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X-ray detectors based on dual-site-doped perovskite single crystals exhibit excellent sensitivity of 2.6 x 10(4) mu C Gy(air)(-1) cm(-2) under a low field of 1 V cm(-1). The detectable dose rate is as low as 7.09 nGy(air) s(-1). The operational stability is beyond half a year. Although three-dimensional metal halide perovskite (ABX(3)) single crystals are promising next-generation materials for radiation detection, state-of-the-art perovskite X-ray detectors include methylammonium as A-site cations, limiting the operational stability. Previous efforts to improve the stability using formamidinium-caesium-alloyed A-site cations usually sacrifice the detection performance because of high trap densities. Here we successfully solve this trade-off between stability and detection performance by synergistic composition engineering, where we include A-site alloys to decrease the trap density and B-site dopants to release the microstrain induced by A-site alloying. As such, we develop high-performance perovskite X-ray detectors with excellent stability. Our X-ray detectors exhibit high sensitivity of (2.6 +/- 0.1) x 10(4) mu C Gy(air)(-1) cm(-2) under 1 V cm(-1) and ultralow limit of detection of 7.09 nGy(air) s(-1). In addition, they feature long-term operational stability over half a year and impressive thermal stability up to 125 degrees C. We further demonstrate the promise of our perovskite X-ray detectors for low-bias portable applications with high-quality X-ray imaging and monitoring prototypes. Funding Agencies|National Natural Science Foundation of China [62004182, 61875072, 51863013, 61874052]; Key Research and Development Projects of Jilin Science and Technology Department [20200401044GX]; Excellent Young Foundation of Jiangxi Province [20192BCB23009]; Knut and Alice Wallenberg Foundation [KAW 2019.0082]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University ((faculty grant SFO-Mat-LiU) [2009-00971]

Mechanisms of nucleation have been debated for more than a century, despite successes of classical nucleation theory. The nucleation process has been recently argued as involving a nonclassical mechanism (the "two-step" mechanism) in which an intermediate step occurs before the formation of a nascent ordered phase. However, a thorough understanding of this mechanism, in terms of both microscopic kinetics and thermodynamics, remains experimentally challenging. Here

High-performance de/anti-icing overlayers which can be deposited on diverse surfaces offer great potential in many industrial settings and daily life, yet a versatile overlayer applicable to all-weather conditions (high humidity, low temperature, raining, snowing, etc.) is in high demand for practical applications. This study presents the fabrication and application of a superhydrophobic overlayer with a bioinspired hierarchical surface which additionally possesses photothermal and electrothermal functionalities, so it can operate as a de/anti-icing layer in extreme environments. The overlayer, with a papilla-like microstructure similar to that of a lotus leaf, features polydopamine-decorated layered basic zinc acetate microparticles distributed in the framework of multiwalled carbon nanotubes. Specifically, the overlayer is superhydrophobic, and its capability of suppressing the condensation of water droplets and growth of ice crystals is verified by both in situ environmental scanning electron microscopy observations and freezing experiments. Moreover, the overlayer can be warmed up to 74 and 105 °C under the excitation of sunlight and direct current bias, respectively, which is sufficiently high for deicing in severe weather. It is worth mentioning that the overlayer is produced by a spray-coating technique; therefore, it is suitable for large-scale deployment on arbitrary substrate materials. The findings provide insights into a new strategy for engineering multifunctional overlayers and can lead to expanding applications of composite coatings.

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.

The gate dielectric layer is an important component in building a field-effect transistor. Here, we report the synthesis of a layered rhombohedral-structured MnAl

In this study, we report on the thermal oxidation of few-layer ZrS3 flakes as a function of temperature and heating time. We characterize the changes to the material crystal structure caused by the...

Heterogeneous ice nucleation on atmospheric aerosols strongly affects the earth's climate, and at the microscopic level, surface-irregularity-induced ice crystallization behaviors are common but crucial. Because of the lack of visual evidence and effective experimental methods, the mechanism of atomic-structure-dependent ice formation on aerosol surfaces is poorly understood. Here we chose highly oriented pyrolytic graphite (HOPG) to represent soot (a primary aerosol), and environmental scanning electron microscopy (ESEM) was performed for in situ observations of ice formation. We found that hexagonal ice crystals show an aligned growth pattern via a two-stage pathway with one a axis coinciding with the direction of atomic step edges on the HOPG surface. Additionally, the ice crystals grow at a noticeably higher speed along this direction. This study reveals the role of atomic surface defects in heterogeneous ice nucleation and may pave the way to control icing-related processes in practical applications.

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.

We report a straightforward strategy to design efficient N doped porous carbon (NPC) electrocatalyst that has a high concentration of easily accessible active sites for the CO2 reduction reaction (CO2 RR). The NPC with large amounts of active N (pyridinic and graphitic N) and highly porous structure is prepared by using an oxygen-rich metal-organic framework (Zn-MOF-74) precursor. The amount of active N species can be tuned by optimizing the calcination temperature and time. Owing to the large pore sizes, the active sites are well exposed to electrolyte for CO2 RR. The NPC exhibits superior CO2 RR activity with a small onset potential of -0.35 V and a high faradaic efficiency (FE) of 98.4 % towards CO at -0.55 V vs. RHE, one of the highest values among NPC-based CO2 RR electrocatalysts. This work advances an effective and facile way towards highly active and cost-effective alternatives to noble-metal CO2 RR electrocatalysts for practical applications.

NiO has been found to be highly outstanding in producing H2 and O2 from H2O through magnetic stirring, while its capability for the reduction of CO2 through mechanical stimulation has not been investigated. Presently, NiO particles have been employed to promote the conversion of H2O and CO2 enclosed in reactors into flammable gases through magnetic stirring. For a 150 mL glass reactor filled with 50 mL water, 1.00 g of NiO particles, and 1 atm of CO2, 24 h of magnetic stirring using a home-made Teflon magnetic rotary disk resulted in the formation of 33.80 ppm CO, 10.10 ppm CH4, and 12,868.80 ppm H2. More importantly, the reduction of CO2 was found to be substantially enhanced through coating some polymers and metals on the reactor bottoms, including 25.64 ppm CO and 70.97 ppm CH4 obtained for a PVC-coated reactor and 30.68 ppm CO, 52.78 ppm CH4, 3.82 ppm C2H6, and 2.18 ppm C2H4 obtained for a stainless steel-coated reactor. Hydroxyl radicals were detected using fluorescence spectroscopy for NiO particles under magnetic stirring in water. A tribo-catalytic mechanism has been proposed for the conversion of H2O and CO2 into flammable gases by NiO particles under magnetic stirring that is based on the excitation of electron-hole pairs in NiO by mechanical energy absorbed through friction. These findings not only reveal a great potential for mechanical energy to be utilized for CO2 conversion but are also valuable for fundamental studies.

The deep-level traps induced by charged defects at the grain boundaries (GBs) of polycrystalline organic–inorganic halide perovskite (OIHP) films serve as major recombination centres, which limit the device performance. Herein, we incorporate specially designed poly(3-aminothiophenol)-coated gold (Au@PAT) nanoparticles into the perovskite absorber, in order to examine the influence of plasmonic resonance on carrier dynamics in perovskite solar cells. Local changes in the photophysical properties of the OIHP films reveal that plasmon excitation could fill trap sites at the GB region through photo-brightening, whereas transient absorption spectroscopy and density functional theory calculations correlate this photo-brightening of trap states with plasmon-induced interfacial processes. As a result, the device achieved the best efficiency of 22.0% with robust operational stability. Our work provides unambiguous evidence for plasmon-induced trap occupation in OIHP and reveals that plasmonic nanostructures may be one type of efficient additives to overcome the recombination losses in perovskite solar cells and thin-film solar cells in general., The incorporation of plasmonic core-shell nanostructures at the grain boundaries of perovskite films reduces the charge recombination loss through photo-brightening of trap states.

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.

In this study, mechanical vibration is used for hydrogen generation and decomposition of dye molecules, with the help of BiFeO3 (BFO) square nanosheets. A high hydrogen production rate of ≈124.1 μmol g-1 is achieved under mechanical vibration (100 W) for 1 h at the resonant frequency of the BFO nanosheets. The decomposition ratio of Rhodamine B dye reaches up to ≈94.1 % after mechanical vibration of the BFO catalyst for 50 min. The vibration-induced catalysis of the BFO square nanosheets may be attributed to the piezocatalytic properties of BFO and the high specific surface area of the nanosheets. The uncompensated piezoelectric charges on the surfaces of BFO nanosheets induced by mechanical vibration result in a built-in electric field across the nanosheets. Unlike a photocatalyst for water splitting, which requires a proper band edge position for hydrogen evolution, such a requirement is not needed in piezocatalytic water splitting, where the band tilting under the induced piezoelectric field will make the conduction band of BFO more negative than the H2 /H2 O redox potential (0 V) for hydrogen generation.

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 (

The all-solid-state flexible supercapacitor (AFSC), one of the most flourishing energy storage devices for portable and wearable electronics, attracts substantial attentions due to their high flexibility, compact size, improved safety, and environmental friendliness. Nevertheless, the current AFSCs usually show low energy density, which extremely hinders their practical applications. Herein, ultra-thin β-Ni(OH)2 nanoplates with thickness of 2.4 ± 0.2 nm are in-situ grown uniformly on Ni foam by one step hydrothermal treatment. Thanks to the ultra-thin nanostructure, β-Ni(OH)2 nanoplates shows a specific capacitance of 1,452 F g−1 at the scan rate of 3 mV s−1. In addition, the assembled asymmetric AFSC [Ni(OH)2//Activated carbon] shows a specific capacitance of 198 F g−1. It is worth noting that the energy density of the AFSC can reach 62 Wh kg−1 while keeping a high power density of 1.5 kW kg−1. Furthermore, the fabricated AFSCs exhibit satisfied fatigue behavior and excellent flexibility, and about 82 and 86% of the capacities were retained after 5,000 cycles and folding over 1,500 times, respectively. Two AFSC in series connection can drive the electronic watch and to run stably for 10 min under the bending conditions, showing a great potential for powering portable and wearable electronic devices.

The all-solid-state flexible supercapacitor (AFSC), one of the most flourishing energy storage devices for portable and wearable electronics, attracts substantial attentions due to their high flexibility, compact size, improved safety, and environmental friendliness. Nevertheless, the current AFSCs usually show low energy density, which extremely hinders their practical applications. Herein, ultra-thin β-Ni(OH)2 nanoplates with thickness of 2.4 ± 0.2 nm are in-situ grown uniformly on Ni foam by one step hydrothermal treatment. Thanks to the ultra-thin nanostructure, β-Ni(OH)2 nanoplates shows a specific capacitance of 1,452 F g−1 at the scan rate of 3 mV s−1. In addition, the assembled asymmetric AFSC [Ni(OH)2//Activated carbon] shows a specific capacitance of 198 F g−1. It is worth noting that the energy density of the AFSC can reach 62 Wh kg−1 while keeping a high power density of 1.5 kW kg−1. Furthermore, the fabricated AFSCs exhibit satisfied fatigue behavior and excellent flexibility, and about 82 and 86% of the capacities were retained after 5,000 cycles and folding over 1,500 times, respectively. Two AFSC in series connection can drive the electronic watch and to run stably for 10 min under the bending conditions, showing a great potential for powering portable and wearable electronic devices.

We report on the growth of high-quality stoichiometric layered Cr

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.