Rapid and sensitive detection of dissolved gases in seawater is quite essential for the investigation of global carbon cycle. Large quantities of in situ optical detection techniques showed the restricted measurement efficiency, owing to the single gas sensor without the identification ability of multiple gases. In this work, a novel gas-liquid Raman detection method of monitoring the multi-component dissolved gases was proposed based on a continuous gas-liquid separator under a large difference of partial pressure. The limit of detection (LOD) of the gas Raman spectrometer could arrive at about 14 ppm for N2 gas. Moreover, based on the continuous gas-liquid separation process, the detection time of the dissolved gases could be largely decreased to about 200 s compared with that of the traditional detection method (30 min). Effect of equilibrium time on gas-liquid separation process indicated that the extracted efficiency and decay time of these dissolved gases was CO2 >O2 >N2. In addition, the analysis of the relationship between equilibrium time and flow speed indicated that the decay time decreased with the increase of the flow speed. The validation and application of the developed system presented its great potential for studying the components and spatiotemporal distribution of dissolved gases in seawater.

Owing to the environmental friendliness, high specific energy, high theoretical capacity, and low cost, lithium-sulfur (Li–S) battery has drawn great attention as the next-generation device. However, the poor conductivity of the sulfur and lithium sulfides, large volumetric expansion of S to Li2S after lithiation, and the dissolution of lithium polysulfides in electrolyte, lead to low specific capacity, high cyclic capacity loss, and bad cycle performance. Here, we propose a heterojunction structure of multiferroic BiFeO3 anchored on hollow spheric TiO2 coated on Celgard separator to overcome the “shuttle effect” of dissolved intermediate polysulfides, improving poor conductivity of S and its discharge products Li2S2/Li2S, and inhibiting lithium dendrites. The multiferroic BiFeO3 provides a spontaneous polarization to trap polysulfides, and hollow spheric TiO2 divides a large surface area for sulfur expansion and improves the poor conductivity of S and BiFeO3 simultaneously. As a result, the discharge capacity remained at 754 mAh g−1 with coulombic efficiency over 99.2% and 83.7% retention of the initial specific capacity after 800 cycles at 1.0C.

The high-precision self-calibration radiation reference source is currently the research focus of satellite remote sensing calibration. In order to meet the requirements of quantitative applications such as climate monitoring, low-light radiation metering and single photon source radiance measurement, in view of the application requirements and technical requirements of visible to near infrared low-light radiometer, a compact three-channel low-light radiance meter based on correlated photon self-calibration is designed. This design method can improve the measurement accuracy of low light irradiance by using objective physical effect instead of physical standard, reducing the cumulative error caused by standard transfer chain. The absolute calibration of the detector responsivity can be achieved by the spontaneous parameter downconversion effect, and the absolute radiation observation can be achieved without relying on the external reference. Based on this study, combined with the special application requirements of radiance meter, a numerical model of spectral rate and geometric transmission characteristics of wide spectrum correlated photons is established, and two basic operating modes of self-calibration and radiation observation are determined. The interaction between 355 nm pump source and nonlinear medium generates three-wave mixing, and the correlated photons are generated by class I non-collinear spontaneous parametric downconversion, the combined effect of monochromatic pump photon flow and quantum vacuum noise on non-centrosymmetric nonlinear crystal makes each incident photon spontaneously split into two photons with lower energy with a certain probability, called signal photons and idle photons respectively, they have a wide sptrum distribution from pump wave frequency to lattice resonance frequency. Correlated photon source has the technical characteristics of time and space correlation, natural wide spectrum and absolute reproducibility, so it has high absolute accuracy. Integrated design of self-calibration and radiation observation can monitor and correct changes in response characteristics in real time, maintain long-term stability of response characteristics, and improve traceability and accuracy of observation data. This design method solve the key technologies such as preparation and value transfer of correlated photon sources, suppression of pump stray light, high precision and high efficiency coupling of correlated photons, UV radiation resistance of space single-photon detectors, packaging reinforcement technology of space single-photon detectors, self-calibration and integrated design of radiation observation. The spectral measurement range of the low-light radiance meter is from 460 nm to 1 550 nm,the measurement range of radiance is 1x10(-9)similar to 1x10(-6) W/(cm(2)center dot sr center dot nm). In the design,the integration,miniaturization and modularization of the whole system are considered,and the eight spectral bands are integrated into a three-channel structure, solving the preparation of wide spectrum dependent photon source, optical multiplexing of calibration optical path, radiation measurement, high precision coincidence measurement and full optical path calibration of radiance meter, and achieving high precision radiation observation from visible to near infrared and periodic self-calibration research targets. In the self-calibration mode,the multiplex optical path module periodically introduces the spontaneous parametric down-conversion correlated photons,and the photon counting and coincidence detection module are used to calibrate the absolute quantum efficiency of the three channels. In the radiation observation mode,the multiplex optical path module introduces the low-light level target radiation and obtains the absolute spectral radiance of the observation target in the band of 460 similar to 1 550 nm at the same time. The calibration coefficient obtained by the self-calibration mode is used to correct the observation results. The effects of link error limited by radiation reference value transfer,optical decay of optical path and electronic decay of optical path on the measurement accuracy of microradiance are fundamentally solved. The visible near-infrared band adopts free space coupling mode and the short-wave infrared band adopts multi-mode fiber coupling mode. Through design optimization analysis,the focusing spots of the first and second channels meet the 300 mu m pixel requirement of Si single photon detector, and the focusing spot of the third channel meets the 62.5 mu m core diameter and 0.22 numerical aperture requirement of multi-mode fiber,all of them can be received by the detector photosensitive surface,meeting the design objectives. The method based on correlated photon calibration does not need to trace the high-precision primary standard in the laboratory and the lengthy standard transfer chain. By using the correlated photon generated in the process of parametric down-conversion,the calibration source of time,space and polarization can be obtained,and the high-precision observation of the low-light spectrum radiance from visible to near infrared band can be realized. The solution to the scientific problem of low-light observation instrument in space platform measurement can obtain higher calibration accuracy,and play an important role in climate monitoring,low-light radiation metrology,single-photon source radiance measurement and so on.

As an elemental semiconductor, tellurium (Te) has been famous for its high hole-mobility, excellent ambient stability and topological states. Here, we realize the controllable synthesis of horizontal Te nanoribbon arrays (TRAs) with an angular interval of 60°on mica substrates by physical vapor deposition strategy. The growth of Te nanoribbons (TRs) is driven by two factors, where the intrinsic quasi-one-dimensional spiral chain structure promotes the elongation of their length; the epitaxy relationship between [110] direction of Te and [110] direction of mica facilitates the oriented growth and the expansion of their width. The bending of TRs which have not been reported is induced by grain boundary. Field-effect transistors based on TRs demonstrate high mobility and on/off ratio corresponding to 397 cm2 V-1 s-1 and 1.5×105, respectively. These phenomena supply an opportunity to deep insight into the vapor-transport synthesis of low-dimensional Te and explore its underlying application in monolithic integration.

2D BiCuSeO is an intrinsic p-type degenerate semiconductor due to its self-doping effect, which possesses great potential to fabricate high-performance 2D-2D tunnel field-effect transistors (TFETs). However, the controllable synthesis of multinary 2D materials by chemical vapor deposition (CVD) is still a challenge due to the restriction of thermodynamics. Here, the CVD synthesis of quaternary 2D BiCuSeO nanosheets is realized. As-grown BiCuSeO nanosheets with thickness down to ≈6.1 nm (≈7 layers) and domain size of ≈277 µm show excellent ambient stability. Intrinsic p-type degeneracy of BiCuSeO, capable of maintaining even in a few layers, is comprehensively unveiled. By varying the thicknesses and temperatures, the carrier concentration of BiCuSeO nanosheets can be adjusted in the range of 1019 to 1021 cm-3 , and the Hall mobility of BiCuSeO is ≈191 cm2 V-1 s-1 (at 2 K). Furthermore, taking advantage of the p-type degeneracy of BiCuSeO, a prototypical BiCuSeO/MoS2 TFET is fabricated. The emergence of the negative differential resistance trend and multifunctional diodes by modulating the gate voltage and temperature reveal the great practical implementation potential of BiCuSeO nanosheets. These results pave way for the CVD synthesis of multinary 2D materials and rational design of high-performance tunnel devices.

A 31-inch 4K flexible active-matrix organic light-emitting diode (AMOLED) display integrating with gate driver on the array (GOA) technology has been proposed and fabricated on a polyimide substrate. The GOA circuits, composed of two series-connected thin-film transistors (TFTs) and dual low-voltage power structure, are introduced to decrease the leakage current in TFTs. They are arranged symmetrically along the sides of the display. Inkjet printing (IJP) OLED process is used to reduce the number of sub-pixels from four (R/G/B/W) in commercial white OLED process to three (R/G/B) and a high pixel density in the display (144 pixels per inch) is achieved. Moreover, top-gated (TG) amorphous indium-gallium-zinc oxide (IGZO) TFTs with good electrical and mechanical reliability, have been successfully utilized to decrease the capacitance load in the display and improve signal transfer speed in GOA. Finally, this 31-inch flexible AMOLED display was operated for 500h under accelerating test conditions of 60°C and 90% humidity.

Surface-enhanced Raman scattering (SERS) has become the key technology for identification and quantification of various chemical molecules, biomolecules, viruses, and other pathogens in biology, electro-/photochemistry, clinical medicine, and food and environmental science fields. The great challenge in the SERS field is how to increase the coverage rate of an enhanced electromagnetic field and simultaneously reduce the electric field gradient. Here, two-dimensional Au plasmonic nanostructure arrays with a periodic one-dimensional plasmon nanocavity are fabricated by self-assembly and reactive ion etching technology, which exhibit an appreciable Raman enhancement factor of 1.02 X 10(8), ultrahigh and uniform EM intensity, and over 50% EM coverage rate (usually less than 10%). Benefiting from these excellent properties and photoinduced charge transfer effect, the SERS sensors not only exhibit outstanding light absorption efficiency (up to 90%) but also demonstrate excellent SERS performance in trace detection of multiple harmful chemicals with excellent limit of detection (up to about 10(-10)-10(-12) M), low relative standard deviation (7.3-9.1%), and good dual-analyte detection ability. This work presents a solid progress toward the fabrication of a highly enhanced plasmon nanocavity with wide-range and low field gradient properties for extensive SERS application.

The emergence of 2D polarized materials, including ferromagnetic, ferrovalley, and ferroelectric materials, has demonstrated unique quantum behaviors at atomic scales. These polarization behaviors are tightly bonded to the new degrees of freedom (DOFs) for next generation information storage and processing, which have been dramatically developed in the past few years. Here, the basic 2D polarized materials system and related devices’ application in spintronics, valleytronics, and electronics are reviewed. Specifically, the underlying physical mechanism accompanied with symmetry broken theory and the modulation process through heterostructure engineering are highlighted. These summarized works focusing on the 2D polarization would continue to enrich the cognition of 2D quantum system and promising practical applications.

Ternary two-dimensional (2D) semiconductors with controllable wide bandgap, high ultraviolet (UV) absorption coefficient, and critical tuning freedom degree of stoichiometry variation have a great application prospect for UV detection. However, as-reported ternary 2D semiconductors often possess a bandgap below 3.0 eV, which must be further enlarged to achieve comprehensively improved UV, especially deep-UV (DUV), detection capacity. Herein, sub-one-unit-cell 2D monolayer BiOBr nanoflakes (≈0.57 nm) with a large size of 70 µm are synthesized for high-performance DUV detection due to the large bandgap of 3.69 eV. Phototransistors based on the 2D ultrathin BiOBr nanoflakes deliver remarkable DUV detection performance including ultrahigh photoresponsivity (Rλ , 12739.13 A W-1 ), ultrahigh external quantum efficiency (EQE, 6.46 × 106 %), and excellent detectivity (D*, 8.37 × 1012 Jones) at 245 nm with a gate voltage (Vg ) of 35 V attributed to the photogating effects. The ultrafast response (τrise = 102 µs) can be achieved by utilizing photoconduction effects at Vg of -40 V. The combination of photocurrent generation mechanisms for BiOBr-based phototransistors controlled by Vg can pave a way for designing novel 2D optoelectronic materials to achieve optimal device performance.

Lithium-sulfur (Li-S) batteries are one of the most promising next-generation energy-storage systems. Nevertheless, the sluggish sulfur redox and shuttle effect in Li-S batteries are the major obstacles to their commercial application. Previous investigations on adsorption for LiPSs have made great progress but cannot restrain the shuttle effect. Catalysts can enhance the reaction kinetics, and then alleviate the shuttle effect. The synergistic relationship between adsorption and catalysis has become the hotspot for research into suppressing the shuttle effect and improving battery performance. Herein, the adsorption-catalysis synergy in Li-S batteries is reviewed, the adsorption-catalysis designs are divided into four categories: adsorption-catalysis for LiPSs aggregation, polythionate or thiosulfate generation, and sulfur radical formation, as well as other adsorption-catalysis. Then advanced strategies, future perspectives, and challenges are proposed to aim at long-life and high-efficiency Li-S batteries.

The physical Schottky parameters of devices based on Schottky contact are important to analyze the working mechanism. This article theoretically studies the parameter characteristics of the current–voltage curve of two back‐to‐back connected Schottky contacts via the thermionic emission model, and it is found that not all the parameters are able to be extracted under some constraints. Compared with some classical extraction methods, a straightforward strategy to approach the Schottky intrinsic parameters by solving equations during the characteristic interval are presented. In addition, this method is verified on several representative standard curves and experimental curves, and the extracted parameters are highly compatible with those curves. The current extraction method will be of great significance for the design and preparation of Schottky‐based devices.

Power consumption is one of the most challenging bottlenecks for complementary metal‐oxide–semiconductor integration. Negative‐capacitance field‐effect transistors (NC‐FETs) offer a promising platform to break the thermionic limit defined by the Boltzmann tyranny and architect energy‐efficient devices. However, it is a great challenge to achieving ultralow‐subthreshold‐swing (SS) (10 mV dec −1 ) and small‐hysteresis NC‐FETs simultaneously at room temperature, which has only been reported using the hafnium zirconium oxide system. Here, based on a ferroelectric LiNbO 3 thin film with great spontaneous polarization, an ultralow‐SS NC‐FET with small hysteresis is designed. The LiNbO 3 NC‐FET platform exhibits a record‐low SS of 4.97 mV dec −1 with great repeatability due to the superior capacitance matching characteristic as evidenced by the negative differential resistance phenomenon. By modulating the structure and operating parameters (such as channel length ( L ch ), drain–sourse bias ( V ds ), and gate bias ( V g )) of devices, an optimized SS from ≈40 to ≈10 mV dec −1 and hysteresis from ≈900 to ≈60 mV are achieved simultaneously. The results provide a new potential method for future highly integrated electronic and optical integrated energy‐efficient devices.

The ultrabroadband spectrum detection from ultraviolet (UV) to long-wavelength infrared (LWIR) is promising for diversified optoelectronic applications of imaging, sensing, and communication. However, the current LWIR-detecting devices suffer from low photoresponsivity, high cost, and cryogenic environment. Herein, a high-performance ultrabroadband photodetector is demonstrated with detecting range from UV to LWIR based on air-stable nonlayered ultrathin Fe3 O4 nanosheets synthesized via a space-confined chemical vapor deposition (CVD) method. Ultrahigh photoresponsivity (R) of 561.2 A W-1 , external quantum efficiency (EQE) of 6.6 × 103 %, and detectivity (D*) of 7.42 × 108 Jones are achieved at the wavelength of 10.6 µm. The multimechanism synergistic effect of photoconductive effect and bolometric effect demonstrates the high sensitivity for light with any light intensities. The outstanding device performance and complementary mixing photoresponse mechanisms open up new potential applications of nonlayered 2D materials for future infrared optoelectronic devices.

The electrochemical nitrogen reduction reaction (NRR), as an environmentally friendly method to convert nitrogen to ammonia at ambient temperature and pressure, has attracted the attention of numerous researchers. However, when compared with industrial production, electrochemical NRR often suffers from unsatisfactory yields and poor Faraday efficiency (FE). Recently, various structure engineering strategies have aimed to introduce extra active sites or enhance intrinsic activity to optimize the activation and hydrogenation of N-2. In this review, recent progress in atomic structure modification is summarized and discussed to design high-efficiency NRR catalysts, with a focus on defect engineering (heteroatom doping and atom vacancy), surface orientation and amorphization, as well as heterostructure engineering. In addition, existing challenges and future development directions are proposed to obtain more credible NRR catalysts with high catalytic performance and selectivity.

2D magnetic materials have generated an enormous amount of attention due to their unique 2D-limited magnetism and their potential applications in spintronic devices. Recently, most of this research has focused on 2D van der Waals layered magnetic materials exfoliated from the bulk with random size and thicknesses. Controllable growth of these materials is still a great challenge. In contrast, 2D nonlayered magnetic materials have rarely been investigated, not especially regarding their preparation. CrnX (X = S, Se and Te; 0 < n < 1), a class of nonlayered transition metal dichalcogenides, has rapidly attracted extensive attention due to its abundance of structural compounds and unique magnetic properties. Herein, the controlled synthesis of ultrathin CrSe crystals, with grain size reaching the sub-millimeter scale, on mica substrates via an ambient pressure chemical vapor deposition (CVD) method is demonstrated. A continuous CrSe film can also be achieved via precise control of the key growth parameters. Importantly, the CVD-grown 2D CrSe crystals possess obvious ferromagnetic properties at temperatures below 280 K, which has not been observed experimentally before. This work broadens the scope of the CVD growth of 2D magnetic materials and highlights their significant application possibilities in spintronics.

以磷酸铁、铁粉、磷酸锂和葡萄糖为原料采用球磨后煅烧的方法制备了振实密度为1.45 g/cm3的LiFePO4@C,比商用磷酸铁锂材料的振实密度提高约20％.与其他方法相比,该方法原料成本低,合成过程原料利用率接近100％,易于实现工业化生产.通过对原料中铁磷摩尔比例的探究,最终确定了铁磷摩尔比为0.96:1的条件下合成的LiFePO4@C具有较优异的电化学性能,在0.1,1C的条件下放电比容量分别为155,140mAh/g,此外,通过添加高导电率的碳纳米管,使其高倍性能也得到显著提升.

Lithium-sulfur (Li-S) batteries are of considerable interest for high-density energy storage. However, the adoption of Li-S batteries to date has been severely plagued by the polysulfide shuttling effect, whereby polysulfide molecules dissolve into the electrolyte and shuttle across the separator to react with the anode materials, leading to a rapidly fading capacity. Herein, by directly coating a thin layer of reduced graphene oxide (rGO)/sodium lignosulfonate (SL) composite on the standard polypropylene (PP) separator, we produce a rGO@SL/PP separator with abundant negatively charged sulfonic groups in the porous lignin network, which effectively suppress the translocation of the negatively charged polysulfide (PS) ions without compromising the transport of positively charged Li+ ions. Using the rGO@SL/PP separator, we demonstrate a highly robust Li-S battery with a capacity retention of 74% over 1,000 cycles. This study defines an effective strategy to inhibit the PS shuttling effect for highly robust Li-S batteries.

Two-dimensional (2D) magnetic materials provide an ideal platform for the application in spintronic devices due to their unique spin states in nanometer scale. However, recent research on the exfoliated monolayer magnetic materials suffers from the instability in ambient atmosphere, which needs extraordinary protection. Hence the controllable synthesis of 2D magnetic materials with good quality and stability should be addressed. Here we report for the first time the van der Waals (vdW) epitaxial growth of one-unit-cell-thick air-stable ferrimagnet Cr2S3 semiconductor via a facile chemical vapor deposition method. Single crystal Cr2S3 with the domain size reaching to 200 μm is achieved. Most importantly, we observe the as grown Cr2S3 with a Néel temperature ( TN) of up to 120 K and a maximum saturation magnetic momentum of up to 65 μemu. As the temperature decreases, the samples show a transition from soft magnet to hard magnet with the highest coercivity of 1000 Oe. The one-unit-cell-thick Cr2S3 devices show a p-type transfer behavior with an on/off ratio over 103. Our work highlights Cr2S3 monolayer as an ideal magnetic semiconductor for 2D spintronic devices. The vdW epitaxy of nonlayered magnets introduces a new route for realizing magnetism in 2D limit and provides more application potential in the 2D spintronics.

The design of highly efficient electrocatalysts containing non-precious metals is crucial for promoting overall water splitting in alkaline media. In particular, Janus catalysts simultaneously facilitating the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are desirable. Herein, we fabricated a unique hierarchical heterostructure via growing Ni4W6O21(OH)2·4H2O (denoted as Ni-W-O) nanosheets on NiMoO4 rods, which was indispensable for regulating the morphology of the Ni-W-O structure. This heterostructure of Ni-W-O/NiMoO4 could be utilized as an electrocatalyst to realize superior activity for overall water splitting in 1.0 M KOH. It substantially promoted overall water splitting with 1.6 V at 30 mA cm-2, outperforming numerous bifunctional electrocatalysts under the same conditions. Notably, the remarkable stability for continuously splitting water endowed this hierarchical heterostructure with potential applications on a large scale. This work emphasizes the effectively controlled growth of heterostructured non-noble-metal catalysts for energy-conversion reaction.

Controlling the conduction behavior of 2D materials is an important prerequisite to achieve their electronic and optoelectronic applications. However, most of the reported approaches are aware of the shortcomings of inflexibility and complexity, which limits the possibility of multifunctional integration. Here, taking advantage of van der Waals heterostructure engineering, a simple method to achieve a dynamically controlled binary channel in a semivertical MoTe2/MoS2 field effect transistor is proposed. It is enabled by the high switchability between tunneling and thermal transports through simply changing the sign of voltage bias. In addition, the proposed system allows for multifunctional integration of transistor with on/off ratio >10(7) and diode with rectification ratio >10(6). Moreover, the devices show screen capability to negative photoresponse effect that is widely observed in ambipolar materials, hence improving the photodetection reliability and sensitivity. This study broadens the functionalities of van der Waals heterostructures and opens up more possibilities to realize multifunctional devices.