n-Type boron ß-diketone-containing conjugated polymers for high-performance room temperature ammonia sensors.

Organic semiconductor (OSC) gas sensors with good mechanical flexibility have received considerable attention as commercial and wearable devices. However, due to poor resistance to moisture and low conductivity, the improvement in the sensing capability of individual OSCs is limited. Reported here is a promising pathway to construct a series of conjugated organic polymers (COPs) with well-defined pyrimidine (Py-COP) or boron ß-diketone (BF-COP) units. Unlike traditional metal- or carbon-based hybrid materials, the developed COPs can provide abundant absorption sites for gaseous analytes. As a result, the as-prepared BF-COP results in an excellent sensing response of over 1500 (Ra/Rg) toward 40 ppm of NH3 at room temperature, which is the highest value among those of pristine COPs as n-type sensing materials. Notably, they can maintain their initial sensing responses for two months and 90% relative humidity resistance. Combining the results of in situ Fourier transform infrared spectroscopy and theoretical calculations, the ß-diketone skeleton is found to activate the surface electronic environment, verifying that the electron-deficient B ← O groups are adsorption centers. The B/N-heterocyclic decoration effectively modulates the redox properties and electronic interactions, as well as perturbs charge transfer in typical π-conjugated COPs. These results offer insight into developing highly efficient OSC gas sensors, which potentially have broadened sensing applications in the areas of organoboron chemistry.

Nitrogen acquisition strategy and its effects on invasiveness of a subtropical invasive plant.

Introduction: Preference and plasticity in nitrogen (N) form uptake are the main strategies with which plants absorb soil N. However, little effort has been made to explore effects of N form acquisition strategies, especially the plasticity, on invasiveness of exotic plants, although many studies have determined the effects of N levels (e.g. N deposition). Methods: To address this problem, we studied the differences in N form acquisition strategies between the invasive plant Solidago canadensis and its co-occurring native plant Artemisia lavandulaefolia, effects of soil N environments, and the relationship between N form acquisition strategy of S. canadensis and its invasiveness using a 15N-labeling technique in three habitats at four field sites. Results: Total biomass, root biomass, and the uptakes of soil dissolved inorganic N (DIN) per quadrat were higher for the invasive relative to the native species in all three habitats. The invader always preferred dominant soil N forms: NH4 + in habitats with NH4 + as the dominant DIN and NO3 - in habitats with NO3 - as the dominant DIN, while A. lavandulaefolia consistently preferred NO3 - in all habitats. Plasticity in N form uptake was higher in the invasive relative to the native species, especially in the farmland. Plant N form acquisition strategy was influenced by both DIN levels and the proportions of different N forms (NO3 -/NH4 +) as judged by their negative effects on the proportional contributions of NH4 + to plant N (f NH4 +) and the preference for NH4 + (ß NH4 +). In addition, total biomass was positively associated with f NH4 + or ß NH4 + for S. canadensis, while negatively for A. lavandulaefolia. Interestingly, the species may prefer to absorb NH4 + when soil DIN and/or NO3 -/NH4 + ratio were low, and root to shoot ratio may be affected by plant nutrient status per se, rather than by soil nutrient availability. Discussion: Our results indicate that the superior N form acquisition strategy of the invader contributes to its higher N uptake, and therefore to its invasiveness in different habitats, improving our understanding of invasiveness of exotic plants in diverse habitats in terms of utilization of different N forms.

Time-slicing high dynamic range 3D imaging.

Fringe projection profilometry (FPP) has been widely used in 3D measurement due to its high precision and non-contact properties. Nevertheless, it still faces great challenges in measuring scenes with complex reflectivity, in which the dynamic range of the reflected light field of the scene is significantly higher than that of the image detector. In this paper, we propose a time-slicing strategy for high dynamics range 3D imaging by projecting a series of sinusoidal fringe patterns with short and equal length exposure time and performing the fusion of different numbers of short exposure images according to the local gray-value distribution of the images. Moreover, to further improve the measurement efficiency, we realize phase unwrapping using complementary Gray code patterns, which are binary and insensitive to the image sensor's nonlinear response to the reflected light from the scene under test. Experiments are conducted to demonstrate the feasibility and efficiency of the proposed method.

Projected feature assisted coarse to fine point cloud registration method for large-size 3D measurement.

Fringe projection profilometry has gained significant interest due to its high precision, enhanced resolution, and simplified design. Typically, the spatial and perspective measurement capability is restricted by the lenses of the camera and projector in accordance with the principles of geometric optics. Therefore, large-size object measurement requires data acquisition from multiple perspectives, followed by point cloud splicing. Current point cloud registration methods usually rely on 2D feature textures, 3D structural elements, or supplementary tools, which will increase costs or limit the scope of the application. To address large-size 3D measurement more efficiently, we propose a low-cost and feasible method that combines active projection textures, color channel multiplexing, image feature matching and coarse-to-fine point registration strategies. Using a composite structured light with red speckle patterns for larger areas and blue sinusoidal fringe patterns for smaller ones, projected onto the surface, which allows us to accomplish simultaneous 3D reconstruction and point cloud registration. Experimental results demonstrate that the proposed method is effective for the 3D measurement of large-size and weak-textured objects.

Robust Self-Supported SnO2-Mn2O3@CC Electrode for Efficient Electrochemical Degradation of Cationic Blue X-GRRL Dye.

Exploration of highly efficient and robust catalyst is pivotal for electrocatalytic degradation of dye wastewater, but it still is a challenge. Here, we develop a three-dimensional self-supported SnO2-Mn2O3 hybrid nanosheets grown on carbon cloth (noted by SnO2-Mn2O3@CC) electrode via a simple hydrothermal method and annealing treatment. Benefitting from the interlaced nanosheets architecture that enlarges the surface area and the synergetic component effect that accelerates the interfacial electronic transfer, SnO2-Mn2O3@CC electrode exhibits a superior electrocatalytic degradation efficiency for cationic blue X-GRRL dye in comparison with the single metal oxide electrode containing SnO2@CC and Mn2O3@CC. The degradation efficiency of cationic blue X-GRRL on SnO2-Mn2O3@CC electrode can reach up to 97.55% within 50 min. Furthermore, self-supported architecture of nanosheets on carbon cloth framework contributes to a robust stability compared with the traditional electrode via the multiple dip/brush coating accompanied by the thermal decomposition method. SnO2-Mn2O3@CC electrode exhibits excellent recyclability, which can still retain a degradation efficiency of 94.12% after six cycles. This work may provide a new pathway for the design and exploration of highly efficient and robust electrooxidation catalysts for dye degradation.

Advantages of growth and competitive ability of the invasive plant Solanum rostratum over two co-occurring natives and the effects of nitrogen levels and forms.

Introduction: Atmospheric nitrogen (N) deposition has often been considered as a driver of exotic plant invasions. However, most related studies focused on the effects of soil N levels, and few on those of N forms, and few related studies were conducted in the fields. Methods: In this study, we grew Solanum rostratum, a notorious invader in arid/semi-arid and barren habitats, and two coexisting native plants Leymus chinensis and Agropyron cristatum in mono- and mixed cultures in the fields in Baicheng, northeast China, and investigated the effects of N levels and forms on the invasiveness of S. rostratum. Results: Compared with the two native plants, S. rostratum had higher aboveground and total biomass in both mono- and mixed monocultures under all N treatments, and higher competitive ability under almost all N treatments. N addition enhanced the growth and competitive advantage of the invader under most conditions, and facilitated invasion success of S. rostratum. The growth and competitive ability of the invader were higher under low nitrate relative to low ammonium treatment. The advantages of the invader were associated with its higher total leaf area and lower root to shoot ratio compared with the two native plants. The invader also had a higher light-saturated photosynthetic rate than the two native plants in mixed culture (not significant under high nitrate condition), but not in monoculture. Discussion: Our results indicated that N (especially nitrate) deposition may also promote invasion of exotic plants in arid/semi-arid and barren habitats, and the effects of N forms and interspecific competition need to be taken into consideration when studying the effects of N deposition on invasion of exotic plants.

Hybrid 1D/3D-Structured Perovskite as a Highly Selective and Stable Sensor for NO2 Detection at Room Temperature.

To exploit high-performance and stable sensing materials with a room working temperature is pivotal for portable and mobile sensor devices. However, the common sensors based on metal oxide semiconductors usually need a higher working temperature (usually above 300 °C) to achieve a good response toward gas detection. Currently, metal halide perovskites have begun to rise as a promising candidate for gas monitoring at room temperature but suffer phase instability. Herein, we construct 1D/3D PyPbI3/FA0.83Cs0.17PbI3 (denoted by PyPbI3/FACs) bilayer perovskite by post-processing spin-coating Pyrrolidinium hydroiodide (PyI) salt on top of 3D FACs film. Benefitting from the 1D PyPbI3 coating layer, the phase stability of 1D/3D PyPbI3/FACs significantly improves. Simultaneously, the gas sensor based on the 1D/3D PyPbI3/FACs bilayer perovskite presents a superior selectivity and sensitivity toward NO2 detection at room temperature, with a low detection limit of 220 ppb. Exposed to a 50 ± 3% relative humidity (RH) level environment for a consecutive six days, the 1D/3D PyPbI3/FACs perovskite-based sensor toward 10 ppm NO2 can still maintain a rapid response with a slight attenuation. Gas sensors based on hybrid 1D/3D-structured perovskite in this work may provide a new pathway for highly sensitive and stable gas sensors in room working temperature, accelerating its practical application and portable device.

Sampled-Data Output Feedback Control for Nonlinear Uncertain Systems Using Predictor-Based Continuous-Discrete Observer.

In this article, we investigate the problem of sampled-data robust output feedback control for a class of nonlinear uncertain systems with time-varying disturbance and measurement delay based on continuous-discrete observer. An augmented system that includes the nonlinear uncertain system and disturbance model is first found, and by using the delayed sampled-data output, we then propose a novel predictor-based continuous-discrete observer to estimate the unknown state and disturbance information. After that, in order to attenuate the undesirable influences of nonlinear uncertainties and disturbance, a sampled-data robust output feedback controller is developed based on disturbance/uncertainty estimation and attenuation technique. It shows that under the proposed control method, the states of overall hybrid nonlinear system can converge to a bounded region centered at the origin. The main benefit of the proposed control method is that in the presence of measurement delay, the influences of time-varying disturbance and nonlinear uncertainties can be effectively attenuated with the help of feedback domination method and prediction technique. Finally, the effectiveness of the proposed control method is demonstrated via the simulation results of a numerical example and a practical example.

Periodic Event-Triggered Control for Networked Control Systems With External Disturbance and Input and Output Delays.

This article investigates the problem of periodic event-triggered output-feedback control for networked control systems in the presence of external disturbance and input and output delays. With the aid of the prediction technique, we first develop the predictor-based-extended state observer to reconstruct the system information, including the unknown state and disturbance. The periodic event-triggered output-feedback control law is then designed via the disturbance/uncertainty estimation and attenuation (DUEA) method, such that the communication times can be remarkably reduced and, at the same time, the disturbance rejection ability can be effectively enhanced. Under the predictor-based event-triggered control method, the influence of the time delays is effectively attenuated, and the effect of external disturbance is considerably attenuated due to the prediction technique and the DUEA method. By using the small-gain arguments, this article gives some sufficient stability conditions for the overall control system, and the explicit computations of sampling/updating period and time delays are presented as well. Finally, we employ a practical example and show some comparative simulation results to demonstrate the advantages of the predictor-based event-triggered control method proposed in this article.

Only Sunda and Chinese pangolin (Pholidota) are naturally distributed in China.

Actually, only two pangolin species occur naturally in China, namely the Chinese pangolin (Manis pentadactyla) and the Sunda pangolin (Manis javanica). The Sunda pangolin was found to occur naturally in Yunnan, China, but only with a narrow distribution in the Xishuangbanna and Pu'er City. The Indian pangolin (Manis crassicaudata) did not occur in China. The previous claim that this species is naturally distributed in China was found to originate from a mistake in the book "The Mammals of China and Mongolia" written by Allen in 1938.

The Scalable Solid-State Synthesis of a Ni5P4/Ni2P-FeNi Alloy Encapsulated into a Hierarchical Porous Carbon Framework for Efficient Oxygen Evolution Reactions.

The exploration of high-performance and low-cost electrocatalysts towards the oxygen evolution reaction (OER) is essential for large-scale water/seawater splitting. Herein, we develop a strategy involving the in situ generation of a template and pore-former to encapsulate a Ni5P4/Ni2P heterojunction and dispersive FeNi alloy hybrid particles into a three-dimensional hierarchical porous graphitic carbon framework (labeled as Ni5P4/Ni2P-FeNi@C) via a room-temperature solid-state grinding and sodium-carbonate-assisted pyrolysis method. The synergistic effect of the components and the architecture provides a large surface area with a sufficient number of active sites and a hierarchical porous pathway for efficient electron transfer and mass diffusion. Furthermore, a graphitic carbon coating layer restrains the corrosion of alloy particles to boost the long-term durability of the catalyst. Consequently, the Ni5P4/Ni2P-FeNi@C catalyst exhibits extraordinary OER activity with a low overpotential of 242 mV (10 mA cm-2), outperforming the commercial RuO2 catalyst in 1 M KOH. Meanwhile, a scale-up of the Ni5P4/Ni2P-FeNi@C catalyst created by a ball-milling method displays a similar level of activity to the above grinding method. In 1 M KOH + seawater electrolyte, Ni5P4/Ni2P-FeNi@C also displays excellent stability; it can continuously operate for 160 h with a negligible potential increase of 2 mV. This work may provide a new avenue for facile mass production of an efficient electrocatalyst for water/seawater splitting and diverse other applications.

Nickel-Cobalt Hydrogen Phosphate on Nickel Nitride Supported on Nickel Foam for Alkaline Seawater Electrolysis.

Developing high-performance non-noble bifunctional catalysts is pivotal for large-scale seawater electrolysis but remains a challenge. Here we report a sandwichlike NiCo(HPO4)2@Ni3N/NF (denoted by NiCoHPi@Ni3N/NF) catalyst. Vertical Ni3N nanosheet arrays are first grown and supported on nickel foam, and then a bimetallic NiCoHPi coating is decorated on Ni3N nanosheets by one-step electrodeposition. The hierarchical sandwich like structure offers a large surface area and plenty of catalytic active sites, and the coupling of interconnected Ni3N and NiCoHPi accelerates the electron transfer. Moreover, the surficial hydrogen phosphate ions contribute to a proper OH- absorption capacity due to the Lewis acid-base reaction. As a result, the NiCoHPi@Ni3N/NF catalyst exhibits good OER and HER activity, requiring overpotentials of 365 mV (for OER) and 174 mV (for HER) to deliver 100 mA cm-2 in the alkaline simulated seawater electrolyte. When assembled the NiCoHPi@Ni3N/NF catalyst as both the anode and cathode, it only needs 1.86 V to reach 100 mA cm-2 in alkaline simulated seawater electrolyte. This work may inspire the design and exploration of self-supported hierarchical composite electrocatalysts for hydrogen production from the electrolysis of seawater.

Predictor-Based Periodic Event-Triggered Control for Dual-Rate Networked Control Systems With Disturbances.

This article considers the problem of periodic event-triggered control design for dual-rate networked control systems subject to nonvanishing disturbance. The plant considered in this article is a kind of dual-rate networked control system, where the sensor samples the measurement output at a slow rate and the actuator updates the control input at a fast rate. Despite the slow-rate sampling of the sensor, a new output predictor-based observer is proposed to accurately estimate system state and disturbance in the intersample time interval, and an active anti-disturbance controller that updates at a fast rate is accordingly proposed, such that the desirable control performance and disturbance rejection performance can be achieved. At each fast-rate updating time instant, we use the prediction technique to generate a data packet, including the computed current control input and the predicted values of the control inputs for the future finite steps, and design a new periodic event-triggered mechanism to determine whether to transmit the data packet via a communication network or not. The proposed control method is easily implemented in digital platform since it has a discrete-time form. To verify the effectiveness of the proposed control method, we finally present the simulation results of a practical speed control system.

Microscopic investigations on the surface-state dependent moisture stability of a hybrid perovskite.

Hybrid organic-inorganic perovskite (HOIP) materials have caught significant attention in photovoltaics and photoelectronics for their outstanding photovoltaic properties. However, their instability to various environment, such as illumination, temperature, moisture and oxygen, hinders their way to commercialization. To figure out the interaction mechanism between H2O and CH3NH3PbI3 (MAPbI3), extensive theoretical studies have been carried out; however, the experimental results are insufficient and inconsistent. Here, we systematically investigate and compare the influence of H2O on MAPbI3 perovskite films with or without DMF) post-annealing in dark or light condition. The interaction between H2O and the surface of pristine MAPbI3 leads to the fusion of grain boundaries thus grain growth into micron level in short-time moisture exposure. While the penetration of H2O into MAPbI3 results in swelled crystalline whisker, cracking into smaller grains in long-time exposure upon the release of H2O. However, no degradation occurs in dark condition. As the DMF post-annealing treatment changes the surface states of MAPbI3, the interactions between the external H2O and internal MAPbI3 significantly varies from the pristine MAPbI3. Three different surface states with different topographies have influence on the interaction process and mechanism with H2O, leading to different decomposition rates, the striped surface that is the most rough among the three and experiencing the minimum change in surface potential with exposure to 80% humidity decomposes into PbI2 fastest. However, the addition of light will once again affect the aforementioned process. It is found that even ambient light could severely speed up the moisture-induced decomposition of MAPbI3, while the N,N-dimethylformamide (DMF) post-annealing treatment significantly improves the stability of MAPbI3 films upon exposure to humidity and illumination, benefiting from the MAI-deficient thus H2O resistant surface.

Output-Based Dynamic Event-Triggered Mechanisms for Disturbance Rejection Control of Networked Nonlinear Systems.

This paper proposes a new output-based dynamic event-triggered mechanism (ETM) for disturbance rejection control of a class of networked nonlinear uncertain systems subject to additive time-varying disturbance. In the proposed control method, a new robust output feedback controller is first designed based on a generalized proportional-integral observer to attenuate/compensate the undesirable influence of nonlinear uncertainties and disturbances. Different from the static ETM, two new dynamic variables are defined, and thereafter, two kinds of different discrete-time dynamic ETMs are developed only using the sampled-data output signal, such that a better tradeoff between the communication properties and the control properties can be obtained. It is shown that under the proposed control methods, the global bounded stability of the closed-loop hybrid system can be guaranteed by choosing some appropriate parameters. Finally, the numerical simulations of a single link robot arm are conducted to demonstrate the feasibility and efficacy of the proposed control approach.

Reversible self-powered fluorescent electrochromic windows driven by perovskite solar cells.

Self-powered electrofluorochromic devices (EFCDs) have attracted particular attention for smart windows of green buildings. In this work, we report a perovskite solar cell (PSC) driven self-powered EFCD. For the first time, electrochromic material polyoxometalates (POMs) and a fluorescent component are made into wet adhesives. A special design feature is that POMs and magnesium composed a battery powering the EFCD bleaching, and the device can be quickly coloured after connecting with the PSCs by the electrical power generated through solar energy conversion. Therefore, without any additional external bias, the fabricated EFCD undergoes an electrochromic transition from white semitransparent to dark blue-tinted, and under UV it presents reversible fluorescence switching between yellow and dark.

Sampled-Data-Based Event-Triggered Active Disturbance Rejection Control for Disturbed Systems in Networked Environment.

This paper develops a methodology on sampled-data-based event-triggered active disturbance rejection control (ET-ADRC) for disturbed systems in networked environment when only using measurable outputs. By using disturbance/uncertainty estimation and attenuation technique, an event-based sampled-data composite controller is proposed together with a discrete-time extended state observer. Under the presented new framework, the newest state and disturbance estimates as well as the control signals are not transmitted via the common sensor-controller network, but instead communicated and calculated until a discrete-time event-triggering condition is violated. Compared with the periodic updates in the traditional time-triggered active disturbance rejection control, the proposed ET-ADRC scheme can remarkably reduce the communication frequency while maintaining a satisfactory closed-loop system performance. The proposed discrete-time control scheme provides the engineers with a manner of direct and easier implementation via networked digital computers. It is shown that the bounded stability of the closed-loop system can be guaranteed. Finally, an application design example of a dc-dc buck converter with experimental results is conducted to illustrate the efficiency of the proposed control scheme.

Polar Solvent Induced Lattice Distortion of Cubic CsPbI3 Nanocubes and Hierarchical Self-Assembly into Orthorhombic Single-Crystalline Nanowires.

Despite the recent surge of interest in inorganic lead halide perovskite nanocrystals, there are still significant gaps in their stability disturbance and the understanding of their destabilization, assembly, and growth processes. Here, we discover that polar solvent molecules can induce the lattice distortion of ligand-stabilized cubic CsPbI3, leading to the phase transition into orthorhombic phase, which is unfavorable for photovoltaic applications. Such lattice distortion triggers the dipole moment on CsPbI3 nanocubes, which subsequently initiates the hierarchical self-assembly of CsPbI3 nanocubes into single-crystalline nanowires. The systematic investigations and in situ monitoring on the kinetics of the self-assembly process disclose that the more amount or the stronger polarity of solvent can induce the more rapid self-assembly and phase transition. These results not only elucidate the destabilization mechanism of cubic CsPbI3 nanocrystals, but also open up opportunities to synthesize and store cubic CsPbI3 for their practical applications in photovoltaics and optoelectronics.

Stable Sodium Storage of Red Phosphorus Anode Enabled by a Dual-Protection Strategy.

Red phosphorus is appealing for anode use in sodium-ion batteries. However, the synthesis of electrochemically stable red P anodes remains challenging due to a notable volume variation upon (de)sodiation, and limited synthetic methods arising from the low ignition and sublimation temperatures. To address the above problems, we herein successfully develop an industrially adaptable process for scalable synthesis of affordable phosphorus/carbon (APC) anode materials with an excellent electrochemical performance at a significantly reduced cost. The key to our success is a delicately designed, self-organized, strongly interactive porous P/C structure filled with sodium alginate binder, which maintains the structural integrity of anode and enhances the electrical contact of red P upon its volume variation via a dual protection from porous structure and strong surface interactions. The APC anodes hence present ultrahigh initial Coulombic efficiency (86.2%), excellent cycling stability, and superior rate capability. The industrially adaptable process and excellent electrochemical performance endow the novel APC nano/microspheres with promising applications in high-performance Na-ion batteries.

SiOx Encapsulated in Graphene Bubble Film: An Ultrastable Li-Ion Battery Anode.

SiOx is proposed as one of the most promising anodes for Li-ion batteries (LIBs) for its advantageous capacity and stable Li uptake/release electrochemistry, yet its practical application is still a big challenge. Here encapsulation of SiOx nanoparticles into conductive graphene bubble film via a facile and scalable self-assembly in solution is shown. The SiOx nanoparticles are closely wrapped in multilayered graphene to reconstruct a flake-graphite-like macrostructure, which promises uniform and agglomeration-free distribution of SiOx in the carbon while ensures a high mechanical strength and a high tap density of the composite. The composites present unprecedented cycling stability and excellent rate capabilities upon Li storage, rendering an opportunity for its anode use in the next-generation high-energy LIBs.