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Compared to extremely high efficiencies achieved by their normal mesoscopic counterparts, significant improvement in those of inverted mesoporous perovskite solar cells (PSCs) has yet to be made. The incorporation of plasmonic nanostructures into mesoporous films has been reported to improve their optoelectronic properties through plasmon resonance effects. Herein, gold nanoparticles coated with a thin layer of a semiconductor (NiOx) are introduced into a mesoporous NiOx layer. Using illumination-dependent characterization, we identify a plasmon-assisted metal-to-semiconductor charge transfer (PACT) mechanism. The hole injection from the Au core into the NiOx shell is not only achieved in the dark due to the ohmic contact nature at the Au@NiOx heterostructure, but also facilitated under illumination due to the plasmon-induced interfacial processes. The charge transfer is observed to substantially downshift the valence band edge and enhance the photoconductivity, as well as favor trap filling of the mesoporous NiOx film, which can lower the effective energy barrier and facilitate hole extraction in PSCs. Consequently, embedding Au@NiOx into the mesoporous layer elevates all of the device parameters simultaneously, with a power conversion efficiency of 20.6% in inverted mesostructured PSCs. These results advance our physical understanding of metal–semiconductor heterostructures and offer additional strategies for manipulating the carrier dynamics of PSCs.

Lithium sulfur batteries (LSBs) draw extensive interest because of the ultra-high capacity and low material cost. However, the sluggish lithium polysulfides (LIPSs) conversion processes are detrimental to cycle stability and rate capability, inhibiting the commercial application of LSBs. Here we present the well-designed FeCo alloy catalysts anchored on porous carbon (FeCo-C) as sulfur host to improve the electrochemical performance by accelerating the conversion reactions. The FeCo alloy demonstrates high catalytic effect and strong adsorption capability of LIPSs, in which potential polarization can be greatly decreased and “shuttle effects” can be largely avoided. As a result, the obtained S/FeCo-C composites show an initial specific capacity of 791.9 mAh g−1 at a large current density of 2 C and maintain 502.5 mAh g−1 even after 500 cycles. Moreover, 720 mAh g−1 (corresponding to 70% retention) can be achieved after 100 cycles at 0.2 C with a high sulfur content of 80 wt%, enabling high sulfur utilization. This work not only provides a new insight to investigate the conversion kinetics of LiPSs, but also opens up a new avenue for advanced lithium sulfur batteries.

Coriolis effect, regarded as one of the universal physical law, describes the phenomenon that an arbitrary object will deflect left relative to the original speed when the object is laid on a reference frame with clockwise rotation, and vice versa. In this Letter, we designed a specialized piezoelectric metamaterial which is consist of a piezoelectric sensing element, an elastic rubber, and a mass element by using the finite element method (FEM). The FEM results suggested that the deflection behavior in this type of piezoelectric metamaterial, could strictly break the Coriolis effect and a negative Coriolis effect was observed. The exploration of negative Coriolis effect in piezoelectric metamaterial would provide theoretical guideline for the further design of ultrasensitive gyroscopes.

Flexoelectricity refers to the mechanical-electro coupling between strain gradient and electric polarization, and conversely, the electro-mechanical coupling between electric field gradient and mechanical stress. This unique effect shows a promising size effect which is usually large as the material dimension is shrunk down. Moreover, it could break the limitation of centrosymmetry, and has been found in numerous kinds of materials which cover insulators, liquid crystals, biological materials, and semiconductors. In this review, we will give a brief report about the recent discoveries in flexoelectricity, focusing on the flexoelectric materials and their applications. The theoretical developments in this field are also addressed. In the end, the perspective of flexoelectricity and some open questions which still remain unsolved are commented upon.

Extraordinary room-temperature CO sensing capabilities have been surprisingly discovered for Pd-SnO2 composite nanoceramics, yet the mechanism behind them is still largely unknown. In this work, some interesting insights into the room-temperature CO sensing behaviors of Pd-SnO2 system have been revealed through a comparative study among samples of different Pd contents and different heat-treatment temperatures. Pressed compacts of Pd-SnO2 nano-mixtures with 0.125–10 wt% Pd have been prepared and heat-treated in air over a wide temperature range of 600–1200 °C. While most samples show no responses to CO at room temperature, those of relatively low Pd content (≤ 2 wt%) and heat-treated at unusually high temperatures (e.g. ≥ 1000 °C for samples of 2 wt% Pd) exhibit extraordinary room-temperature CO sensing capabilities, such as a response of 5, a response time of 30 s and a recovery time of 40 s for 0.005% CO – 20% O2 – N2. X-ray photoelectron spectroscopy analyses indicate that Pd2+ is present in all heat-treated samples, but Pd4+ can only be detected in those samples with extraordinary room-temperature CO sensing capabilities. Further experiments suggest that SnO2 plays an indispensable role in forming Pd4+ in Pd-SnO2 system at unusually high temperatures, and Pd4+ leads to extraordinary room-temperature CO sensing process via CO chemisorption on SnO2. These results clearly show a magic effect of charge states of catalysts on the performance of room-temperature metal oxide gas sensors and highlight the importance of creating novel chemical states of catalysts under some unusual conditions.

Summary Among all the solutions to improve long-term stability of perovskite solar cells, p-i-n heterojunction with all-metal-oxide charge transporting layers show their attractive features. However, these devices require an efficient electron-transporting layer (ETL) fabricated on top of the perovskites in which the commonly used oxide nanocrystals are limited by their imperfect surface. Here, a novel surface-passivation strategy was adopted by anchoring ZnO nanoparticles with fullerene nano-shells (Fa-ZnO) to mitigate trap states and passivate surface hydroxyl groups. We evidence the Fa-ZnO can be easily processed on top of perovskite as a high-quality ETL that improves electron extraction efficiency and suppresses ion diffusion/moisture penetration. In addition, the presence of fullerene shells allows Fa-ZnO nanoparticles to penetrate into perovskite precursors before crystallization, resulting in n-type sensitized configuration. With mesoscopic NiOx as hole-collecting contact, the p-n dual sensitization configuration has enabled all-metal-oxide devices to achieve state-of-the-art efficiencies of 21.1% with greatly improved performance longevity.

Although tremendous progress has been made in preparing sulfur nanoparticles to achieve high-rate lithium sulfur (Li-S) batteries, the synthetic methods involved are usually toxic, complicated and costly. To solve the above problem, a simple and green method through high pressure steam is developed to prepare sulfur nanoparticles (

Tin-doped indium oxide (ITO)/Au/ITO sandwich structures with varying top and bottom ITO film thicknesses were deposited by magnetron sputtering. The effects of varying thickness of the two ITO films on the structural, electrical, and optical properties of the sandwich structures were investigated. X-ray diffraction spectra showed that by inserting an ultrathin Au film, the average grain size of the top ITO layer was significantly increased, but not for the bottom one. The optical properties of the sandwich structures were measured by transmittance measurement and spectroscopic ellipsometry. In the symmetric structure, where the top and the bottom ITO layers had the same thickness, we demonstrated that the crossover wavelength can be changed from the visible range (830 nm) to the near-infrared range (1490 nm) by increasing the top as well as bottom ITO thickness, corresponding to a plasmonic tuning ability of over 600 nm. The evaluation of this trilayer structure as a plasmonic device was asserted based on three quality factors. A comparison of the performance of this trilayer structure with conventional materials was also discussed.

Harvesting environmental energy to generate electricity is a key scientific and technological endeavour of our time. Photovoltaic conversion and electromechanical transduction are two common energy-harvesting mechanisms based on, respectively, semiconducting junctions and piezoelectric insulators. However, the different material families on which these transduction phenomena are based complicate their integration into single devices. Here we demonstrate that halide perovskites, a family of highly efficient photovoltaic materials1,2,3, display a photoflexoelectric effect whereby, under a combination of illumination and oscillation driven by a piezoelectric actuator, they generate orders of magnitude higher flexoelectricity than in the dark. We also show that photoflexoelectricity is not exclusive to halides but a general property of semiconductors that potentially enables simultaneous electromechanical and photovoltaic transduction and harvesting in unison from multiple energy inputs., This work was supported by the National Natural Science Foundation of China under grant nos. 51962020, 51972157, 11574126 and 11604135, and partly by the National Key Research and Development Plan of China (2017YFB0406300). L.S. and S.K. thank Nanchang University for support. G.C. acknowledges support from the Generalitat de Catalunya (Grant 2017 SGR 579) and from MINECO (National Plan MAT2016-77100-C2-1-P and Severo Ochoa SEV-2017-0706). M.S. acknowledges the support of MINECO through grants no. MAT2016-77100-C2-2-P and no. SEV-2015-0496, Generalitat de Catalunya (grant no. 2017 SGR1506) and the European Research Council under the European Union’s Horizon 2020 research and innovation programme (grant no. 724529). We thank D Torres for the graphic design of Fig. 2a,b.

Mesoporous nickel hydroxides Ni(OH) 2 /graphene nanohybrids were fabricated via heteroassembly of oppositely charged exfoliated Ni(OH) 2 and graphite oxide (GO) nanosheets in formamide. The resulting hybrids exhibited a hierarchically porous networks composed of Ni(OH) 2 and reduced graphite oxide (rGO) nanosheets. When the atomic ratio of Ni to C in hybrids was optimized to be 0.63, the resulting hybrids exhibited a specific capacitance of 1488 F/g at a scan rate of 1 mV/s with an excellent cycling stability. Originating from their heterogeneous compositions and hierarchically porous structures, almost all of their Faradic capacitance and non-Faradic capacitance could be employed. The rationally designed Ni(OH) 2 /rGO nanohybrids with completely engineered interface were used as cathode for asymmetric supercapacitors (ASCs). Optimized Ni(OH) 2 /rGO//AC ASC exhibited a high capacitance of 102.3 F/g. Therefore, a high energy density of 36.7 Wh/Kg and power density of 7.98 KW/Kg have been realized. Hence the present Ni(OH) 2 /rGO hybrids should be promising candidates as high-performance supercapacitors for energy storage and conversion.

A microscopic understanding of the mechanism of direct ice formation from water vapor has a significant benefit for controlling the processes involving ice condensation and evaporation. However, previous studies on this topic have been limited to theoretical simulations or optical observations. Here, by in situ observation via environmental scanning electron microscopy (ESEM), we revealed that hexagonal ice crystals are developed by a step-by-step pathway in a supersaturated water vapor environment. Furthermore, we also discerned that such steps came from two different origins, which are screw dislocations and initial steps. In addition, the relationship between the edge-length (of hexagonal ice crystals) and the growth time was quantitatively studied at controlled temperatures and pressures by experimental data fitting. This study shows that qualitative and quantitative observations of ice formation can be made with simple setups, and it should inspire future investigations toward important physicochemic...

In this work, a high efficient mechano-/pyro- bi-catalysis for dye wastewater decomposition is found in the hydrothermally-synthesized NaNbO3 nanofibers through piezoelectrically and pyroelectrically harvesting vibration and cold-hot energy. In response to vibration together with 15–50 °C cold-hot cycles, the bi-catalytic decomposition ratio of NaNbO3 nanofibers can be up to 86.5%, which is higher than that of the pyro-catalysis of ~ 63.3% or the mechano-catalysis of ~ 75.8%. Such mechano-/pyro- bi-catalysis of NaNbO3 nanofibers possesses the advantages of high efficiency, environmental benignity and being easily scaled up. Therefore, NaNbO3 may become a potential candidate for mechano-/pyro- bi-catalysis through utilizing ubiquitous vibration and thermal energy.

We deposited WS2 thin films by pulsed laser deposition on sapphire substrates at room temperature, and studied the effect of post-annealing temperature on the quality of the WS2 films. By comparing the full-width-at-half-maximum of the characteristic WS2 Raman peaks, we explored the relationship between the post-annealing temperature and the crystallinity of WS2 films. Optoelectronic measurements conducted on post-annealed WS2 film-based photodetectors showed improvement with rising annealing temperatures. Our study revealed the possibility of preparing large-area dichalcogenides for optoelectronic applications.

Carbon materials are deemed to be competitive candidate electrode materials for energy storage systems. It is still a great challenge to explore advanced carbon-based electrode materials for high-performance supercapacitors by a facile, economical and efficient method. In this work, N-, P-, S-, O-self-doped carbon nanosheets with high surface area and well-developed porosity are successfully prepared by pyrolysis carbonization and post KOH activation from silkworm excrement, a novel abundant, low-cost and eco-friendly agricultural waste. Thanks to their unique multi-heteroatom doping and porous structure, the obtained carbon materials exhibit high charge storage capacity with a specific capacitance of 401 F g−1 at a current density of 0.5 A g−1 in 6 M KOH and good cycling stability with a capacitance retention of 93.8% over 10000 cycles. A symmetric supercapacitor device using 1 M Na2SO4 aqueous solution as the electrolyte can deliver a specific capacitance of 41.7 F g−1 at a current density of 0.5 A g−1, and a high energy density of 23.17 Wh kg−1 at a power density of 500 W kg−1 with a wide voltage window of 2.0 V. This work develops a new strategy to produce favorable carbon-based electrode materials for supercapacitors with high electrochemical performances.

Layered metal sulfides (MoS2, WS2, SnS2, and SnS) offer high potential as advanced anode materials in sodium ion batteries upon integration with highly-conductive graphene materials. However, in addition to being costly and time-consuming, existing strategies for synthesizing sulfides/graphene composites often involve complicated procedures. It is therefore essential to develop a simple yet scalable pathway to construct sulfide/graphene composites for practical applications. Here, we highlight a one-step, template-free, high-throughput “self-bubbling” method for producing MoS2/graphene composites, which is suitable for large-scale production of sulfide/graphene composites. The final product featured MoS2 nanoflakes distributed in three-dimensional macroporous monolithic graphene. Moreover, this unique MoS2/graphene composite achieved remarkable electrochemical performance when being applied to Na-ion battery anodes; namely, excellent cycling stability (474 mA h g−1 at 0.1 A g−1 after 100 cycles) and high rate capability (406 mA h g−1 at 0.25 A g−1 and 359 mA h g−1 at 0.5 A g−1). This self-bubbling approach should be applicable to delivering other graphene-based composites for emerging applications such as energy storage, catalysis, and sensing.

Surface modification is an essential step in engineering high performance nickel-rich layered (NLO) cathode materials that can withstand the increasingly harsh environment encountered in lithium-ion batteries. However, most traditional technologies suffer disadvantages such as low diffusion kinetics, processing difficulties and/or compatibility issues. Here, based on the dual-Kirkendall effect, we report an efficient, self-guided way for fabricating a multifunctional NiTiO3 (NTO) nanocoating to stabilize the cathode/electrolyte interface for NLO. The NTO nanocoating can epitaxially and chemically bond to the surface framework of NLO particles and eliminate surface lithium residues by evolving into a Li–Ni–Ti–O mixed phase coating that is mainly composed of Li2−xTiO3. Taking full advantage of such a novel multifunctional NTO nanocoating, the structural degradation in NLO cathodes can be effectively suppressed, leading to excellent rate capability and cyclability. This method provides insights into novel surface chemistry that prevents high performance layered electrode materials from structural degradation.

Aurivillius oxyfluoride perovskites exhibit great potential in photocatalysis, which are generally prepared by high-temperature solid-state reactions and some impurity phases are always unavoidable. Herein, a new low-temperature solution method has been successfully developed for the synthesis of Bi2NbO5F and Bi2TaO5F pure phases. The electron microscopy results reveal that the products were composed of the hierarchical hollow spheres with porous surface. The formation and growth mechanisms of the products were proposed based on the time-dependent evolution. The experimental band gaps of Bi2NbO5F (2.86 eV) and Bi2TaO5F (2.95 eV) were also first obtained. The photodegradation tests demonstrated that the products could be effectively served as catalysts for degradation of Rhodamine B and methyl orange under UV-light irradiation via the photocatalytic reaction, and also could be used in visible-light degradation of Rhodamine B via the photosensitization process. This low-temperature solution preparation of Aurivillius oxyfluorides opens a new facile route to tackle the versatile chemistry of various oxyfluoride perovskites.

As a promising cathode material for Li-ion batteries (LIBs), Li-rich layered oxide (LLO) has attracted the most interest due to its superior performance and attractive characteristics, such as, extremely high capacity and energy density, low cost, and environmental friendliness. However, LLO cathode materials are facing a fundamental challenge of performance degradation as a result of the intrinsically poor rate capability and structural instability. Here we report the synthesis of high performance spinel/LLO heterostructured composite with aligned Li-ion channels by a composition modulated epitaxy method. The hetero-epitaxial nanostructure provides highly anisotropic Li-ion diffusion channels in spinel/LLO composite that significantly improve the electrochemical performance. Discharge capacities as high as 307, 282, 269, 227, 200 mA h g −1 at 0.1, 0.5, 1.0, 3.0 and 5.0 C rates, respectively, and reversible capacity of 286 mA h g −1 after 100 cycles at 0.2 C rate can be attained. This work sheds light on the comprehensive design of heterostructured composites for high-performance electrode applications and opens up new opportunities for next-generation LIBs.

Bismuth compounds have been greatly spurred due to their extensive applicaton in photocatalysis which is a promising technique for environmental decontamination. In this research, Bi2TiO4F2 hierarchically porous hollow spheres are successfully prepared by a simple solvothermal method. X-ray powder diffraction patterns show that the sample has an Aurivillius-type layered perovskite structure. The electron microscopy analyses reveal that the obtained hierarchical hollow spheres have a porous surface composed of interlaced nanoplates. The formation and growth mechanisms of the product are proposed based on the time-dependent evolution experiments. The band gap of the prepared Bi2TiO4F2 sample is measured to about 2.85 eV. The photocatalytic activity and mechanisms are systematically explored. The results demonstrate that the product can be effectively served as catalyst for degradation of Rhodamine B and methyl orange under UV-light irradiation via the photocatalytic reaction, and also can be used in visible-light degradation of Rhodamine B via the photosensitization process.

High-performance Li-rich layered oxide (LRLO) cathode material is appealing for next-generation Li-ion batteries owing to its high specific capacity (>300 mAh g–1). Despite intense studies in the past decade, the low initial Coulombic efficiency and unsatisfactory cycling stability of LRLO still remain as great challenges for its practical applications. Here, we report a rational design of the orthogonally arranged {010}-oriented LRLO nanoplates with built-in anisotropic Li+ ion transport tunnels. Such a novel structure enables fast Li+ ion intercalation and deintercalation kinetics and enhances structural stability of LRLO. Theoretical calculations and experimental characterizations demonstrate the successful synthesis of target cathode material that delivers an initial discharge capacity as high as 303 mAh g–1 with an initial Coulombic efficiency of 93%. After 200 cycles at 1.0 C rate, an excellent capacity retention of 92% can be attained. Our method reported here opens a door to the development of hig...

Carbon coated Li3V2(PO4)3 composites were prepared by a modified carbothermal reduction method. The method has the advantages of being simple and scalable, while the whole synthesis is devoid of any reducing/protecting gases, therefore, it can be directly carried out in muffle furnace. The obtained Li3V2(PO4)3@C composites have particles sizes from 500 nm to 3 μm, and with homogeneous carbon coating layer thickness of about 7 nm. The battery based on this Li3V2(PO4)3@C composites cathode exhibits a specific discharge capacity of 130.9 mA h g−1 at 0.1 C, and exhibits an initial specific discharge capacity of 102.8 mA h g−1 even at 10 C and almost keeps 96.6% of initial capacity retention after 500 cycles. The performance enhancement can be directly ascribed to the robust structure merits of the Li3V2(PO4)3@C composites synthesized by the modified carbothermal reduction method. Furthermore, the as-developed method has the potential to be expanded to other lithium transition-metal phosphates (such as lithium iron phosphate), which conventionally need to be sintered in reductive or protective atmospheres.

Fe-doped HTaWO6 (H1−3xFexTaWO6, x = 0.23) nanotubes as highly active solid acid catalysts were prepared via an exfoliation–scrolling–exchange process. The specific surface area and pore volume of undoped nanotubes (20.8 m2 g−1, 0.057 cm3 g−1) were remarkably enhanced through Fe3+ ion-exchange (>100 m2 g−1, 0.547 cm3 g−1). Doping Fe ions into the nanotubes endowed them with improved thermal stability due to the stronger interaction between the intercalated Fe3+ ions and the host layers. This interaction also facilitated the preservation of effective Bronsted acid sites and the generation of new acid sites. The integration of these functional roles resulted in Fe-doped nanotubes with high acidic catalytic activities in the Friedel–Crafts alkylation of anisole and the esterification of acetic acid. Facile accessibility to active sites, generation of effective Bronsted acid sites, high stability of the tubular structure and strong acid sites were found to synergistically contribute to the excellent acidic catalytic efficiency. Additionally, the activity of cycled nanocatalysts can be easily recovered through annealing treatment.

Despite the high potential of using hydrothermal methods in the industrial production of TiO2 one-dimensional nanostructures (nanotubes, nanowires, etc.) for either environmental or energy applications, there has been much debate on the crystalline structure of the resultant hydrothermal product due to its weak crystallinity and small size. As a result, a range of titanates have been proposed as possible structures for the as-synthesized product. Herein, by using in situ transmission electron microscopy and a highly stable heating system, we microscopically explore the hydrothermally synthesized TiO2-derived single-crystal nanorods and their subsequent structural conversion upon annealing. In our case, a full set of evidence obtained from chemical, crystallographic, and valence state analyses suggests that the as-synthesized product possesses a Na0.8Ti4O8 structure, and undergoes a monoclinic-to-monoclinic transition (topochemical transformation) towards TiO2 (B) via desodiation and reorientation of TiO6 octahedra under constant heating. The as-observed kinetic restructuring process is further examined through density functional theory calculations, revealing the energy-favourable nature of the process. Such an observation at high spatial resolution demonstrates itself as an effective complement to conventional characterization methods, and may pave the way for large-scale synthesis of TiO2-based nanostructures.

Co3O4 as an electrode material has been widely used for energy storage. However, it has low capacity and is generally associated with poor cycle life and stability. We designed the Co3O4 hollow tube arrays on Ni foam though a facial strategy based on the ZnO sacrificial template method. Benefit from the unique hollow structure advantage and the low resistance brought by the use of self-supporting method without binder. Compared to Co3O4 directly grown on a substrate, the as-prepared hollow Co3O4 structure exhibits large electrochemical capacity of 748.1 C g−1 at 1 A g−1, the result is larger than that of pure Co3O4 directly growing on the substrate without adding Zn2+ as the template. Furthermore, a hybrid supercapacitor device Zn@Co//AC reaches the specific energy of 60.91 Wh kg−1 under the specific power of 450 W kg−1.

With a similar electronic structure as that of platinum, molybdenum carbide (Mo2C) holds significant potential as a high performance catalyst across many chemical reactions. Empirically, the precise control of particle size, shape, and surface nature during synthesis largely determines the catalytic performance of nanoparticles, giving rise to the need of clarifying the underlying growth characteristics in the nucleation and growth of Mo2C. However, the high-temperature annealing involved during the growth of carbides makes it difficult to directly observe and understand the nucleation and growth processes. Here, we report on the use of advanced in situ transmission electron microscopy with atomic resolution to reveal a three-stage mechanism during the growth of Mo2C nanoparticles over a wide temperature range: initial nucleation via a mechanism consistent with spinodal decomposition, subsequent particle coalescence and monomer attachment, and final surface faceting to well-defined particles with minimum ...

Well-organized epsilon-MnO2 hollow spheres/reduced graphene oxide (MnO2HS/RGO) composites have been successfully constructed via a facile and one-pot synthetic route. The ε-MnO2 hollow spheres with the diameter of ∼500 nm were grown in situ with homogeneous distribution on both sides of graphene oxide (GO) sheets in aqueous suspensions. The formation mechanism of the MnO2HS/RGO composites has been systematically investigated, and a high specific capacitance and good cycling capability were achieved on using the composites as supercapacitors. The galvanostatic charge/discharge curves show a specific capacitance of 471.5 F g(-1) at 0.8 A g(-1). The hollow structures of ε-MnO2 and the crumpled RGO sheets can enhance the electroactive surface area and improve the electrical conductivity, thus further facilitating the charge transport. The MnO2HS/RGO composite exhibits a high capacitance of 272 F g(-1) at 3 A g(-1) (92% retention) even after 1000 cycles. The prominent electrochemical performance might be attributed to the combination of the pseudo-capacitance of the MnO2 nanospheres with a hollow structure and to the good electrical conductivity of the RGO sheets. This work explores a new concept in designing metal oxides/RGO composites as electrode materials.

Wearable supercapacitors have attracted considerable research interest in recent years. However, most of the wearable supercapacitors reported are either in the form of fibers or based on carbon cloth which have to be knitted into commercial cloth for wearable applications. Here we report the growth of Cu(OH)2 nanobelt arrays directly on commercial Dacron cloth which serves as a positive electrode for supercapacitors. The as-prepared electrode has a high specific capacitance of 217 mF·cm−2 at a current density of 0.5 mA·cm−2 with a capacitance retention of 90% at a current density of 2 mA·cm−2 after 3000 charge/discharge cycles. A flexible all-solid-state asymmetrical supercapacitor is fabricated by sandwiching the Dacron cloth supported Cu(OH)2 nanobelt arrays (positive electrode) between two carbon nanofiber matrices (negative electrodes), using KOH-PVA gel as the electrolyte and as the separator. A high areal capacitance of 195.8 mF·cm−2 at a current density of 1 mA·cm−2 can be achieved. The textile supercapacitor exhibits an energy density of 3.6 × 10−2 mWh·cm−2 at a power density of 0.6 mW·cm−2 with a voltage window of 1.2 V. This sandwich type of supercapacitor based on commercial Dacron cloth opens a novel way of integrating supercapacitors into textiles, showing great promise for wearable electronic applications.

Silver nanofibers (Ag NFs) have attracted considerable attention for their potential applications in transparent electrodes to replace indium tin oxide (ITO). One of the key factors for hindering the performance of transparent electrodes is the junction resistance between nanofibers. Here, we combine an electrospinning method and electroless deposition to fabricate a Ag NFs transparent conducting electrode (TCE). Ultra-long PVDF/SnCl2 nanofibers were firstly fabricated onto a flexible substrate as the template of Ag TCE. Subsequently, electroless deposition was adopted to deposit Ag onto the nanofiber template to decrease the junction resistance. The morphology and composition of the Ag NFs are systematically analyzed. The as-fabricated Ag TCE shows a conductivity of 73.55 Ω □−1 and 15.35 Ω □−1 (transmittance of 84% and 75%) and maintains its conductive properties even after 100 bending cycles. Importantly, the figure of merit Φ = T10/Rs, Ω □−1, commonly used to evaluate the performance of transparent conducting electrodes, calculated for our Ag NF TCE is 2.3 × 10−3 Ω □−1 (T ∼ 84%, Rs ∼ 73.55 Ω □−1). This value is much higher than that of other transparent electrodes, such as SWCNT (∼0.8 × 10−3 Ω □−1), graphene (∼0.3 × 10−3 Ω □−1), Ni film (∼0.7 × 10−3 Ω □−1). In addition, this Ag NFs transparent electrode is fabricated under ambient temperature and applicable to various substrates. Our results present a facile method for fabricating a TCE with relatively low Ag materials cost and reducing the junction resistance between nanofibers.

We report on the growth of high-quality stoichiometric layered Cr2Se3 single crystals with metallic and noncollinear antiferromagnetic ground state using the chemical vapor transport (CVT) method. The crystals show weak ferromagnetism in the in-plane and out-of-plane directions below the Neel temperature (T N), however, the field-cooled out-of-plane magnetization at 500 Oe and 10 K (∼0.24 μ B/f.u.) is approximately 15 times larger than that of the in-plane one, indicating strong c-axis easy uniaxial magnetic anisotropy, which is further supported by the in-plane and out-of-plane isothermal anisotropic magnetic hysteresis loops and the angular dependent magnetoresistance (MR). The latter also reveals a decrease of the coercive field of the crystal upon the tilting of the weak ferromagnetic easy axis away from the direction of the magnetic field. Further, the out-of-plane isothermal MR are negative below T N and show butterfly shapes for T < 10 K and couple with the magnetic hysteresis M(H) loop. These results may help researchers better understand the interplay between the weak ferromagnetism and the magnetotransport properties of 2D itinerant noncollinear antiferromagnetic systems.

The nucleation of crystals from ubiquitous solid-state reactions impacts a wide range of natural and synthetic processes and is fundamental to physical and chemical synthesis. However, the microscopic organization mechanism of amorphous precursors to nanoscale clusters of ordered atoms (nucleus) in an all-solid environment is inaccessible by common experimental probes. Here, by using in situ transmission electron microscopy in combination with theoretical simulations, we show in the reactive formation of a metal carbide that nucleation actually occurs via a two-step mechanism, in which a spinodal-structured amorphous intermediate reorganizes from an amorphous precursor and precedes the emergence of a crystalline nucleus, rather than direct one-step nucleation from classical consideration. We further isolated a series of sophisticated dynamics during formation and development of the nucleus in real-space and interpreted them by thermodynamic favorability. We anticipate that such an indirect organization mechanism which contains a metastable intermedium among the free energy gap between precursors and nanocrystals has its chance in underlying most solid-state crystallizations, whereas the as-established experimental method represents a step forward in exploring fundamentals in chemical reaction, material engineering, etc.

In this letter, we report on significant flexoelectric fatigue in lead-free (K,Na,Li)(Nb,Sb)O3 (KNNLS) ceramics. In the ferroelectric phase of KNNLS, the observed effective transverse flexoelectric coefficient, which is initially as high as 1 μC/m, decreases nonlinearly with increasing cycles of strain gradient, and the fatigue regulation is well reproduced by a stretched exponential function. By comparing the time dependence of dielectric permittivity and ferroelectricity in KNNLS ceramics, we conclude that large flexoelectric and flexocoupling coefficients in the ferroelectric phase originate mainly from ferroelectricity and that the related flexoelectric fatigue is likely due to the pinning effect of ferroelectric domains.

Metal-phosphorus-trichalcogenides (MPTs), represented by NiPS3, FePS3, etc, are newly developed 2D wide-bandgap semiconductors and have been proposed as excellent candidates for ultraviolet (UV) optoelectronics. In spite of having superior advantages for solar-blind UV photodetectors, including those free of surface trap states, being highly compatible with versatile integrations as well as having an appropriate band gap, to date relevant study is rare. In this work, the photoresponse characteristic of UV detectors based on few-layer FePS3 has been comprehensively investigated. The responsivity of the photodetector, which is observed to be determined by bias gate voltage, may achieve as high as 171.6 mAW-1 under the illumination of 254 nm weak light, which is comparable to most commercial UV detectors. Notably, both negative and positive photoconductivities exist in the FePS3 photodetectors and can be controllably switched with bias voltage. The eminent and novel photoresponse property paves the way for the further development and practical use of 2D MPTs in high-performance UV photodetections.

In this paper, high-performance conducting Al-doped ZnO (AZO) electrodes were deposited on transparent and flexible muscovite mica substrates. The use of mica as a substrate material makes a van der Waals epitaxy possible, which significantly improves the structural, electrical, and optical properties of deposited AZO single-crystal-like films. AZO/mica retains its low electric resistivity, even after continuous bending of up to 1000 times on account of the unique layered structure of mica. When used as a transparent heater, AZO/mica shows an ultrahigh heating rate (200 °C/s) across large areas, which is a record among flexible transparent heaters.

A microscopic understanding of the growth mechanism of two-dimensional materials is of particular importance for controllable synthesis of functional nanostructures. Because of the lack of direct and insightful observations, how to control the orientation and the size of two-dimensional material grains is still under debate. Here we discern distinct formation stages for MoS2 flakes from the thermolysis of ammonium thiomolybdates using in situ transmission electron microscopy. In the initial stage (400 °C), vertically aligned MoS2 structures grow in a layer-by-layer mode. With the increasing temperature of up to 780 °C, the orientation of MoS2 structures becomes horizontal. When the growth temperature reaches 850 °C, the crystalline size of MoS2 increases by merging adjacent flakes. Our study shows direct observations of MoS2 growth as the temperature evolves, and sheds light on the controllable orientation and grain size of two-dimensional materials., MoS2 nanostructures are potentially useful in electronic applications. Here, Fei et al. show using in situ electron microscopy that MoS2 grows in a vertical manner at low temperature, then rotates to horizontal structures, and finally develops in size by merging adjacent flakes at high temperature.

Flexoelectricity couples strain gradient to polarization and usually exhibits a large coefficient in the paraelectric phase of the ferroelectric perovskites. In this study, we employed the relaxor 0.3Pb(In1/2Nb1/2)O3-0.35Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 (PIN-PMN-PT) single crystals to study the relationship between flexoelectric coefficients and the crystal structure. The flexoelectric coefficients in PIN-PMN-PT single crystal are found to vary from 57 μC/m at orthorhombic/monoclinic phase to 135 μC/m at tetragonal phase, and decreases to less than 27 μC/m in the temperature above Tm. This result discloses that ferroelectricity can significantly enhance the flexoelectricity in this kind of perovskite.