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Graphitic carbon nitride (g-C3N4) is considered a potential photoactive semiconductor for photocatalytic hydrogen evolution (PHE). Although being active in producing hydrogen, it is in general suffering from severe charge recombination rate, low mobility of charge and narrow visible light response range largely, which has restricted its greater application. Existing reviews on g-C3N4 are lacking of systematic and summative view on the effects of the physical-chemical structure-activity relationship between g-C3N4 and the modification involving phosphorus (P). Many studies indicate that adding P into g-C3N4 could effectively elevate the photo-activity. Underlying reasons for the observed improved photo-activity are discussed in this review. Here, P-containing g-C3N4 photocatalysts are grouped into the categories of P elemental doping, composite with elemental P, as well as the addition of metal phosphide as cocatalysts. These P-containing g-C3N4 possess novel properties demonstrating favorable photocatalytic activities as compared with the other elemental (such as O, S, B)-based materials. Therefore, in this mini review, we summarize and discuss the advances on the P-containing g-C3N4 photocatalysts, including the preparation strategies, physicochemical properties, the application for hydrogen production as well as the related reaction mechanism. Importantly, the physical-chemical structure-activity relationship between g-C3N4 and the integrated P is revealed. Finally, an overview of the current research status and challenges on future is presented, which would be helpful in designing and developing other P-containing photocatalysts for various photocatalytic applications.

Bimetallic compounds are a kind of important catalytic materials in heterogeneous catalysis. In this work, we first employed n-butyllithium as reducing agent to synthesize Ir and IrFex (x is the Fe/Ir molar ratio and equal to 0.49, 0.90, and 2.80) nanocrystals (NCs), and then used an adsorption strategy to load them on the surface of ordered mesoporous ceria (meso-CeO2) derived from the KIT-6-templating route to obtain the 0.48 wt% Ir/meso-CeO2 (denoted as 0.48Ir/meso-CeO2) and 0.53–0.89 wt% IrFex/meso-CeO2 (denoted as 0.53IrFe0.49/meso-CeO2, 0.59IrFe0.90/meso-CeO2, and 0.89IrFe2.80/meso-CeO2) samples. Physicochemical properties of the samples were characterized by means of various techniques. It is shown that all of the samples possessed a cubic crystal phase, an ordered mesoporous architecture, and a surface area of 84–124 m2/g, in which the IrFex NCs with an average size of ca. 2 nm were highly dispersed on the meso-CeO2 surface. Among all of the samples, 0.59IrFe0.90/meso-CeO2 performed the best for acetylene combustion (T10% =155 °C, T50% =162 °C, and T90% =165 °C at space velocity = 20,000 mL/(g h)). Furthermore, 0.59IrFe0.90/meso-CeO2 showed good water- and carbon dioxide-resistant performance, and its partial deactivation due to the introduction of SO2 was reversible. The possible reaction mechanisms over Ir/meso-CeO2 or IrFex/meso-CeO2 were also discussed. We conclude that the well dispersed IrFe0.90 NCs, high adsorbed oxygen and acetylene amounts, low-temperature reducibility, and strong interaction between IrFe0.90 NCs and meso-CeO2 were responsible for the good catalytic performance of 0.59IrFe0.90/meso-CeO2.

Binary composite catalyst of g-C3N4 and BiOI has been shown to have tremendous potential in visible light catalytic degradation of organic pollutant. However, the adjustment of scale and morphology of the heterojunction composite catalyst (g-C3N4/BiOI) has attracted unprecedented attention for improving the photocatalytic efficiency. Herein, a facile preparation method of Z-scheme heterojunction composite catalyst of zero-dimensional g-C3N4 growing on two-dimensional BiOI (0D/2D g-C3N4/BiOI) was proposed, which features with a self-assembled organic supramolecular as precursor intercalating into the laminar 2D BiOI to prepare a highly dispersed 0D g-C3N4 in situ growth on it. The result demonstrates that the as-prepared 0D/2D g-C3N4/BiOI is superior to non-noble metal heterojunction catalysts and comparable to some noble metal catalysts and exhibits a 22.1 times higher kinetic constant for tetracycline hydrochloride degradation than that of g-C3N4 with a degradation rate of 92.1%. Additionally, 0D/2D g-C3N4/BiOI also indicates excellent stability of cyclic photocatalysis and resistance to ionic interference. The underlying photocatalytic degradation mechanism is considered that the generated superoxide radical (·O2−) of 0D/2D g-C3N4/BiOI can intensely catalyse the refractory organic matter, including tetracycline hydrochloride, tetracycline hydrochloride, methyl orange, and p-chlorophenol. This work provides a universal approach to construct 0D/2D heterojunction composite catalyst to enhance the photocatalytic performance.

The fully inorganic perovskite lead cesium bromide single crystal (CsPbBr3 SC) is considered as an excellent candidate semiconductor for photodetectors because of its superior humidity resistance, thermal stability, and light stability compared with organic-inorganic hybrid perovskites as well as its photoelectric properties such as large light absorption coefficient and ultralong carrier migration distance. In this Letter, we utilize the inverse temperature solubility of CsPbBr3 in ternary solvents to grow large-sized CsPbBr3 SCs. By the use of the (101) plane, CsPbBr3 SC-based photodetectors are fabricated, which exhibit excellent polarized light response characteristics. The photocurrent relies on the polarization angle in a sinusoidal fashion and shows strong anisotropic optoelectronic properties. The photodetection performance perpendicular to the y axis is significantly higher than that parallel to the y axis, and the dichroic ratio under 405 nm illumination at a bias voltage of 1 V reaches 2.65. The experimental results are consistent with the results of first-principles calculations.

Two-dimensional (2D) material-based heterojunction solar cells have attracted significant interest due to their potential in low-cost photovoltaic applications. Herein, a novel MXene/GaAs heterojunction solar cell with high efficiency and excellent stability has been achieved via a facile one-step method of drop casting for the first time. The high work function of the transparent MXene and the enhanced interfacial interaction between the MXene and GaAs contribute to the formation of a high-quality Schottky diode, resulting in a high initial power conversion efficiency (PCE) of 9.69%, surpassing those of other reported 2D material/semiconductor heterojunction solar cells. Moreover, after the deposition of a ZnS/MgF2 composite coating, the as-prepared MXene/GaAs heterojunction solar cell exhibits an average PCE of 12.5% with stability over 30 days in air. This work is of great importance for obtaining high-efficiency and air-stable solar cells for light-harvesting for sustainable development.

Soft robots provide compliant object-machine interactions, but they exhibit insufficient material stability, which restricts them from working in harsh environments. Herein, we developed a class of soft robotic skins based on two-dimensional materials (2DMs) and gelatin hydrogels, featuring skin-like multifunctionality (stretchability, thermoregulation, threat protection, and strain sensing). The 2DM-integrated hydrogel (2DM/H) skins enabled soft robots to execute designated missions in the presence of high levels of heat and various environmental threats while maintaining mild machine temperatures. Via adopting different 2DMs (graphene oxide (GO), montmorillonite (MMT), and titanium carbide (MXene)), the 2DM/H-protected robots were able to perform soft grasping in organic liquids (GO/H) and open fire (MMT/H), and in the presence of electromagnetic radiation and biocontamination (MXene/H). Through blending MXene nanosheets into gelatin, the MXene-blended hydrogel (M-H) skin became strain sensitive, and a GO/M-H gripper exhibited the high-level integration of skin-mimicking capabilities. Finally, we incorporated 2DM/H skins onto an origami-inspired walker robot and a soft batoid-like robot to execute vision-guided searching in fire and underwater locomotion/navigation in chemical spills.

Fully inorganic perovskite materials of the Cs–Pb–Br system have been developing rapidly because of their overwhelming stabilities and splendid optoelectronic performance. However, there are few investigations on the parallel system of Cs–Pb–Cl, let alone the two-dimensional (2D) CsPb2Cl5. To fill in the gaps about CsPb2Cl5, we successfully grew large-scale CsPb2Cl5 single crystals (SCs) and partially substituted by Br. The quintessential 2D crystal structure determines the morphology character of slices, with a tetragonal system (I4/mcm). The ledge-connected [Cs–Cl]10 polyhedrons and face-connected [Pb–Cl]8 polyhedrons endow them with asymmetry and further bring crystal lattice distortions, which is beneficial for self-trapped exciton (STE) emission. Additionally, the band gap of the transparent CsPb2Cl5 SC is confirmed to be ∼4.01 eV. The photoluminescence (PL) of CsPb2Cl5 SC is dependent on the excitation energies. Exciton emission centered at 2.32 eV is predominant under higher energy excitation (>3.85 eV), whereas STE emission centered at 1.8 eV with a broad band (FWHM > 120 nm) is the unique emission when the excitation energy is lower than 3.85 eV. In addition, appropriate replacement of Cl with Br can bring larger lattice distortion and facilitate STE emission.

The optoelectronic performances of MAPbI3 are related to film morphology and crystal orientation. However, it is difficult to directly quantify the optoelectronic anisotropy in thin films because c...

Silicone elastomers with high mechanical stability have been conventionally adopted for the fabrication of emerging soft robots. However, these elastomers exhibit limited electrical and thermal properties that restrict the development of functional soft robots. A promising approach is to integrate carbon nanomaterials into hydrogels to develop multifunctional robotic skin with high deformability and diverse built-in functions for fabricated soft machines. Herein, a scalable approach was developed to fabricate a conductive hydrogel by integrating pristine multi-walled carbon nanotubes (MWNTs) into gelatin solution followed by the introduction of a crosslinking agent (i.e., glutaraldehyde). After the addition of glutaraldehyde, the viscosity of MWNT-gelatin dispersion increased with time, and a viscous precursor paste for conductive hydrogels was achieved for various scalable coating techniques including doctor blading. After large-area printing, the MWNT-gelatin paste continued to crosslink, and an MWNT-integrated gelatin hydrogel (MW-hydrogel) was obtained. The MW-hydrogels were highly deformable, and the electrical resistance of conductive MW-hydrogels was responsive to various mechanical deformations, enabling their applications in electronic robotic skin to monitor the actuations of soft robots in real time. Also, the MW-hydrogels were further utilized as flame-retardant skin for a soft robotic gripper, which could manipulate and rescue irregularly shaped objects from a fire scene.

The uniaxial tensile mechanical properties of D1 wheel steel and U71MnG rail steel were investigated experimentally at a wide range of strain rates from 0.0001 to 100 s−1. Influence of the strain rate on stress–strain response, ductility, fracture morphology and energy absorption was analyzed and discussed, respectively. Both D1 wheel steel and U71MnG rail steel are demonstrated to be strain rate sensitive, and D1 wheel steel specimens generally exhibit a larger elongation and a better ductility than U71MnG rail steel specimens at each strain rate. The fracture mechanism of D1 wheel steel is a ductile fracture at lower strain rates and quasi-ductile fracture at higher strain rates, while U71MnG rail steel tends to a quasi-ductile fracture at lower strain rates and a brittle fracture at higher strain rates. The specific energy absorption values of D1 wheel steel and U71MnG rail steel increase with the increase in true strain and elevated strain rate. Finally, the Johnson–Cook model is adopted to predict the stress–strain response of wheel/rail steels studied, and a better agreement is found.

The mesoporous M–Al (M = Ce, La, Co, Ce–La, and Ce–Co) catalysts were synthesized by adopting a modified “one-pot” evaporation-induced self-assembly (EISA) strategy with ultrasound or microwave irr...

Mismatched deformation in a bilayer composite with rigid coating on a soft substrate results in complex and uniform topographic patterns, yet it remains challenging to heterogeneously pattern the upper coatings with various localized structures. Herein, a heterogeneous, 3D microstructure composed of Ti3C2Tx titanium carbide (MXene) and single-walled carbon nanotubes (SWNTs) was fabricated using a one-step deformation of a thermally responsive substrate with designed open holes. The mechanically deformed SWNT-MXene (s-MXene) structure was next transferred onto an elastomeric substrate, and the resulting s-MXene/elastomer bilayer device exhibited three localized surface patterns, including isotropic crumples, periodic wrinkles, and large papillae-like microstructures. By adjusting the number and pattern, the s-MXene papillae arrays exhibited superhydrophobicity (>170°), strong and tunable adhesive force (52.3-110.6 μN), and ultra-large liquid capacity (up to 35 μL) for programmable microdroplet manipulation. The electrically conductive nature of s-MXene further enabled proper thermal management on microdroplets via Joule heating for miniaturized antibacterial tests. The s-MXene papillae were further fabricated in a piezoresistive pressure sensor with high sensitivity (11.47 kPa-1). The output current changes of s-MXene sensors were highly sensitive to voice vibrations and responded identically with prerecorded profiles, promising their application in accurate voice acquisition and recognition.

Hydrazine detection is of great significance in the fields of chemical industry, environment, life, health, and so on. A novel photoacoustic probe is designed and synthesized for hydrazine detection, using cyanine with strong near-infrared absorbance as the core. The probe has strong photoacoustic signal at 808 nm. When the probe molecules interact with the hydrazine, the absorbance intensities of probe at 808 nm and 550 nm decrease and increase with the increase of hydrazine concentration, respectively. The optical density ratio of D (808)/ D (550) in the range of 0-5 μmol/L hydrazine concentration has a good linear relationship with the change of concentration. Meanwhile, photoacoustic intensity of probe at 808 nm P (808) gradually decreases with the increase of hydrazine concentration, and shows a good linear relationship in the range of 0-10 μmol/L, with a detection limit of 0.50 μmol/L. The probe is easy to synthesis and can achieve photoacoustic detection of hydrazine rapidly and efficiently, which provids a new solution for the development of in vivo detection of hydrazine.

Static and dynamic flexural tests were carried out with a 100-mm-diameter split Hopkinson pressure bar (SHPB) apparatus on rubber concrete for which the fine aggregate was replaced with rubber particles made from waste tires at various volume ratios (0%, 10%, 20%, 30%, 40%, and 50%). The incident and transmission bars of the SHPB apparatus were each sleeved on a modified pad for a three-point flexural test. Experimental results showed that the flexural strength and mid-span displacement of the rubber concrete had a strain-rate effect. The rubber concrete had a more sensitive strain rate than the normal concrete when the replacement ratio of rubber particles was below 30%. However, excessive rubber content (40% and 50%) decreased the sensitivity of strain rate. The strain-rate effect of the rubber concrete was due to a short test duration, which caused more aggregates to be broken, and compressive behavior during the tests. Rubber concrete with a replacement ratio of 30% demonstrated the greatest deformability and had a lower cracking speed than the normal concrete. These results demonstrated that, under a dynamic flexural load, rubber particles can reduce the brittleness of concrete without excessive mixing.

The existence of the organic component (MA) in MAPbBr3 guarantees its cubic crystal lattice stabilities to satisfy the tolerance factor but increases the chemical instability risk when encountering moisture, oxidation, and heat. Mixed cations, particularly when using cesium cation (Cs+), prove to be an effective way of improving both stability and optoelectronic performances of hybrid perovskite films applied in solar cells. However, the intrinsic effect of Cs+ on the crystal structure, lattice defects, and optoelectronic properties of MAPbBr3 is still unclear till now because grain boundary numbers and interface defect densities in films increase complexity; so, it is not easy to explore the intrinsic nature of how Cs+ affects the optoelectronic properties of MAPbBr3. Single crystals (SCs) of MAPbBr3 provide an ideal medium to investigate the influence of Cs+ on the crystal structure and optoelectronic performances. Herein, we grew a series of MA1–xCsxPbBr3 SCs. This reveals that Cs+ inhibits the growth ...

The transient responses of car body and side windows for CRH2 high-speed trains passing by each other in a tunnel at different meeting conditions were investigated numerically using the Finite Element (FE) software LS-DYNA/explicit algorithm. Nine meeting cases including the case of meeting at the same speed and at the different speeds were respectively examined, where the moving pressure waves loaded on the surfaces of the observed train were obtained from the previous aerodynamics simulation. The typical transient responses (i.e., the stress and lateral displacement) of car body and side windows were analyzed, and the contribution of pressure wave to structural design strength of car body was also discussed. A comparison between the dynamic pressure wave loading simulation and the equivalent quasi-static loading simulation was also made. The simulation results indicate that both the von-Mises equivalent stress and lateral displacement of the car body are sensitive to the meeting speed. The side windows are subjected to the tensile stress in the most of response stage, and the maximum Y-directional stress of each monitor point presents a rapid increase with the increased meeting speed. The contribution rate of pressure wave to structural strength of the car body increases with the meeting speed. Besides, the dynamic pressure wave loading simulation method is demonstrated to be a better choice to investigate the transient response of the carriage. These research results are significant for ensuring the safety of the trains traveling in tunnels and elevating the safety of side windows.

The dynamic response and design optimization of clamped sandwich panels comprising two aluminum alloy face-sheets and a layered-gradient closed-cell aluminum foam core subjected to air-blast loading were examined in this study. The numerical approach was first validated by blast test results of sandwich panels with monolithic aluminum foam cores, and then the dynamic responses of layered-gradient core sandwich panels were briefly discussed in terms of deflection response and energy absorption. Two surrogate model methods (i.e., response surface method – RSM, and radial basis function – RBF) were adopted to construct objective response functions, and the single-objective adaptive response surface method (ARSM) and multi-objective genetic algorithm (MOGA) were used for the defined optimization problem. The optimization results show the trade-off relationships among the maximum energy absorption, minimum structural mass and minimum deflection, and the advantage of “Pareto front” in such design circumstances. Furthermore, the applicability and accuracy of RSM and RBF agent models in the multi-objective design optimization (MDO) of sandwich panels with layered-gradient foam cores under air-blast loading were also compared and revealed.

CH3NH3PbBr3 (MAPbBr3), one of the classical members in the organic–inorganic hybrid perovskite family that presents excellent advantages in high photon absorption efficiency and long carrier transp...

Due to the high density of surface states introduced in the nanorods growth process and subsequent exposure to air, electrons will be trapped in these states and recombine with photo-generated holes, which leads to a high loss of photo-generated carriers and creates a large onset potential for carrier transport. Here, we report a simple and low-cost surface treatment method, which utilizes H3PO4 to passivate surface states in the as-grown InGaN nanorods. Using optimized surface passivation condition, surface trapping states in as-grown InGaN nanorods can be removed by eliminating surface Indium aggregation, reducing the surface oxides, and saturating the dangling bonds. Hence, carrier recombination mediated by these surface states is weakened, as well as applied bias potential required for carrier transport is lowered. The optimized H3PO4-treated nanorods photoanode shows a larger photovoltage and a smaller charge transfer resistance to the electrolyte. Resultantly, a significant negative shift of onset potential from 0.7 to 0.3 V vs. RHE for the treated photoanode is achieved. Moreover, the optimized H3PO4-treated photoanode exhibits a high photocurrent density of 18 mA/cm2 at 1.23 V vs. RHE and a maximum applied bias photon-to-current efficiency value of 1.09%, whereas as-grown InGaN photoanode reaches only 0.64%.

Quasi-static and dynamic splitting tensile tests were performed on three high-strength concretes with different compressive strengths – 60 MPa, 80 MPa and 110 MPa, denoted by C60, C80 and C110 respectively – to examine their tensile properties. Quasi-static tests were conducted at a strain rate of ∼2 × 10−6 s−1, using a Shimadzu Universal Testing Machine; and dynamic tests were performed at strain rates of ∼1–10 s−1, using an 80 mm-diameter split Hopkinson pressure bar (SHPB) device. Strain gauging and digital image correlation (DIC) techniques were employed to determine the deformation in specimens. From the force applied and the average tensile strain at the specimen centre, obtained from strain gauge measurements, the uniaxial tensile stress–strain response at that location was derived, by adopting an elastic-plastic analysis, whereby tensile plastic hardening is assumed to be piecewise linear. The effects of strain rate on the tensile response were also examined and analysed. For all three high-strength concretes, significant rate dependence was observed; the yield stress, tensile strength and failure strain all increase with strain rate, and their dynamic values are much higher than their static values. The Dynamic increase factor (DIF), i.e. the ratio between the dynamic and static tensile strengths, was calculated to quantify the rate sensitivity. Similar DIFs were obtained for C60, C80 and C110, and the DIFs determined were compared with predictions based on two empirical formulae, i.e. the CEB-FIP model (2010), and that proposed by Malvar and Ross, which are frequently used for normal-strength concrete. These two formulae appear inadequate in defining the rate dependence of high-strength concrete. Consequently, a bilinear description of the DIF as a function of lo g 10 ( ɛ ˙ ) , with a transition at a strain rate at 1 s−1, was proposed for high-strength concrete, based on the experimental data.

We conducted explosion field tests on rubber concrete slabs with steel reinforcement, including four kinds of concretes with different mix proportions of volume fractions of rubber particles (0%, 10%, 30%, and 50%, termed NC, RC10, RC30, and RC50, respectively). In addition, we compared the measured overpressure at the center of a slab with some empirical models to verify the accuracy our model. Field testing results showed that the tensile zone damage of rubber concrete slabs is smaller than that of normal concrete slabs under large explosive charges. Additionally, we validated a numerical simulation employing Multi-Material ALE and Lagrangian algorithms using the data from field experiments and employed it to further study the deformation process during the field test. Finally, we showed that rubber concrete slabs with steel reinforcements are practical structures for blast resistance, especially when subjected to a large energy detonation.

The low-velocity impact response of sandwich beams with aluminum alloy face-sheets and three core configurations (i.e., the positive layered-gradient core, negative layered-gradient core and non-gradient monolithic core) was first investigated by using a drop-weight machine. The impact bending tests were performed on specimens at five impact energy levels – 9.80 J, 22.05 J, 39.19 J, 61.24 J and 88.18 J – by varying the drop height of the weight. Based on experimental results, the corresponding numerical simulations and a multi-objective design optimization were performed. The experimental results show that all sandwich beams fail via the global bending deformation without local crack/fracture under lower initial impact energy, while they fail via larger bending deformation accompanied by obvious core tensile crack at mid-span and core shear at clamped ends with the increased initial impact energy. The resistance of both gradient core sandwich beams to impact flexure loading is weaker than that of non-gradient monolithic core sandwich beams. Simulation results indicate that the ratio of energy absorbed by core decreases with the increased impact energy, while the ratio of energy absorbed by face-sheets increases with the increased impact energy. The boundary condition is demonstrated to have great influence on the force-displacement response for all sandwich beams. Finally, the corresponding Pareto fronts representing a group of best trade-off designs were obtained.

As one type of organic–inorganic hybrid lead halide perovskites, MAPbX3 has attracted immense interests in applications of optoelectronic devices because of its remarkable properties. However, the ...

Due to their excellent luminescent properties such as high stability, narrow band emission, and strong luminescence, hybrid organic–inorganic lead perovskites have great potential for application in optoelectronic devices. Compared to their conventional 3D counterparts, 2D perovskites exhibit enhanced moisture stability. Moreover, with the enhancement of exciton binding energy and limitation of charge carriers, 2D layered perovskites are considered ideal candidate materials for efficient light-emitting diodes (LEDs). However, hybrid organic–inorganic lead perovskites contain highly toxic Pb, which is considered as a major environmental pollutant and health hazard. Therefore, the further larger-scale applications are limited. Thus, exploiting the impressive properties and practical applications of 2D layered structure Pb-free hybrid organic–inorganic perovskites in the LED field is necessary. In the present work, a centimeter-size square 2D layered Pb-free (CH3NH3)2MnCl4 single crystal was grown successfully with diverse crystal morphologies from two different solutions. This material could be excited by light in different wavelength bands. The main peak in its emission spectrum is located at 608 nm and the full width at half maximum (FWHM) is 72 nm. Furthermore, we prepared an LED using the (CH3NH3)2MnCl4 single crystal, which exhibited good luminescence properties, emitting obvious red light with a QE of 2.4% upon excitation at 417 nm and used for white light illumination.

Atomically thin nanomaterials represent a unique paradigm for interfacing with biological systems due to their mechanical flexibility, exceptional interfacial area, and ease of chemical functionalization. In particular, these two-dimensional (2D) materials are able to bend, curve, and fold in response to biologically-generated forces or other external stimuli. Such origami-like folding of 2D materials into wrinkled or crumpled topographies allows them to withstand large deformations by accordion-like unfolding, with implications for stretchable and shape-changing devices. Here, we review how mechanically manipulated 2D materials can interact with biological systems across a multitude of length scales. We focus on recent work where wrinkling, crumpling, or bending of 2D materials permits new chemical and material properties, with four case studies: (i) programming biomolecular reactivity and enhanced sensing, (ii) directed adhesion and encapsulation of bacteria or mammalian cells, (iii) stimuli-responsive actuators and soft robotics, and (iv) stretchable barrier technologies and wearable human-scale sensors. Finally, we consider future directions for manufacturing, materials and systems integration, as well as biocompatibility. Taken together, these 2D materials may enable new avenues for ultrasensitive molecular detection, biomaterial scaffolds, soft machines, and wearable technologies.

There has been great interest in the use of cesium lead bromide (CsPbBr3), which is one of the most important members of the all-inorganic perovskite family, due to its superior optoelectronic performance and higher stability. Recently, it has been demonstrated that it is advantageous to use CsPbBr3 microrods and nanowires in photodetectors because of their higher crystallinity, low amount of defects, and easy control of carrier transport along a specific direction as compared to their counterparts of single crystals and thin films. However, there is a shortage of adequate investigations that describe how to control the growth of CsPbBr3 microrods and nanowires so that they retain the optoelectronic performance of single CsPbBr3 microrods. Therefore, we are reporting how to control the growth of orientated dispersive super-long CsPbBr3 microrod single crystals (CsPbBr3 MSCs) via a simple anti-solvent method. The crucial factor in controlling the growth of dispersive super-long CsPbBr3 MSCs is the regulation of the rapid nucleation rate and slowing of the growth rate via controlling the diffusion velocity of anti-solvent methanol. We also reveal the growth mechanism of CsPbBr3 MSCs as layer-by-layer growth that originates from the 2D nucleus. The CsPbBr3 MSCs are revealed grew in the direction of [010], with the (101) facet exposed. Moreover, photodetectors based on one CsPbBr3 MSC were fabricated, and the detectivity (D) and the on/off ratio were as high as 3.67 × 1012 Jones and 988, respectively, suggesting a very strong optoelectronic response as photodetectors. The mechanism that the Cs ions and Cs vacancies use to move to negative and positive electrodes along the channels constructed by [PbBr6]4− in the [010] direction of the CsPbBr3 MSC (101) facet was revealed, after activation by the applied electrical field, which is beneficial to enhance the optoelectronic response but does not reduce the device stability.

International audience; Silicone rubbers are promising materials that have extensively been used in many areas, including wearable electronic devices, actuator materials in soft robotics, and energy harvesters. Ecoflex, a commercially available polymer, is a group of silicone rubbers appearing with various Shore hardnesses that has become popular in recent years. While silicone rubbers in their real applications are subjected to repeated loadingunloading conditions, their mechanical behaviour under cyclic loading in different deformation modes and the corresponding stress recovery behaviour are yet to be well investigated. In this contribution, we conduct loading-unloading cyclic experiments in different time gaps between the first cycle and the second cycle to demonstrate the stress recovery behaviour after stress softening happens during the first cycle. For that, three different modes of deformations, i.e., uniaxial tension, planar tension, and equibiaxial tension tests are selected. Besides, Shore hardness dependence with different strain levels is also taken into consideration. The results show that the stress softening could recover significantly with time. These findings will help to understand the mechanical behaviour of Ecoflex silicone rubbers before selecting them in practical applications that are exposed to repeated loading-unloading cycles.

Elemental red phosphorus (red P) is a new class of photocatalysts with a desirable bandgap of ∼1.7 eV and has a strong visible-light response. Here, we show that the efficiency of red P is limited by severe electron trapping at deep traps that are intrinsic to the different crystal facets of the red P. To overcome this, we synthesized the red P/RGO (reduced graphene oxide) composite in a one-step ampoule chemical vapor deposition synthesis that formed a conducive interface between the red P photocatalyst and the RGO acceptor for efficient interfacial charge transport. As substantiated through photoelectrochemical characterization and ultrafast (femtoseconds) transient absorption spectroscopy, the interfacing with RGO provided a rapid pathway for the photocharges in red P to be interfacially separated, thereby circumventing the slower the charge trapping process. As a result, up to a sevenfold increase in the photocatalytic hydrogen production rate (apparent quantum yield = 3.1% at 650 nm) was obtained for the red P/RGO relative to the pristine red P.

We report a new strategy to fabricate a core-shell TiO2@g-C3N4 composite for photoelectrochemical water splitting. The heterojunction structure is prepared by chemically wrapping exfoliated thin layer g-C3N4 nanosheets on the surface of anatase TiO2 particles. The TiO2@g-C3N4 sample demonstrates high visible-light photoactivity towards water splitting, resulting in an increase in photocurrent density by a factor of 2.5 times compared to the bare TiO2. This is ascribed to the inhibition of electron-hole pair recombination due to the synergistic effect between TiO2 and g-C3N4, which enhances the charge transfer and separation. The prolonged lifetime of the charges is confirmed by using the transient absorption spectroscopic measurements.

Organic-inorganic hybrid methylammonium lead iodide perovskite (MAPbI3) has attracted extensive attention in a series of optoelectronic devices. The photoelectric properties of the MAPbI3 single crystal have been revealed to be much better than those of it polycrystalline counterparts. However, its poor moisture and heat resistance severely limited further development. The introduction of Cs+ into polycrystalline films has shown to be an effective way to enhance its moisture resistance through a passivation effect. However, the entrance abilities of Cs+ into a MAPbI3 crystal lattice and the influence on photoelectric properties of a single crystal were not clear until now. Therefore, we attempted to grow large MA1- xCs xPbI3 single crystals to introduce Cs+ into the crystal lattice. The existence of Cs+ brought lattice shrinkage and enhanced stability of the MAPbI3 single crystal. A moderate quantity of Cs+ (2%) proved to heighten the photoelectric properties, whereas an excess quantity of Cs+ (5%) brought more shallow defects, which ultimately deteriorated the photoelectric properties.

The dynamic response of clamped square sandwich panels with layered-gradient closed-cell aluminum foam cores under the impact of metallic foam projectiles is investigated. The present solutions are...

The improvement of hydrogen storage materials is a key issue for storage and delivery of hydrogen energy before its potential can be realized. As hydrogen storage media, rare-earth hydrogen storage materials have been systematically studied in order to improve storage capacity, kinetics, thermodynamics and electrochemical performance. In this review, we focus on recent research progress of gaseous sorption and electrochemical hydrogen storage properties of rare-earth alloys and highlight their commercial applications including hydrogen storage tanks and nickel metal hydride batteries. Furthermore, development trend and prospective of rare-earth hydrogen storage materials are discussed.

The dynamic compressive behavior of closed-cell aluminum foams with different relative densities at a wide range of strain rates up to 4000 s−1 was investigated using a 37-mm Split Hopkinson Pressure Bar (SHPB) apparatus. The 30-mm-diameter specimens with two thicknesses (i.e., 6 and 10 mm) and three nominal relative densities (i.e., 0.11, 0.16, and 0.21) were fabricated. The influences of strain rate, relative density, specimen thickness on the mechanical properties of aluminum foams (e.g., stress–strain relationship, collapse stress, plateau stress, densification strain, and energy absorption) were examined. The results indicate that the collapse stress, plateau stress, and densification strain of the aluminum foams with three relative densities exhibit obvious strain rate sensitivity. The collapse stress and plateau stress have a stronger density sensitivity and relatively weaker strain rate sensitivity. The specimen thickness has a very slight influence on the specimen strength at a lower strain rate (600 s−1), but this leads to a greater influence at a higher strain rate (2000 s−1). The energy absorption capacity of the closed-cell aluminum foams increases with increased relative density and strain rate in both quasi-static and dynamic compression. Finally, a multiparameter nonlinear elasto-plastic constitutive model was proposed to describe the typical three-stage features of stress–strain response in aluminum foams. There was acceptable agreement between theoretical predictions and experimental results.

The present study performed quasi-static and dynamic compressive and splitting tensile tests on unsaturated polyester polymer concrete (UPPC) at four different curing ages (6 h, 3 days, 7 days, and 28 days). We examined a total of 136 specimens, specifically 24 cubic specimens and 12 cylindrical specimens for quasi-static tests and 45 cylinders and 55 FBD specimens for dynamic compressive and tensile tests, respectively. The experimental results indicated that UPPC exhibited rapid strength enhancement in the early stages of curing, and the natural curing condition-treated cubic specimens exhibited 6-h compressive and splitting tensile strengths of 40 MPa and 6.5 MPa, respectively, which was almost the 50–60% of the 28-day strengths. The UPPC is also sensitive to the strain rate, such that both the compressive and splitting tensile strengths exhibited significant increases following an increase in the strain rate. Conversely, the strain rate sensitivity decreased with the curing age. We deemed the CEB-FIP equation for normal cement concrete to be inadequate for estimating the strain rate sensitivity of UPPC.

Static and dynamic split tensile tests were conducted on rubber concrete with varied volume fractions of rubber particles that replaced fine aggregate (10%, 20%, 30%, 40%, and 50%, named as RC10, RC20, RC30, RC40, and RC50, respectively). The flattened Brazilian disc specimens were applied to determine the tensile properties and energy absorption capabilities under high strain rate by an SHPB (Split Hopkinson Pressure Bar) and medium strain rate by a drop-hammer testing machine. With a high-speed camera, the crack growth of specimens in the SHPB and drop-hammer impacting tests was observed and validated. The experimental result of five rubber concretes and one normal concrete without rubber particles was obtained, and the strain-rate effect on tensile strength of rubber concretes and normal concrete was confirmed. For high strain rate, RC10, RC20 and RC30 were sensitive to strain rate dependence, but rate dependence of RC40 and RC50 was lower than normal concrete. RC30 exhibited the most sensitivity and excellent energy absorption capability in static and dynamic tests. Excessive rubber content did not continually increase the toughness of the concrete under dynamic loadings.

Organic-inorganic hybrid methylammonium lead iodide perovskite (MAPbI3) is considered as new generation optoelectronic material. MAPbI3 single crystal is proved more excellent than its polycrystalline film and nano state counterparts, though the discrepancy is still pending. Referring MAPbI3 single crystal applications, physical anisotropy stands in its breach. However, it has not been drawn enough attentions till now. In this study, taking advantages of the natural exposed (100) and (112) facets of MAPbI3 single crystal grown from γ-butyrolactone (GBL) solution, the anisotropic optoelectronic performances based on of these two lattice planes were systematically explored through planar metal-semiconductor-metal (MSM) devices. An order enhanced photocurrents, 135% increased responsivity, and 128% heightened EQE on (112) plane device than those on (100) plane device under 5 V bias with irradiation power of 1 mW, remarkably demonstrated that (112) plane was more excellent in optoelectronic performances and light harvesting capability.

Hybrid perovskite MAPbCl3 is considered to be one of the most promising candidates applied in visible-blind UV-photo-detectors due to its outstanding optoelectronic properties. It is proved that the MAPbCl3 single crystal is more excellent than its polycrystalline counterpart because of its fewer defects and grain boundaries. When referring to a single crystal, the crystal orientation or crystal structure anisotropy is an inevitable topic, because structure anisotropy can affect or decide the optoelectronic properties of single crystals. In this study, both cubic and triangular prism MAPbCl3 single crystals with (100) and (110) crystallographic planes were successfully grown from mixed solutions. The crystal growth process, crystal structure and optical absorption were investigated. Moreover, by fabricating metal–semiconductor–metal (MSM) photo-detectors using Au interdigital electrodes on both (100) and (110) planes, the optoelectronic anisotropy was explored by comparing photocurrents, responsivity, external quantum efficiency and detectivity. According to the crystal structure and calculated charge density, the optoelectronic anisotropy in the MAPbCl3 single crystal was revealed.

Hybrid organic-inorganic lead halide perovskites (HOIPs) have received significant attention because of their impressive performances in the fields of solar cells and photoelectric detection. In the past five years, great efforts have been made to improve the crystallinity, reduce grain boundaries, and enhance the stabilities of perovskite films. Compared with films, HOIP single crystals possess fewer grain boundaries and stronger optoelectronic properties and can be applied in optoelectronic devices. As the most popular HOIP member, single crystals of MAPbX3 (X = Br, Cl) are deemed as important candidates for ultraviolet-visible photodetectors, in which the crystal structure anisotropy largely affects the detection performance. In this study, high-quality cubic single crystals of MAPbBr3 and MAPbCl3 were successfully grown from solutions. Taking advantages of their smooth (100) facets, planar metal-semiconductor-metal photodetectors were fabricated using Au interdigitated electrodes. The optoelectronic performances under nonpolarized and linearly polarized lights were explored. The optoelectronic performances were dependent on linearly polarized lights. Interestingly, both responsivity and external quantum efficiency were greatly enhanced under the excitation with linearly polarized lights. Moreover, the polarization-related optical absorptions and the electron densities within the (100) plane could be used to interpret different optoelectronic performances of single crystals of MAPbX3 (X = Br, Cl) under various linearly polarized lights.

MAPbI3 is deemed as the most prominent member in hybrid perovskites family because of its extremely optoelectronic properties. However, some issues and puzzles are still in expectation of their answers, such as stabilities, hysteresis, ferroelectricity, and so on. To bridge the distinctions between MAPbI3 single crystal and thin films, large-size single crystals are demanded. On the contrary, crystal structure anisotropy-dependent optoelectronic properties is an inevitable topic. A series of large-size MAPbI3 single crystals with (220) facets exposed were successfully grown, using high concentration solutions and large-size seed crystals to match growth rates of (100) and (220) facets. The optoelectronic properties of photocurrents, responsivity, EQE, and detectivity clearly showed significant anisotropy of optoelectronic properties in MAPbI3 single crystal. According to ion migration theory, the anisotropy of optoelectronic properties was interpreted. We hope this result will be helpful to guide oriented...

The optical properties of nanofluids need to be specified accurately to determine the effectiveness of nanofluids in photocatalytic reactions. In this study, the Monte Carlo method combined with the Mie scattering phase function was developed to calculate the optical properties and radiative transfer of TiO 2 nanofluids. The scattering effects caused by the directional scattering properties of the nanoparticles were considered during radiative transfer analysis of nanofluids. Size parameter ( χ ) was adopted as the criteria to divide the nanoparticles into two categories: small particle ( χ χ ≫ 1). The spectral transmissivity, absorption coefficient, extinction coefficient, and scattering characteristics of TiO 2 nanofluids were theoretically analyzed. The numerical results indicate that the optical properties of nanofluids with small particles vary smoothly with wavelength, while the optical properties of nanofluids with large particles oscillate with wavelength due to diffraction peaks. This study concluded that the scattering effects need to be considered during investigation of optical properties and radiative transfer of nanofluids.

A series of Pb(Zr1-xTix)O3 multilayer films alternatively stacked by Pb(Zr0.52Ti0.48)O3 and Pb(Zr0.35Ti0.65)O3 layers have been deposited on corning glass by magnetron sputtering. The films demonstrate pure perovskite structure and good crystallinity. A large tetragonality (c/a) of ∼1.061 and a shift of ∼0.08 eV for optical bandgap were investigated at layer engineered films. In addition, these samples exhibited a wild tunable electro-optic behavior from tens to ∼250.2 pm/V, as well as fast switching time of down to a few microseconds. The giant EO coefficient was attribute the strain-polarization coupling effect and also comparable to that of epitaxial (001) single crystal PZT thin films. The combination of high transparency, large EO effect, fast switching time, and huge phase transition temperature in PZT-based thin films show the potential on electro-optics from laser to information telecommunication. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Accepted version

Few-layer graphene reinforced nickel matrix (GNs/Ni) composites were fabricated by a facile in-situ processing strategy involving the transformation from solid carbon precursors to graphene reinforcements under the vacuum hot-press sintering. It enabled the homogeneous distribution of reinforcements, the effective interfacial bonding between graphene nanosheets and Ni matrix, as well as the resisted grain growth during the high-temperature consolidation process. The GNs/Ni composites exhibited exceptionally enhancement of the strength and ductility simultaneously. The composite with 0.3 wt% graphene achieved the optimal yield strength, tensile strength, and fracture elongation of 285 MPa, 611 MPa, and 56%, respectively, which were enhanced by 1.16, 1.34 and 1.37 folds compared to those of pure Ni bulk. The microstructures before and after tensile deformation demonstrated that the strengthening effect of in-situ grown graphene in the Ni matrix was attributed to the grain refinement and effective load transfer, while the toughening effect was related to the crack bridging and graphene pull-out mechanisms.

The design and synthesis of g-C3N4 with favourable physical-chemical architecture are important factors in influencing its photoactivity. Herein, a phosphorus (P) vapor assisted synthetic strategy was employed to fabricate the P-doped hollow g-C3N4 photocatalysts with ultrathin shell structure (

In this work, we constructed a red phosphorus (RP)/TiO2 composite system via a chemical vapor deposition strategy. The evolution of the fibrous phased RP nanorods on the surface of anatase TiO2 spheres was rationally adjusted by controlling the composition of precursors. The optimal RP/TiO2 composite exhibited a significantly enhanced visible-light-driven photocatalytic H2 generation rate of 681 μmol h−1 g−1. The tightly interior surface bonding between RP and TiO2 greatly promoted the efficient charge transfer and redistribution by suppressing the charge recombination and self-trapping processes within TiO2, resulting in prolonged lifetimes of the active charges during the photocatalytic process as investigated in detailed using femtosecond time-resolved transient absorption (fs-TA) spectroscopy.

The dynamic properties of a granite rock employed in crushed form as coarse aggregate in high-strength concrete, were experimentally characterised, and the average values obtained were assumed to be representative of the properties of the coarse aggregate. Cylindrical specimens were core-drilled from the granite rock, then cut into various lengths for different tests, i.e. static and dynamic uniaxial compression, as well as static and dynamic splitting tension (Brazilian tests). From the data obtained, the effects of strain rate on the mechanical properties (e.g. stress-strain relationship, tensile and compressive strengths) were analysed. Significant rate dependence was observed for both tensile and compressive responses, and this was quantified via a dynamic increase factor (DIF, the ratio between the dynamic and static strength). For compression, the DIF follows the CEB-FIP 2010 equation frequently used to describe the rate sensitivity of normal-strength concrete. The tensile response shows a stronger rate dependence than the compressive response, and its DIF deviates from predictions based on the CEB-FIP equation, which underestimates the tensile DIF, and defines a much higher strain rate at which transition from a gradual to a rapid increase in the DIF occurs. An empirical DIF formula, derived from fitting of experimental data, is proposed to describe the tensile rate sensitivity. Apart from experimental characterisation, efforts were also directed at identifying a constitutive model to describe the dynamic behaviour of the granite coarse aggregate, and the Johnson-Holmquist 2 (JH-2) model, commonly used to capture the impact response of brittle materials (e.g. rock, ceramic) was chosen. The dynamic tensile and compressive properties obtained from experiments, were employed to determine the material parameters in the JH-2 model. Finite element modelling of the dynamic compression and splitting tension tests was performed, using the JH-2 model and the material constants derived, to describe the behaviour of the granite specimen. The simulation results correlate well with experimental measurements.

Development of metal-free carbon-based electrocatalysts with high-efficiency and excellent durability towards both oxygen and hydrogen evolution reactions (OER and HER) in a single electrolyte system is crucial yet challenging for sustainable energy generation. In this work, we report a facile and scalable strategy for fabricating self-supporting boron carbon oxynitride nanofibrous (BCNONF) mats with controllable boron contents via electrospinning and subsequent thermal treatment. Notably, the optimal BCNONF mat affords outstanding OER performance in alkaline electrolyte with low overpotential of 403 mV at 10 mA·cm−2, small Tafel slop of 72.9 mV·dec−1, and high stability (88.1% current density retention after 10 h), outperforming the commercial Ir/C benchmark. Moreover, it can serve as a remarkable HER catalyst with better stability than that of the commercial Pt/C counterpart in the same electrolyte, indicating its bifunctional characteristics. When employed as both anode and cathode of an electrolyzer, the self-supporting BCNONF mats exhibit superior activities with a potential of only 1.79 V at 10 mA·cm−2 and high long-term durability (90.6% current density retention after 50 h) for overall water splitting. Furthermore, density functional theory (DFT) calculations reveal that the remarkable OER and HER bifunctional performance of the BCNONF catalyst are originated from the reduced adsorption strength of O atom and the stronger H* adsorption on the BCNO surface as compared to those on CNO surface, which in turn facilitate efficient interfacial charge transfer between the electrocatalytic intermediates and the BCNONF catalyst.

Safety associated with ammonia requires the development of gas sensors for various applications, including food spoilage detection and livestock farming management. Radio-frequency identification (RFID) is a promising technology to fabricate a wireless gas sensor for remote concentration readouts. However, most of the reported RFID-enabled gas sensors determined the analyte concentration by using the reflection coefficient (S11) of sensor tag as an indicator, which was prone to be disturbed by measurement variations and external disturbances. Herein, we reported a wireless gas sensor with high tolerance to measurement variations through recognizing the resonant frequency (f) of sensor tag, enabling reliable detection of ammonia and various biogenic amines in real time. Compared with other conducting 2D materials, molybdenum disulfide (MoS2) exhibits tunable semiconducting properties and high specific surface area, which can serve a promising candidate for RFID-based gas sensors. By immobilizing silver nanoparticles-decorated molybdenum disulfide nanosheets (Ag@MoS2) on a nested split-ring resonator (SRR), the SRR sensor tag exhibited significant f downshifts at increasing ammonia concentrations, featuring with high sensitivity to ammonia (0.097 ppm–1, based on relative f changes), low detection limit ( 10,000 to provide reliable readouts of localized concentrations of biogenic amines.