO-AC and NGO-ZnO-AC decreased from 67.74 m²/g of the parent AC to 32.54 and 11.43 m²/g, respectively. The fabricated NGO-ZnO-AC showed excellent adsorptive behaviors towards CrO2-₄ and Cu2+ ions, outperforming both ZnO-AC and AC.

Although perovskite light-emitting diodes (PeLEDs) are promising for next-generation displays and lighting, their efficiency is still considerably below that of conventional inorganic and organic counterparts. Significant efforts in various aspects of the electroluminescence process are required to achieve high-performance PeLEDs. Here, we present an improved flexible PeLED structure based on the rational interface engineering for energy-efficient photon generation and enhanced light outcoupling. The interface-stimulated crystallization and defect passivation of the perovskite emitter are synergistically realized by tuning the underlying interlayer, leading to the suppression of trap-mediated nonradiative recombination losses. Besides approaching highly emissive perovskite layers, the outcoupling of trapped light is also enhanced by combining the silver nanowires-based electrode with quasi-random nanopatterns on flexible plastic substrate. Upon the collective optimization of the device structure, a record external quantum efficiency of 24.5% is achieved for flexible PeLEDs based on green-emitting CsPbBr3 perovskite.

White organic light-emitting diodes (WOLEDs) using thermally activated delayed fluorescence (TADF)-based single emissive layer (SEL) have attracted enormous attention because of their simple device structure and full exciton utilization potential for high efficiency. However, WOLEDs made of an all-TADF SEL usually exhibit serious efficiency roll-off and poor color stability due to serious exciton-annihilation and unbalanced radiative decays of different TADF emitters. Herein, a new strategy is proposed to manipulate the TADF-sensitized fluorescence process by combining dual-host systems of high triplet energy with a conventional fluorescent emitter of complementary color. The multiple energy-funneling paths are modulated and short-range Dexter energy transfer is largely suppressed due to the steric effect of peripheral tert-butyl group in the blue TADF sensitizer. The resulting all-fluorescent WOLEDs achieve an unprecedentedly high external quantum efficiency of 21.8% with balanced white emission of Commission Internationale de l'Eclairage coordinate of (0.292, 0.343), accompanied with good color stability, reduced efficiency roll-off, and prolonged operational lifetime. These findings demonstrate the validity of this strategy for precisely allocating the exciton harvesting in SEL WOLEDs.

Urea electrolysis is a potential energy-efficient hydrogen (H2) production method that can simultaneously purify urea-rich wastewater. However, the lack of inexpensive and effective electrocatalyst...

Nickel–zinc (Ni–Zn) batteries are currently regarded as promising energy storage devices due to their high efficiency, high output voltage and good safety. However, the low energy density and poor rate performance caused by insufficient active sites and slow electron/ion transportation impede their future development in large-scale applications. To improve their electrochemical performance, we designed a new Ni-based composite with a unique structure by anchoring Ni–NiO nanoparticles onto a naturally derived and networked cellulose nanofiber carbon (denoted as Ni–NiO/CC), which can work as a robust cathode for Ni–Zn batteries. Benefiting from the elaborate structure that can speed up charge transportation and increase the number of active sites of cathode materials, the capacity of Ni–NiO/CC is remarkably improved from 2.3 mA h g−1 to 184 mA h g−1 at 0.625 A g−1. The as-fabricated Ni–NiO/CC//Zn battery delivers high capacity (256 mA h g−1 at 0.625 A g−1), superior rate performance (68.5% capacity retention at 25 A g−1), and good cycling durability (87.5% retention after 2000 cycles). More importantly, the maximum power density of the Ni–NiO/CC//Zn battery is 41.6 kW kg−1, presenting a peak energy density of 441.7 W h kg−1. This work promotes the facile manipulation of nanostructured electrodes based on sustainable biomass for green and advanced aqueous rechargeable batteries.

High-efficiency orange and red thermally activated delayed fluorescent (TADF) organic light-emitting diodes were fabricated based on a pair of isomers 3,6,11-triAC-BPQ and 3,6,12-triAC-BPQ, containing a rigid dibenzo[f,h]pyrido[2,3-b]quinoxaline (BPQ) core and three 9,9-dimethyl-9,10-dihydroacridine (Ac) donors. Both materials exhibited red emission in neat films and small singlet–triplet energy gaps. Compared with the stable intramolecular charge transfer (ICT) state of 3,6,12-triAC-BPQ, 3,6,11-triAC-BPQ showed hybridized local and charge transfer (HLCT) character due to the H-bond between the 11-position Ac and 10-position N atom. As a result, the doped film of 3,6,11-triAC-BPQ showed a high photoluminescence quantum yield (PLQY) and the related device showed a high external quantum efficiency (EQE) of 22.0% in the orange–red region.

All-inorganic perovskite solar cells (PSCs) have become one of the most attractive research fields in recent years due to their excellent thermal stability and light stability as compared with their organic-inorganic hybrid counterparts. However, there is still a long way to go for their commercial application due to their low efficiency and poor stability under humidity conditions. Herein, an overview of the recent progress of all-inorganic PSCs based on interface engineering is provided. The main roles of interface engineering, adjusting energy-level alignment, enhancing charge transport capacity, passivating interface defects, modulating morphology of perovskite films, stabilizing perovskite phase, broadening spectral absorption, eliminating electrical hysteresis and enhancing operational stability, are summarized with examples, which paves the way for highly efficient and stable all-inorganic PSCs. Some of the latest progress in incorporating dopants to charge transport materials and modifying interface properties in all-inorganic PSCs are also covered.

A sandwich-type supercapacitor consisting of self-healing layers and electrode layers can easily delaminate during deformation, thereby seriously affecting its reliability. In this work, a type of omni-healable electrode (denoted as CS@PANa–Fe3+–LiCl) is reported, which completely integrates a three-dimensional (3D) electrode material, a self-healing hydrogel and an electrolyte. Consequently, the ease of delamination and the large contact resistance due to the sandwich-type structure can be effectively overcome. Herein, the 3D porous carbon sponge (CS) serves both as an electroactive material and a carrier for the Fe3+-crosslinked sodium polyacrylate–LiCl (denoted as PANa–Fe3+–LiCl) hydrogel electrolyte. Combining the high electrical conductivity and good capacitance of the CS with the high ionic conductivity and excellent self-healability of the PANa–Fe3+–LiCl hydrogel electrolyte, the omnidirectionally integrated electrode exhibits good electrochemical and mechanical properties as well as excellent self-healing characteristics; furthermore, its capacity retention rate remains high (91.6%) even after five cutting/healing cycles. The as-fabricated CS@PA-SC device exhibits full self-healability, high energy density, good cycling stability, and integration characteristics. This investigation offers a facile and versatile strategy to integrate omni-healable electrodes that can be utilized to construct completely self-healable supercapacitors for wearable electronics.

Exploiting effective orange-red thermally activated delayed fluorescent (TADF) emitters is still challenging. In this work, we proposed a method by using a crooked donor (D) moiety instead of its conventional planar form to balance the opposite influences of frontier molecular orbital overlap on the reverse intersystem crossing and the singlet radiative decay rate. A novel orange-red TADF emitter, named 2-(4-(9,9-dimethyl-4-phenylacridin-10(9H)-yl)phenyl)anthracene-9,10-dione (AQ-PhDMAC), was accordingly designed and synthesized. Owing to the steric effect of the α-phenyl ring in 9,9-dimethyl-4-phenyl-9,10-dihydroacridine (α-PhDMAC), a relatively small singlet–triplet energy splitting of 0.22 eV and a high fluorescence quantum yield of 0.89 can be realized simultaneously. The orange-red organic light-emitting diode based on AQ-PhDMAC exhibited a maximum external quantum efficiency of 18.1%, much improved compared with the 13.7% efficiency of the α-phenyl ring-free control emitter (AQ-DMAC). These results propose a new viewpoint that enforcing crooked D segments by large steric hindrance actually has a great potential for applications in orange-red TADF molecular design, to improve their electroluminescence efficiency.

A sulfur (S) atom generally undergoes sp3 hybridization when linking two moieties, not only for the sulfane status but also its fully oxidized form, sulfone. In the research reported here an S atom was used as a bridge to construct two thermally activated delayed fluorescence (TADF) emitters, Trz-S-DMAc and Trz-SO2-DMAc. The only difference between these two emitters is the valence of the S atoms in the bridges; however, their electron distributions are greatly affected and the charge-transfer (CT) transitions can be well-modulated between intermolecular and intramolecular modes. In a Trz-S-DMAc molecule, the S atom breaks the conjugation between donor (D) and acceptor (A) moieties, and their CT transition can only then occur with other Trz-S-DMAc molecules. The OLEDs based on Trz-S-DMAc achieve the best external quantum efficiency (EQE) of 18.1% at a high concentration of 55 wt% and maintain a satisfactory EQE of 13.0% for a non-doped device. Whereas for Trz-SO2-DMAc, the sulfone group acts as a second A moiety rather than a simple bridge. The Trz-SO2-DMAc is thus a typical TADF emitter with an effective intramolecular CT transition. The optimized OLED based on Trz-SO2-DMAc achieves a maximum EQE of 18.3%, whereas a significant efficiency drop can be observed with increasing doping concentrations. It is expected that these results will help to increase the understanding of how to link donor and acceptor moieties via sp3 atoms to construct TADF emitters and the roles of the different CT transitions.

Thermally activated delayed fluorescence (TADF) emitters have attracted great attention for their use in organic light-emitting diodes since they can potentially realize 100% internal quantum efficiency by utilizing both singlet and triplet excitons due to an efficient reverse intersystem crossing process. However, forming a rational molecular design strategy is still challenging for high-performance TADF emitters. It is critical to understand the key factors that affect the performance of TADF materials. In this regard, this review focuses on the recent progress made in the design and synthesis of TADF materials controlled by the position and number of donor and acceptor units in different molecular structures. Reasonable molecular design principles have been summarized with the photophysical and electroluminescence characteristics of TADF materials. Furthermore, design guidelines and future prospects for high-performance TADF emitters are proposed for their future development.

For the development of solution-processed organic light-emitting diodes (OLEDs), it is highly desirable yet challenging to realize solution-processable non-doped thermally activated delayed fluorescence (TADF) emitters due to their high efficiency and excellent compatibility to the wet methods. Herein, two pairs of blue TADF isomers are designed and synthesized with a hetero-donor configuration for the realization of high photoluminescent quantum yield. The incorporation of two tert-butyl groups in the molecules can effectively increase the molecular solubility and reduce the aggregation-caused self-quenching of excitons in neat films by inhibiting the intramolecular vibrational relaxation and the intermolecular π–π stacking. Solution-processed non-doped OLEDs are achieved with these blue TADF emitters, exhibiting the record-high external quantum efficiencies (EQE) of 25.8%. Furthermore, an all-TADF white OLED with an EQE of 27.3% is also achieved by employing a single emitting layer with the blue TADF emitter as a host for an orange-red TADF dopant.

This study aims to perform free vibration and buckling analyses of circular cylindrical shells made of three-dimensional (3D) graphene foam. Three kinds of porosity distribution are considered incl...

Visual imaging that can extract three-dimensional (3D) space or polarization information on the target is essential in broad sciences and technologies. The simultaneous acquisition of them usually demands expensive equipment and sophisticated operations. Therefore, it is of great significance to exploit convenient approaches for four-dimensional (3D and polarization) visual imaging. Here, we present an efficient solution based on self-assembled asymmetric liquid crystal microlenses, with freely manipulated phase profiles and symmetry-breaking properties. Accordingly, characteristics of multifocal functionality and polarization selectivity are exhibited, along with the underlying mechanisms. Moreover, with a specific sample featured by radially increased unit sizes and azimuthally varied domain orientations, the discriminability of four-dimensional information is extracted in a single snapshot

This paper proposes the dual-wavelength transmission technique for improving the performance of the gain-saturated semiconductor optical amplifier (SOA)-based free-space optical (FSO) communication link. When the gain saturated SOA is used to suppress turbulence-induced scintillation, extinction ratio (ER) degradation effect occurs owing to the high-dynamic gain frequency characteristics for intensity modulation and direct detection (IM/DD) system. The proposed method uses small-spacing dual-wavelength (signal and supplemental wavelengths) transmission to compensate ER degradation by mitigating the gain difference between the bits ‘1’ and ‘0’. Regarding the supplemental wavelength, continuous wave (CW) with various average powers and differential signal (DS) transmissions are experimentally investigated. The proposed technique is evaluated under various turbulence channel strengths. The experimental results show that the bit-error rate (BER) performance is significantly improved via effective ER degradation compensation and scintillation suppression.

This paper presents an optical method to determine the scattering characteristics of dielectric rough targets in the terahertz band. Based on the complex permittivity of alloy Al (Aluminum) and painted Al obtained from the reflectance spectra, the analytical bidirectional reflection distribution function (BRDF) spectra of rough surfaces are simulated using physical optics. The effects of surface roughness, complex permittivity, incident angle, and wavelength are analyzed. With the optimization of artificial immune network genetic algorithms, it is demonstrated that the optimized five-parameter BRDF empirical model fits the analytical BRDF spectra over a wide range of incidence angles. Then, the radar cross section (RCS) of electrically large targets can be simulated by the relationship between the differential scattering coefficient and BRDF. The obtained RCS of the rough sphere from optimized BRDF model is in good agreement with the numerical analysis that was obtained. The proposed method is suitable for obtaining the scattering properties of large dielectric targets with different surfaces compared with traditional high-frequency electromagnetic (EM) techniques. The backscattered and bistatic terahertz RCS of a cylinder, cone and NASA almond are simulated. The proposed method shows the potential for the application of BRDF in the areas of scattering analysis and remote sensing.

While tremendous progress has recently been made in perovskite light‐emitting diodes (PeLEDs), large‐area blue devices feature inferior performance due to uneven morphologies and vast defects in the solution‐processed perovskite films. To alleviate these issues, a facile and reliable interface engineering scheme is reported for manipulating the crystallization of perovskite films enabled by a multifunctional molecule 2‐amino‐1,3‐propanediol (APDO)‐triggered “anchoring effect” at the grain‐growth interface. Sky‐blue perovskite films with large‐area uniformity and low trap states are obtained, showing the distinctly improved radiative recombination and hole‐transport capability. Based on the APDO‐induced interface engineering, synergistical boost in device performance is achieved for large‐area sky‐blue PeLED (measuring at 100 mm2) with a peak external quantum efficiency (EQE) of 9.2% and a highly prolonged operational lifetime. A decent EQE up to 6.1% is demonstrated for the largest sky‐blue device emitting at 400 mm2., A facile and effective grain‐growth manipulation scheme enabled by interface “anchoring effect” is proposed for high‐quality sky‐blue perovskite emitter. Remarkable boost in device performance is achieved for large‐scale sky‐blue perovskite LEDs with peak external quantum efficiencies of 9.2% and 6.1% measured at scales of 100 and 400 mm2, respectively.

Actuators mimic the unique motion of bacteria, which are realized by self-organizing photoresponsive cholesteric liquid crystals., Rotation-translation conversion is a popular way to achieve power transmission in machinery, but it is rarely selected by nature. One unique case is that of bacteria swimming, which is based on the collective reorganization and rotation of flagella. Here, we mimic such motion using the light-driven evolution of a self-organized periodic arch pattern. The range and direction of translation are altered by separately varying the alignment period and the stimulating photon energy. Programmable self-propelling actuators are realized via a specific molecular assembly within a photoresponsive cholesteric medium. Through rationally presetting alignments, parallel transports of microspheres in customized trajectories are demonstrated, including convergence, divergence, gathering, and orbital revolution. This work extends the understanding of the rotation-translation conversion performed in an exquisitely self-organized system and may inspire future designs for functional materials and intelligent robotics.